Pressure Seal Instruction Manual
Contents
1. 2 I lt A AN E uu 2 525 Ew O S gt 055 gt lt lt ABE 2 gt 22 mos o E zz E Oz 2 525 26 222 R di BPA 9 gt 2 2 ao R N 27 D Gr gt SSN 223 EG 7 AS N Fi N N NDAB SINCE V 1846 Powell Pressure Seal Valves are built to high standards of precision and accuracy and must pass rigid inspection before leaving the factory It is imperative that the valves be properly installed maintained and operated to assure satisfactory performance The purpose of this service manual is to instruct installation crews maintenance foremen and operating personnel in these fundamentals This manual should be kept available to these presonnel at all times so that they may become familiar with the details of these valves Powell Pressure Seal Valves are intended for high pressure high temperature services of all fluids where severe coking is not a factor They are guaranteed to be in good condition however we assume no responsibility for damage to valves due to faulty installation improper operation or other conditions beyond our control THIS BOOK IS REGISTERED IN THE NAME OF SERIAL NO ADAPTO GEAR OPERATED VALVES Upper Assembly ANGLE VALVES Bonnet Take Up Screw Design B2. f LS 5542 AN 001 00220020700 4 SN N v 77 Bonnet Stud Design EYEBOLT amp NUT TAKE UP SCREW SPLIT THRUST RING FACE RING YOKEARM BONNET PROTECTIVE RING STEM BODY EYEBOLT amp NUT YOKEARM EYEBOLT CLAMP BONNET STUD amp NUT YOKEARM STUD amp NUT SEGMENTAL THRUST RING GASKET STEM BODY O S amp Y GATE VALVE BONNET LOCKNUT DESIGN MONS Ai R STEM BUSHING NUT N AR 2 0 SPA DNL ENEY N 2 ges NJ NNS STEM BUSHING 512 AN STEM BUSHING RETAINING NUT 52 AR SET SCREW GREASE FITTING 2 ARES BEARING THRUST WASHERS Si HERS YOKEARM 22 13 E li Lid 12 2 PACKING GLAND FLANGE PACKING GLAND EYEBOLT amp NUT FYN 22 2 LT STJERT TISS uL 155 EYEBOLT CLAMP PACKING M D Z TT fm ss seen E HER 1 BONNET LOCKNUT BC AS BONNET LOCKNUT WASHER KNOCKOUT HOLE Zu 20 SEGMENTAL THRUST RING GASKET IN 7 SS AY 2 mr STEM 2 45472777 29 22222223 SEAT RING 127 ES WEDGE 2 BODY DISASSEMBLY BONNET LOCKNUT DESIGN T 2228 KE A 15 sri Kh 1 a Make sure there is no pressure in the valve ISSN b sling should be provided for removing the yokearm and upper assembly
3. SS ic SS 7A 022252 e TT FI 2 Place the valve in the half open position This relieves any pressure trapped in the bonnet chamber ZA v 077111 b Remove eyebolt nuts and eyebolt bolt nuts Remove eyebolt bolts eyebolts and eyebolt clamp BEST NN 654843 22 SS 111 222 LAA SAWN RSS 25 c Remove the yokearm nuts SN STN PR 2 d Completely loosen bonnet locknut UV A 22 2 e Tap the bonnet until it slides into the body and frees the segmental thrust ring 11 222 272 551 zm ZZ 6 1 4 A M LNG NS 2 SN 22 88886 2272 c gt 18 2223 222222 lt lt N 226022245 18 MZ NY MG ical ANG T GIT ZZ ii a b d a b 249 Close the valve Continue to turn the handwheel in a clockwise direction This will separate the yokearm from the body Stop separating the yokearm when it is approximately 2 apart from the body Apply penetrating oil to the segmental thrust ring and gasket seating area Insert pin in the knockout hole and remove the segmental thrust ring as illustrated on page 42 Insert equally spaced spreader block of equal height approximately 2 thick between the bo
4. 2 RETAINER PLATE ANEN EIN 2 PROTECTIVE RING SSN KNOCKOUT HOLE a t N AS v N Y GUIDE PIN 52 BODY ids 2 22 2 SEGMENTAL THRUST 1 S SS IX DISC KEY 2 gt 2 220 UV SENT RING GLOBE NON RETURN STOP CHECK VALVE BONNET STUD DESIGN HAMMERBLOW HANDWHEEL CROSSARM GEAR BEARING CAP SCREW BEARING CAP amp BRACKET OIL SEAL RETAINER PLATE STEM BUSHING NUT SS GREASE FITTING EY ANTI FRICTION BEARINGS EYEBOLT amp NUT PACKING GLAND FLANGE PACKING GLAND PACKING KNOCKOUT HOLE SEGMENTAL THRUST RING GASKET BONNET DISC STOP PIN BODY DISC GUIDE STEM SEAT RING 2 1 key Sy ED GKEY BUSHING 252 EYEBOLT CLAMP EYEBOLT BOLT amp NUT BONNET STUD amp NUT YOKEARM STUD amp NUT PACKING WASHER PROTECTIVE RING 65 5 66 5 67 Jc POWELL VALVES EOPLE WHO KNOW VALVES KNOW POWELL
5. residue from the lapping and bearing check operations must be removed from all parts including the body 255 UPPER GUIDE PLATE FIGURE 5 COMPONENT PARTS OF THE PRESURE SEAL JOINT SEGMENTAL THRUST RING SEGMENTAL THRUST RING Four Segments Eight Segments HARDENED STAINLESS STEEL PROTECTIVE RING METAL GASKET 57 DETAIL OF THE POWELL PRESSURE SEAL JOINT KNOCKOUT HOLE SEGMENTAL THRUST RING HARDENED STAINLESS MAN STEEL PROTECTIVE RING RING amp PROTECTIVE RING 010 5 BODY BONNET SEALING SURFACE SEALING SURFACE KNOCKOUT HOLE SEGMENTAL THRUST RING HARDENED STAINLESS MAXIM UM UM CLEARANCE STEEL PROTECTIVE RING BETWEEN SEGMENTAL RING amp PROTECTIVE RING 010 GASKET BONNET BODY 284 SEALING SURFA SEALING SURFACE DELTA DESIGN 58 Y GLOBE VALVE BONNET TAKE UP SCREW DESIGN BOLTED YOKEARM STYLE HANDWHEEL STEM BUSHING HANDWHEEL NUT YOKEARM STEM PACKING GLAND SPLIT THRUST RING TAKE UP FLANGE PACKING WASHER 1 U hE FY PAY GREASE SEGMENTAL THRUST RING FITTING CRORE 1 8 SCREW 7 LOCKNUT WASHER d DI K N Jan DISC LOCKNUT X ATI 4 e EYEBOLT amp NUT ONS S SS SES PACKING SG TAKE UP SCREW S FACE RING BODY CE TI UTTILLID YOKEARM STUD amp NUT THRUST WASHER KNOCK
6. It is essential to install a new gasket whenever the pressure seal joint is broken See page 47 for special instructions b Protective ring is oversize and must be machined or ground to fit valve N2 SS NN SN S N c Putthe packing washer and gland on the S SSE A 4 stem 4 8 Place the yokearm assembly over the stem As soon as the stem protrudes through the base of the yokearm install the face ring the take up flange with eyebolts installed and grand flange Continue to lower the yokearm assembly and screw the stem bushing onto the stem by turning the handwheel in a counterclockwise direction b Raise the wedge off the seat and screw yokearm into the body making sure not to force the wedge into the body If the wedge seats raise the wedge by turning the handwheel in a counterclockwise direction EUR 5 Close valve b Install packing with the cut in the packing rings staggered 4 rr c Install the split thrust ring and take up screws The take up screws are to be LI ITT ITT Unus NNN Nr NS thoroughly lubricated with oil and graphite HANG g v 2 prior to installation d Install and tighten the eyebolt nuts AA 122222 223 SS 2224 6 Open valve until back seat shoulder seats solidly in the bonnet to set the gasket Zs SSS B
7. KNOCKOUT HOLE GASKET BODY PACKING GLAND FLANGE PACKING GLAND TAKE UP FLANGE PACKING PACKING WASHER YOKEARM KNOCKOUT HOLE GASKET BONNET BODY 217 2 Sy 27222290 SUT TT TITTIES N d UNS M N yi 22 2 IN ig N C22 Fy 2 ew oe NS 1065 y T RSS NN 17 KA ss Bonnet Locknut Design ATT SS RS g Y 2122 WY IN 2 NN PER NN KL oe i Bonnet Take Up Screw Design Bolted Yokearm Style 8 PACKING GLAND FLANGE PACKING GLAND PACKING BONNET LOCKNUT BONNET LOCKNUT WASHER SEGMENTAL THRUST RING PROTECTIVE RING BONNET STEM EYEBOLT amp NUT TAKE UP SCREW SPLIT THRUST RING YOKEARM STUD amp NUT FACE RING SEGMENTAL THRUST RING PROTECTIVE RING STEM PACKING GLAND FLANGE PACKING GLAND TAKE UP FLANGE PACKING PACKING WASHER GASKET PACKING GLAND FLANGE PACKING GLAND PACKING PACKING WASHER KNOCKOUT HOLE PROTECTIVE RING BONNET et TW 1122 BAT SV HANS AWA SAA Bonnet Take Up Screw Design Threaded Yokearm Style SAN LRS _ 2 4 4 N IN 222 PU TT
8. E E S N Ne b Tighten the take up screws to the torque NO valves specified in Table I E HAB SA HAS nU B TABLEI NA SAN 22 27 2 Screw Size Torque 22 2 ft Ibs Ah D 45 3 3 111 3 4 150 TAI 33 O S amp Y GATE VALVE BONNET STUD DESIGN STEM BUSHING NUT NAN OIL SEAL m is HA LE ASS H IDA WE 112277 GREASE FITTING x STEM BUSHING N GLAND SHELF ONES P dram Ma OP JL 1 PT PACKING GLAND FLANGE VET NERS PACKING GLAND N NH EN Nd BN PACKING WASHER 2 KNOCKOUT HOLE EN 222 PROTECTIVE RING Kex 52 NN BONNET 7 22 22222 as fam X Y SS aus rm 207 5 SUNS NN I HANDWHEEL KEY HANDWHEEL BEARING CAP SCREW ANTI FRICTION BEARINGS OIL SEAL YOKEARM EYEBOLT amp NUT EYEBOLT CLAMP BONNET STUD amp NUT YOKEARM STUD amp NUT SEGMENTAL THRUST RING GASKET STEM BODY SEAT RING WEDGE DISASSEMBLY BONNET STUD TYPE 1 a Make sure there is no pressure in the valve b Asling should be provided for removing the yokearm and upper assembly 2 a Placethe valve
9. 6 a Closethe valve This will permit the bonnet to rest lightly in the body b The yokearm and upper assembly should now be removed intact This may be done by turning the handwheel in a clockwise direction until the stem bushing comes free of the stem A sling should be used for lifting the upper assembly after it has been freed The packing gland flange is removed during this operation as it clears the top of the stem For other types of Upper Assemblies such as Bevel Gear etc see pages 43 44 45 and 46 7 Liftthe bonnet along with the gland protective ring and gasket out of the body care being taken not to scar the gasket seating surface of the body 8 a Mark the wedge and body so that the wedge may be re installed in the same orientation b Remove the stem and wedge If no work is to be done on the wedge it should be reinstalled in the body carefully so no damage is done to the seating surfaces 28 REASSEMBLY BONNET STUD DESIGN 1 a The gasket seating surfaces of the body and bonnet should be lapped and free of any scars See pages 48 and 49 b Seatring and wedge seating surfaces should be inspected and repaired if necessary See pages 50 and 51 for instructions for repairing gate valve seats pages 52 through 56 for instructions for repairing globe and angle type valve seats c Clean the body and bonnet seating surfaces 2 a Putthe wedge and stem in place making sure the w
10. 92225225 OG OG ENN 222 RK pA yokearm will now lower against the spreader blocks GE KD li C ee Li SESS EN 28 5 8 111 72 2 Se el 52754 525 2 252 225 25 2 SN LEGE EZ oo 32 gt 2252 2255 NE 1 Pr Y UA b 2 22 INNS wT ot WAAAY INN NNN l VA pat 559777 gt 7 29 Continue to turn handwheel in counterclockwise direction As the back seat shoulder of the stem seats against the bonnet the bonnet gasket and protective ring will be raised from the body Close the valve This will permit the bonnet to rest lightly in the body The yokearm and upper assembly should now be done by turning the handwheel in a clockwise direction until the stem bushing comes free of the stem A sling should be used for lifting the upper assembly after it has been freed The packing gland flange take up flange and face ring are removed during this operation as they clear the top of the stem For other types of U
11. AND COUNTERCLOCKWISE COMPOUND EVENLY ON THE BEVELED SURFACE APPROXIMATELY A QUARTER TURN RAISE THE LAP KEEPING THE OTHER SURFACES CLEAN OFF THE SEAT SLIGHTLY AT FREQUENT INTERVALS AND TURN APPROXIMATELY A HALF TURN AND CONTINUE LAPPING Y CLEAN THE LAPPED SURFACES AND RUB A SMALL AMOUNT OF BLUING ON THE LAP ROTATE THE LAP APPROX 15 DEGREES OVER THE BONNET SEATING SURFACES AND THEN CHECK THE SURFACE FOR IMPERFECTIONS IF THE SURFACE IS NOT PERFECT MORE LAPPING IS REQUIRED 48 WITH BEVEL AGREE WITH THE ANGLE THE BODY SHOULD BE USED SPREAD A VERY FINE COMPOUD ON THE BEVELED SURFACE OF THE LAP INSERT THE LAP INTO THE BODY KEEPING THE OTHER SURFACES CLEAN LAP THE SEAT BY ROTATING THE LAP CLOCKWISE AND COUNTERCLOCKWISE APPROXIMATELY A QUARTER TURN RAISE THE LAP OFF THE SEAT SLIGHTLY AT FREQUENT INTERVALS AND TURN APPROXIMATELY A HALF TURN AND CONTINUE LAPPING CHECK THE SEAT PERIODICALLY WITH BLUING AS PREVIOUSLY DESCRIBED IF THE SEAT IS NOT PERFECT MORE LAPPING IS REQUIRED 49 INSTRUCTIONS FOR REPAIR GATE VALVE SEATS FIGURE 1 FIGURE 2 WEDGES A wedge circling plate should be used to remove mars or scoring from the wedge seating faces This can be accomplished either manually as illustrated in Figure 2 with oscillating movement of the circling plate and pressure applied downward on the handles or by rotating the circling plate with a right angle drive air wrench driving
12. the plate through the square in the top of the plate and pressure applied to the wrench above the square as illustrated in Figure 3 SEAT RINGS A seat ring circling plate rotated by means of a right angle drive air wrench and pressure applied by a pressure bar should be used to remove mars or scoring from seat ring faces as illustrated in Figure 1 FIGURE 3 Emery paper is installed between the circling plate and the guide plate prior to the circling operation on the wedge and or seat rings Grit No 40 80 or 150 emery paper is used depending on the severity of mar or scoring on the seating face Progressive circling operations should be accomplished starting with the initial grit of emery paper used through each of the finer grits the final polishing operation being with No 150 grit 50 After completion of the circling and polishing operations the seating surfaces of the wedge seat rings should be thoroughly cleaned A small amount of bluing should then be rubbed on both faces of the wedge the wedge installed in the body in the seated position and tapped with a brass bar The wedge should then be removed from the body by tapping on the outside of the valve body to jar the wedge loose Both faces should be examined to insure that there is a complete round bearing Prior to reassembly of the valve the inside of the body and the entire wedge should be examined and any grit from the circling operation removed The face
13. the upper assembly after it has been freed The packing gland flange take up flange and face ring are removed during this operation as they clear the top of the stem For other types of Upper Assemblies such as Bevel Gear etc see pages 43 44 45 and 46 FA A A 21 7 Liftthe bonnet along with the gland protective ring and gasket out of the body care being taken not to scar the gasket seating surface of the body 8 a Mark the wedge and body so that the wedge may be re installed in the same orientation b Remove the wedge and stem If no work is to be done on the wedge it should be re installed in the body carefully so no damage is done to the seating surfaces 22 REASSEMBLY BONNET TAKE UP SCREW DESIGN BOLTED YOKEARM STYLE 1 a The gasket seating surfaces of the bonnet and body should be lapped and free of any scars See pages 48 and 49 b Seatring and wedge seating surfaces should be inspected and repaired if necessary See pages 50 and 51 for instructions for repairing gate valve seats pages 52 through 56 for instructions for repairing globe and angle type valve seats c Clean the body and bonnet seating surfaces V R hr N ALL 2 Put the wedge and stem in place making 27 sure the wedge has the same orientation as when disassembled b Insert the bonnet into the body 23 3 Putanew gaske
14. E RING SEGMENTAL THRUST RING GASKET BONNET STEM DISC LOCKNUT WASHER DISC LOCKNUT 2 BODY N 272 iN E SN THRUST WASHER 2 IND DISC amp GUIDE GANG ANS LL 22222 Np 27 e SEAT RING 61 GLOBE VALVE BONNET STUD DESIGN TYPE B SEGMENTAL GUIDE RETAINING RING STEM BUSHING NUT RETAINER PLATE GREASE FITTING M 7 HAMMER mnm VA CROSSARM an AY 848 SCREW RERA NN ANTI FRICTION BEARINGS STEM BUSHING AEN 2 AE SET SCREW 2 VS YOKEARM d KEY BUSHING Ny Eis PACKING GLAND FLANGE EYEBOLT amp NUT EYEBOLT CLAMP PACKING Ll BONNET STUD amp NUT PACKING WASHER SSS KNOCKOUT HOLE T GASKET WV GUIDE PIN SP 2222 PACKING GLAND EYEBOLT BOLT amp NUT BONNET YOKEARM STUD amp NUT SEGMENTAL THRUST RING PROTECTIVE RING SEGMENTAL GUIDE RETAINING RING STEM DISC GUIDE BODY DISC SEAT RING Y CHECK VALVE KNOCKOUT HOLE SEGMENTAL THRUST RING PROTECTIVE RING CAP STUDS amp NUTS Y CHECK VALVE THREADED RETAINER STYLE CAP STUD amp NUT RETAINER PLATE CAP PROTECTIVE RING DISC GASKET SEAT RING 4 BODY 63 HORIZONTAL CHECK VALVE TYPE B SEGMENTAL GUIDE RETAINING RING CAP STUDS amp NUTS un m
15. EAKS should be corrected promptly by tightening the packing gland nuts Failure to do this may result in damaged packing and inability to stop the leak until new packing is installed 2 Powell Pressure Seal Valves have a BACK SEAT on the stem which seats against a stellited guide in the bonnet when the valve is fully opened This seat will hold pressure if both surfaces are clean however this is difficult to determine and consequently packing a valve under pressure is hazardous and not recommended 3 LUBRICATION of the stem bushing is required periodically This is accomplished by grease fitting on the side of the bushing housing Lubricant should be added until it starts to extrude around the stem threads Mobil Grease Type AA No 2 or equal is recommended 4 5 SPECIAL TOOLS are available for the general maintenance of Powell Pressure Seal Valves a Torque Wrench b Laps for pressure seal joint c Grinder for pressure seal body seat d Tools for repairing valve sealing surfaces REPLACEMENT PARTS are seldom necessary when a Powell Pressure Seal Valve is properly installed and maintained However it is wise to stock packing for each valve If a valve be disassembled for any reason a new gasket should be installed VALVE IDENTIFICATION AND REFERENCE 1 2 3 A NAMEPLATE is located on the yokearm of all pressure seal Gate and Globe Valves and on neck of body on all Check Valves When ORDERING REPAIR PARTS
16. HOUSING BALL BEARING OIL SEAL END BUSHING d de OIL SEAL DRIVE SLEEVE ONS PIPE PLUG CAP SCREW WHEEL GEAR CAP EZR BALLS j m RETAINING RING BASE Ill um ADAPTOR er 2201 SLEEVE HANDLE OIL SEAL BEARING CAP 1m STEM BUSHING GREASE FITTING ANTI FRICTION BEARINGS YOKEARM ALTITTIITTIT 111111111110 rn TT CMT JED 45 UPPER ASSEMBLY OF GEARED BLOW HANDWHEEL For Portable Air Wrench Operation INDICATE LINES HEX FOR AIR WRENCH 1 2 1 0008 NES e Great RE N SSE d LASS frit 1 74 222220222 DU JU y REALT 46 SPECIAL INSTRUCTIONS FOR LAPPING OR GRINDING OR THE PRESSURE SEAL GASKET SEAT THE BODY FOR VALVES WITH TAPERED BODY NECK DESIGN If the pressure seal gasket seat in the body has steam cuts extensive lapping may be necessary This results in a dropping of the pressure seal seat in the body The maximum allowable clearance between the segmental thrust rings and the protective ring is 010 inches see drawing page 58 If extensive lapping causes a greater clearance an oversize protective ring must be installed These are normally supplied 1 16 over
17. ING LIST as a part of the permanent records of these valves UNLOADING of valves should be done with care Remember that although a valve is a rugged piece of equipment it may still be damaged by abusive handling Skidded valves should not be removed from skids until immediately before installation LIFTING LUGS incorporated on the yokearm of many Pressure Seal Valves greatly facilitate handling IMPROPER INSTALLATION of a valve can have very serious consequences resulting in possible malfunction which may necessitate extensive and costly repairs Compliance with the following recommendations will do much to assure satisfactory performance of the valve after installation 1 CLEANING of fluid passage seating surfaces of all valves should be accomplished before installation 2 Provisions should be made for SUPPORTING THE VALVES and adjacent piping so that pipe line stresses will not be transmitted to the valve bodies 3 WELDING and stress relieving should conform to the A S M E Boiler Code Valve stems should be opened slightly during preheat welding post heating operations 4 CLEANING OF THE PIPE LINES in which valves are installed and all connecting lines is essential before the unit is put in operation Welding beads scale and foreign matter in the lines cause damage to the valve seats resulting in leakage 5 INSULATION should not be applied to the valve above the knockout holes OPERATION AND MAINTENANCE 1 PACKING L
18. N STEM BUSHING RETAINING NUT NVI ENS NY NR SET SCREW 554 BEARING THRUST WASHERS N YOKEARM f HRS EYEBOLT amp NUT umi TAKE UP SCREW li AW M SPLIT THRUST RING ENG YOKEARM STUD NUT SAY S RSS FACE RING SEGMENTAL THRUST RING AN PROTECTIVE RING BANG 2 STEM 2 BODY LT LI e 4 AH 2 212 N DISASSEMBLY BONNET TAKE UP SCREW DESIGN BOLTED YOKEARM STYLE 17 2 52 LA SSS Vi S X 2 S NRA N 2 2 2 Ny N AN 2 Loud Spe 7 PA KSS Se DIS IIS ry 1 Make sure there is no pressure in the valve 2 2 2 b Asling should be provided for removing the yokearm and upper assembly A 22 SSS 127 ec lt 2 SN 15 2 Placethe valve in the half open position 5 AR This relieves any pressure trapped in the IA bonnet chamber d b Remove nuts from the eyebolts 7 QA Y E 422 08001 c Remove the yokearm nuts firftnirsssd 281081011828 22 22 29 N 46 E A y 2222 ANN d Remove the take up screws and split thrust ring 2 T7777 2 NG e Tap the bonnet until it slides into the body and frees the segmental thrust ring 19 3 Closethe valve b Continue t
19. OUT HOLE PROTECTIVE RING GLAND FLANGE 59 ANGLE VALVE BONNET TAKE UP SCREW DESIGN BOLTED YOKEARM STYLE DELTA SEAL GASKET STEM BUSHING NUT HAMMERBLOW HANDWHEEL RETAINER PLATE EM REASE FITTING 3 22 CROSSARM TV SPACER COLLAR OIL SEAL 5 FRA NR BEARING CAP SCREW GREASE FITTING pus BEARING CAP ANTI FRICTION BEARINGS 2 STEM BUSHING EYEBOLT amp 7 22 aa KEY BUSHING YOKEARM PACKING GLAND FLANGE PACKING GLAND NTT 22 OIL SEAL Y p CD KEY TAKE UP SCREW PACKING SPLIT THRUST RING 1 7 TAKE UP FLANGE lt FACE RING PACKING WASHER KNOCKOUT HOLE PROTECTIVE RING BONNET ILILILIILEZZ ota RS 5 SN 27 AN SEGMENTAL THRUST RING E GASKET BONNET STUD amp NUT ren TAKE UP SCREW po DISC SEAT RING BODY SKETCH SHOWING SQUARE NECK FLANGE 60 GLOBE VALVE BONNET STUD DESIGN HANDWHEEL NUT athe 2 HANDWHEEL Im STEM BUSHING AE GREASE FITTING 223 SET SCREW LT amp NUT HETE mA EYEBO U SLN PACKING GLAND FLANGE PACKING GLAND M EYEBOLT CLAMP N PACKING N EYEBOLT BOLT amp NUT BONNET STUD amp NUT YOKE PACKING WASHER ARM STUD amp NUT KNOCKOUT HOLE PROTECTIV
20. damage is done to the seating surfaces 22 2442 REASSEMBLY BONNET LOCKNUT DESIGN 1 8 sisa The gasket seating surfaces of the bonnet and body should be lapped and free of any scars See pages 48 and 49 Seat Ring and wedge seating surfaces should be inspected and repaired if necessary See pages 50 and 51 for instructions for repairing gate valve seats pages 52 through 56 for instructions for repairing globe and angle type valve seats Clean the body and bonnet seating surfaces Put the wedge and stem in place making sure the wedge has the same orientation as when disassembled Insert the bonnet into the body 3 b c d 4 8 NN EL 2 N 2 222 2 71 WY 72722 a 555 5555 yy 16 Put a new gasket in place making sure all surfaces are clean It is essential to install a new gasket whenever the pressure seal joint is broken See page 47 for special instructions Protective ring is oversize and must be machined or ground to fit valve Insert the segmental thrust ring see sketch on page 42 Put the packing washer and gland on the stem Place the yokearm assembly over the stem As soon as the stem protrudes through the base of the yokearm install the bonnet locknut washer the bonne
21. dy and yokearm contact surfaces Turn the handwheel counter clockwise The yokearm will now lower against the spreader blocks 5 Continue to turn the handwheel in a counter clockwise direction As the back seat of the stem seats against the bonnet the bonnet gasket and protective ring will be raised from the body i S ED Y nl NN ENS em 12772277 6 Closethe valve This will permit the bonnet to rest lightly in the body b The yokearm and upper assembly should now be removed intact This may be done by turning the hand wheel in a clockwise direction until the stem bushing comes free of the stem A sling should be used for lifting the upper assembly after it has been freed The packing gland flange bonnet 7 locknut and bonnet locknut washer are 7 removed during this operation as they clear 7 the top of the stem 2 2 22 4 9 2 For other types of Upper Assemblies such as Bevel Gear etc see pages 43 44 45 and 46 13 7 Lift the bonnet along with the gland protective ring and gasket out of the body care being taken not to scar the gasket seating surface of the body 1 8 a Mark the wedge and body so that the wedge may be re installed in the same orientation b Remove the wedge and stem If no work is to be done on the wedge it should be re installed in the body carefully so no
22. eat using the same procedures ball seat on the disc should be examined and any damage repaired before proceeding with the lapping of the disc to the seat On swivel disc design globe and angle valves it will be necessary to remove the disc locknut washer to eliminate the end play in the stem and disc assembly also insert pin in regrinding pin hole on the side of the hexagon of the disc nut making sure that the pin goes through the regrinding pin hole in the stem to insure rotation of the disc with the stem by means of the valve handwheel during the lapping operation On globe and angle valves which have a one piece stem and disc it will be necessary to install the special handle provided to facilitate rotation The key in the handle collar fits the keyway in the stem and the handle is maintained in position on the stem by means of lockscrews On non return stop check and check type valves a disc driver is bolted to the disc at the tapped holes in the top of the disc as illustrated in Figure 5 to facilitate rotation of the disc The upper lap guide and spring arrangement are again used as previously described for lapping operations with the lap Lapping operation should be accomplished following the procedures as previously described After completion of lapping check for bearing as previously outlined A full round narrow bearing should be obtained to insure a tight seat Prior to assembly all parts should be thoroughly cleaned
23. edge has the same orientation as when disassembled b Insert the bonnet into the body 39 3 Putanew gasket in place making sure all surfaces are clean It is essential to install a new gasket whenever the pressure seal joint is broken See page 47 for special instructions 72272728 b Protective ring is oversized and must be machined or ground to fit valve c Insert the segmental thrust ring See sketch on page 42 d Putthe packing washer and gland on the stem 4 Placethe yokearm assembly over the stem As soon as the stem protrudes through the base of the yokearm install the gland flange Continue to lower the yokarm and screw the bushing onto the stem NEP gt 4 28 722722224 dE b Raisethe wedge off the seat slightly SS M S 553 NS 5 Thoroughly lubricate the threads of the N N bonnet studs with a mixture of oil and 5 5 graphite 211 2 2 For other types of upper Assemblies such as Bevel Gear etc see pages 43 44 45 and 46 40 d 283 ih BD LN XY d e 6 BA Ne wi 55 b ANINA NW BAS all 11 LL M Vag 6 41 Install eyebolt clamp and eyebolts Install and tighten the nuts on the yokearm studs Close valve Install packing with the cut in the pack
24. i 6 Open valve until back seat shoulder seats solidly in the bonnet to set the gasket 2 2244 771622 b Tighten the take up screws to the torque values specified in Table I TABLEI Screw Size Torque inches ft Ibs 1 2 45 5 8 90 3 4 150 7 8 240 1 368 1 1 8 533 25 HANDWHEEL GREASE FITTING T PACKING GLAND FLANGE WIZ PACKING GLAND TAKE UP FLANGE PACKING PACKING WASHER GASKET 5 GATE VALVE BONNET TAKE UP SCREW DESIGN THREADED YOKEARM STYLE STEM BUSHING NUT 2222 222222 E IN l l X HANDWHEEL KEY NN 222 LAT iN 2222 202 K 7 A STEM BUSHING RETAINING NUT 2 SCREW N 2 2 SET SCRE NESS STEM BUSHING WS DR YOKEARM IZ EYEBOLT amp NUT 22 JF lt a NL Tie TAKE UP SCREW 05 SPLIT THRUST RING M D Bs ARS FACE RIN WAS 2 28 NG BONNET 7A Gr 27 PROTECTIVE RING OD WS 2 2 STEM 2 2 BODY 2 65525 7 GNU H WA 26 DISASSEMBLY BONNET TAKE UP SCREW DESIGN THREADED YOKEARM STYLE 55 2 ES 41 S ERIILIIDIMILUK 22 1 LIII 5 Tz I ES TO S55 NN MINT NE 1 Make sure there
25. in the half open position This relieves any pressure trapped in the bonnet chamber b Remove nuts from the eyebolts and remove the eyebolt clamp c Remove the yokearm nuts d Remove the bonnet nuts e Tap the bonnet until it slides into the body dra and frees the segmental thrust ring 3 8 b N N Sess sss 12 SSS Is d 4 8 b 36 Close the valve Continue to turn the handwheel in a clockwise direction This will separate the yokearm from the body Stop separating the yokearm when it is approximately 3 apart from the body Apply penetrating oil to the segmental thrust ring and gasket seating area Insert pin in the knockout hole and remove the segmental thrust ring as illustrated on page 42 Insert equally spaced spreader blocks of equal height approximately 3 thick between the body and yokearm contact surfaces Turn the handwheel counterclockwise The yokearm will now lower against the spreader blocks c WEE E D 227254 95 EN LILL 22 g 2 7222748 5 Continue to turn the handwheel in a counter clockwise direction As the back seat shoulder of the stem seats against the bonnet the bonnet gasket and protective ring will be raised from the body T a d eX D 21 pq 7 i a 24 AT 2 et s
26. ing rings staggered Install and tighten nuts on eyebolts Open valve until back seat shoulder seats solidly in the bonnet to set the gasket Install and tighten the nuts on the bonnet studs to the torque valves as specified in Table I TABLEI Screw Size Torque inches ft Ibs 1 2 45 5 8 90 3 4 150 7 8 240 1 368 1 1 8 533 1 1 4 750 1 3 8 1020 1 1 2 1200 Types of Segmental Thrust Rings showing the location of the segments in relation to the Knockout Holes Knockout Pin Segments on Valve Center lines must be removed first 21 Pin Eight Segment Ring 3425 Upper Assembly of Bevel Gear Operated Valves gt Handwheel Pinion Shaft Stem Bushing Nut Pinion En ET gl B gt 2 KF hu f rni qm Con Stem Gear lt Ln m Anti tal nti Friction I Bearings n 13 A Oil Seal 27 Ld Oil Seal nm ES n ONO m T Bearing Cap and Bracket OR E Yokearm 1 11101 AR JH o Upper Assembly of Spur gear Operated Valves Handwheel Pinion Shaft f Stem Bushing Nut Stem Gear Stem Bushing Anti Friction Bearings Oil Seal Yokearm Bearing Cap and Bracket Upper Assembly of Motor Operated Valves UPPER ASSEMBLY ADAPTO GEAR OPERATED VALVES PINION amp SHAFT HANDWHEEL
27. is no pressure in the valve SSA WANS b sling should be provided for removing the yokearm and upper assembly BS 7 2 2 Placethe valve the half open position T This relieves any pressure trapped in the bonnet chamber b Remove nuts from eyebolts c Remove the take up screws and split thrust ring d Unscrew yokearm from the body If the back seat shoulder of the stem seats against the bonnet during the unscrewing of the yokearm it will be necessary to turn the handwheel in a clockwise direction to lower the stem and wedge into the body before proceeding with the unscrewing of the yokearm Note that the threads on the yokearm are right hand 27 Close the valve b Continue to turn handwheel in clockwise direction This will separate the yokearm from the body Stop separating the yokearm when it is approximately 2 apart from the body He 72227455 m S gt SIS SU A Br SN Apply penetrating oil to the thrust ring and gasket seating area NNNSSSNSNNN NNN NN 2 get 4 799 51 22 a Insert equally spaces spreader block of equal c N height between the body and yoke arm contact surfaces b Turn the handwheel counterclockwise The
28. ith strips of 40 grit emery paper inserted between the lap plate and the lower guide plate as illustrated in Figure 1 Follow with another circling operation using 80 grit emery paper and a final polishing operation using 150 grit emery paper FIGURE 1 252 An upper lap guide assembly should be used during all circling and polishing operations The upper guide assembly is to be bolted to the top of the body on all globe angle and non return stop check type valves and screwed into the neck of the threaded retainer style check valves Most guide assemblies for other style check valves are provided with brackets which extend down over the O D of the body and lock screws facilitate holding the guide in place If this feature is not provided it will be satisfactory in most cases to proceed without bolting the guide assembly to the body Rotation of the lap should be by means of an air wrench attached to the top of the lap shank Figure 2 illustrates typical tool set up used in the circling and polishing operations 222 FIGURE 2 53 SPRING HANDLE UPPER LAP GUIDE LAP SEAT RING SEAT RING LAP SPRING UPPER LAP GUIDE HANDLE FIGURE 4 54 circling and polishing operations the body seat or seat ring should be followed by lapping operation using the lap without the strips of emery paper Spread a fine lapping compound evenly on the beveled surface of the lap The
29. ng Standard Alloy Cast Steels Cast Carbon Steel AS T M Specification A216 Grade WCB Powell P 200 Cast Chromium Molybdenum Steel A S T M Specification A217 Grade WC6 Powell P 211 3 Cast Chromium Molybdenum Steel A S T M Specification A217 Grade WC9 Powell P 416 Cast Chromium Nickel Steel A S T M Specification A351 Grade CF8 Powell P 172 Cast Chromium Molybdenum Nickel Steel A S T M Specification A351 Grade CF8M Powell P 174 Valves can also be furnished in Special Alloy Cast Steels for special services where ultra high temperatures and other un usual conditions are encountered All Powell Pressure Seal Valves are kerosene tested before shipment DISASSEMBLY AND REASSEMBLY OF THE PRESSURE SEAL JOINT Disassembly and reassembly of the Pressure Seal Joint is simple if directions are followed Powell Pressure Seal Valves utilize four types of design 1 Bonnet Locknut Design 2 Bonnet Take Up Screw Design Bolted Yokearm Style 3 Bonnet Take up Screw Design Threaded Yokearm Style and 4 Bonnet Stud Design Although Gate Valves are illustrated with the disassembly and reassembly instructions for the various types of Powell Pressure Seal Joint Designs on the following pages these instructions also apply with minor modifications to Globe Angle Non Return Stop Check and Check Valves EYEBOLT amp NUT EYEBOLT CLAMP YOKEARM STUDS amp NUTS PACKING WASHER YOKEARM
30. o turn the handwheel in a clockwise direction This will separate the yokearm from the body Stop separating the yokearm when it is approximately 2 apart from the body c Apply penetrating oil to the segmental thrust ring and gasket seating area d Insert pin in the knockout hole and remove the segmental thrust ring as illustrated on page 42 7 2 AA Wiig 17272 KAN a D 4 a Insert equally spaced spreader block of equal height approximately 2 thick between the body and yokearm contact surfaces b Turn the handwheel counterclockwise The yokearm will now lower against the spreader blocks AL N rud He 10227102 I I pct SN 2203 AS SE 2 KS 959421 2277 2 NS TEM Es 17 2 5 Continue to turn the handwheel in a counterclockwise direction As the back seat of the stem seats against the bonnet the bonnet gasket and protective ring will be raised from the body BERE S 20 27 imn n ri M 27 MG 6 Close the valve This will permit the bonnet to rest lightly in the body 1 ig b The yokearm and upper assembly should now be removed intact This may be done by turning the handwheel in a clockwise direction until the stem bushing comes free of the stem A sling should be used for lifting
31. olted Yokearm Style Instruction for Repair of Valve Seats CHECK VALVES Check Check Threaded Retainer Style Horizontal Check COMPONENT PARTS OF PRESSURE SEAL JOINT DIAGRAMATIC DESCRIPTION Pressure Seat Joint Bonnet Locknut Design Bonnet Take Up Screw Design Bolted Yokearm Style Bonnet Take Up Screw Design Threaded Yokearm Style Bonnet Stud Design Angle Valve Check Valve Horizontal Check Valve Y Gate Valve Locknut Design Gate Valve Take Up Screw Design Bolted Yokearm Style Gate Valve Take Up Screw Design Threaded Yokearm Style Gate Valve O S amp Y Bonnet Stud Design Globe Valve Globe Valve Bonnet Stud Design Globe Valve Bonnet Stud Design Hammer Blow Handwheel Globe Non Return Stop Check Valve DISASSEMBLY Bonnet Locknut Design Bonnet Take Up Screw Design Threaded Body to Yokearm Design Bonnet Stud Design GATE VALVES Bonnet Locknut Design Bonnet Take Up Screw Design Bolted Yokearm Style Bonnet Take Up Screw Design Threaded Yokearm Style Bonnet Stud Design Instructions for Repair of Seats Tools for Repairing Seats GEARING UPPER ASSEMBLY Bevel Gear Operated Spur Gear Operated Motor Operated Adapto Gear Operated Geared Hammer Blow Hand Wheel Air Wrench Operation Page 45 60 52 53 54 55 56 63 63 64 57 6 7 27 35 10 INDEX GLOBE VALVES Take Up Screw Design Bonnet Stud Design B
32. onnet Stud Design Hammer Blow Handwheel Non Return Stop Check Instructions for Repair of Seats INSTALLATION Cleaning the Pipe Lines Cleaning the Valve Insulation Lifting Lugs Packing Lists Supporting the Valve Unloading Welding LAPPING Pressure Seal Joint Body Lapping Bonnet Lapping Globe Angle Check amp Non Return Valve Cleaning Compound Special Instructions MOTOR OPERATED VALVES Upper Assembly OPERATION amp MAINTENANCE Back Seat Lubrication Packing Leaks Special Tools Replacement Parts PRESSURE SEAL JOINT Description Detail Drawing Component Parts Segmental Thrust Rings REASSEMBLY Bonnet Locknut Design Bonnet Take Up Screw Design Bolted Yokearm Style Bonnet Take Up Screw Design Threaded Yokearm Style Bonnet Stud Design SECTIONAL DRAWINGS amp PART NAMES Angle Valves Check Valves Gate Valves Globe Valves Non Return Stop Check Valve VALVE IDENTIFICATION Body Lettering Name Plate Ordering Repair Parts Referring to a Valve Page 59 61 62 65 52 53 54 55 56 BRHHHKHA HHH 48 49 49 47 47 48 48 47 44 15 23 31 60 63 64 10 18 26 34 59 61 62 65 CA INSTALLATION When your valves arrive you will find an envelope containing a PACKING LIST an itemized statement of all valves and parts included in the shipment The Receiving Clerk should check and account for each item on the list Keep this PACK
33. or REFERRING TO A VALVE for any reason whatsoever reference should always be made to the serial number located at the bottom right hand corner of the nameplate In addition size and figure number also located on the nameplate should be included The lettering side of the body has the following information Pressure Rating Melt No A S T M Grade of Steel POWELL Cast Steel Accurately machined Acme threads prolong ihe life of the stem and bushing Tapered roller bearings for ease of operation Lifting lugs facilitate handling the valve during erec fion and maintenance Also provides means for sup porting the weight of the valve Swing eyeholts and gland shelves facilitate repacking Inner row of studs establish the initial 560 of the Pressure Seal Joint Outer row of studs secures the yokeorm to the body The bonnet joint remains tight under all operating conditions as the sealing pressure is always many fimes greater than the pressure of the fluid in the line there by eliminating lenkage The higher the internal pres sure the greater the sealing pressure Streamline confour of body simplifies application and reduces cost of insulation and effects marked savings in space and weight Stellite faced back seat and stem guide insure tight sealing and accurate guiding of stem Streamlined passage mokes possible maximum flow wi
34. pper Assemblies such as Bevel Gear etc see pages 43 44 45 and 46 11 111 11 1 1 1 1 A 221 3 SAILLILLILLULLLLZZLA 25 ASS m p7 445 Y SS 7 8 Lift the bonnet along with the gland protective ring and gasket out of the body care being taken not to scar the gasket seating surface of the body a Mark the wedge and body so that the wedge may be re installed in the same orientation b Remove the wedge and stem If no work is to be done on the wedge it should be re installed in the body carefully so no damage is done to the seating surfaces 30 REASSEMBLY BONNET TAKE UP SCREW DESIGN THREADED YOKEARM STYLE 1 a The gasket seating surfaces of the bonnet and body should be lapped and free of any scars See pages 48 and 49 b Seatring and wedge seating surfaces should be inspected and repaired if necessary See pages 50 and 51 for instructions for repairing gate valve seats pages 52 through 56 for instructions for repairing globe and angle type valve seats c Clean the body and bonnet seating surfaces 2 a Putthe wedge and stem in place making sure the wedge has the same orientation as when disassembled 7 SSN SS b Insert the bonnet into the body NSNNN SS NNN N 31 3 Putanew gasket in place making sure all surfaces are clean
35. s of the wedge and seat rings should be thoroughly cleaned Tools For Repairing Gate Valve Seats Part No Description 1 Wedge Circling Plate 2 Seat Ring Circling Plate 3 Pressure Bar 4 Right Angle Drive Air Wrench 51 INSTRUCTIONS FOR REPAIR OF GLOBE AND ANGLE TYPE VALVE SEATS Seat and disc seating surfaces should be examined visually for damage such as grooves resulting from erosion pits or mars resulting from entrapment of foreign material between the seating surfaces or out of round condition of the body or seat ring seating surface In most instances it will be necessary to run a bearing check by rubbing a small amount of bluing on the disc seating surface inserting the stem and disc assembly into the body and using the bonnet as a guide rotate the stem and disc assembly approximately 15 degrees After removing the bonnet and stem and disc assembly from the body examine the body or seat ring seating surface If the bluing transferred to the body or seat ring seating surface does not result in a complete round bearing the seat can be assumed to be out of round and this condition must be eliminated as the first step on repairing the seats Where indentations grooves pit marks mars or other imperfections on the body seat or seat ring are greater than approximately 0 010 deep or where an out of round condition is indicated the initial step in repairing the seat should be a circling operation using a lap w
36. size in thickness and must be faced off to fit After prolonged lapping the lap may have worn off angle A machine cut should be taken off the lap to correct this angle prior to final lapping Special grinding tools are available that greatly accelerate repair of a valve that requires considerable metal removal from the seat Final lapping should always be performed after grinding On GLOBE ANGLE CHECK and NON RETURN VALVES equipped with renewable guides either Type or Type design it may be necessary to face off the bottom of the cap or bonnet to compensate for the additional depth of the body pressure seal gasket seat This is illustrated below Insert Screw in tapped hole Surfaces to be faced on to act as a jac Bonnet jack for removing Segmental Guide Retaining Ring TYPE A TYPE B THE BONNET If the pressure seal seat in the bonnet has steam cuts it is recommended that the seating surface be faced off on a lathe and then lapped 47 INSTRUCTIONS FOR LAPPING PRESSURE SEAL JOINT AFTER THE VALVE HAS BEEN DISASSEMBLED THE INSIDE OF THE BODY AND OUTSIDE OF THE BONNET SHOULD BE CLEANED AND THE BODY SEATING SURFACE AND THE BONNET SEATING SURFACE EXAMINED SEE JOINT DETAIL PAGE 58 IF EITHER OF THESE SEATS ARE MARRED OR SCORED THEY SHOULD BE LAPPED A LAP WITH A MATCHING INSIDE BEVEL SHOULD BE PLACE THE LAP OVER THE BONNET AND ROTATE THE USED FOR THE BONNET SPREAD A FINE LAPPING LAP CLOCKWISE
37. t in place making sure all surfaces are clean It is essential to install a new gasket whenever the pressure seal joint is broken See page 47 for special instructions b Protective ring is oversize and must be machined or ground to fit body 22223 Insert the segmental thrust ring See sketch on page 42 d Putthe packing washer and gland on the stem 4 Placethe yokearm assembly over the stem As soon as the stem protrudes through the base of the yokearm install the face ring the take up flange with eyebolts installed and gland flange Continue to lower the yokearm assembly and screw the stem bushing onto the stem by turning the handwheel in a counterclockwise direction N 202292002 d oyi SA 2 b Raise the wedge off the seat slightly For other types of Upper Assemblies such as Bevel Gear etc see pages 43 44 45 and 46 294 9 SSSR 5 Install and tighten nuts the yokearm studs MSN 7 723272 b Close valve As SE c Install packing with the cut in the packing rings staggered d Install the split thrust ring and take up screws The take up screws are to be thoroughly lubricated with a mixture of oil and graphite prior to installation e Install and tighten eyebolt nuts y V
38. t locknut and the gland flange Continue to lower the yokearm and screw the bushing onto the stem The threads in the bonnet locknut are to be thoroughly lubricated with a mixture of oil and graphite prior to the installation of bonnet locknut b Raisethe wedge off the seat slightly For other types of Upper Assemblies such as Bevel Gear etc see pages 43 44 45 and 46 b d 2 N 2 1122 WY UP Z Zu RB 2 227 zw 2472 4 7222 gi 2 3 RU VARS 9 RS S LJ NS b N i i N aZ K PE v Spy SJ 2 S Ne Ec a LM 17 Install eyebolt clamp and eyebolts Install and tighten nuts on the yokearm studs Close valve Install packing with the cut in the packing rings staggered Install and tighten nuts on eyebolts Open valve until back seat shoulder seats solidly in the bonnet to set the gasket Tighten the bonnet locknut as tight as possible with an 18 driving bar and a three pound hammer HANDWHEEL STEM BUSHING GREASE FITTING PACKING GLAND FLANGE PACKING GLAND TAKE UP FLANGE PACKING PACKING WASHER KNOCKOUT HOLE GASKET BONNET O S Y GATE VALVE BONNET TAKE UP SCREW DESIGN BOLTED YOKEARM STYLE N 22 STEM BUSHING NUT AN tay SG O
39. th minimum turbulence Stellite faced flexible H type wedge prevents sticking due to temperature changes and pipe line stresses Seat rings are Stellite faced and securely welded in place One piece flexible wedge with weld deposited stellite facings insures pressure tightness prevents wedge from sticking and reduces operating torque needed to open valve It also offers less resistance to unseating due to temperature changes Pressure Seal Valves By inserting knock out pin in drilled hole segmental thrust ring can be easily driven out of retaining groove Segmental thrust ring absorbs all the thrust applied by internal pressure A hardened stainless steel protective ring prevents de formation of the top portion of the soft metallic gasket The gasket can be removed freely without damage to the sealing area in the body The gasket sealing area in the body may be easily lapped if required an outstanding feature in Powell Pressure Seal Valve Design This unique angular relationship of body bonnet and gasket a Powell exclusive feature provides a superior joint Body Guides provide minimum wearing of seating sur faces Tee Head connection with close clearances provides maximum control and reduced vibration Design of Tee Head prevents side strain on stem POWELL CAST STEELS OWELL Pressure Seal Valves can be furnished in any of the followi
40. upper guide assembly is to be used during the seat lapping operation The lap handle should be inserted into the hole near the top of the lap shank It is important that only light pressure be applied to the lap handle during lapping operations Lap the seat by rotating the lap clockwise and counterclockwise approximately a quarter of a turn Strokes should be light and the lap raised off the seat slightly and the lap rotated to a new position at frequent intervals Apply fresh lapping compound frequently and continue lapping until imperfections are removed The seat should be checked periodically with bluing following the method previously outlined If the results of the bluing check do not indicate a full round bearing additional lapping will be required On larger size valves it will be necessary to partially support the lap by means of a spring as illustrated in Figure 3 to insure that the pressure of the lap against the seat is light This method of support is recommended for large size valves which are installed in the line with the body neck up When globe or angle valves are installed in the neck down position or in any position where the neck is below the horizontal it will be necessary to hold the lap in place on the seat with light pressure applied to the lap by means of a spring between the lap guide assembly and the lap as illustrated in Figure 4 The seat lapping operations using a lap should be followed by lapping the valve disc to the s
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