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ruska model 2485 pressure calibration system user`s manual

1. 4 16 4 8 VALVE OPERATING PROCEDURE FOR MODEL 2485 930 2485 935 4 16 4 8 1 RECHARGING THE HAND PUMP AT ATMOSPHERIC PRESSURE 4 17 4 8 2 PRESSURIZINIG THIE SYSTEM 4 17 4 8 3 ADJUSTING FLOAT POSITION 4 17 4 8 4 RECHARGING THE HAND PUMP WHILE AT PRESSURE 4 17 4 8 5 DISCHARGING THE HAND PUMP WHILE AT PRESSURE 4 17 4 8 6 RETURNING TO ATMOSPHERE 5 ee oe rt te 4 18 4 9 VALVE OPERATING PROCEDURE FOR MODEL 2485 950 4 18 4 9 1 RECHARGING THE HAND PUMP WHILE AT ATMOSPHERE 4 19 4 9 2 GENERATING PRESSURES TO 20 000 PSI 1400 BAR 4 20 4 9 2 1 Pressurizing the SYSTEMA ze harte 4 20 4 9 2 2 Adjusting FlodtPOslflOna eed a 4 20 4 9 2 3 Recharging the Hand Pump While at Pressure 4 20 4 9 2 4 Discharging the Hand Pump While at Pressure 4 20 4 9 2 5 Returning to Atmosphere 4 21 4 9 3 GENERATING PRESSURES GREATER THAN 20 000 PSI 1400 BAR 4 21 4 9 3 1 gt Generaling Pressure using 4 21 4 9 3 2 Adjusting Float Positions 4 21 4 9 3 3 Recharging the Hand Pump While at Pressure 4 22 4 9 3 4 Recharging the Intensifier While at Pressure 4 22 4 9 3 5 Discharging the Intensifier While at Pressure 4 23 4 9
2. d otl 4 9 4 6 5 4 Reserved es enon 4 9 4 6 5 5 Installing a Piston Cylinder or Shipping Plug 4 9 4 6 5 6 Installing the Mass Loading Table Assembly 4 9 4 6 6 REMOVING THE SHIPPING PLUG MODEL 2485 935 4 10 4 6 7 CHANGING THE PISTON AND CYLINDER MODEL 2485 935 4 10 OPERATING PROCEDURE FOR THE MODEL 2485 DEADWEIGHT 4 11 4 7 1 ESTABLISHING ATMOSPHERIC PRESSURE 4 11 4 7 2 LEVEL THE INSTRUMENT PLATFORFM 4 12 4 7 3 RECHARGE THE HAND PUMP sn creda bien ee Re 4 12 4 7 4 LOAD THE MASSES AND PRESSURIZE THE SYSTEM 4 12 4 7 4 1 Install Hanger Mass a a AAAA 4 12 4 7 4 2 Load Other MEssESi i I D EN ted adios 4 13 4 7 4 3 Rotate the Masses Hui 4 13 4 7 4 4 Fine 4 13 4 7 4 5 Adjust Float Posilion 4 13 AS AO Assess ODINNY 4 14 4 7 5 EXECUTE PRESSURE MEASUREMENT 4 14 viii 2 76 NEXT PRESSURE eoo nta eta iri pta oda dci dap tante 4 14 4 7 7 RETURN TO ATMOSPFIERE reet cele are 4 14 4 7 8 PREPARATION FOR 4 15 4 7 9 PREPARATION FOR
3. ASS N GGG lt FIGURE 5 6 DISASSEMBLING LOW RANGE QC PC HOLDER MODEL 2485 935 MAINTENANCE amp TROUBLESHOOTING 5 14 Ad Ad08 wacioH SSS 5 1531 UW ON Ls FIGURE 5 7 ASSEMBLING QC PC HOLDER MODEL 2485 935 MAINTENANCE amp TROUBLESHOOTING 5 15 THIS PAGE INTENTIONALLY LEFT BLANK MAINTENANCE amp TROUBLESHOOTING 5 16 APPENDIX A EXPLANATION OF PRESSURE CALCULATION WORKSHEET TABLES 9 AND A11 These tables may be used with gas and hydraulic piston pressure gauges that are operated with an atmospheric reference or vacuum reference P represents the pressure at the piston reference gauge level P represents the pressure desired at the device under test and is the head pressure created by the pressure medium and the difference in height between the piston pressure gauge and the device under test A A minimum of six significant figures must be used in all calculations involving reported constants masses etc The manvfacturer s claims for accuracy assume the local gravity to be known to at least six significant figures B When the piston pressure gauge is used as a standard of pressure it is convenient to perform the pressure to mass calculations in advance of operating the standard Since the piston gauge temperature fluctuates while it is operated a confu
4. TECHNICAL DESCRIPTION 3 8 TABLE 3 1 INSTRUMENT PLATFORM FEATURES Sequence Fi Numb Feat NADE igure Number s eature 001 3 1 thru 3 4 Instrument Cover 002 3 1 thru 3 4 4 3 Mass Loading Table Assembly 003 3 1 thru 3 4 Reservoir Valve A 004 3 1 thru 3 4 Pressure Valve B 005 3 1 3 3 3 4 Intensifier Valve C 006 3 1 3 3 3 4 System Valve D 007 3 4 Pump Position Indicator 008 3 1 thru 3 4 Pump Handle 4 each 009 3 3 3 4 Pump Spindle Cover 010 3 4 Pump Lubrication Port Cover 011 3 4 Bleed Screw Cover 012 3 6 5 1 Safety Head and Rupture Disk Assembly 013 3 thru 3 4 Pressure Monitor 014 3 4 Internal Reservoir Cover 015 3 2 External Reservoir Port 016 3 2 thru 3 4 Reservoir Source Valve 017 3 5 3 6 Reservoir Relief Valve 018 3 1 thru 3 4 4 2 Test Port Manifold and Adapters 019 3 2 thru 3 4 4 2 Test Port Manifold Retaining Nut 020 3 1 3 2 Main Oil Drain Cup 021 3 1 3 2 Auxiliary Oil Drain Cup 022 3 1 thru 3 3 Fixed Support Leg 023 3 1 3 2 Auxiliary Support Leg 024 3 1 thru 3 3 Adjustable Support Legs 2 each 025 3 1 3 2 3 4 Level Vial 026 3 1 3 2 3 4 Drive Motor Assembly 027 3 2 3 4 4 1 Power Receptacle and Fuse Holder 028 3 1 3 4 Drive Motor Power Switch 029 3 2 3 4 Drive Motor Power Lamp 030 3 2 3 4 Drive Belt 031 3 1 3 2 Drive Sleeve 032 3 1 thru 3 3 4 3 Roller Pin 033 3 1 3 4 Float P
5. Carefully rotate the hand pump spindle clockwise to generate pressure Once the pressure monitor indicates the same pressure noted earlier slowly open intensifier valve C 4 9 2 4 Discharging the Hand Pump While at Pressure When reducing pressure in the system the pump may reach the counter clockwise travel limit before the desired pressure is obtained To allow further depressurization of the system the hand pump may be discharged while the system remains at pressure To discharge the hand pump while the system is at pressure first verify that reservoir valve A intensifier valve C and system valve D are open then adjust the hand pump position so that approximately one quarter of the pump travel remains in the counter clockwise direction Close intensifier valve C and note the system pressure indicated on the pressure monitor for use later in this section Carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar Open pressure valve B and rotate the hand pump spindle clockwise until approximately one quarter of the pump travel remains in the clockwise direction Close pressure valve B and carefully rotate the hand pump spindle clockwise to generate pressure Once the pressure monitor indicates the same pressure noted earlier in this section slowly open intensifier valve C SYSTEM OPERATION 4 20 4 9 2 5 Returning To Atmosphere Rotate the hand pump spindle counter cloc
6. DESCRIPTION 001 INSTRUMENT COVER The instrument cover can be removed to access the internal hardware for maintenance or repair The left and right cover panels are secured by thumb screws at the edges of the panels on the front top and rear of the instrument 002 MASS LOADING TABLE ASSEMBLY The mass loading table assembly secures the piston cylinder assembly in the main pressure housing and transmits the load of the mass set to the piston piston cylinder assembly installed in the main pressure housing is protected from damage due to pressure release while under load as well as when the load is removed with pressure applied by thrust bearings inside the mass loading table assembly Refer to sections 3 2 2 and 3 2 3 for further discussion of the mass loading table assembly 003 RESERVOIR VALVE A Reservoir valve A is opened to recharge the hand pump and closed to provide a positive cutoff to the reservoir to allow pressurization of the instrument 3 1 TECHNICAL DESCRIPTION SEQUENCE FUNCTIONAL NUMBER 004 005 006 007 008 009 DESCRIPTION PRESSURE VALVE B Pressure valve B serves two functions In the low pressure version model 2485 930 pressure valve B allows recharging of the hand pump while the system remains at pressure by isolating the pump and reservoir from the system In the high pressure version model 2485 950 which includes an integral pressure intensifier pressure valve B is used as the reservoir
7. RUSKA MODEL 2485 PRESSURE CALIBRATION SYSTEM USER S MANUAL PRESSURE CALIBRATION SYSTEM MODEL 2485 USER S MANUAL RUSKA INSTRUMENT CORPORATION 10311 WESTPARK DR HOUSTON TEXAS 77042 713 975 0547 FAX 713 975 6338 e mail ruska ruska com Release 2485 1D02 Revision F Date November 15 2002 WARRANTY Ruska Instrument Corporation warrants its products to conform to or exceed the specifications as set forth in its catalogs in use at the time of sale and reserves the right at its own discretion without notice and without making similar changes in articles previously manufactured to make changes in materials designs finish or specifications Ruska Instrument Corporation warrants products of its own factory against defects of material or workmanship for a period of one year from date of shipment Liability of Ruska Instrument Corporation under this warranty shall be limited to replacing free of charge FOB Houston Texas any such parts proving defective within the period of this warranty but will not be responsible for transportation charges or consequential damages This warranty is not made for products manufactured by others which are illustrated and described in RUSKA catalogs or incorporated in RUSKA products in essentially the same form as supplied by the original manufacturer However Ruska Instrument Corporation agrees to use its best efforts to have original suppliers make good their warranties 11 COPYR
8. On occasion the hand pump will approach the full clockwise travel limit while the system is under pressure The hand pump may be recharged while the system remains at pressure To recharge the hand pump while the system is at pressure close system valve D and note the system pressure indicated on the pressure monitor Carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar Open reservoir valve A and continue rotating the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise one quarter turn and close reservoir valve Carefully rotate the hand pump spindle clockwise to generate pressure Once the pressure monitor indicates the same pressure noted earlier slowly open system valve D 4 9 3 4 Recharging the Intensifier While at Pressure On occasion the intensifier will reach the full stroke limit while the system is under pressure The intensifier may be recharged while the system remains at pressure There are two indications to the operator when the intensifier plunger has reached the full stroke limit If the intensifier is at full stroke prior to closing intensifier valve C for high pressure operation as described in Section 4 9 4 1 the pressure monitor indication will not change in rate as the pump pressure approaches approximately one fifth the test port pressure Th
9. approximately even with the backup ring Insert the long end of the tool into the backup ring and packing Hold the tool in place while slowly rotating the hand pump The fluid displaced by the pump should push the seal and backup ring out of the column DO NOT EXCEED 100 PSI and WEAR SAFETY GLASSES When the seal is free from the column the seal and backup ring may be lifted out of the column using the tool Replacing the seal 1 29 5 5 2 2 Install the seal retainer the backup ring and a fresh seal onto the tool as shown in Figure 5 4 Lubricate the parts with a few drops of test media Carefully insert the components into the pressure housing Thread the seal retainer into the housing until it is firmly seated excessive torque is not necessary Install the drive sleeve and drive belt Install the QCPC holder as described in 4 6 6 2 PISTON CYLINDER CLEANING Optimum performance of a deadweight gage requires a functional piston cylinder assembly The piston cylinder assembly must be clean to operate properly and preclude permanent damage Typically hydraulic piston cylinder assemblies once clean and when handled properly will not likely require periodic cleaning Deliberate and careful handling and proper storage of a piston cylinder assembly in the storage container or main pressure housing will prolong the life of the assembly and MAINTENANCE amp TROUBLESHOOTING 5 4 help to prevent contaminati
10. 00 EACH 94 664 WRENCH ADJUSTABLE 12 1 00 EACH 94 686 WRENCH OPEN END 3 4 X 7 8 1 00 EACH 99189 RUSKA GLOVES 1 00 PAIR FOR HANDLING MASSES 99199 008 PIN WRENCH STRAIGHT 1 4 1 00 EACH APPENDIX B B 2
11. 02 Updated manual per DC RO 22207 iv REVISION HISTORY RELEASE 2485 1D02 Revision A 04 10 91 Original release RELEASE 2485 1D02 Revision B 07 12 91 Minor text changes RELEASE 2485 1D02 Revision C 09 30 93 Modifications to add 5000 bar 2485 to manual ECO 18273 RELEASE 2485 1D02 Revision D 03 06 02 Corrected Figure 4 2 DC RO 23269 RELEASE 2485 1D02 Revision E 06 28 02 Added Addendum 2485 New Features to manual DC RO 23418 RELEASE 2485 1D02 Revision F 11 15 02 Updated manual DC RO 22207 WARNING PRESSURIZED VESSELS AND ASSOCIATED EQUIPMENT ARE POTENTIALLY DANGEROUS THE APPARATUS DESCRIBED IN THIS MANUAL SHOULD BE OPERATED ONLY BY PERSONNEL TRAINED IN PROCEDURES THAT WILL ASSURE SAFETY TO THEMSELVES TO OTHERS AND TO THE EQUIPMENT DO NOT EXCEED SAFE MAXIMUM GENERATED PRESSURES AS FOLLOWS 2485 930 20 000 PSI 1 400 BAR 2485 935 40 000 PSI 2 800 BAR 2485 950 HAND PUMP SYSTEM 20 000 PSI 1 400 BAR 2485 950 MAIN HOUSING amp TEST PORT MANIFOLD 72 500 PSI 5 000 BAR ALWAYS USE REPLACEMENT PARTS SPECIFIED BY RUSKA INSTRUMENT CORPORATION WHEN ANY MAINTENANCE IS PERFORMED TURN OFF POWER AND REMOVE POWER CORD CAUTION DO NOT MIX FLUID TYPES FLUID TYPES AVAILABLE SPINESSTIC 22 OIL DIOCTYL SEBACATE DOS DO NOT EXCEED THE SAFE WORKING PRESSURES FOR THE TEST PORT MANIFOLD ADAPTERS REFER MARKINGS ON THE ADAPTERS AND TO FIGURE 4 2 FOR SAFE OPE
12. 1 2 83 J 4 5 6 7 8 9 wo 1 17 A419 Temp Coef Ps Pmedium Masses to Remainder i 1 9x NOMINAL Mass Pmedium Pair pw xh 2 elt FX Ki 453 59237 PRESSURE Density Ib in 91 980 665 A 9 CALCULATIONS THIS PAGE INTENTIONALLY LEFT BLANK CALCULATIONS A 10 PISTON PRESSURE GAUGE PRESSURE CALCULATION WORKSHEET SI UNITS RUSKA Date Expected Temperature t C Reference Plane Difference h m Aofe3 1 c t 23 a Mass Set Serial No Local Gravity g m sec Piston Serial No Air Density g cm kg m Av 23 at 23 C m Gravity amp Buoyancy K b Tare Mass kg b Reference Pressure Pa mtorr Pa 1 C f medium E Remainder Temp Coef I 2 P xA Column 9 x NOMINAL Mass Density Pmedium Pair AX Fett 2 1000g kg x c PRESSURE kg m 11 CALCULATIONS THIS PAGE INTENTIONALLY LEFT BLANK CALCULATIONS A 12 APPENDIX B SETUP KIT BILLS OF MATERIAL SETUP KIT 2485 202 MODEL NUMBER 2485 930 amp 2485 950 PART QUANTITY amp NUMBER DESCRIPTION UNIT OF NOTES MEASURE 2411 702 010 RTD PRT HOLDER 1 8 NPT X 3 16 1 00 EACH 2465 100 PISTON amp CYLINDER CLEANING KIT 1 00 EACH 2485 102 001 LOW RANGE CYLINDER CLEANING TOOL
13. 2456 piston gauge monitor or other device TECHNICAL DESCRIPTION 3 6 SEQUENCE FUNCTIONAL NUMBER DESCRIPTION 035 OPTIONAL THERMOMETER ASSEMBLY A liquid in glass thermometer with protective metal sleeve and mounting hardware is available as Option Ruska P N 2485 202 913 Temperature measurement is required to minimize the thermal effects when operating the 2485 Piston Pressure Gage An electronic thermometer PRT is also available as an option 036 MASS SET Each individual piece in the mass set is completely machined from non magnetic 300 series stainless steel in kilogram denominations to provide easy direct comparison to mass standards in the meter kilogram second system of measure The final mass is adjusted to within 15 parts per million of the nominal denomination in units of apparent mass versus brass standards density reference 8 4 g cm The adjustment is performed in such a way as to maintain a balance about the centerline by milling a symmetrical pattern of holes on the bottom surface of the mass concentric with the axis The mass set includes a hanger mass for maintaining a low center of gravity while supporting the full load nineteen 5 kilogram platters and incremental denominations in a 5 3 2 1 sequence down through 200 grams Each mass in the set is marked with the nominal mass denomination a sequence number and the serial number of the set for traceability When supplemented with a laboratory style mass se
14. 3 6 Discharging the Hand Pump While at Pressure 4 23 4 9 3 7 Returning to Atmosphere 4 24 4 10 OPTIONAL HARDWARE e ha deti eral dn aia 4 24 4 10 1 THERMOMETER niet ore d cos hon Wad 4 24 4 10 2 ELECTRONIC FLOAT POSITION 4 24 4 10 3 ELECTRONIC TEMPERATURE SENSOR 4 24 SECTION 5 0 MAINTENANCE AND TROUBLESHOOTING 30 INTRODUCTION s sect L EA mua au a 5 1 952 MAINTENANCE U Pep L AAY EA etnis da 5 1 5 2 1 INSTRUMENT PLATFORM 5 1 S2 p Dra JOSE vid A Q ee Net 5 1 5 2 1 2 Instrument Platform Cleaning 5 1 5 2 1 3 Level Vial Adjustment ae nee 5 1 5 2 1 4 Instrument Platform Lubricotion 5 2 5 2 1 5 Packing Adjustment NEN 5 2 5 2 1 6 Rupture Disk Replacements sce 5 2 5 2 1 7 Instrument Cover Removal and Replacement 5 3 5 2 1 8 Seal and O ring 5 3 5 2 1 9 Changing the Seal in the Pressure Column 5 4 x 5 2 2 PISTON GYEINBER CLEANING 5 4 5 2 3 ALTERNATE PISTON CYLIND
15. 4 2 1022 Gosine l AA Pec Susa 2 5 2 1 2 3 Buoyant Effect of the AIT ect oce ek a e ud a 2 5 2 1 2 4 Combined Gravity and Air Buoyancy Correction 2 6 2 1 2 5 Surface Tension Wo de ec d d 2 7 2 1 3 PRES CORRECTIONS AND OTHER MISCELLANEOUS FACTORS 2 7 2 1 3 1 Hydraulic Fluid Pressure 2 7 2 1 3 2 Pneumatic Pressure Grodients 2 8 2 1 3 3 Reference Pressure Heaod 2 8 2 1 3 4 Float Boston N died l aS pet 2 8 2 1 3 5 Minimum Pressure ana an 2 9 2 2 PRESSURE TO MASS EQUATION 2 9 23 MASS TO PRESSURE EQUATION seen are 2 9 2 4 CONDITIONS FAVORABLE FOR A 2 10 245 ACCURACY AND TRACEABILITY 2 11 2 5 1 DEADWEIGHT GAGE MASSES 2 11 2 5 2 DEADWEIGHT GAGE PISTON 2 11 2 01 BIBLIOGRAPHY uu ER o d Peso Ga EPA AT 2 13 SECTION 3 0 TECHNICAL DESCRIPTION 3 1 3 2 4 1 4 2 4 3 4 4 4 6 4 7 INSTRUMENT OVERVIEW 2 42 3 1 INSTRUMENT FEATURES AND FUNCTIONS 3 1 3 2 1 INSTRUMENT PLATFORM FUNCT
16. 9 MPa To calculate the density of Nitrogen at pressures from 0 01 MPa gauge to 6 9 MPa use the following equation DENSITY kg m 1 585 E 06 x P where P PRESSURE in Pa absolute if P is in gauge convert it to Pa absolute by adding barometric pressure e g P 101325 HELIUM DENSITY SI UNITS 6 9 MPa TO 100 MPa To calculate the density of Nitrogen at pressures from 6 9 MPa gauge to 100 MPa use the following equation DENSITY kg m 0 3136 01 1 508 P 3 886 E 03 P where PRESSURE in MPa absolute if P is in gauge convert it to MPa absolute by adding barometric pressure e g P 0 101325 TABLE A 1 CONVERSION FACTORS TO CONVERT FROM TO MULTIPLY BY Pa N m 1 N m Pa 1 MPa 10 MPa Pa 10 N m MPa 10 N m 10 PSI 1 450377 X 10 PSI Pa 6894 76 MPa PSI 145 0377 PSI MPa 6 89476 X 10 where Pa pascal MPa megapascal N newton m meter PSI pounds per square inch A 7 CALCULATIONS THIS PAGE INTENTIONALLY LEFT BLANK CALCULATIONS A 8 pem PISTON PRESSURE GAUGE PRESSURE CALCULATION WORKSHEET ENGLISH UNITS RUSKA Date Expected Temperature t C Reference Plane Difference h inch 1 c t 23 C inch Mass Set Serial No Local Gravity g cm sec Piston Serial No Air Density Par g cm Ib in Av 23 at 23 C inch Gravity amp b4 Ipsi Tare Apparent Mass pound b2 Ipsi Reference Pressure Pa mtorr psi 1 C L
17. Bell amp Sons London 1952 Cross J L Reduction of Data for Piston Gage Pressure Measurements NBS Monograph 65 1963 Dadson R 5 The Accurate Measurement of High Pressures and the Precise Calibration of Pressure Balances Proc Conf Thermodynamic and Transport Properties of Fluids London pp 32 42 1957 Institute of Mechanical Engineers Design and test of Standards of Mass NBS Circular No 3 Dec 1918 Included in NBS Handbook 77 Volume III Johnson D P J L Cross J D Hill and H A Bowman Elastic Distortion Error in the Dead Weight Piston Ind Engineering Chem 40 2046 1957 Johnson D P and D H Newhall The Piston Gage is a Precise Measuring Instrument Trans of ASME April 1953 Newhall D H and L H Abbot Controlled Clearance Piston Measurements and Jan Feb 1970 Pressure Measurement Measurements amp Data Home Study Course No 17 Measurements and Data September October 1969 Tate D R Gravity Measurements and the Standards Laboratory National Bureau of Standards Technical Note No 491 1969 Heydemann and Welch Chapter 4 Part 3 Pure and Applied Chemistry Butterworths Kirk K Mosher Ruska Instrument Corporation The Traceability Chain of the Piston Pressure Gage to presented at the Canadian National Conference of Standards Laboratories 1991 Ken Kolb Ruska Instrumen
18. a well preserved mass set is typically about 3 or 4 years Heavily used or less well preserved sets will likely require more frequent calibrations Calibration of deadweight gage masses is typically performed through direct comparison of individual masses with standards of known mass measured on a precision balance or mass comparator The calibration report for a mass set used with a high accuracy deadweight gage will typically include individual mass and density values as well as uncertainty and traceability information Masses used with lower accuracy deadweight gages may not list individual mass values only nominal values of mass or pressure and a tolerance to which they were measured or adjusted In either case the calibration documentation is an important part of the mass set and should be preserved with the same care as the individual masses 2 5 2 DEADWEIGHT GAGE PISTON As with the mass set preservation of the high precision operating surfaces of the piston cylinder assembly will prolong the reliability and long term stability of the deadweight gage piston Always handle the piston cylinder assembly in accordance with the instructions provided in the operating manual Proper handling of these assemblies will typically result in a recalibration schedule of about 3 or 4 years 2 11 PISTON PRESSURE GAGE Calibration of a deadweight gage piston cylinder assembly is typically performed through direct intercomparison with a standard piston c
19. assembly Refer to Figures 3 1 through 3 3 for locating the roller pin and drive motor power switch 4 7 4 4 Fine Load Adjustment When the model 2485 is used to generate a specific pressure a small adjustment of the load may be required This adjustment to compensate for conditions such as local gravity air buoyancy and temperature is typically performed through the use of a laboratory mass set with denominations from 100 grams to 10 milligrams This load adjustment is placed directly on the mass loading table and should be removed prior to changing the load to generate a subsequent pressure 4 7 4 5 Adjust Float Position Once the desired load is applied to the piston use the hand pump to adjust the pressure so that the piston is slightly above the mid float position As the system stabilizes the normal sink rate of the piston will carry it through mid float The mid float position can be measured manually or electronically When the bottom edge of the hanger mass sequence 01 bisects the float position line located just above the pulley on the drive sleeve the piston is at mid float The position of the hanger mass can be observed in the float position mirror block assembly mounted on the instrument platform as shown in Figures 3 1 and 34 more accurate measurement of float position can be made using the electronic float position option 4 13 SYSTEM OPERATION 4 7 4 6 Assess Stability The operator must make a judgment as to the st
20. cutoff valve for pressures up to 20 000 psi 1400 bar and is opened when activating the intensifier to generate pressures up to 72 500 psi 5000 bar INTENSIFIER VALVE C The high pressure version model 2485 950 includes an integral intensifier After charging the system to approximately 20 000 psi 1400 bar intensifier valve C is closed to activate the intensifier for pressure generation up to 72 500 psi 5000 bar SYSTEM VALVE D System valve D on the high pressure version model 2485 950 serves two functions The primary function of system valve D is to allow recharging of the integral intensifier without removing the pressure from the system secondary function of system valve D is fine adjustment of the float position of the high pressure pistons when the friction of the seals in the intensifier do not allow such fine control PUMP POSITION INDICATOR The model 2485 incorporates a hand operated positive displacement screw type pump for generating hydraulic pressure The position of the hand pump plunger and the amount of remaining stroke is indicated by the relative position of the pump position indicator located in the opening in the top of the instrument cover PUMP HANDLES The instrument is supplied with four pump handles for optimum control of the pump handles can be secured to the pump spindle nut by gentle tightening using a wrench on the milled flats near the spindle nut end of each handle PUMP SPIND
21. deadweight gage is available in three configurations a low pressure version model 2485 930 rated to 20 000 psi 1400 bar a medium pressure version 2485 935 rated to 40 000 psi 2800 bar and a high pressure version model 2485 950 rated to 72 500 psi 5000 bar The high pressure version incorporates an integral intensifier for operation above the 20 000 psi 1400 bar Operation of the intensifier requires the use of additional valves and plumbing and a slightly different valve operating procedure for generating pressures The following sections describe the general operation of the instrument in terms generic to both high pressure and low pressure versions as well as specific valve operating procedures for generating pressure with each version of the instrument 4 2 PRECAUTIONS WARNING Pressurizing vessels and associated equipment are potentially dangerous The apparatus described in this manual should be operated only by personnel trained in procedures that will assure safety to themselves to others and to the equipment Safe and proper operation of this system requires that the operator have a thorough knowledge of the operation of the system and follows a strict procedure for pressurizing and depressurizing the system to prevent damage to the delicate internal components and to prevent injury to personnel Operation of the hand pump and valves must be performed in such a way as to maintain control of the system at all times A
22. is noticed stop and open the reservoir valve Continue threading the QCPC into the column When the QCPC is fully installed insert the tool part number 99199 0087 into the spanner hole in the side of the QCPC and make sure it is firmly seated Verify that both valves are open before removing the top shipping cap from the QCPC Remove the top shipping cap from the QCPC If excess oil is present on either the top of the piston or the mating surface on the table support remove it by wiping them with a lint free wiping paper Kimwipe or equal Install the table assembly onto the top of the QCPC seat it firmly using the tool part number 94 618 The rotation roller assembly is found stored inside the shipping plug If the rotation motor is to be used remove the roller assembly from the shipping plug and install it into the mass rotating sleeve See Figure 4 5 If the rotation motor is not being used the roller assembly may be left inside the shipping plug Install the unused shipping caps onto the shipping plug this will prevent dust from contaminating the surfaces as well as keeping the pieces together See Figure 3 15 4 6 7 CHANGING THE PISTON AND CYLINDER MODEL 2485 935 Please refer to Figure 4 7A and 4 7B If there is pressure in the system rotate the hand pump until the pressure is below 500 psi Slowly open both valves to assure no pressure is trapped in the system Recharge the hand pump Rotate the hand pump to the end of travel in
23. located at the front and rear of the right side of the instrument platform The voltage selector switch position must be verified prior to applying power As shown in Figure 4 3 the selected voltage is displayed through a small window in the power cord receptacle on the rear of the drive motor assembly If the incorrect voltage is displayed the voltage selector switch position and the fuses must be changed To change the voltage selector switch position and fuses open the voltage selector fuse holder compartment on the power receptacle using flat blade screwdriver in the slot directly above the voltage display window Remove the voltage selector wheel rotate to the proper setting and reinstall CAUTION Do not rotate the selector wheel while it is installed Slide out both fuse holder trays and verify that the proper fuses are installed Close the voltage selector fuse holder cover and verify that the proper voltage is displayed SYSTEM OPERATION 4 2 power pigtail with female plug Style 60320 emerges from the lower surface of drive motor assembly This pigtail supplies power to the fill pump assembly mounted below the base See Figure 3 9 This pigtail may have come loose during shipping Verify that this pigtail is securely inserted into the male socket power inlet on the fill pump sub assembly Read the sections regarding fill pump operation before energizing the fill pump Ensure that the drive belt is properly p
24. old seal off of the stem and discard DO NOT USE ANY SHARP OBJECT TO REMOVE THE SEAL Lubricate the new seal part number 72 33 with a small amount of the deadweight gage oil and carefully slide it onto the manifold stem The flared end of the seal should be oriented toward the bottom of the manifold stem 4 5 SYSTEM OPERATION CAUTION device or system connected to the test port manifold or other test port on the 2485 must be clean and free of contamination to prevent the damage to the precision deadweight gage components If the deadweight gage is to be used to calibrate devices that are not known to be clean an external filter trap such as Ruska model 2436 800 can be used up to 40 000 psi 2800 bar Use of a fine mesh filter to trap minute particulates can result in reduced sensitivity of the deadweight system obtain maximum sensitivity and the highest level of i oressure measurement the device under test must be clean Connect the device under test and any required adapters to the test port manifold refer to Figure 4 4 Rotate the hand pump clockwise to adjust the oil level in the auxiliary pressure housing to within approximately 2 mm of the top Guide the lower stem of the manifold into the auxiliary pressure housing Open the appropriate valve to the reservoir and hand tighten the test port manifold retaining nut The test port manifold is now sealed and the device under test can be bled of air if necessary by pumpi
25. or system used to provide traceability As comparative measurements are performed at each level in a measurement chain used to transfer the knowledge about a reference device to a test device the potential for error increases These additional errors generally but not exclusively are the result of performances parameters such as those stated above Significant additional contributions may be the result of environmental factors operator intervention and human error These are the most difficult to assess and eliminate yet may contribute the greatest errors To take full advantage of the performance characteristics of precision deadweight gages which require substantial operator manipulation and mathematical computation appropriate precautions must be taken to minimize the risk of gross errors and to reduce the miscellaneous influences 2 5 1 DEADWEIGHT GAGE MASSES The components of a deadweight gage mass set are calibrated to provide knowledge of individual mass values as well as an estimate of the contribution to the total uncertainty in the pressure measured with the instrument Preservation of the condition of the masses is crucial to long term stability and reliability Proper handling such as careful and deliberate loading and unloading removal of incidental contamination such as fingerprints and deadweight gage oil and proper storage of the masses will prolong the reliability of the calibration values The recalibration schedule for
26. probe FILL PUMP ASSEMBLY MODEL 2485 930 AND 2485 935 The fill pump is a motorized pump which facilitates the bleeding of external lines or device under test Before using the fill pump check the reservoir level to assure an ample amount of fluid is available Next loosen the reservoir lid to allow air into the reservoir The reservoir valve and the system valve must be open Energize the pump by toggling the control switch on the left hand side of the drive motor assembly see 028 Open a line or bleed a fitting at the high point of the circuit to allow the escape of trapped air Operating the fill pump with the system and reservoir valves closed should do no harm to the system however operating the pump for more than 2 3 minutes with the valves closed will warm the hydraulic oil above ambient temperature and is therefore not recommended The pump may be damaged if the reservoir is allowed to run dry 4 3 3 PREPARATION FOR USE The model 2485 is shipped from the factory with a small amount of pressure trapped in the system After completing the installation according to section 4 3 2 follow the step 4 3 SYSTEM OPERATION by step procedure described below to safely remove the pressure from the instrument and prepare the instrument for use 1 Rotate the Reservoir Source Valve on the rear of the instrument to the internal reservoir position 2 Thread the four pump handles carefully into the hand pump spindle nut on the front of the in
27. 0 mg trim adjustment A general guideline for selecting the appropriate piston cylinder is to select the lowest range that covers the pressures in the particular application If two ranges are required for a particular evaluation use the lower range up to its maximum rating and overlap one or two pressures using the higher range 4 7 SYSTEM OPERATION 4 6 4 PISTON CYLINDER IDENTIFICATION model 2485 piston cylinder assemblies are permanently marked with the pressure unit increment designator the assembly serial number and the word top to ensure proper orientation when installed into the main pressure housing The top of each piston is rounded to ensure alignment and proper operation of the mass loading table assembly It is crucial that the piston and cylinder be installed in the proper orientation Refer to Figure 3 11 and Figure 4 5 for a detailed view of the piston cylinder markings and orientation When a 2485 piston cylinder assembly is not installed in the instrument it should be stored in the shipping storage container supplied with each assembly The label on the container identifies the denomination and serial number of the piston cylinder assembly The container can be stored in the mass set storage box that contains the incremental platters and the hanger mass 4 6 5 PISTON CYLINDER INSTALLATION AND EXCHANGE 2485 930 and 2485 950 CAUTION Whenever handling the precision piston cylinder components of the model 2485 deadweig
28. 1 00 EACH 2485 1002 USERS MANUAL 1 00 EACH 2485 920 MIRROR BLOCK 1 00 EACH FOR FLOAT POSITION 2485 KIT 001 ADAPTER KIT 1 00 EACH FOR AUXILIARY CONNECTOR BLOCK 26 216 FUSE 1 AMP SLOW BLOW SIZE 3AB 2 00 EACH 54 700 437 DRIVE BELT 2485 1 00 EACH FOR ROTATION SLEEVE 54 703 008 O RING VITON 3 16 I D X 1 16 CROSS 6 00 EACH FOR EXTENDED SECTION RANGE P C 54 703 117 O RING VITON 13 16 X 3 32 CROSS SECTION 2 00 EACH FOR P Cs OTHER THAN EXTENDED RANGE 54 703 14 O RING VITON 1 2 1 D X 1 16 CROSS 6 00 EACH FOR EXTENDED SECTION RANGE P C 72 33 SEAL 1 4 X 1 2 PLOYPAK 4 00 EACH FOR CONNECTOR BLOCK 86 802 TUBING CLEAR PLASTIC 3 8 ODX 1 16 WX 5 00 FEET WASTE MEDIA 1 4 ID DRAIN LINE 94 607 WRENCH HEX KEY 1 8 1 00 EACH 94 608 WRENCH HEX KEY 3 32 1 00 EACH 94 617 WRENCH PIN SPANNER 2 DIAMETER W 1 4 1 00 EACH PIN 94 618 WRENCH PIN SPANNER 2 25 DIAMETER W 1 00 EACH 1 4 PIN 94 628 WRENCH OPEN END 1 4 X 5 16 1 00 EACH 94 629 WRENCH OPEN END 5 8 X 11 16 1 00 EACH 94 632 WRENCH OPEN END 1 2 X 9 16 1 00 EACH 94 637 WRENCH OPEN END 7 16 X 1 2 1 00 EACH 94 664 WRENCH ADJUSTABLE 12 1 00 EACH 94 686 WRENCH OPEN END 3 4 X 7 8 1 00 EACH 99189 RUSKA GLOVES 1 00 PAIR FOR HANDLING MASSES APPENDIX B SETUP KIT 2485 203 MODEL NUMBER 2485 935 PART NUMBER DESCRIPTION QTY amp UNIT OF NOTES MEASURE 24
29. 11 702 010 RTD PRT HOLDER 1 8 NPT X 3 16 1 00 EACH 2465 100 PISTON amp CYLINDER CLEANING KIT 1 00 EACH 2485 102 001 LOW RANGE CYLINDER CLEANING TOOL 1 00 EACH 2485 1002 USERS MANUAL 1 00 EACH 2485 203 001 GLAND REMOVAL TOOL 1 00 EACH FOR PRESSURE COLUMN 2485 203 002 P C ASSEMBLY TOOL 1 00 EACH FOR QUICK CHANGE P C HOLDER 2485 920 MIRROR BLOCK 1 00 EACH 2485 935 007 BACKUP RING 1 00 EACH FOR PRESSURE COLUMN 2485 KIT 001 ADAPTER KIT 1 00 EACH FOR AUXILIARY CONNECTOR BLOCK 26 216 FUSE 1 AMP SLOW BLOW SIZE 3AB 2 00 EACH 54 603 008 O RING VITON 3 16 I D X 1 16 CROSS 10 00 EACH FOR 40 K PSI P C SECTION 60 DUROMETER 54 700 437 DRIVE BELT 2485 1 00 EACH FOR ROTATION SLEEVE 54 703 117 O RING VITON 13 16 X 3 32 CROSS SECTION 2 00 EACH FOR P Cs OTHER THAN 40 KPSI 72 33 SEAL 1 4 X 1 2 POLYPAK 4 00 EACH FOR CONNECTOR BLOCK 72 43 SEAL 625 OD X 375 ID POLYPAK 4 00 EACH FOR HAND PUMP AND COLUMN 86 802 TUBING CLEAR PLASTIC 3 8 ODX 1 16 WX 5 00 FT WASTE MEDIA 1 4 ID DRAIN LINE 91 398 DISK SPRING WASHER 505 X 1 0 2 00 EACH FOR 40K QCPC HOLDER 94 607 WRENCH HEX KEY 1 8 1 00 EACH 94 608 3 32 1 00 94 617 WRENCH PIN SPANNER 2 DIAMETER W 1 4 1 00 EACH PIN 94 618 WRENCH PIN SPANNER 2 25 DIAMETER W 1 00 EACH 1 4 PIN 94 628 WRENCH OPEN END 1 4 X 5 16 1 00 EACH 94 629 WRENCH OPEN END 5 8 X 11 16 1 00 EACH 94 632 WRENCH OPEN END 1 2 X 9 16 1 00 EACH 94 637 WRENCH OPEN END 7 16 X 1 2 1
30. 4 9 3 6 Discharging the Hand Pump While at Pressure When reducing pressure in the system the hand pump may reach the counter clockwise travel limit before the desired pressure is obtained To allow further depressurization of the system the hand pump may be discharged while the system remains at pressure To discharge the hand pump while the system is at pressure verify that pressure valve B is open and adjust the hand pump position so that approximately one quarter of the 4 23 SYSTEM OPERATION pump travel remains in the counter clockwise direction Close system valve D and note the system pressure indicated on the pressure monitor Carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar Open reservoir valve A and rotate the hand pump spindle clockwise until approximately one quarter of the pump travel remains in the clockwise direction Close reservoir valve A and carefully rotate the hand pump spindle clockwise to generate pressure Once the pressure monitor indicates the same pressure noted earlier in this section slowly open system valve D 4 9 3 7 Returning to Atmosphere Carefully rotate the hand pump spindle counter clockwise until the piston is at the lower travel limit and the pressure monitor indicates between zero and 500 psi 35 bar Slowly open reservoir valve A Continue to rotate the hand pump spindle counter clockwise until the pump position indicator app
31. 5 950 WITHOUT COVER TECHNICAL DESCRIPTION 3 14 H 7 u 7 W FIGURE 3 6 TOP VIEW 2485 950 WITHOUT COVER TECHNICAL DESCRIPTION 3 15 PISTON CYLINDER ASSY HANGER M SEQUENCE PISTON CYLINDER ASSY noo A O N BOX 2 BOX 3 n 2 1 LN HET uA OD n FIGURE 3 7 MASS SET IN BOXES TECHNICAL DESCRIPTION 3 16 FIGURE 3 8 INSTRUMENT PLATFORM WITH PARTIAL MASS SET LOADED MODEL 2485 930 AND 2485 935 TECHNICAL DESCRIPTION Z PUMP SUCTION FIGURE 3 9
32. 80665 m s not used for 5 1 units 5 The density of a fluid increases as a function of pressure The increased density results in a greater head pressure for a given column height With most hydraulic systems the change in fluid density is so small relative tot he magnitude of the system pressure required to change the fluid density that hydraulic head corrections are usually not adjusted for different system pressures and the density of the fluid is usually treated as a constant Further because head corrections are typically relatively small temperature and gravity adjustments to fluid head corrections are typically ignored However it is recommended that the influences are calculated thereby allowing the user to determine if they are to be ignored or included in the total system error budget The datum for pressure head corrections when using a hydraulic deadweight gage is generally located at a position near the bottom of the piston cylinder assembly This vertical position is often referred to as the horizontal plane of reference as all positions within the system in the same horizontal plane will have the same pressure This position is usually selected for convenience so that the effects of fluid buoyancy on the 2 7 PISTON PRESSURE GAGE submerged portion of the piston and the pressure head correction for that position cancel and can be ignored This position is located at the physical bottom of a piston of uniform geometry Fo
33. ADAPTERS 4 25 MASS LOADING TABLE INSTALLED 4 26 MASS LOADING TABLE AND 4 26 REMOVING WITH Q C HOLDER MODEL 2485 935 4 27 INSTALLING WITH HOLDER MODEL 2485 935 4 28 SAFETY HEAD AND RUPTURE eoa he tread 5 10 LOW RANGE CYLINDER CLEANING ua a 5 11 MID HIGH RANGE CYLINDER CLEANING 5 11 CHANGING THE COLUMN SEAL sa row 5 12 DISASSEMBLING 40k P C HOLDER 2 uada dn na 5 13 DISASSEMBLING LOW RANGE QC HOLDER 5 14 ASSEMBLING P C NOLDER 52446 ee 5 15 TEMPERATURE CORRECTION SI UNITS TO 100 MPa 10 TEMPERATURE CORRECTION ENGLISH UNITS 1 000 PSI 11 TEMPERATURE CORRECTION ENGLISH UNITS 16 000 PSI 12 Xi TABLE 1 1 TABLE 1 2 TABLE 2 1 TABLE 3 1 TABLE A 1 LIST OF TABLES PISTON CYLINDER SELECTION ua ana 1 2 TOTAL UNCERTAINTY IN PRESSURE t een 1 4 TYPICAL THERMAL COEFFICIENTS aaa arena 2 4 INSTRUMENT PLATFORM FEATURES eu 3 9 CONVERSION FACTORS L a nennen Xli SECTION 1 0 SPECIFICATIONS 1 1 GENERAL SPECIFICATIONS Instrument Pressure Range Safety Test Pressure Pressure Media Accuracy Class Instrument Pla
34. EM OPERATION When using the model 2485 deadweight gage to calibrate a transducer Bourdon tube gage zero pressure is often required for the initial and final observations With the appropriate valves open to the reservoir refer to Sections 4 8 and 4 9 atmospheric pressure is allowed to act on the sensing element through the reservoir which acts as a monometer If the reference plane of the instrument under evaluation is not at the same height as the fluid in the reservoir there is a small pressure exerted on the instrument under evaluation The magnitude of this pressure is equal to the difference in height between the reservoir level and the reference plane of the instrument under evaluation multiplied by the density of the fluid approximately 0 03 psi per inch or 0 08 bar per meter For many high resolution and low pressure instruments a manometer may be necessary to establish a precise zero for the instrument under evaluation 4 7 2 LEVEL THE INSTRUMENT PLATFORM Adjust the level of the instrument as necessary each time the instrument is repositioned and each time a significant mass load change has been made Rotate the adjustable support legs until the level vial indicates a level condition Refer to Figures 3 1 through 3 4 to locate the adjustable support legs and the level vial 4 7 3 RECHARGE THE HAND PUMP Precision pressure measurements rely on the thermal stability of the pressure system The action of changing pressure in
35. ER CLEANING METHOD 5 5 5 24 MASS GET CLEANING 52 ase toda cud 5 5 5 2 5 DISASSEMBLY OF THE QCPC HOLDER 5 5 5 2 6 ASSEMBLY OF THE QCPC HOLDER 5 6 5 3 TROUBLESHOOTING COMMON PROBLEMS 5 6 5 3 1 AIR TRAPPED IN THE SYSTEM u el aa 5 6 9 9 2 PRESSURE LEAK Sint rae S ena 5 7 93 9392 DRIVE MOTOR sn ea toram mie 5 8 5 3 4 TROUBLESHOOTING amp CHANGES IN OPERATING 5 9 3 4 OPTIONS Sa u atas capa gp oed OE BGA 5 9 5 4 1 ELECTRONIC FLOAT POSITION aa 22 22 5 9 5 4 2 ELECTRONIC TEMPERATURE SENSOR 5 9 APPENDIX CALCULATIONS EXPLANATION OF PRESSURE CALCULATION WORKSHEET APPENDIX B SETUP KIT BILLS OF MATERIAL B 1 FIGURE 2 1 FIGURE 2 2 FIGURE 2 3 FIGURE 3 1 FIGURE 3 2 FIGURE 3 3 FIGURE 3 4 FIGURE 3 5 FIGURE 3 6 FIGURE 3 7 FIGURE 3 8 FIGURE 3 9 FIGURE 3 10 FIGURE 3 11 FIGURE 3 12 FIGURE 3 13 FIGURE 3 14 FIGURE 3 15 FIGURE 4 1 FIGURE 4 2 FIGURE 4 3 FIGURE 4 4 FIGURE 4 5 FIGURE 4 6 FIGURE 4 7A FIGURE 4 7B FIGURE 5 1 FIGURE 5 2 FIGURE 5 3 FIGURE 5 4 FIGURE 5 5 FIGURE 5 6 FIGURE 5 7 FIGU
36. F CYLINDFR RE ENTRANT CYLINDER CONTROLLED CLEARANCE CYLINDER Figures 2 1 2 2 and 2 3 illustrate the three most common types of cylinder arrangements When the simple cylinder of Figure 2 1 is subjected to an increase in pressure the fluid exerting a relatively large total force normal to the surface of confinement expands the cylinder wall near Point A and results in an elastic dilation of the cylinder bore As the pressure is increased the cylinder expands and the effective area increases The change in effective area is usually a linear function of the applied pressure The piston also suffers distortion from the pressure of the operating fluid but to a much lesser extent than the cylinder It is evident the that the simple cylinder of Figure 2 1 would be inadequate for a primary piston pressure gage unless some reliable means of predicting the change in area were available The increase in the effective area of the simple cylinder is also accompanied by an increase in the leakage of the fluid past the piston Indeed the leakage becomes so great that at some pressure the floating time will not be sufficient for an accurate pressure measurement In Figure 2 2 the pressure fluid is allowed to surround the body of the cylinder The pressure drop occurs across the cylinder wall near the top of the cylinder at B but in the opposite direction to that of the simple cylinder in Figure 2 1 In consequence the elastic distortion is directed tow
37. IGHT NOTICE Copyright 1993 by Ruska Instrument Corporation All rights reserved This document may not be reproduced in part or in whole without the express written consent of Ruska Instrument Corporation DISCLAIMER No representations or warranties are made with respect to the contents of this user s manual Further Ruska Instrument Corporation reserves the right to revise this manual and to make changes from time to time in the content hereof without obligation to notify any person of such revision TRADEMARK NOTICE RUSKA Trademarks or tradenames are subject to state and federal laws concerning their unauthorized use or other infringements The fact that the product marks or names in this manual do not bear a trademark symbol DOES NOT mean that the product name or mark is not registered as a trademark or tradename Any queries concerning the ownership or existence of any trademarks or tradenames mentioned in this manual should be independently confirmed with the manufacturer or distributor of the product is a trademark of Ruska Instrument Corporation iii REVISION NOTICE DESCRIPTION 2485 1D02 A 04 10 91 Original release 2485 1D02 B 07 12 91 Minor text changes 2485 1D02 C 09 30 93 Added 5000 bar information ECO 18273 2485 1D02 D 03 06 02 Corrected Figure 4 2 DC RO 23269 2485 1D02 E 06 28 02 Included Addendum 2485 New Features to manual DC RO 23418 2485 1002 11 15
38. IONAL DESCRIPTION 3 1 3 2 2 MASS LOADING TABLE ASSEMBLY a sa a ea 3 7 3 2 9 INSTALLATION 41 tradet agen ONA RO 3 7 3 2 4 MODEL 2485 PISTON CYLINDER ASSEMBLIES 3 8 3 2 5 HIGH PRESSURE PISTON CYLINDER ASSEMBLIES 3 8 SECTION 4 0 MODEL 2485 SYSTEM OPERATION INTRODUCTION a Ce ts elk GRA 4 1 PREGAUTIONSSE BES eC 4 1 INSTALLATION AND PREPARATION FOR USE 4 2 4 3 T SELECTING ALLOCATION ea a cee et R 4 2 4 3 2 SETTING UP THE INSTRUMENT 4 2 4 3 3 PREPARATION FOR USE ae ec ES a 4 3 MASS ET rH RE DS OA Ev 4 5 TEST PORT MANIFOLD CONNECTIONS 4 5 MASS LOADING TABLE REMOVAL AND INSTALLATION 4 6 PISTON CYLINDER ASSEMBLIES ss ss 4 7 4 6 1 PISTON CYLINDER ASSEMBLIES 4 7 4 6 Aes 4 7 4 6 3 SELECTING A RANGE una ted iets dest rete ln 4 7 4 6 4 PISTON CYLINDER IDENTIFICATION 4 8 4 6 5 PISTON CYLINDER INSTALLATION AND 4 8 4 6 5 1 Removing the Mass Loading Table Assembly 4 8 4 6 5 2 Removing a Piston Cylinder Assembly or Shipping Plug 4 8 4565529724
39. LE COVER The pump spindle cover prevents contact with the spindle lubrication TECHNICAL DESCRIPTION 3 2 SEQUENCE FUNCTIONAL NUMBER 010 011 012 013 014 015 016 DESCRIPTION PUMP LUBRICATION PORT COVER The pump lubrication port cover prevents contamination from entering the pump lubrication port AIR BLEED SCREW COVER 2485 930 amp 2485 950 The air bleed screw cover prevents contamination from entering the instrument through the air bleed screw access port in the top of the instrument cover SAFETY HEAD AND RUPTURE DISK ASSEMBLY To prevent over pressure of the hand pump assembly a safety head and rupture disk assembly is installed into a special port in the side of the pump housing Should the pump pressure exceed the rupture disk rating the pressure will be vented to the internal reservoir thereby preventing damage to the instrument or the operator A replacement rupture disk must be installed prior to further operation Refer to Section 5 0 for specific instruments on replacing the rupture disk PRESSURE MONITOR Dial Gage The pressure monitor provides a direct reading of the pressure applied to the hand pump In the high pressure version model 2485 950 when the integral intensifier is activated the pressure monitor also indicates approximately 1 5th of the system pressure INTERNAL RESERVOIR COVER The instrument is provided with a 250cc capacity internal reservoir The internal reservoir cove
40. PANNER TOOL STRAIGHT PIN S DIAMETER 1 4 2 SPANNER TOOL SECTION 5 0 MAINTENANCE AND TROUBLESHOOTING 5 1 INTRODUCTION When operated according to the recommended procedures the model 2485 deadweight gage requires only minimal maintenance to sustain operation for extended periods The most important factor in the operation of the instrument is diligent and methodical handling of the piston cylinder assemblies and the mass set Improper use will lead not only to unexpected maintenance and repair but can also increase the risk of injury to the operator Following the guidelines in this section will minimize the risk of damage to the instrument and injury to the operator and will prolong the life of the instrument There are several deadweight gage performance characteristics described in the following sections that should be expected during normal operation These include pressurization rates sink rates and others If the instrument fails to provide such feedback to the operator the condition should be investigated prior to continued operation of the instrument Refer to Section 5 3 for troubleshooting common problems 5 2 MAINTENANCE This section describes the maintenance steps required to preserve the performance of the deadweight gage system including the instrument platform the mass set and the piston cylinder assemblies Although the maintenance requirements for this system are minimal those that relate to the routin
41. RATING PRESSURE vi TABLE OF CONTENTS WARRANTPYS Sis asa muu O ROA A RR OR ON ak ii COPYRIGHT NOTICES S Snout tn eate uk a aia gS sa iii REVISION NOTICE uuu nay z WAR GA bot iv REVI SIOING FAIS HOR bete ne dua detinet ca nate malade be des V WARNING E NOT aD gu R POD RA vi TABLE u RE ak CAPE vii u say na basta a ct BIRSA si queen duet bota ad On a dal dodi a NR LUNES SECTION 1 0 SPECIFICATIONS L G ENERALSPECIFIGATIONS iei Rie Erb 1 1 12 PISTON CYLINDER SPECIFICATIONS 1 1 1 3 MASS SET SPECIFICATION S RE 1 3 l4 ACCURACY SPECIFICATIONS oo RII E DER ERRARE Cede 1 4 SECTION 2 0 PISTON PRESSURE GAGE 2 1 MEASUREMENT CONSIDERATIONS 2 1 2 1 1 EFFECTIVE AREA OF THE PISTON CYLINDER ASSEMBLY 2 2 2 1 1 1 Types of Piston Pressure Goges 2 2 2 1 1 2 Elastic Distortion of the Piston Cylinder Assembly 2 3 21 12 Tepef tUe dite ad catches 2 3 2 172 C91 9l REL NCC TE Waal RE TN 2 4 2 1 2 1 Gravitational Acceleration 2
42. RE A 1 FIGURE A 2 FIGURE A 3 LIST OF FIGURES SIMPLE CYLINDER aet absente add aaa 2 2 REEENTRANF CYLINDER seneo n OG ed dodo Qan a SNE ES 2 2 CONTROLLED CLEARANCE CYLINDER 2 2 FRONT VIEWS Sas a E Kali dal Re 3 10 REAR VIEWS aa een 3 11 RIGHT SIDE VIEW ene end Fak E des AA 3 12 TOP da pe EC 3 13 RIGHT SIDE VIEW 2485 950 WITHOUT 3 14 TOP VIEW 2485 950 WITHOUT COVER 3 15 MASS SET IN BOXES 3 16 INSTRUMENT PLATFORM WITH PARTIAL MASS SET LOADED 3 17 REAR ina Cd HR ed 3 18 SECTION VIEW OF PRESSURE 3 19 SECTION VIEW OF COLUMN ASSEMBLY 3 20 SECTION VIEW OF COLUMN ASSEMBLY 3 21 SECTION VIEW OF COLUMN ASSEMBLY 3 22 QUICK CHANGE P C HOLDER WITH SHIPPING CAPS INSTALLED 3 23 STORAGE OF SHIPPING CAPS AND SHIPPING 3 23 LO amp MID PRESSURE PLUMBING SCHEMATIC 4 15 HI PRESSURE PLUMBING SCHEMATIC 4 19 VOLTAGE SELECTOR SWITCH oi 4 25 TEST PORT MANIFOLD AND
43. REAR VIEW MODEL 2485 903 AND 2485 935 TECHNICAL DESCRIPTION 3 18 1 Z S 7 NY Z Z WS AR N x DKK FIGURE 3 10 SECTION VIEW OF PRESSURE COLUMN EXTENDED RANGE COLUMN AND EXTENDED RANGE P C MODEL 2485 950 3 19 TECHNICAL DESCRIPTION ese ZD RBA e a AN Bp 2 SS SQN N A 2485 940 002 gt SASS 2 Z Z 2 Z Z Z Z HAHA N ai x N NN u X FIGURE 3 11 SECTION VIEW OF COLUMN ASSEMBLY MODEL 2485 930 OR 2485 950 WITH LOW RANGE P C TECHNICAL DESCRIPTION 3 20 BEARING amp WAS 2 92450 9 2 o0 FIGURE 3 12 SECTION VIEW OF COLUMN ASSEMBLY MODEL 2485 935 3 21 TECHNICAL DESCRIPTION BARS SUN m a ue a NE FIGURE 3 13 SECTION VIEW OF COLUMN ASSEMBLY WITH SHIPPING PLUG INSTALLED MODEL 2485 935 TECHNICAL DESCRIPTION 3 22 FIGURE 3 14 QUICK CHANGE P C HOLDER WITH SHIPPING CAPS INSTALLED MODEL 2485 935 FIGURE 3 15 STORAGE OF SHIPPING CAPS AND SHIPPING PLUG MODEL 2485 935 3 23 TECHNICAL DESCRIPTION THIS PAGE INTENTIONALLY LEFT BLANK TECHNICAL DESCRIPTION 3 24 SECTION 4 0 MODEL 2485 SYSTEM OPERATION 4 1 INTRODUCTION The model 2485
44. S 81 3 N M If a torque wrench is not available tighten the packing gland approximately 1 16 turn pr M fucum Pressurize the system and check for leaks 7 If the packing still leaks relieve all pressure from the system and repeat steps 2 thru 5 If packing does not seal after several attempts it needs to be replaced Contact Ruska for parts and procedures 8 Reinstall the packing gland locking device 9 Reinstall the instrument covers 5 2 1 6 Rupture Disk Replacement If the pressure in the hand pump exceeds the rating of the rupture disk in the safety head the rupture disk will burst and must be replaced with one of the same rating before the instrument can safely be returned to service Refer to Appendix B for the part number MAINTENANCE amp TROUBLESHOOTING 5 2 and rating of the rupture disk Replace the rupture disk according to the following instructions CAUTION Do not attempt to recharge the hand pump until the rupture disk has been replaced as air will be pulled into the hydraulic system Remove the instrument cover according to Section 5 2 1 7 Close reservoir valve A and pressure valve B and if applicable model 2485 950 intensifier valve Remove the tubing from the reservoir end of the safety head Figure 5 1 Remove the safety head from the hand pump housing Remove the torque nut from the main body and extract the spent rupture disk Insert the new rupture disk into the body replace the hol
45. TON CYLINDER SELECTION TABLE 1 1 Nominal eom amp Minimum R 9661 Unit Pressure Range Medium Number of Measure P10 10 psi Kg 10 60 to 1000 psi DOS 2485 981 P100 100 psi Kg 100 600 10000 psi DOS 2485 982 P200 200 psi Kg 200 1200 20000 psi DOS 2485 983 P400 400 psi Kg 400 2400 40000 psi DOS 2485 987 P600 600 psi Kg 900 3900 60000 psi DOS 2485 997 0 5 0 5 0 5 3 50 005 2485 984 B5 5 bar Kg 5 30 500 bar DOS 2485 985 10 10 bar Kg 10 60 1000 bar 005 2485 986 B50 50 bar Kg 75 325 5000 bar DOS 2485 989 P10 10 psi Kg 10 60 to 1 000 psi 22 2485 991 P100 100 psi Kg 100 600 10000 psi 22 2485 992 P200 200 psi Kg 200 1200 20000 psi 522 2485 993 P600 600 psi Kg 900 3900 to 40000 psi S22 2485 999 0 5 0 5 0 5 3 50 522 2485 994 5 5 5 30 500 522 2485 995 10 10 bar Kg 10 60 1000 522 2485 996 B50 50 bar Kg 75 325 2750 bar 22 2485 998 SPECIFICATIONS 1 2 1 3 MASS SET SPECIFICATIONS Mass Material Storage case Dimensions Masses Included Mass Denominations Adjustment Tolerance Mass Identification Calibration Tolerance Nonmagnetic austenitic 300 series stainless steel First Case Height 33 7 cm 13 2 in Width 33 0 cm 13 in Depth 25 4 cm 10 in Weight 16 kg 35 Ib Other Cases Height 31 8 cm 12 5 in Width 33 0 cm 13 in De
46. a onto which it is applied P F A where P pressure force and A cross sectional area Some of the influences stated above have a direct effect on the area of the piston cylinder assembly while other factors affect the force or the pressure Corrections based on these influences are described accordingly in the following sections Two final equations combining all the corrections are described at the end of the section one equation for computing the mass required to generate a desired pressure and a second for computing the pressure generated for a given load As there are many engineering units established for pressure measurements it is important to ensure that the units affixed to each parameter used in the computations are matched to the engineering pressure unit desired Further explanation and worksheets are included in Appendix A 2 1 PISTON PRESSURE GAGE 2 1 1 EFFECTIVE AREA OF THE PISTON CYLINDER ASSEMBLY 2 1 1 1 Types of Piston Pressure Gages The piston pressure gage is sometimes regarded as an absolute instrument because of the principle by which it measures pressure An absolute instrument is defined here as one capable of measuring a quantity in the fundamental units of mass length time etc It may be suggested that only certain types of piston pressure gages qualify in this category Secondary Pressure LZ p ress DL In FIGURE 2 1 FIGURE 2 2 FIGURE 2 3 SIMPI
47. ability of the pressure system and allow adequate time for the thermal effects of pressurization to diminish For high precision pressure measurements the stabilization period may be in excess of 20 minutes One indication of the relative stability of the system is the rate at which the piston descends into the cylinder In a system that has just been pressurized the rate of piston descent or sink rate will be relatively rapid and may be excessive This is the same indication as when the pressure system is leaking except that with time a leak free system will attain equilibrium and the sink rate will return to normal A rapid decrease in pressure will result in an abnormally slow sink rate This thermal effect can be so great that the piston will actually rise in the cylinder until the system approaches equilibrium Any abnormal sink rate is an indication of instability in the pressure or leaks in the system During the thermal stabilization period adjust the hand pump as necessary to maintain the float position of the piston In addition the temperature of the piston may change slightly during the stabilization period and any fine load adjustment applied in Section 4 7 4 4 to correct for thermal effects should be re evaluated just prior to the final pressure measurement 4 7 5 EXECUTE PRESSURE MEASUREMENT Once the appropriate load is applied the thermal effects have adequately diminished and the piston is rotating at the mid float positio
48. actors such as volume rte of pressurization internal surface area of the system and fluid characteristics the time required for equilibration may exceed 30 minutes Typically however only 5 to 10 minutes are required for adequate operation of the deadweight gage Other factors also induce temporary effects on the pressure and sink rate A pocket of gas trapped in a hydraulic system will tend to dissolve into the oil upon pressurization This action may not be instantaneous and as the gas pocket dissolves the pressure will tend to decrease Occasionally the seals and packing in valves may yield under the stress of pressurization This deflection also may not be instantaneous and can result in an abnormal sink rate Only after the effects of these influences have subsided and provided that no significant leaks are present in the system as would be indicated by an abnormally high sink rate at the end of the thermal stabilization period can reliable pressure measurements be made PISTON PRESSURE GAGE 2 10 2 5 ACCURACY AND TRACEABILITY The validity of a measurement made using a deadweight gage or any other device is influenced by numerous factors other than basic performance parameters such as linearity repeatability and hysteresis to list a few Typically the largest contribution to ihe estimate of total uncertainty the bounds within which the true value lies often referred to as accuracy is the uncertainty assigned to the standard
49. ains in the clockwise direction Close reservoir valve A and carefully rotate the hand pump spindle clockwise to generate pressure Once the pressure monitor indicates the same pressure noted earlier slowly open pressure valve B 4 8 6 RETURNING TO ATMOSPHERE Verify that pressure valve B is open rotate the hand pump spindle counter clockwise until the piston is at the lower travel limit and the pressure monitor indicates between zero and 500 psi 35 bar Slowly open reservoir valve A 4 9 VALVE OPERATING PROCEDURE FOR MODEL 2485 950 See Plumbing Schematic Figure 4 2 This section describes the proper valve operating procedures for the various functions of the model 2485 950 deadweight gage instrument platform CAUTION The operator of any pressurized equipment must always be aware of the condition and status of the equipment to avoid the risk of damage and personal injury CAUTION Reservoir valve A and pressure valve B perform different functions in the 2485 930 and 2485 950 instrument platforms The valve operating procedures for the 2485 930 should not be used when operating the 2485 950 The following procedures reference the valve positions open and closed The operator must manipulate the valves in such a way that their status can easily be determined When the procedure refers to opening a multi turn valve the valve should not be allowed to remain in the full open state rather if it has been fully opened it should then b
50. ard the piston tending to decease the effective area of the assembly Again the change in the area with pressure places a limit on the usefulness of the re entrant cylinder as a primary instrument Some benefit does result however from the use of the re entrant cylinder because higher pressures may be attained without a loss in float PISTON PRESSURE GAGE 2 2 time small sacrifice is made in the float time at lower pressures because the total clearance between piston and cylinder is generally greater with a simple cylinder design In the controlled clearance design of Figure 2 3 the cylinder is surrounded by a chamber to which a secondary pressure system is connected Adjustment of the secondary or chamber pressure permits the operator to change the clearance between the cylinder and piston at will A series of observations involving piston sink rates at various jacket pressures leads to the empirical determination of the effective area of the assembly High performance piston pressure gages may be constructed using simple or re entrant cylinders Determination of the distortion coefficients and effective area of such gages may be made by direct comparison with a controlled clearance gage Although elastic distortion affects all types of piston pressure gages the magnitude may be small enough that it can be ignored 2 1 1 2 Elastic Distortion of the Piston Cylinder Assembly As the pressure is increased within a piston pressure gage th
51. ation NOTE Pressurization of the instrument to more than about 500 psi 35 bar is unnecessary at this point If more than one quarter turn is required to obtain a pressure reading some amount of air is likely trapped in the hydraulic system and should be removed prior to continuing Instructions for removal of air from the system are included in Section 5 0 Maintenance and Troubleshooting If a pressure change is noted within about one half rotation of the hand pump spindle the time required to remove this air may be a greater inconvenience than SYSTEM OPERATION 4 4 operating the system in such a condition A small amount of air trapped in the system will gradually dissipate and work its way out of the system during normal operation 11 Repeat steps 4 and 5 12 Verify that the hydraulic pressure has been removed from the system When making connections to the pressure ports or test port manifold or when installing a piston cylinder assembly Reservoir Valve A or Pressure Valve B depending on the model version low pressure model 2485 930 or high pressure model 2485 950 must be closed Instructions for each of these operations and for general pressure generation for each version of the 2485 are described in the following sections 13 Install the mirror block assembly part number 2485 920 on the front left corner of the instrument platform as shown in Figures 3 1 and 3 4 4 3 4 MASS SET Although not essential it
52. ations are included in Section 5 0 Maintenance and Troubleshooting 4 6 3 SELECTING A RANGE There are several factors to consider in the selection of the appropriate denomination piston cylinder assembly for a particular application In the order of general significance they are pressure range nominal and minimum pressure increment pressure resolution using a trim mass set load resolution accuracy at minimum pressure and overall performance characteristics such as free rotation time and float time or sink rate Most deadweight gages experience a loss in performance at the extreme low end of the pressure range This is usually apparent in the reduced amount of time that the load will remain spinning This loss in performance is typically accounted for through a nominal increase as a percentage of reading in the uncertainty assigned to pressures generated below about 5 or 10 percent of the maximum pressure range depending on the quality of the deadweight gage Typically the smaller the load on the piston the shorter the rotation time and the more precise any trim adjustment must be An example of this load resolution factor follows The pressure generated by a piston operating at the full load of 100 kilograms would changes one part per million ppm for a change in the load of 100 milligrams mg The change in the pressure generated by a higher range piston with a total load of only 5 kilograms however would change 20 ppm for the same 10
53. below If the system response is now normal reservoir vale A leaks and must repaired Otherwise remove the pressure and rotate the reservoir source valve to the appropriate position NOTE The reservoir supply plumbing incorporates a relief valve to prevent accidental over pressurization of the supply plumbing The relief vale is set at the factory to 150 psi 10 bar For model 2485 950 repeat the above test for pressure valve B To test pressure vale B for model 2485 930 close reservoir valve A and pressurize the system to 100 psi Close pressure valve and open reservoir valve A If the pressure monitor attached to the test port manifold indicates leakage through pressure valve B it must be repaired 5 3 3 DRIVE MOTOR If the mass stack does not rotate when power is applied to the drive motor use the following procedure to diagnose the failure If the motor does not rotate when the proper power is applied disconnect the power check the power setting and if necessary replace the fuse refer to Section 4 3 2 If this fails the motor may be damaged If the drive motor operates properly but the drive sleeve does not rotate verify that the drive belt is clean not damaged and is properly adjusted Verify that the drive sleeve bushings are not damaged and are properly lubricated If the drive motor operates properly and the drive sleeve rotates but the mass loading table does not verify that the roller pin is properly in
54. ckwise approximately one quarter turn to remove the spindle nut backlash 4 8 2 PRESSURIZING THE SYSTEM Close reservoir valve and rotate the hand pump spindle clockwise If the pressure system is sealed and no air is trapped in the hydraulic system the pressure should begin to increase within one quarter turn of the hand pump spindle Refer to Section 5 3 for troubleshooting 4 8 3 ADJUSTING FLOAT POSITION As the pressure approaches that required to float the piston reduce the rate of hand pump spindle rotation and slowly approach the proper float position If the float position or system pressure is too high rotate the hand pump spindle counter clockwise until the proper pressure or float position is obtained Rotate the hand pump spindle an additional one quarter turn counter clockwise and then carefully clockwise to restore the pressure or float position and to remove any spindle nut backlash This will prevent the pump plunger from creeping out of the pump housing which could result in erroneous pressure readings 4 8 4 RECHARGING THE HAND PUMP WHILE AT PRESSURE On occasion the hand pump will reach the full clockwise travel limit preventing further pressurization The hand pump may be recharged while the system remains at pressure To recharge the hand pump while the system is at pressure verify that pressure valve B is open and note the system pressure indicated on the pressure monitor Close pressure valve B and carefully rota
55. d down ring and torque nut and torque to between 100 and 110 foot pounds Fill the end of the safety head assembly opposite the reservoir plumbing with clean deadweight gage oil and install the safety head assembly into the hand pump housing but do not tighten Slowly rotate the hand pump spindle clockwise until oil seeps from the safety head mounting port see note below Carefully tighten the safety head assembly to the hand pump housing and replace the reservoir tubing on the opposite end of the safety head assembly Refer to Section 5 3 for troubleshooting leaks and air trapped in the system NOTE If the hand pump does not have enough travel to force oil through the safety head port temporarily tighten the safety head assembly and recharge the hand pump per Section 4 8 or 4 9 Loosen the safety from the hand pump housing and rotate the hand spindle to force oil through the safety head 5 2 1 7 Instrument Cover Removal and Replacement Several aspects of the instrument platform maintenance require removal of the instrument cover This section describes the steps necessary to remove and reinstall the instrument cover Remove the test port manifold and nut per Section 4 4 Close the appropriate valve to isolate the reservoir from the system Remove the handles from valves A and B the reservoir source valve and if applicable model 2485 950 valves C and D Remove the screws securing the instrument covers and carefully lift the cover sectio
56. d from M FK where M apparent mass record in Column 9 F force required on piston as found in Column 8 multiplier which was determined by previous equation FOR SI UNITS K 1 p p where g acceleration due to local gravity in m sec Par density of air in g cm see Equation 4 Pan density of apparent mass CALCULATIONS A 2 for Apparent Mass versus Brass 8 4 g cm for Apparent Mass versus Stainless Steel 8 0 g cm When selecting masses from the calibration report assure that the values selected are in the same Apparent Mass unit of measure that was used to calculate the K or K values The apparent mass Column 9 is obtained from M FK where M apparent mass versus brass record in Column 9 F force required on piston as found in Column 8 K multiplier which was obtained by previous equation When the masses are applied to the piston in an evacuated bell jar the above equations for K and K can still be used In this situation the density of air will be zero which will cause the buoyancy portion of the equation to become 1 Also the results will indicate the quantity of true mass not apparent mass thot must be applied to the piston E Column 1 P is the desired pressure at the reference plane of the device being calibrated F Column 2 is the mass density of the pressure medium being used in the piston pressure gauge system For hydraulic piston pressure gauges th
57. e closed approximately one half turn If a valve is positioned at any place between nearly full open and approximately one half turn open the operator can assess the open status of the valve by simply rotating the handle in either direction If the valve has been left in the full open position it will be difficult to determine whether the valve is open or closed If the valve is closed and the operator believes it to be open permanent damage to the valve seat can occur if the stem is over torqued SYSTEM OPERATION 4 18 22772 L Z FIGURE 4 2 HI PRESSURE PLUMBING SCHEMATIC NOTE Whenever operating the valves use only the minimum torque required to close the valve and open the valve very slowly when there is a differential pressure across the valve 4 9 1 RECHARGING THE HAND PUMP WHILE AT ATMOSPHERE With reservoir valve A and pressure valve B open rotate the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise approximately one quarter turn to remove any spindle nut backlash 4 19 SYSTEM OPERATION 4 9 2 GENERATING PRESSURES TO 20 000 PSI 1400 BAR 4 9 2 1 Pressurizing the System Open valve A C and D Close pressure valve B and rotate the hand pump spindle clockwise If the pressure system is sealed no air is trapped in the hydraulic system the pressure should begin to increase within one qua
58. e resulting in the abnormal sink rate This adiabatic effect must be allowed to dissipate before troubleshooting all but the largest of leaks Figures 4 1 and 4 2 are plumbing schematics that can be used to identify the appropriate valves to isolate segments the system Most leaks in fittings will result in 5 7 MAINTENANCE amp TROUBLESHOOTING droplets of oil forming at the fitting tubing or bleed port for the connection Leaks in valves and seals may be more difficult to isolate Leaks in core packing of reservoir vale and pressure valve B are usually more apparent at pressures below 500 psi 35 bar To test these valves install a shipping plug in the main pressure housing according to Section 4 6 4 and connect a pressure monitor with 50 psi 5 bar or better resolution to the test port manifold Recharge the hand pump according to Section 4 8 or 4 9 as applicable Verify that pressure valve B is open and if applicable model 2485 950 valves C and D are open Close reservoir valve A and slowly rotate the hand pump clockwise to generate approximately 100 psi If the pressure can not be generated there may be a air trapped in the system or there may be a leak If reservoir valve A appears to be leaking open reservoir vale A and recharge the hand pump Verify that valve A is open and rotate the reservoir source valve ONE QUARTER turn to position half way between internal and external Carefully pressurize to 100 psi see note
59. e handling are critical to the longevity and reliability of the instrument 5 2 1 INSTRUMENT PLATFORM MAINTENANCE The instrument platform requires little maintenance Functional integrity and esthetic preservation are primarily the result of careful manipulation of the instrument Several components however may require occasional verification adjustment or repair 5 2 1 1 Oil Drain Hose Route oil drain hose to appropriate container 5 2 1 2 Instrument Platform Cleaning Occasionally oil or other contamination will accumulate in various locations on the instrument platform Wipe any contamination and accumulated oil from the top and bottom surfaces of the instrument platform The instrument cover may require removal to adequately clean the instrument platform Refer to Section 5 2 1 7 for instructions on removing the instrument cover 5 2 1 3 Level Vial Adjustment Optimum performance and reliability of the pressure measurements made using a deadweight gage rely on the piston axis being vertical When properly adjusted the level mounted to the instrument platform is a simple and reliable reference Proper adjustment of the level vial should be verified periodically 5 1 MAINTENANCE amp TROUBLESHOOTING If the main pressure housing or level vial has been removed or damaged readjustment of the level vial may be necessary The level vial should be adjusted such that when the bubble in the level vial is centered the top surface of
60. e more typical indication is that when the intensifier plunger reaches the full stroke limit while pressurizing the test port the pressure monitor will indicate a sudden increase in the rate of pressurization The pressure at which this occurs is important to the following procedure To recharge the intensifier while the system is at pressure note the pump pressure as described above and close system valve D Carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar Open reservoir valve A and continue rotating the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise one quarter turn VERY SLOWLY open intensifier valve C Close pressure valve B and rotate the hand pump spindle clockwise As the pump begins to develop pressure the intensifier plunger will move towards the low pressure end of travel Continuing the rotation of the hand pump will force the intensifier plunger to the fully recharged position as indicated by a sudden increase in the pressure indicated on the pressure monitor Carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar and open pressure valve B Continue rotating the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rota
61. e resulting stress produces a temporary and reversible deformation of the piston cylinder components The result is a change in the effective area of the piston cylinder assembly If the change in the area is a linear function of the applied pressure the relationship may be described by the equality A A 1 bp where Effective area at pressure p Effective area of the piston cylinder assembly at zero pressure b Coefficient of elastic distortion the fractional change in area per unit of pressure and p Nominal system pressure acting on the piston cylinder assembly For higher pressure instruments the pressure effect may be non linear and is commonly expressed by the equality A A 1 bp where A Effective area at pressure p Effective area of the piston cylinder assembly at zero pressure b Coefficient of elastic distortion as a function of pressure the fractional change in area per unit of pressure and b Coefficient of elastic distortion as a function of the square of the pressure the fractional change in area per unit of pressure squared Square of nominal system pressure 2 1 1 3 Temperature Piston pressure gages are temperature sensitive and for accurate measurements corrections must be applied for deviations from the reference temperature When the temperature of a piston cylinder assembly is above the reference temperature the 2 3 PISTON PRESSURE GAGE effective ar
62. ea will be larger than at the reference temperature and the pressure for a given load will be less When the temperature of the piston cylinder assembly is below the reference the effective area will be smaller and the pressure for the same load will be greater Depending on the magnitude these thermal changes may have a significant effect on the measurements Corrections for temperature are applied at the time of a measurement using the following relation 4o 1 C t where Effective area corrected to working temperature Ag Effective area at the reference temperature Coefficient of thermal expansion the fractional change in area per unit of temperature t Piston cylinder working temperature and r Piston cylinder reference temperature The thermal coefficient for a piston cylinder assembly is directly dependent on the materials used appropriate value for the coefficient as well as the reference temperature are listed in the calibration report for the piston cylinder assembly Some typical thermal coefficients and materials are shown in the following table refer to the calibration report for actual values TABLE 2 1 TYPICAL THERMAL COEFFICIENTS Piston Cylinder Thermal Coefficient Material Material per degrees Celsius WC WC 9 1 x 10 Steel WC 1 58 10 Steel Steel 2 0x 10 WC Tungsten Carbide 2 1 2 FORCE 2 1 2 1 Gravitational Acceleration Pressure is a function o
63. essure section 2 1 3 1 R Reference pressure absolute mode typically 100 mTorr Effective area corrected to working temperature Section 2 1 1 Mass force conversion factor Section 2 1 2 2 3 MASS TO PRESSURE EQUATION Some measurement condition may require that a load be applied to the deadweight gage to measure an unknown pressure The exact pressure generated for a given load can be computed from the following equation that combines the corrections described in the previous sections Step by step instructions and worksheets are also included Appendix A 0 where Pu 5 Pressure at reference plane of device under test M Total mass loaded on the piston apparent mass for gage mode true mass for absolute mode to generate the pressure includes tare mass and surface tension K Mass force conversion factor 2 9 PISTON PRESSURE GAGE Effective area corrected to working temperature R Reference pressure absolute mode typically 100 mTorr and H Head pressure 2 4 CONDITIONS FAVORABLE FOR A MEASUREMENT Precision pressure measurements using a deadweight gage can only be made when all miscellaneous disturbances such as vibration air drafts and personnel traffic have been minimized or eliminated Further if an operator is inadequately trained in the proper operation of the equipment or whose judgment is impaired by distractions or other influences there is discernible r
64. essure acting on the reference port of the test device will be less than that acting on the standard For normal air density this correction equates to approximately 5 2 x 10 psi per foot 1 18 x 10 KPa per meter The correction is in the opposite direction of the system pressure head correction but is of a constant magnitude and hence will be most significant at the lower calibration pressures The reference pressure head correction can be simplified by assuming nominal equality of the density of the system gas and the reference pressure gas atmosphere Then using a system gas density for a gage pressure taken from a chart for absolute pressures the result will likely be beyond the performance of all but the most sensitive devices 2 1 3 4 Position The optimum operating position of a piston pressure gage is known as mid float This position near mid stroke of the piston is the calibrated position and the position where pressure head corrections will be valid Significant deviations from this position can result in head pressure errors but will likely result in greater errors as a result of slight variations in the taper or other geometric aspect of the piston or cylinder of a given assembly Typically the pressure in a system is adjusted to obtain a float position slightly above mid float and the normal leakage of the pressure medium through the clearance between the piston and cylinder will allow the piston to slowly descend thr
65. etween zero and 500 psi 35 bar Open reservoir valve A then VERY SLOWLY open intensifier valve C Continue rotating the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise one quarter turn and close reservoir valve A Rotate the hand pump spindle clockwise until the intensifier plunger reaches the full stroke limit This may require as much as 26 full rotations of the hand pump spindle The indication that the intensifier plunger has reached the full stroke limit is that the pressure monitor will indicate a rapid increase in pump pressure Carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar Open reservoir valve A and continue rotating the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise one quarter turn and close pressure valve Rotate the hand pump spindle clockwise TWO FULL TURNS open pressure valve B and close reservoir valve A and intensifier valve C Rotate the hand pump spindle clockwise to generate pressure Continue to rotate the hand pump spindle clockwise until the pressure monitor indicates the pressure noted earlier in this section then slowly open system valve D Rotate the hand pump spindle counter clockwise to continue reducing the system pressure
66. f force per unit area Any action that affects the force applied to the piston proportionally affects the pressure generated with the piston Masses applied to a piston are accelerated in a downward direction by the gravitational attraction of the earth thereby exerting a force on the piston Gravitational acceleration varies from location to location thus so do the forces exerted on the piston by a given mass The gravitational acceleration at different locations within the continental United States and the resulting variations in pressure for a piston pressure gage vary by more than 0 17 per cent Corrections for these gravitational variances are performed according to the following equality F M G G PISTON PRESSURE GAGE 2 4 where Downward force M Mass of object Gl Local Gravitational Acceleration in m s and Gs Standard Gravitational Acceleration 9 80665 m s 2 1 2 2 Cosine Error It is important to note that the gravitational effect is in a vertical direction If the axial motion of the piston is not vertical the force acting on the piston and hence the pressure generated is reduced as a function of the cosine of the angular deviation from vertical This situation is often referred to as a cosine error but can be corrected for using the following equation F F 0 where Fa axial force acting on the piston F vertical force and 0 angular deviation of piston axis from vertical An angular displace
67. f some of the adapters they may not be rated to the full pressure of the instrument Refer to Figure 4 2 for appropriate pressure rating of each adapter 019 TEST PORT MANIFOLD RETAINING NUT The test port manifold retaining nut secures the test port manifold to the auxiliary pressure housing to provide a positive seal at full instrument pressure Securing the test port manifold to the auxiliary pressure housing with the retaining nut requires no tools 020 OIL DRAIN LINE During operation of the instrument oil passes between the precision surfaces of the piston and cylinder assembly This oil drains down the main pressure housing and lubricates the drive sleeve bearings As the oil flows out of the drive sleeve it drains through a hole in the instrument base Beneath the base the oil is collected in a clear plastic tube This tube is equipped with a barbed connection An additional length of tubing is found in the setup kit Mate the tubing found in the set up kit with the barbed connection on the oil drain line This will allow the waste hydraulic oil to be piped to an acceptable refuse container Please dispose of the waste oil properly NEVER REUSE waste hydraulic oil 021 FILL PUMP ASSEMBLY 2485 930 amp 2485 935 The fill pump is a motorized pump which facilitates the bleeding of external lines or device under test The pump is powered from the drive motor assembly A power pigtail extends from the bottom of the drive motor housin
68. factured from high grade tungsten carbide The precision surfaces of each piston cylinder assembly are finish lapped and matched to provide optimum performance with minimal leakage over wide pressure range The high level of performance achieved with the 2485 piston cylinder assemblies is such that only three ranges are required to cover the total pressure range of the instrument while maintaining optimum accuracy Various intermediate ranges are available however to suit specific applications The effective area of each piston cylinder assembly is adjusted such that for a given load in kilogram denominations it will generate nominal pressure increments in either English units psi or 5 1 units bar All assemblies are permanently identified with a pressure unit increment designator and a unique serial number for traceability An example of the pressure unit increment designator for one of the English piston cylinder assemblies is P200 The P designates the unit of measure psi and 200 indicates the nominal increment For each kilogram loaded on the piston the nominal pressure increment will be 200 psi For a piston cylinder assembly with a BO 5 pressure unit increment designator 5 1 units each kilogram would generate 0 5 bar A 50 piston cylinder will generate 50 bar per kilogram or 5000 bar 72 500 psi for the full mass load of 100 kilograms The model 2485 cylinders are simple in configuration and there are no mounting flanges
69. g and plugs into a power inlet receptacle on the back side of the pump assembly TECHNICAL DESCRIPTION 3 4 SEQUENCE FUNCTIONAL NUMBER 022 023 024 025 026 027 028 DESCRIPTION FIXED SUPPORT LEG The instrument platform is supported by three legs One of these legs is fixed and is not adjustable This fixed support leg is positioned directly below the main pressure housing to prevent deflection of the instrument base when the load is applied This lack of deflection in the instrument base provides more stable adjustment of the instrument level AUXILIARY SUPPORT LEG Should the operator attempt to move the instrument while a mass load is applied the auxiliary support leg will prevent the instrument from tipping over ADJUSTABLE SUPPORT LEGS The model 2485 incorporates two adjustable support legs positioned at the front and rear of the right side Adjustment of these legs may be required upon installation of the instrument and according to the level vial attached to the instrument base each time a significant change is made to the mass load LEVEL VIAL A sensitive bulls eye level vial is mounted at the front of the instrument platform to provide easy measurement of the level of the instrument When the axis of rotation of the piston cylinder assembly is significantly off of vertical the bubble in the level vial will be conspicuously out of center DRIVE MOTOR ASSEMBLY The principal use of the drive mo
70. hould be free from excessive personnel traffic and air drafts Airborne dust is also undesirable but clean room standards are not required The workbench on which the instrument is to be installed must be sturdy enough to safely support up to 400 pounds 180 Kg without significant deformation Ample working space should be allowed where tools worksheets or other technical data can easily be manipulated If the instrument includes the drive motor option or electronic float position temperature option a suitable power source is required at the installation location The power source must be either 115 VAC or 230 VAC and 50 or 60 Hz and must be rated to at least 15 watts 4 3 2 SETTING UP THE INSTRUMENT PLATFORM Remove the instrument platform from its shipping box and place it on the workbench Make sure that the circular foot plates are located flat against the workbench surface and that no foreign material is trapped between the foot plates and the workbench Remove any packing materials from the instrument platform and main pressure housing and from inside the internal reservoir Inspect the instrument platform for shipping damage Move the instrument platform to the proper position on the workbench keeping in mind that the final position may be influenced by any pressure connecting lines required to accommodate other equipment Level the instrument platform according to the bulls eye level vial by rotating the two adjustable support legs
71. ht gage use plastic or thin rubber gloves or several thicknesses of low lint paper wipers such as Kimberly Clark Type 900 Kimwipes Ruska part number 58 392 to prevent finger oils and salts from contacting the components 4 6 5 1 Removing the Mass Loading Table Assembly Remove all pressure from the system and close the appropriate valve to isolate the reservoir Refer to Sections 4 8 and 4 9 for the specific valve operating sequence Remove the tare compensator disk and mass loading table assembly according to Section 4 5 and place them in an appropriate location 4 6 5 2 Removing a Piston Cylinder Assembly or Shipping Plug 2485 930 amp 2485 950 The procedure for removing a piston cylinder assembly from the main pressure housing includes several critical steps Read the entire procedure carefully before beginning Complete Section 4 6 4 1 before proceeding If a shipping plug is installed rather than a piston cylinder assembly remove it by simply grasping the top edge of the plug and rocking it gently side to side Once the plug is free of the housing place it in the appropriate storage location To remove a piston cylinder assembly from the pressure housing use an appropriate insulation between piston cylinder components and fingers and grasp the top edge of the cylinder with the left hand Place the forefinger of the left hand directly above the piston Slowly rotate the hand pump spindle clockwise until the piston extends approx
72. imately 1 2 inch 1 cm above the cylinder Place the forefinger of the left hand on the top edge of SYSTEM OPERATION 4 8 the piston and apply a slight downward and lateral force to the piston This will prevent the piston from exiting the top of the cylinder while turning the hand pump It will also prevent the piston from exiting the bottom of the cylinder once the assembly is removed from the pressure housing Rotate the hand pump clockwise approximately 3 or 4 turns to free the cylinder from the pressure housing Carefully lift the piston cylinder assembly out of the pressure housing and place it in the appropriate storage container Cover the piston cylinder assembly in the storage container with clean oil and secure the storage container top Wipe any excess oil from the storage container and place it in the appropriate storage location 4 6 5 3 4 6 5 4 Reserved 4 6 5 5 Installing a Piston Cylinder or Shipping Plug 2485 930 amp 2485 950 Before installing a piston cylinder assembly or shipping plug into the pressure housing inspect the o ring cylinder seal If the o ring is worn or leaks when pressurized it should be replaced before continuing Carefully locate the o ring in the appropriate sealing groove Place a clean low lint wiper on the workbench Carefully remove the top of the piston cylinder storage container and set it aside Using the appropriate insulation between piston cylinder components and fingers place the forefi
73. in the system the system may become virtually inoperable The high compressibility of the air prevents significant pressure from building in the system until the air has been adequately compressed This condition may use up a substantial portion of the available hand pump travel system with little or no trapped air however will require only one quarter turn of the hand pump spindle before pressure builds in the system If more than one quarter turn of the hand pump spindle is required to generate pressure in the system it may be contaminated with air There are several other situations besides air being trapped in the system which can also result slow pressurization A large volume connected to the test port manifold will cause the system pressure to build more slowly than with a smaller volume attached More of the hand pump travel or more hand pump strokes may be required to fully pressurize a large volume If an instrument such as the Ruska Model 2413 Differential Pressure Cell which incorporates a diaphragm type sensor that must move to the end of a cavity before pressure builds is attached to the system the response of the hand pump will appear as if air is trapped in the system but is the normal response for the application MAINTENANCE amp TROUBLESHOOTING 5 6 After confirming that air has indeed been trapped in the system the valves can be manipulated to isolate portions of the system to determine where the greatest amo
74. is number can be considered constant for all pressures Ruska Instrument has two types of hydraulic piston fluids available One is a Spinesstic 22 part number 55 500 which has density of 0 031 pounds per cubic inch 858 kilograms per cubic meter The other is a Dioctyl Sebacate DOS part number 55 521 1 which has a density of 0 033 pounds per cubic inch 913 kilograms per cubic meter For gas medium piston gauges the values in Column 2 will be different for different system pressures Equations are provided to calculate the density of air or nitrogen as a function of the system pressure G Column 3 is required to adjust the mass density of the pressure medium for local gravity It is also used to correct the pressure head that exist between the reference ports of the piston gauge and device under test H Column 4 P is the pressure correction that is required if the reference plane of the device being calibrated is not the same plane as the reference plane of the piston pressure gauge The difference between the two planes h is positive if the reference plane of the device being calibrated is higher than the reference plane of the piston pressure gauge l Column 5 is the pressure required at the reference plane of the piston pressure gauge to produce the desired pressure at the reference plane of the device being calibrated When the piston gauge is operating in the absolute mode the Reference pressure Pp is subtracted to obtain
75. is recommended that the masses be loaded and stored in sequence according to the sequence number marked on each piece When placing the masses into the storage boxes fill box 5 first then 4 and 3 Place the highest sequence number 5 kilogram mass at the rear of the box moving toward the front with the lower numbered masses The 3 kilogram mass is stored in the front of the box 5 The 2 kilogram through 0 2 kilogram masses the hanger mass sequence number 01 and the piston cylinder assemblies are stored in box 1 4 4 TEST PORT MANIFOLD CONNECTIONS CAUTION All pressure must be removed from the system prior to disconnecting the test port manifold from the auxiliary pressure housing The test port manifold should be disconnected from the auxiliary pressure housing before attaching a device or instrument to be tested Remove all pressure from the system and close the appropriate valve to isolate the reservoir Refer to sections 4 8 and 4 9 for the specific valve operating sequence Loosen the test port manifold retaining nut until it is free of the threads on the auxiliary pressure housing Turn the hand pump clockwise approximately 3 or 4 turns then carefully lift the test port manifold off of the auxiliary pressure housing Inspect the seal on the lower end of the test port manifold If the seal is excessively worn or leaks when pressurized it should be replaced before continuing To replace the seal carefully rotate and slide the
76. isk of personal injury and damage of delicate instrumentation When operating a precision deadweight piston gage one concern is the amount of time available to make a measurement The major influence on the time available to make a measurement is the amount of time the piston remains in the region near the calibrated mid float position This float time is directly dependent on the sink rate of the piston the rate at which the piston descends into the cylinder displacing the fluid that leaks through the annular clearance provided to lubricate the piston There are several conditions of normal operation of a deadweight gage that temporarily bias the sink rate When a volume of fluid gas or oil is compressed a sudden rise occurs in the temperature of the fluid As this heat dissipates into the surrounding containment the temperature of the fluid is reduced and the pressure decreases accordingly If the containment is a deadweight piston gage the piston will rapidly descend into the cylinder resulting in an unusually high sink rate until such a time as the fluid and containment reach thermal equilibrium This thermal or adiabatic effect is bi directional When the fluid is depressurized it undergoes a sudden decrease in temperature As the fluid absorbs heat from the containment the resulting sink rate will be abnormally low until the system again reaches equilibrium In fact this effect may result in a rise in float position Depending on f
77. kwise until the piston is at the lower travel limit and the pressure monitor indicates between zero and 500 psi 35 bar then slowly open pressure valve B 4 9 3 GENERATING PRESSURES GREATER THAN 20 000 PSI 1400 BAR CAUTION Although not essential it is recommended that the procedure in Section 4 9 3 be followed to generate approximately 20 000 psi 1400 bar to pre charge the intensifier prior to proceeding with the procedure in Section 4 9 4 If the low pressure procedure is not performed first the likelihood of recharging the intensifier while at pressure is much greater 4 9 3 1 Generating Pressure Generate between 18 000 and 20 000 psi 1250 and 1400 bar using the procedure described in Section 4 9 3 Close intensifier valve C and carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar Open pressure valve B and rotate the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise approximately one quarter turn to remove any spindle nut backlash Close reservoir valve A and rotate the hand pump spindle clockwise to generate pressure As pressure develops in the hand pump it will increase rather rapidly until the intensifier plunger begins to move At this point the intensifier will begin to increase the pressure in the test port As the intensifier builds pressure i
78. l acceleration 9 80665 m s 5 2 1 2 5 Surface Tension For many hydraulic deadweight gages the surface tension of the pressure medium acting on the piston exerts a downward force that is significant to some pressure measurements The effects of surface tension are commonly included in the total mass value provided for the tare components but may be applied as a separate correction 2 1 3 PRESSURE CORRECTIONS AND OTHER MISCELLANEOUS FACTORS 2 1 3 1 Hydraulic Fluid Pressure Gradients When gravity acts on a column of fluid such as in a liquid manometer a pressure is generated at the bottom of the column nominally equal to the height of the column multiplied by the density of the fluid The same pressure gradient exists in a hydraulic deadweight gage calibration system For two different positions within the calibration system a difference in pressure exists that is nominally equal to the density of the fluid multiplied by the vertical separation between the two positions The horizontal separation between these positions has no influence on the pressure gradient The correction for the pressure head can be accomplished using the following equation H h D GIG where H Head pressure h Column height positive value if the test device reference plane is higher than the reference plane of the standard D Pressure fluid density Local gravitational acceleration in m s G Standard gravitational acceleration 9
79. mately 2 000 psi 140 bar as per Section 4 8 for model 2485 930 or Section 4 9 for model 2485 950 Then without rotating the hand pump spindle remove the handles from the hand pump This will ensure that no air becomes trapped in the system during shipment or storage WARNING If a liquid in glass thermometer 15 being used remove it from the base and package it separately for shipment or storage 4 15 SYSTEM OPERATION WARNING The maximum pressure rating for the low pressure shipping plug is 20 000 psi 1400 bar Do not exceed this pressure with the low pressure shipping plug installed Rotate the reservoir source valve on the rear of the instrument platform ONE QUARTER TURN Remove the oil from the internal reservoir down to a level flush with the fitting at the bottom of the reservoir Wipe any excess oil from the base plate and pressure housing Remove clean and store the reservoir cover and the oil drain cups Place a clean dry paper wiper in the internal reservoir to prevent contamination of the reservoir Place a small strip of soft open cell foam approximately 1 cm x 1 cm x 10 cm around bottom of the mass loading table assembly between the table top and the retaining nut This will prevent the mass loading table assembly from vibrating during transport 4 7 9 PREPARATION FOR STORAGE SHIPPING MODEL 2485 935 When the model 2485 deadweight gage is not in use the pressure should be removed and the appropriate val
80. ment of 0 25 degrees from vertical results in a reduction in pressure of approximately 10 parts per million Since a significant deviation from vertical may also affect the performance of a deadweight gage it is common to adjust the piston to vertical within a fraction of a degree using a sensitive spirit level typically attached to the instrument base rather than measure the angle and applying corrections 2 1 2 3 Buoyant Effect of the Air Archimedes principle shows that the vertical force exerted by an object submerged in a fluid is reduced by an amount equal to the mass of the fluid displaced The magnitude of this buoyant force can be determined as a function of the volume of the object and the density of the fluid displaced Since the volume of an object can be determined as a function of its mass and density and the volumes of masses used on a piston gage are usually not measured directly it is common to determine the buoyant force due tot he air surrounding the masses as a function of the density of the objects and the ambient air as follows F F DID where F Resultont Verticol Force F Original Vertical Force D Air Density nominally 0 0012 g cm and D Mass Reference Density Refer to reference number 4 for further discussion of apparent mass 2 5 PISTON PRESSURE GAGE For most piston gages the mass values are usually reported in units of apparent mass versus brass standards or apparent mass versus stainle
81. n a pressure measurement can be made with confidence 4 7 6 NEXT PRESSURE Once a pressure measurement is complete carefully stop the rotation of the mass stack Repeat Sections 4 7 4 2 through 4 7 5 for each desired pressure When changing the deadweight gage pressure to a higher level first increase the load then increase the pressure When descending to a lower pressure first reduce the pressure then reduce the load CAUTION When removing masses from the deadweight gage while the system is pressurized the piston may rise to the top of travel This movement must be anticipated and controlled to prevent damage to the equipment 4 7 7 RETURN TO ATMOSPHERE When all pressure measurements have been made return the instrument to atmospheric pressure Unload the masses from the deadweight gage and store them in the appropriate location SYSTEM OPERATION 4 14 A V A FIGURE 4 1 LO amp MID PRESS PLUMBING SCHEMATIC 4 7 8 PREPARATION FOR STORAGE SHIPPING MODEL 2485 930 amp 2485 950 When the model 2485 deadweight gage is not in use the pressure should be removed and the appropriate valves open to the reservoir The following section describes the recommended steps to prepare the instrument platform for shipment or long term storage Remove all the masses loaded on the deadweight gage including the hanger mass Install the shipping plug according to Section 4 6 4 Fully recharge the hand pump and generate approxi
82. n the high pressure system the pressure monitor will also indicate an increase in the low pressure system but not at the same rate as before the intensifier plunger began to move This is due to the intensifier plunger movement changing the volume of the low pressure system The relative rate of pressure change in the hand pump as indicated by the pressure monitor is an important indication in the operation of the system If the pressure does not change at the appropriate pressure according to the intensifier ratio the intensifier has reached the high pressure travel limit and must be recharged before continuing Refer to Section 4 9 4 4 for instructions on recharging the intensifier 4 9 3 2 Adjusting Float Position As the pressure approaches that required to float the piston reduce the rate of hand pump spindle rotation and slowly approach the proper float position If the float position or system pressure is too high rotate the hand pump spindle counter clockwise until the proper pressure or float position is obtained Rotate the hand pump spindle one additional turn counter clockwise and then carefully clockwise to operate the intensifier and adjust the float position This will provide better control of the float 4 21 SYSTEM OPERATION position by remove any spindle nut backlash and developing enough pump pressure to overcome the friction of the seals in the intensifier 4 9 3 3 Recharging the Hand Pump While at Pressure
83. nal trim is computed using the following formula and loaded onto the piston gauge Temp Coef x actual temperature expected temperature 1 CALCULATIONS C The Symbol 4 represents the effective area of the piston and its cylinder at atmospheric pressure when operating at temperature t it is obtained from the relation A 1 At where Ad oap reported area of the piston at 23 degrees Celsius thermal coefficient of superficial expansion At 1 23 D Gravity and Buoyancy Correction When the masses are applied to the piston in the presence of the buoyant atmosphere buoyancy corrections are necessary and are combined with gravity corrections For convenience the combined correction K or K is applied as a multiplier with the result indicating the quantity of apparent mass that is required to produce the desired force F on the piston FOR ENGLISH UNITS K 8 81 Low where acceleration due to standard gravity 980 665 cm sec 2 acceleration due to local gravity in cm sec Por density of air in g cm see Equation 4 Pm density of apparent mass for Apparent Mass versus Brass 8 4 g cm for Apparent Mass versus Stainless Steel 8 0 g cm When selecting masses from the calibration report assure that the values selected are in the same Apparent Mass unit of measure that was used to calculate the or K values The apparent mass Column 9 is obtaine
84. ncrement designator marked on the tare compensator disk and the nominal mass designation marked on the masses 4 7 4 2 Load Other Masses Carefully load the next required mass onto the hanger mass When loading the masses onto the deadweight gage verify that they are in the proper sequence and align the identification markings for quick and easy viewing once installed Once a new mass load forces the piston to the bottom of travel this may not occur with larger diameter pistons or small changes in the load carefully rotate the load see Section 4 7 4 3 1 to 2 turns before continuing Apply any required additional load up to an increase of 20 kilograms 4 large platters and verify level per Section 4 7 2 Increase the pressure until the piston is floating and repeat this section 4 7 4 2 until the desired load and pressure are obtained 4 7 4 3 Rotate the Masses To generate precise pressures with the model 2485 deadweight gage the masses must be rotating For manual rotation of the masses the drive motor is disabled by removing the roller pin slowly begin rotation of the mass stack carefully increasing to approximately 20 revolutions per minute 3 seconds per revolution Hand rotation should be accomplished by grasping the sleeve weight near its top surface and rotating For motorized rotation simply engage the motor by depressing the drive motor power switch For motorized operation the roller pin must be installed in the drive sleeve
85. nd calibration procedures for the electronic temperature option are included in the operating manual for the display device SYSTEM OPERATION 4 24 FIGURE 4 3 VOLTAGE SELECTOR SWITCH INSTRUM_ 1 CORPOR US FIGURE 4 4 TEST PORT MANIFOLD AND ADAPTERS 4 25 SYSTEM OPERATION AN gt SS Ka SEAN 2 Z Z AN a FIGURE 4 5 55 LOADING TABLE INSTALLED N R FIGURE 4 6 MASS LOADING TABLE AND PISTON SYSTEM OPERATION 4 26 CN LL AY N N 0222224 lt Nw 0 ger N NNI SA NSTALL 1 SHIPPING K N 1 mis 2 n ult gt 3 mt c Ed med oz nnr tU lt pi d ey E 5 Lin ag eb EA lt ps 71 NNE 39199 008 GHT PIN PANNER TOOL FIGURE 4 7A REMOVING P C WITH Q C P C HOLDER MODEL 2485 935 4 27 SYSTEM OPERATION E S FOR REFERENCE N THE N OOL SHOW OOLS ARE FOUND EMOV L FIGURE 4 7B INSTALLING P C WITH Q C P C HOLDER MODEL 2485 935 SYSTEM OPERATION 4 28
86. ng oil through the test port manifold and device under test 4 5 MASS LOADING TABLE REMOVAL AND INSTALLATION CAUTION All pressure must be removed from the system prior to disconnecting the mass loading table assembly from the main pressure housing Remove all pressure from the system and close the appropriate valve to isolate the reservoir Refer to Sections 4 8 and 4 9 for the specific valve operating sequence Refer to Figures 4 4 and 4 5 Loosen the mass loading table assembly retaining nut until it is free of the threads on the main pressure housing Carefully lift the mass loading table assembly off of the main pressure housing At this point the piston cylinder assembly or a shipping plug will be exposed and appropriate care should be taken to prevent damage or contamination The exposed piston cylinder assembly can be covered with a clean paper wiper to prevent contamination from airborne dust Clean any oil from the mass loading table components prior to reinstallation To install the mass loading table assembly onto the main pressure housing carefully guide the mass loading table assembly retaining nut and cylinder spacer inside the nut over the piston cylinder assembly and cylinder keeper for the higher ranges and tighten the retaining nut As the o ring and or seal compress some amount of feedback in the form of resistance will be felt by the operator Continue to tighten the nut until the o ring seal compressi
87. nger directly above the piston and empty any excess oil out of the storage container Slide the piston cylinder assembly out of the container and set it upright on the clean wipers Turn the hand pump spindle to adjust the oil level in the pressure housing to about the top of the o ring cylinder seal Firmly grasp the top edge of the cylinder with the left hand Place the forefinger of the left hand on the top edge of the piston and apply a slight lateral force to the piston to prevent the piston from existing the bottom of the cylinder when it is moved to the pressure housing Carefully insert the bottom of the piston cylinder assembly into the pressure housing Open the appropriate valve to activate the reservoir While firmly holding the cylinder in place press the piston down into the cylinder then press the cylinder down firmly against the o ring cylinder seal To install a shipping plug rather than a piston cylinder assembly carefully insert the bottom of the shipping container into the pressure housing Open the appropriate valve to activate the reservoir Press the shipping container down firmly against the o ring cylinder seal 4 6 5 6 Installing the Mass Loading Table Assembly 2485 930 amp 2485 950 As described in Section 4 5 carefully guide the mass loading table assembly retaining nut and cylinder spacer inside the nut over the piston cylinder assembly and tighten the retaining nut As the o ring and or seal compress some amou
88. ns from the instrument platform NOTE The Model 2485 can be safely operated without the instrument covers Reinstallation of the instrument cover is performed in the reverse order described above Before reinstalling the cover wipe any excess oil from the instrument platform plumbing and valves Do not tighten the instrument cover mounting screws until all the screws have been installed 5 2 1 8 Seal and O ring Replacement After some period of use the seals and o rings in the instrument platform deteriorate and begin to leak Refer to Section 5 3 for troubleshooting leaks Refer to 5 3 MAINTENANCE amp TROUBLESHOOTING Sections 4 4 and 4 6 for replacing worn seals and o rings on the piston cylinder assemblies and test port manifold assembly Replacement of the seals in the valves hand pump and intensifier model 2485 950 only is beyond the scope of this manual 5 2 1 9 Changing the Seal in the Pressure Column Model 2485 935 Please refer to Figure 5 4 Removing the seal 1 2 Relieve oll pressure from the system open both volves Remove the QCPC holder as described in Section 4 6 6 2 Take to prevent dust and dirt from contaminating the seal area Remove the Drive Sleeve and Drive Belt Use tool part number 2485 203 001 to remove the seal retainer from the column assembly Recharge the pump and then close the reservoir valve Use the hand pump to increase the fluid level in the column until it is
89. nt of feedback in the form of resistance will be felt by the operator Continue to tighten the nut until the o 4 9 SYSTEM OPERATION ring seal compression is complete as indicated by a sudden increase in resistance when the cylinder spacer inside the nut contacts the top of the main pressure housing Secure the nut using the spanner wrench part number 94 618 provided in setup kit part number 2485 202 or 2485 203 4 6 6 REMOVING THE SHIPPING PLUG MODEL 2485 935 Please refer to Figure 3 13 If there is pressure in the system rotate the hand pump until the pressure is below 500 psi Slowly open both valves to assure no pressure is trapped in the system Recharge the hand pump Rotate the hand pump to the end of travel in the counterclockwise direction Use tool part number 94 618 to unscrew the table assembly Use tool part number 99199 008 to unscrew the shipping plug Please refer to Figure 4 78 Close the reservoir valve Rotate the hand pump clockwise to increase the fluid level in the column Bring the fluid level up until it is approximately even with the top of the backup ring Remove the bottom shipping cap from the Quick Change Piston Cylinder holder QCPC Insert the QCPC into the column and rotate clockwise As the QCPC is threaded into the column it will displace fluid and begin to develop pressure in the system As this pressure develops one will notice an increase in the required torque As soon as the increase in torque
90. nts with soap and water Clean the assembly tool 2485 203 001 with soap and water Dry all components thoroughly Lubricate the mating threads and O rings with a small amount of test media Mount the P C assembly tool firmly in a bench vise Check to assure that the O ring is properly installed in the tool Place a finger over the bleed port on the assembly tool Fill the tool approximately 1 2 full of test media For the 40 K P C holder place the jam nut on the tool with the recess for the spring washer facing up Place the spring washer cup side down in the locating recess on top of the jam nut SLOWLY insert the keeper into the assembly tool Stop when a bubble free stream of test media comes up through the center hole in the keeper Place the O ring into the O ring groove Carefully install the Piston amp Cylinder into the keeper With the piston cylinder firmly seated on the O ring the finger may be removed from the bleed hole Tighten the holder body down onto the keeper Use tool part number 94 617 or 94 618 to assure the components are firmly assembled Do not apply excessive torque Install the top shipping cap onto the QCPC holder Fill the bottom shipping cap approximately 1 2 full of test media and install it onto the bottom of the QCPC 5 3 TROUBLESHOOTING COMMON PROBLEMS 5 3 1 AIR TRAPPED IN THE SYSTEM Air trapped in a hydraulic system can be more than an annoyance When a substantial amount of air is trapped
91. ograms or larger installed on the mass loading table If the proper response is not obtained the sensor or the control box may be damaged 5 4 2 ELECTRONIC TEMPERATURE SENSOR If the temperature of the deadweight gage is not being measured correctly by the electronic temperature indicator verify that electrical connection to the sensor is secure If the proper response is not obtained the sensor or the control box may be damaged 5 9 MAINTENANCE amp TROUBLESHOOTING FIGURE 5 1 SAFETY HEAD AND RUPTURE DISK MAINTENANCE amp TROUBLESHOOTING 5 10 FIGURE 5 2 LOW RANGE CYLINDER CLEANING FIGURE 5 3 MID HIGH RANGE CYLINDER CLEANING 5 11 MAINTENANCE amp TROUBLESHOOTING KY LJ N 7 222 U NZ J gt Z X FIGURE 5 4 CHANGING THE COLUMN SEAL MODEL 2485 935 5 12 MAINTENANCE amp TROUBLESHOOTING U x RU S b I gt Z BB Qs Z g gt Z2 2 gt NU ZZ RER gt ES WY 22 2 KEE 5 SSS FIGURE 5 5 DISASSEMBLING 40K QC PC HOLDER MODEL 2485 935 5 13 MAINTENANCE amp TROUBLESHOOTING N N N A P 3 Z 7 za A JSS LLL 2 dc 77 gt R 4 M gt a UA x C
92. on Should a piston cylinder become contaminated however it must be cleaned before resuming operation The piston cylinder cleaning procedure is as follows Fold or twist several light duty wipers Kimberly Clark Type 9005 KimWipes recommended as shown in Figure 5 2 and 5 3 for removing excess oil from the piston and cylinder and for drying parts later in the procedure Wipe the excess oil from the parts Wetting the wipers with a mild solvent such as high grain alcohol or acetone may be helpful Using a clean bottle brush part number 7 682 for the low range cylinder and medium duty paper wipers for other parts thoroughly scrub the piston and cylinder with soap Cashmere Bouquet and lukewarm water Thoroughly rinse the parts and quickly dry with the folded or twisted wipers Set the parts aside for 15 minutes prior to assembly Coat the bottom of the piston in clean deadweight gage oil and carefully insert the piston into the cylinder Place the piston cylinder assembly into the storage container cover with clean deadweight gage oil and secure the top of the container 5 2 3 ALTERNATE PISTON CYLINDER CLEANING METHOD If soap and water are not available the piston cylinder assemblies may be cleaned with a mild solvent such as high grain alcohol or acetone provided no residues remain on the parts prior to assembly This process may not yield as consistent results as cleaning with soap and water 5 2 4 MASS SET CLEANING It is
93. on is complete as indicated by a sudden increase in resistance when the cylinder spacer inside the nut contacts the top of the main pressure housing Secure the nut using the spanner wrench part number 94 618 provided in the installation kit SYSTEM OPERATION 4 6 4 6 PISTON CYLINDER ASSEMBLIES 4 6 1 PISTON CYLINDER ASSEMBLIES When a piston cylinder assembly is not in use it should be placed in the storage container to prevent contamination and damage to the precision finish surfaces When a piston cylinder is submitted for recalibration the mass loading table assembly should accompany the piston cylinder assembly The mass of each of these components as well as the position of the reference plane distance from the top loading surface of the weight loading table to the bottom of the piston should be reevaluated periodically 4 6 2 GENERAL The heart of the model 2485 deadweight gage is the piston cylinder assembly The precision fit of the pistons into the cylinders provides a very high level of sensitivity with very low sink rates Several denominations are available to best match the deadweight gage application In some applications more than one denomination may be required The time required to change ranges in the 2485 deadweight gage is approximately 2 minutes Refer to Figure 4 5 and Table 1 1 for a detailed view and descriptions of the various piston cylinder configurations Complete cleaning instructions for the various configur
94. or other geometric irregularities that can result in complicated stresses in the cylinder Further the cylinder is restrained in the pressure housing in such a way as to minimize stress due to mounting and sealing The mounting arrangement for the piston cylinder assemblies in the pressure housing also allows quick and easy change out of all ranges while providing a maximum level of protection to the precision measuring components 3 2 5 HIGH PRESSURE PISTON CYLINDER ASSEMBLIES Due to the extreme stress at pressures up to 72 500 psi 5000 bar the high pressure piston cylinder assemblies have a slightly different geometry than the lower pressure assemblies The high pressure piston cylinder assemblies retain the non complex configuration with the seal at the bottom of the cylinder The piston and cylinder are however significantly smaller To assure proper alignment of the high pressure assemblies and to ensure positive sealing at the base of the cylinder a special cylinder keeper is installed in the pressure housing prior to installation of the piston cylinder assembly The seal configuration of the keeper allows the use of a standard elastomeric O ring seal at the base of the cylinder while providing positive sealing up to 72 500 psi 5000 bar The design of the keeper sealing surfaces enhances the durability and allows extended use of the seals The lower seal on the keeper is the same configuration as the seal used on the test port manifold
95. osition Mirror Block 034 3 1 3 4 Float Position Sensor Assembly 035 3 1 3 4 Thermometer Assembly optional 036 3 7 3 8 Mass Set 3 9 TECHNICAL DESCRIPTION N Z S FIGURE 3 1 FRONT VIEW MODEL 2485 950 SIMILAR TO 2485 930 TECHNICAL DESCRIPTION 3 10 nnz4 0031 2 P 7 P d FIGURE 3 2 REAR VIEW MODEL 2485 950 SIMILAR TO 2485 930 3 11 TECHNICAL DESCRIPTION FIGURE 3 3 RIGHT SIDE VIEW MODEL 2485 950 SIMILAR TO 2485 930 TECHNICAL DESCRIPTION 3 12 FIGURE 3 4 TOP VIEW MODEL 2485 950 SIMILAR TO 2485 930 TECHNICAL DESCRIPTION Ep Hp FIGURE 3 5 RIGHT SIDE VIEW 248
96. ositioned in the pulleys on the drive motor and the drive sleeve Connect the power cord supplied with the instrument to the power cord receptacle on the drive motor assembly and then to the power outlet at the installation location Depress the 1 on the power switch and verify that the drive sleeve rotates in the clockwise direction Depress the O to switch the power off A thermo well is located in the front right quadrant of the base of he main pressure housing This well allows for the temperature measurement of the column and Piston Cylinder This well will accept a liquid in glass thermometer or an electronic temperature probe PRT An optional thermometer assembly is available from Ruska under the part number 2485 202 913 f an electronic temperature measurement is desired the Ruska 2456 Piston Gage Monitor may be the optimal choice The 2456 piston gage monitor will make an electronic temperature measurement as well as measuring the float position of the mass platters Contact your Ruska Sales representative for more information on the 2465 PGM Tighten the fitting into the housing about 1 4 turn past finger tight If a thermometer is used position the thermometer so the graduations show through the slot in the thermometer support tube and rotate the support tube so that the temperature can be measured with the masses installed It may be beneficial to apply heat sink compound into the temperature will prior to installing the temperature
97. ough the mid float position Assuming adequate time has been allowed for thermal stabilization and PISTON PRESSURE GAGE 2 8 no significant leaks are present in the system this is the time when a measurement should be made 2 1 3 5 Minimum Pressure For most piston pressure gages there is a minimum pressure that can be generated by floating the piston This tare pressure is that which is required to float the minimum load on the deadweight gage which may be the piston alone Although there is usually a substantial degradation in uncertainty percent of reading at tare pressure it is often required as a calibration point It is also however one of the most frequently overlooked considerations in the operation of a deadweight gage and one that if ignored in tabulating the total piston load will result in a substantial error 2 2 PRESSURE TO MASS EQUATION Some measurement condition may require that a specific pressure be generated The exact load required to generate such a pressure can be computed from the following equation that combines the corrections described in the previous sections Step by step instructions and worksheets are also included in Appendix A Pu px Sag R K where M Total mass required on piston apparent mass for gage mode true mass for absolute mode to generate the desired pressure includes tare mass and surface tension Pressure at reference plane of device under test H Head pr
98. pth 20 3 cm 8 in Weight 23 kg 50 Ib 1 each 1 9 kg hanger mass 19 each 5 0 kg large platters each 3 0 kg small platter each 2 0 kg small platter each 1 0 kg small platter each 0 5 kg small platter each 0 3 kg small platter each 0 2 kg small platter each 0 1 kg to 0 01 g trim set ca Each mass in the set is completely machined to the nominal kilogram mass denomination apparent mass versus brass standards e g 8 4 g cm to within the adjustment tolerance of 15 ppm or 3 0 x 10 kilogram whichever is greater Nominal values within this tolerance are traceable to the U S National Institute of Standards and Technology Each mass in the set is permanently marked with the serial number of the set a sequence number and nominal mass denomination masses are calibrated using precision balances and are traceable to the U S National Institute of Standards and Technology Individual mass values are reported to an uncertainty to 5 ppm or 5 0e 07 kilogram whichever is greater Total tare includes mass of piston mass loading table and compensator Optional Class 5 1 Laboratory Mass Set 1 3 SPECIFICTIONS 1 44 ACCURACY SPECIFICATIONS TABLE 1 2 TOTAL UNCERTAINTY IN PRESSURE EXAMPLE ONE Effective Area at 23 Mass Set calibrated values Environment Gravity Air Buoyancy Temperature Sum 2 Sigma EXAMPLE TWO Effective Area at 23 Mass Se
99. r other piston styles where for example there is an enlargement on the bottom of the piston such as a retaining nut the reference plane position is somewhat below the physical bottom of the piston assembly at a position where the bottom of the assembly would be if the nut was the same diameter as the piston while conserving the volume 2 1 3 2 Pneumatic Pressure Gradients In the same way as pressure heads are generated in a hydraulic system they also are prevalent in pneumatic systems The two important differences between hydraulic and pneumatic system pressure heads are that the magnitude of the pneumatic system corrections tend to be significantly less at lease at lower pressures than in a hydraulic system and that unlike the relatively constant hydraulic head the magnitude of the gas head changes significantly with pressure due to the relative high compressibility and resulting density increase associated with gases For further information on pneumatic pressure head corrections refer to the tables included in Appendix A 2 1 3 3 Reference Pressure Head For very low pressure devices referenced to atmosphere and some low pressure differential devices where both the test port and the reference port are pressurized a further correction may be necessary to account for a difference in the reference pressure acting on the test device and the standard For a device referenced to atmosphere and positioned above the standard the atmospheric pr
100. r prevents contamination of the fluid in the reservoir EXTERNAL RESERVOIR PORT 2485 950 ONLY Should the internal reservoir have insufficient capacity for high volumes of work a port is provided on the rear of the instrument for attaching an external high capacity reservoir such as the Ruska model 2419 800 1500cc reservoir and a high flow transfer pump model 5202 When an external reservoir is not connected the external reservoir port becomes a convenient location to attach manometer for establishing a precise measure of zero pressure RESERVOIR SOURCE VALVE 2485 950 ONLY The reservoir source valve is used to select between the internal reservoir and an external reservoir or manometer 3 3 TECHNICAL DESCRIPTION SEQUENCE FUNCTIONAL NUMBER DESCRIPTION 017 RESERVOIR RELIEF VALVE 2485 950 ONLY The internal reservoir plumbing is protected from inadvertent over pressure through the use of a relief valve set to approximately 100 psi 018 TEST PORT MANIFOLD AND ADAPTERS In addition to the test port at the base of the main pressure housing a test port manifold is supplied with an assortment of adapters The test port manifold with the appropriate adapter installed is designed to be mounted to the auxiliary pressure housing without the use of tools The design of the test port manifold allows simple and quick installation of the manifold while promoting durability of the seal CAUTION Due to the thread configuration o
101. rate a reference chamber for evacuating much of the air surrounding the load on the piston this absolute mode of operation the air remaining in the reference chamber usually has an insignificant buoyant effect on the masses although the actual pressure typically near 100 mTorr or 0 002 psi may a substantial portion of the total pressure and should be added to the piston pressure Further because the buoyant force is not significant the true mass values should be used It is important to note that under extreme evacuation there may be additional considerations as well as the potential for a reduced level of performance and an increase in uncertainty 2 1 2 4 Combined Gravity and Air Buoyancy Correction If the effects of varying ambient conditions are within acceptable limits as determined by an error budget it becomes convenient to combine the air buoyancy and gravitational corrections into one term K used as a conversion between mass and force For gage mode operation the conversion is between force and apparent mass For absolute mode operation where nearly all the air is removed from around the masses such that the buoyant effect is typically insignificant the conversion is between force and true mass K 1 D D G G where Mass force conversion factor Air density Mass reference density K D D PISTON PRESSURE GAGE 2 6 Local gravitational acceleration in m s and G Standard gravitationa
102. recommended that the deadweight gage masses be handled using clean gloves such as Ruska number 99189 included in the 2485 202 or 2485 203 set up kit Should the masses become contaminated they may be cleaned using a mild solvent such as high grain alcohol or using soap and water provided that they are thoroughly dried afterwards 5 2 5 DISASSEMBLY OF THE QCPC HOLDER MODEL 2485 935 For the following procedure please refer to Figures 5 5 and 5 6 Mount the P C assembly tool firmly in a bench vise Orient the tool such that it is pointing upward Remove the shipping caps from the QCPC Holder and insert the holder into the tool as shown Loosen the body of the holder using the Spanner tool part number 94 617 or 94 618 After rotating the body of the tool 3 or 4 turns check to make sure that the assembly is not stuck to the holder body This occurs due to the capillary action of the test media around the cylinder If the P C is stuck to the body gently Prod it using a cotton tipped swab Q tip or small wooden stick Do not use a sharp object When the is safely resting on the keeper Unscrew the body with rest of the way remaining components will lift off 5 5 MAINTENANCE amp TROUBLESHOOTING 5 2 6 ASSEMBLY OF THE QCPC HOLDER MODEL 2485 935 For the following procedure please refer to Figure 5 7 Carefully clean the piston and cylinder according to the procedures detailed in Section 5 2 2 Clean all remaining compone
103. roaches the counter clockwise travel limit VERY SLOWLY open intensifier valve C Remember to recharge intensifier before proceeding 4 10 OPTIONAL HARDWARE This section describes the electronic float position and electronic temperature sensor options 4 10 1 THERMOMETER OPTION A liquid in glass thermometer is available as an option Ruska part number 2485 202 913 This thermometer is provided with a protective metal sleeve and mounting hardware 4 10 2 ELECTRONIC FLOAT POSITION The electronic float position option is used to provide high resolution indication of the float position and sink rate of the piston The electronic float position option can increase the reliability and precision of pressure measurements made using the deadweight gage The electronic float position sensor assembly is installed on the instrument platform below the masses The adjustment and calibration procedures for the electronic float position sensor are included in the operating manual for the display device 4 10 3 ELECTRONIC TEMPERATURE SENSOR The electronic temperature option uses a platinum resistance thermometer PRT in conjunction with an electronic display device such as the electronic float position display to provide a reliable digital indication of the deadweight gage temperature The PRT is mounted in the main pressure housing of the deadweight gage in place of the liquid in glass thermometer used when this option is not installed The adjustment a
104. roper float position of the piston cylinder assembly Pressure is applied to the piston cylinder assembly until the piston and mass load are floating at a position where the bottom edge of the hanger mass designation 01 coincides with the line on the drive sleeve The drive sleeve provides the rotary motion for the mass loading table through contact with a roller pin mounted in the top of the drive sleeve The drive sleeve also provides a boundary between the mass load and the oil draining down the side of the main pressure housing 032 ROLLER PIN The roller pin mounted in the top of the drive sleeve provides rotation of the mass loading table assembly through contact with a drive pin in the bottom of the mass loading table The roller pin can be removed by simply grasping the and lifting It is recommended that the roller pin be removed when not required and that motor driven rotation be used only when a small load or other special test requires its use 033 FLOAT POSITION MIRROR BLOCK A small mirror mounted to the float position mirror block at a 45 degree angle provides easy visual observation of the float position of the hanger mass relative to the line on the drive sleeve 034 FLOAT POSITION SENSOR ASSEMBLY An optional electronic float position sensor assembly is available under Ruska part number 2485 913 The electronic sensor allows more precise and simpler measurement of the float position through the use of the Ruska Model
105. rt it to an absolute value by adding barometric pressure e g P 14 7 NITROGEN DENSITY ENGLISH UNITS 1 000 TO 15 000 PSIG To calculate the density of Nitrogen at pressures from 1 000 psig to 15 000 use the following equation DENSITY lbm in 2 37465 x 10 2 74396 x 10 P 9 46069 x 10 P where P PRESSURE in psi absolute if P is in gauge convert it to an absolute value by adding barometric pressure e g P 14 7 NITROGEN DENSITY SI UNITS 0 TO 6 9 MPa To calculate the density of Nitrogen at pressures from 0 01 MPa gauge to 6 9 MPa use the following equation DENSITY kg m 1 1347 E 05 x P where P PRESSURE in Pa absolute if P is in gauge convert it to Pa absolute by adding barometric pressure e g P 101325 NITROGEN DENSITY SI UNITS 6 9 MPa TO 100 MPa To calculate the density of Nitrogen at pressures from 6 9 MPa gauge to 100 MPa use the following equation DENSITY kg m 6 573 11 016 P 0 055087 P where PRESSURE in MPa absolute if P is in gauge convert it to MPa absolute by adding barometric pressure e g P 0 101325 CALCULATIONS 6 ZERO AIR DENSITY SI UNITS 0 MPa TO 20 7 MPa To calculate the density of Zero Air at pressures to 20 7 MPa use the following equation DENSITY kg m 1 17 E 05 x P where P PRESSURE in Pa absolute if P is in gauge convert it to Pa absolute by adding barometric pressure e g P 101325 HELIUM DENSITY SI UNITS 0 TO 6
106. rter turn of the hand pump spindle Refer to Section 5 3 for troubleshooting 4 9 2 2 Adjusting Float Position As the pressure approaches that required to float the piston reduce the rate of hand pump spindle rotation and slowly approach the proper float position If the float position or system pressure is too high rotate the hand pump spindle counter clockwise until the proper pressure or float position is obtained Rotate the hand pump spindle an additional one quarter turn counter clockwise and then carefully clockwise to restore the pressure or float position and to remove any spindle nut backlash This will prevent the pump plunger from creeping out of the pump housing which could result in erroneous pressure readings 4 9 2 3 Recharging the Hand Pump While at Pressure On occasion the hand pump will reach the full clockwise travel limit preventing further pressurization The hand pump may be recharged while the system remains at pressure To recharge the hand pump while the system is at pressure close intensifier valve C and note the pressure indication on the pressure monitor Rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 500 psi 35 bar and open pressure valve B Continue rotating the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise one quarter turn and close pressure valve
107. sing point in the procedure is the necessity for the temperature of the gauge to be predicted prior to operation This expected temperature however is used to allow the pressure calculations to be performed the piston pressure gauge is floating at the intended pressure a final temperature observation is made and then trim masses are loaded onto the piston gauge to correct for any temperature variations that exist between the expected and the actual temperatures The final column in the worksheet is used to calculate the temperature coefficient which defines the amount of trim that is required to correct for this temperature change It is usually prudent to select an expected temperature t which is lower than any temperature that will be experienced This is so that the operator can always add mass to correct for the actual temperature Adding mass is generally more convenient than subtracting mass from the planned loading arrangement Standard metric trim mass set is entirely suitable for this purpose All of the calculations will be performed to this expected temperature t A final trim would be calculated to adjust the piston gauge to the temperature of the piston at the time of the actual measurement This correction is calculated in the last column of the worksheet This column represents the number of grams to be added to the stack of masses for a difference in the actual temperature from the expected temperature t The fi
108. ss 3 Type 1 per ASTM E617 formerly Class S1 per NBS Cir 547 These fractional masses should also be used to adjust the mass load for piston pressure gauge operating temperatures that differ from the expected temperature t These fractional masses could also be used to adjust the mass load for the piston pressure gauge if the reference plane of the device being calibrated is at a different elevation than planned in the original head correction P In the English system the remainder can be recorded in pounds in Column 11 and in grams in Column 12 The conversion factor to convert pound mass to grams is 453 59237 g lbm Q Column 13 is used to calculate a temperature coefficient This temperature coefficient is used to correct for any piston temperature variation from the expected temperature value that was used to calculate the mass loads for the various pressure points in the worksheet See item B above A 5 CALCULATIONS EQUATION 4 AIR DENSITY Air Density Pair in units of g cm is calculated as follows Puy 0 0004646 x P 4990221 6 x U 8556 0815 273 15 t where P Barometric Pressure mmHg t Air Temperature C U Relative Humidity RH NITROGEN DENSITY ENGLISH UNITS 0 TO 1000 PSIG To calculate the density of Nitrogen at pressures from O psig to 1000 psig use the following equation DENSITY Ibm in 2 826 x 10 x P where P PRESSURE in psi absolute if P is in gauge conve
109. ss steel and True Mass If the load on a piston is comprised of various materials with various densities buoyancy corrections using True Mass values would be computed individually for each type of material A single correction to the entire load however can be made by using apparent mass values and substituting the reference density 8 4 g cm for apparent mass versus brass and typically 8 0 g cm for apparent mass versus stainless steel for the true density in the buoyancy correction As with the piston cylinder assembly temperature affects the dimensions of the masses These dimensional changes result in volume changes and hence buoyancy changes The nominal volumetric thermal coefficient for a typical steel used in piston gage masses is approximately 45 x 10 6 per degrees Celsius has only a very small effect and is typically ignored is piston pressure gage applications Changes in air density resulting from barometric temperature and relative humidity changes can be significant to piston pressure gage measurements Appendix A includes tables and equations for computing air density based on these parameters Even though environmental conditions vary continuously the range is usually relatively small Often average barometer temperature and relative humidity values are used for calculating air density and the typical environmental variations are accounted for in the estimate of uncertainty Some piston pressure gages incorpo
110. ssembly lt is most likely that there may be many combinations of available masses that could be used to yield the required Total Mass However it is strongly recommended that an orderly and sequential method by used From the Mass Set Table calibration report first determine if the Sleeve Mass is required which would be the case if the realization of the Total Mass value would require the use of the larger platter masses If yes then subtract its mass value from the Total Mass value which results in a new remainder From this remainder mass value choose the next largest available mass value that may be subtracted If the choice is from one of several nominal mass platters then choose the first one in the available sequence Subtract this value from the remainder which now results in another new remainder mass value Continue this process until the remainder which now results in another new remainder mass value Continue this process until the remainder is smaller than the smallest available mass from the mass set At every step record the selected mass its mass ID number into Column 10 CALCULATIONS A 4 Column 11 remainder from Column 10 is the mass that must be placed on ihe piston pressure gauge to complete the mass needed to set the desired pressure This remainder recorded in Column 11 is realized with the Trim Mass set provided with all Ruska Mass Sets The Ruska supplied Trim Mass Sets are defined as Cla
111. stalled in the top of the drive sleeve refer to Figures 3 1 through 3 3 Verify that the mass loading table assembly is properly installed and is not damaged MAINTENANCE amp TROUBLESHOOTING 5 8 5 3 4 TROUBLESHOOTING AND CHANGES IN OPERATING VOLTAGE DRIVE MOTOR INDICATOR LAMP LIGHTS BUT THE DRIVE MOTOR DOES NOT RUN Disconnect the power cord and check drive motor FILL PUMP INDICATOR LAMP LIGHTS BUT THE FILL PUMP DOES NOT OPERATE Verify that the power pigtail that protrudes from the bottom of the drive motor housing is plugged into the fill pump housing under the back side of the base Replacement fuse required 1 required Ruska Part Number 26 216 1 AMP Slow Blow CHANGING OPERATING VOLTAGE To switch voltages from 110 VAC to 220 VAC disconnect the power and switch the voltage selector on the back of the unit Refer to Figure 4 1 in the User s Manual The unit should operate as well on 50 or 60 Hz power AIR IN THE SYSTEM ALLOWING THE RESERVOIR TO RUN DRY The air may be removed from the system using the instructions detailed in Section 5 3 1 of the Manual 5 4 OPTIONS 5 4 1 ELECTRONIC FLOAT POSITION If the float position of the piston cylinder assembly is not being measured correctly by the electronic float position indicator verify that the electrical connectors to the sensor are secure and that the sensor is properly adjusted refer to Section 4 10 2 NOTE The hanger mass and at least one other mass 2 kil
112. strument CAUTION Do not rotate the hand pump spindle during installation of the handles 3 Carefully tighten the hand pump handles using a wrench on the flats near the pump spindle end of each handle 4 Slowly rotate the hand pump spindle counter clockwise until the pressure displayed on the pressure mounted on the top of the instrument indicates between zero and about 500 psi 35 bar CAUTION Be very careful not to go below zero as air will be pulled into the hydraulic system 5 Carefully open Reservoir Valve A on the right side of the instrument 6 Slowly rotate the hand pump spindle in the clockwise direction while monitoring the oil level in the internal reservoir As the oil level rises above the fitting in the bottom of the reservoir continue to rotate the hand pump in the clockwise direction while looking for gas bubbles in the oil Continue rotating the hand pump until no gas bubbles emerge from the reservoir plumbing 7 Add oil to the reservoir from a fresh clean source until the oil level is near the fitting in the side of the reservoir CAUTION Be certain that the oil added to the reservoir is the same type as that in the instrument 8 Recharge the hand pump by rotating the pump spindle fully counter clockwise then clockwise one quarter turn to remove any backlash in the spindle threads 9 Close Reservoir Valve A 10 Slowly rotate the hand pump spindle clockwise and observe the pressure monitor for an indic
113. t free wiping paper Kimwipe or equal Install the table assembly onto the top of the QCPC seat it firmly using the tool part number 94 618 The rotation roller assembly is found stored inside the shipping plug If the rotation motor is to be used remove the roller assembly from the shipping plug and install it into the mass rotating sleeve See Figure 4 5 If the rotation motor is not being used the roller assembly may be left inside the shipping plug Install the unused shipping caps onto the shipping plug this will prevent dust from contaminating the surfaces as well as keeping the pieces together See Figure 3 15 4 7 OPERATING PROCEDURE FOR THE MODEL 2485 DEADWEIGHT GAGE This section describes the steps necessary to safely generate precise pressures with the model 2485 deadweight gage The steps described below are generic and are applicable to both versions of the instrument Specific valve operating procedures which are different for the two versions of the instrument are detailed in Sections 4 8 and 4 9 Once the operator becomes familiar with the valving techniques for a particular version the following steps should be followed to safely and efficiently generate the desired pressures 4 7 1 ESTABLISHING ATMOSPHERIC PRESSURE Verify that the instrument is at atmospheric pressure as indicated by the pressure monitor and that the reservoir is on line by actuating the appropriate valves according to Sections 4 8 and 4 9 4 11 SYST
114. t nominal values Environment Gravity Air Buoyancy Temperature Sum 2 sigma Typical low range piston cylinder assembly The values used in the examples above are for a standard mass set and a typical low range piston cylinder assembly operating on Spinesstic 22 oil There may be a minimal increase in uncertainty when using other ranges or fluids Refer to the specific calibration report in Appendix C for the appropriate values The total uncertainty may be reduced by direct NIST calibration of the masses and piston cylinder assemblies SPECIFICATIONS 1 4 SECTION 2 0 PISTON PRESSURE GAGE 2 1 MEASUREMENT CONSIDERATIONS Measurements of pressure using a piston pressure gage are limited by disturbances resulting from various influences including environmental effects and operating procedures as well as certain physical aspects of the equipment The effects of these disturbances can be reduced by exercising control over the influence or by measuring the effects and applying corrections Some of the factors that influence pressure measurements are below e Elastic distortion of the piston cylinder assembly Piston cylinder temperature Grovitational acceleration Atmospheric buoyancy Pressure gradients Float position of height s s s 3 Surface tension Vertical alignment of piston axis Pressure results from the application of a force onto an area Numerically it is the quotient of the force divided by the are
115. t typically including 10 mg through 100 g masses the load can be trimmed to generate any pressure within the range and sensitivity of each piston cylinder assembly The mass set is supplied in 5 storage cases The storage case for the hanger mass and incremental platters also accommodates three piston cylinder assemblies Refer to Figures 3 7 and 3 8 3 2 2 MASS LOADING TABLE ASSEMBLY The mass load on the 2485 is transmitted to the piston through a conical arrangement in mass loading table assembly that locates on the spherical end of the piston This locating method which allows any minute imbalance in the load to be self aligning and self balancing promotes a higher level of performance than with a rigidly mounted load which can result in bent broken or worn piston cylinder components piston cylinder protection provided by the precision fit of the components in the 2485 mass loading table assembly eliminates the necessity for a secondary piston and guide bushing which could result in increased friction and reduced performance 3 2 3 INSTALLATION KIT The installation kit part number 2485 202 or 2485 203 contains all the necessary hardware such as wrenches seals and piston cylinder cleaning tools for operating of the model 2485 deadweight gage See Appendix B for detail of the setup kit 3 7 TECHNICAL DESCRIPTION 3 2 4 MODEL 2485 PISTON CYLINDER ASSEMBLIES The piston cylinder assemblies used in the model 2485 are manu
116. t Corporation Reduced Uncertainty and Improved Reliability for the Pneumatic Piston Pressure Gage Through Statistical Process Control published in the Proceedings for the Annual Measurement Science Conference 1991 2 13 PISTON PRESSURE GAGE THIS INTENTIONALLY LEFT BLANK PISTON PRESSURE GAGE 2 14 SECTION 3 0 TECHNICAL DESCRIPTION 3 1 INSTRUMENT OVERVIEW The Ruska Model 2485 deadweight gage is a fully integrated high precision high accuracy piston pressure gage system used as a standard to calibrate pressure transducers and bourdon tube gages and as a precise pressure balance to accurately measure maintain and control pressures up to 20 000 psi 1400 bar in the low pressure version model 2485 930 40 000 psi 2800 bar in the medium pressure version model 2485 935 and up to 72 500 psi 5000 bar in the high pressure version model 2485 950 The model 2485 incorporates all the necessary components for accurate generation of any pressure within the range of the instrument The features and functions of the system components are described below 3 2 INSTRUMENT FEATURES AND FUNCTIONS The instrument features listed in Table 3 1 can be found in the figures listed by each feature Refer to the sequence number shown in Table 3 1 to locate the feature in the appropriate figure Refer to section 3 2 1 for a functional description of each feature 3 2 1 INSTRUMENT PLATFORM FUNCTIONAL DESCRIPTION SEQUENCE FUNCTIONAL NUMBER
117. t of the air has been removed but that which remains eludes discharge the system should be pressurized to several thousand psi over night During this period air trapped in the system will go into solution with the oil After this time period has passed do not decrease the pressure Rather slowly and carefully loosen select fittings one at a time to release the oil As the oil is released maintain the pressure using the hand pump Continue until a significant volume of oil has passed through each of the bleed points usually a full stroke of the hand pump is required Release the pressure recharge the hand pump and repeat the test 5 3 2 PRESSURE LEAKS Eventually every hydraulic system develops a leak This section includes information useful in isolating such leaks in the model 2485 deadweight gage The first indication of a leak in a pressurized system is that the pressure decreases with time Another measure of leaks in a pressurized deadweight gage system is that the piston cylinder sink rate is excessive If the sink rate is abnormally fast there may be a leak in the system If the system has only recently been pressurized decreasing pressure and an abnormally fast sink rate are to be expected The act of pressurization results in heating of the pressure medium the heat dissipates into the system the pressure decreases The piston cylinder acting as a regulator adjusts the volume of the system attempting to maintain the pressur
118. t the conclusion of operation of the instrument the pressure must be removed and the valves set to a position that will not trap pressure in any portion of the system During operation of the system a warning sign notifying personnel of the state of the system should be placed in close proximity to the system Versions of the instrument that include the drive motor option require a grounded 115 or 230 VAC power source To prevent electrical shock when servicing an instrument with drive motor option the power switch must be set to the off position and the power cord disconnected from both the instrument and the power outlet The model 2485 is shipped from the factory in a special configuration A small amount of pressure is trapped in the instrument to prevent air from contaminating the hydraulic system The procedure to remove this pressure described later in this section must be followed to prevent damage to the delicate internal components and to prevent injury to personnel 4 1 SYSTEM OPERATION 4 3 INSTALLATION AND PREPARATION FOR USE 4 3 1 SELECTING A LOCATION The model 2485 should be installed in a location where the temperature is maintained between 18 degrees and 28 degrees Celsius and the relative humidity is between 2096 and 7596 Temperature stability may be more important than the actual temperature A change in the temperature of 1 degree per hour may be excessive for some pressure measurements The installation location s
119. te the hand pump spindle clockwise one quarter turn and close reservoir valve A and intensifier valve Carefully rotate the SYSTEM OPERATION 4 22 hand pump spindle clockwise to generate pressure Once the pressure monitor indicates the same pressure noted earlier in this section slowly open system valve D 4 9 3 5 Discharging the Intensifier While at Pressure If the intensifier was recharged while at pressure it is likely that during depressurization the intensifier will reach the return stroke limit while the system remains pressurized The intensifier may be discharged while the system remains at pressure to allow further depressurization of the system The indication to the operator that the intensifier plunger has reached the return stroke limit is that the pressure monitor will indicate a sudden increase in the rate of depressurization The pressure at which this occurs is important tot he following procedure To discharge the intensifier while the system is at pressure note the pump pressure as described above except that the hand pump spindle must be rotated clockwise until the intensifier again begins to pressurize the test port This condition will be indicated when the pressure monitor shows a sudden decrease in the rate of re pressurization Note this pressure monitor reading for use later in this procedure Close system valve D and carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates b
120. te the hand pump spindle counter clockwise until the piston is at the lower travel limit and the pressure monitor indicates between zero and 500 psi 35 bar Open reservoir valve and continue rotating the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clockwise one quarter turn and close reservoir valve A Carefully rotate the hand pump spindle clockwise to generate pressure Once the pressure monitor indicates the same pressure noted earlier slowly open pressure valve B 4 8 5 DISCHARGING THE HAND PUMP WHILE AT PRESSURE When reducing pressure in the system the pump may reach the counter clockwise travel limit before the desired pressure is obtained To allow further depressurization of the system the hand pump may be discharged while the system remains at pressure To discharge the hand pump while the system is at pressure verify that pressure valve B is open and adjust the hand pump position so that approximately one quarter of the pump travel remains in the counter clockwise direction the system pressure indicated on the pressure monitor Close pressure valve B and carefully rotate the hand pump spindle counter clockwise until the pressure monitor indicates between zero and 4 17 SYSTEM OPERATION 500 psi 35 bar Open reservoir vale and rotate the hand pump spindle clockwise until approximately one quarter of the pump travel rem
121. tform Dimensions Electrical Requirements Temperature Range Humidity Range 2485 930 0 5 to 1375 bar 7 25 to 20 000 psi 2485 950 0 5 to 5 000 bar 7 25 to 72 500 psi gage mode pressures referenced to ambient atmospheric pressure 1 5 times the system working pressure for low pressure system 1 25 times the system working pressure for high pressure system Spinesstic 22 oil 522 Dioctyl Sebacate oil DOS Pressure accuracy to 0 00596 reading from 696 of full scale to full scale and 0 0003 of full scale below 696 traceable to U S National Institute of Standards and Technology Height 50 8 cm 20 in including mass stack 72 cm 20 in with high pressure extension Width 50 8 20 in Depth 35 6 cm 14 in excluding hand pump Handle Weight 40 kg 115 or 230 vac 50 or 60 Hz switchable Operation 18 to 28 Storage 20 to 50 when thermometer is removed Operation 20 to 7596 Storage to 90 1 2 PISTON CYLINDER SPECIFICATIONS Sensitivity Threshold Repeatability Reproducibility Piston Cylinder Material Thermal Coefficient Cylinder Configuration Maximum Sink Rate 0 0001 reading 1 ppm 0 0003 reading 3 ppm 0 0006 reading per year 6 ppm Cemented Tungsten Carbide 6 Cobalt 9 1 x 10 in in deg C 9 1 ppm per deg Simple Minimal Mounting Stress 0 5 mm per minute 0 02 inch per minute Refer to Table 1 2 for a sample error analysis 1 1 SPECIFICTIONS PIS
122. the counterclockwise direction Use tool part number 94 618 to unscrew the table assembly SYSTEM OPERATION 4 10 Install the top shipping cap onto the QCPC holder Use tool part number 99199 008 to unscrew the QCPC Place the bottom shipping cap onto the QCPC It is advised that the bottom cap be 1 2 filled with test media to inhibit the entrance of air bubbles out of the QCPC Store the QCPC upright Close the reservoir valve Rotate the hand pump clockwise to increase the fluid level in column Bring the fluid level up until it is approximately even with the top of the backup ring Remove the bottom shipping cap from the Quick change Piston Cylinder holder QCPC Insert the QCPC into the column and rotate clockwise As the QCPC is threaded into the column it will displace fluid and begin to develop pressure in the system As this pressure develops one will notice an increase in the required torque As soon as the increase in torque is noticed stop and open the reservoir valve Continue threading the QCPC into the column When the QCPC is fully installed insert the tool part number 99199 008 into the spanner hole in the side of the QCPC and make sure it is firmly seated Verify that both valves are open before removing the top shipping cap from the QCPC Remove the top shipping cap from the QCPC If excess oil is present on either the top of the piston or the mating surface on the table support remove it by wiping them with a lin
123. the differential pressure that the piston is required to generate A 3 CALCULATIONS J The value of 1 b P b which is used to determine the piston area at different system pressures is recorded in column 6 For some pistons b and or b are equal to zero Always observe the sign in front of b and b as found in the calibration report K Column 7 is used to record Aot which is the area of the piston at pressure P and at the expected temperature L Column 8 the weight load is the force required on a piston of given area to produce a given pressure F P Aet where F Weight load or force on the piston Pressure as indicated in Column 5 Agir Effective piston area at the expected temperature t M Column 9 is the apparent mass that is required to produce the force listed in Column 8 N Column 10 is a listing of the different masses to be loaded on the piston pressure gauge to create the pressure listed in Column 5 The masses which will be listed here are in addition to the tare components piston surface tension effects bell jar reference pressure etc The mass of the tare components must be subtracted from the mass shown in Column 9 before selection of the miscellaneous masses is started After subtracting the TARE mass from the Total Mass shown in Column 9 we must now subdivide distribute the remaining required mass value among the available masses that will be loaded onto the Piston Table A
124. the main pressure housing is level within 5 minutes of arc 5 2 1 4 Instrument Platform Lubrication Several components of the instrument platform may require periodic lubrication to provide reliable enduring service A drop or two of light machine oil in the threads and swivel sockets of the support legs may be required when the instrument is placed in service and every few years thereafter The hand pump spindle and spindle nut bearings require lubrication to operate properly Both are lubricated at the factory but require inspection when the instrument is placed in service and every few years thereafter Remove the pump lubrication port cover Figure 3 4 add 2 3 drops of clean 90W to 140W oil and replace the pump lubrication port cover During operation of the deadweight gage the oil passing through the minute clearance between the piston and cylinder and the overflow oil during piston cylinder exchange will provide lubrication for the drive sleeve bushings When the instrument is placed in service and during each piston cylinder exchange when the mass loading table assembly has been removed verify that the drive sleeve bushing has an ample amount of lubrication 5 2 1 5 Packing Adjustment for Valves Remove all pressure from the system all valves open Remove the instrument covers Open the valve to the maximum open position Loosen the packing gland locking device Use a torque wrench to tighten the packing gland to 60 FT LB
125. the system induces significant thermal instability To minimize the necessity for recharging the hand pump while at pressure and therefore inducing further thermal instability the hand pump should be fully recharged prior to initial pressurization of the system Refer to Sections 4 8 and 4 9 for the appropriate valving techniques for recharging the hand pump 4 7 4 LOAD THE MASSES AND PRESSURIZE THE SYSTEM The mass loading table assembly of the model 2485 deadweight gage provides a high degree of protection for the piston cylinder assemblies under normal use However the risk of damage or breakage is greatly increased with misuse and abuse The following pressurization routine Sections 4 7 4 1 through 4 7 4 6 will minimize the risk of damage to the precision finish of the piston and cylinder assemblies WARNING Any SUDDEN shift increase or decrease in the load on the piston can result in permanent damage to the piston If when loading and unloading the masses on the deadweight gage CAREFUL consideration is given to prevent damage to the precision finish of the masses adequate protection will be provided for the piston 4 7 4 1 Install the Hanger Mass With ONLY the hanger mass sequence 01 installed on the mass loading table increase the pressure until the piston is floating SYSTEM OPERATION 4 12 NOTE The approximate nominal pressure generated using the model 2485 deadweight gage can be computed from the pressure unit i
126. tor is to maintain consistent relative motion between the piston and cylinder when the inertia of a small mass load is insufficient to maintain adequate free rotation time The drive motor assembly also supplies power to the fill pump assembly 2485 930 amp 2485 935 ONLY POWER RECEPTACLE AND FUSE HOLDER Power to the optional drive motor assembly is switchable between 115 or 230 VAC and 50 or 60 Hz The power RECEPTACLE on the rear of the drive motor assembly contains the necessary fuses to prevent electrical overload of the motor DRIVE MOTOR FILL PUMP POWER SWITCH The drive motor assembly is equipped with a power switch on the left end This power switch controls the drive rotation motor and on the 2485 930 and 2485 935 the switch also controls the motorized fill pump 3 5 TECHNICAL DESCRIPTION SEQUENCE FUNCTIONAL NUMBER DESCRIPTION 029 DRIVE MOTOR POWER LAMP The drive motor assembly includes an indicator lamp to show the state of the electrical motor The lamp is located on the left side of the drive motor assembly next to the power switch 030 DRIVE BELT The rotary action of the drive motor is transferred to the drive sleeve through an elastomeric drive belt installed on the pulleys mounted on the drive motor and the drive sleeve 031 DRIVE SLEEVE A thin line machined around the periphery of the drive sleeve approximately 3 16 of an inch 5 mm above the drive belt pulley is used as a reference for measuring the p
127. unt of air is trapped Figures 4 1 and 4 2 are plumbing schematics that can be used to identify the appropriate valves to isolate segments the system For each segment recharge the hand pump per Section 4 8 or 4 9 as appropriate Verify that the hand pump spindle backlash has been removed and close the appropriate valves to isolate the particular system segment Rotate the hand pump clockwise until pressure begins to build If the rotation is greater than one quarter turn of the hand pump spindle there is a significant amount of air trapped in that segment Remove the air from that segment before proceeding to the next segment The hand pump segment should be tested first If air is trapped in the hand pump it can be removed by loosening the bleed screw located on top of the hand pump housing in front of the pressure monitor Once the hand pump segment is free of air continue to the next segment which will consist of the hand pump segment plus for example the high pressure end of the intensifier model 2485 950 only Note that in this example if the intensifier has not been recharged as described in Section 4 9 it will appear that there is a large amount of air trapped in the system as the intensifier plunger is pushed to the recharge travel limit Once the intensifier is fully recharged recharge the hand pump and repeat the test Air trapped in other segments may require loosening certain fittings to bleed the air from the system If mos
128. ves open to the reservoir The following section describes the recommended steps to prepare the instrument platform for shipment or long term storage Remove all the masses loaded on the deadweight gage including the hanger mass Install the shipping plug with a reverse of the procedures documented in 4 6 6 1 Fully recharge the hand pump and generate approximately 2 000 psi 140 bar Then without rotating the hand pump spindle remove the handles from the hand pump This will ensure that no air becomes trapped in the system during shipment or storage WARNING The maximum pressure rating for the low pressure shipping plug is 20 000 psi 1400 bar Do not exceed this pressure with the pressure shipping plug installed Firmly tighten the cap on the fluid reservoir 4 8 VALVE OPERATING PROCEDURE FOR MODEL 2485 930 2485 935 See Plumbing Schematic Figure 4 1 This section describes the proper valve operating procedures for the various functions of the model 2485 930 deadweight gage instrument platform CAUTION The operator of any pressurized equipment must always be aware of the condition and status of the equipment to avoid the risk of damage and personal injury SYSTEM OPERATION 4 16 4 8 1 RECHARGING THE HAND PUMP AT ATMOSPHERIC PRESSURE With reservoir valve A open rotate the hand pump spindle counter clockwise until the pump position indicator approaches the counter clockwise travel limit Rotate the hand pump spindle clo
129. ylinder having known effective area coefficients The calibration report for a piston cylinder assembly will typically include an effective area at zero pressure pressure and temperature coefficients mass density and surface tension values for the tare components uncertainty estimates and other traceability information The piston calibration process is often referred to as the crossfloat In a typical crossfloat both the standard and test deadweight gages are connected together and operated simultaneously The difference in the pressures generated by the two gages is reduced to a level beyond the performance of the measurements process The degree to which the pressures are matched and the random uncertainty of the measurement process contributes to the total uncertainty is limited by the performance of the system which is only as good as the worst component or aspect of the system To obtain a level of performance in the crossfloat system that is better than a few parts in one hundred thousand not only must both piston cylinder assemblies be of sufficiently high quality but some means of amplification of pressure or float position will also be necessary Several methods of crossfloating using such electronic aids exist that enable adjustment of the loads and matching of the pressure to less than one part per million PISTON PRESSURE GAGE 2 12 2 6 10 11 12 BIBLIOGRAPHY Bridgman P W The physics of High Pressure G

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