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ABSTRACT PAPROCKI, DANIEL. A Quantitative
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1. Compressor Power b oo Ss e Ze K z z N N N A N AV AV Ww amp de Ge d Date Time Figure 38 100 hp Compressor Load Unload Cycle During the load unload cycle the maximum power draw is 115 hp and the minimum power is 60 hp The compressor unloads for approximately 1 5 minutes gradually reducing the power input The compressor unloads to 60 hp for little time almost immediately reloading to full power This operation is not ideal as you would like to see the compressor remain unloaded for as much time as possible Unloading for greater periods of time would lower the average compressor power during operation Currently during the load unload cycle the average compressor power is 85 hp 69 4 3 3 150 hp Air Compressor Data Analysis Figure 39 below depicts the amperage to the 150 hp compressor during the period of January 14 to January 30 150 hp Compressor Amperage a S a Er Si o lt 1 16 1 18 1 20 1 22 1 24 1 26 1 28 Date Figure 39 150 hp Compressor Amperage Figure 40 below is a plot of the 150 hp compressor power The 150 hp compressor is utilizing modulating controls and uses an average of 150 hp while producing compressed air During the logging period from January LA to January 30 the compressor had an average power of 44 hp The compressor does not illustrate the same load unload cycle as the 100 hp 70 com
2. Figure 93 Energy Efficiency Measures 15 The order of the two measures does matter because the reduced system pressure set point will also diminish the leak load After clicking the Edit Review box for the Use Automatic Sequencer the measure can be prepared to simulate savings As previously stated the chosen 139 pressure set point is 95 psig with a variance of plus or minus 3 psig The facility already has a controls system that could have the ability to control with this method however the system is not being used Therefore the implementation of this project could incur a low cost should it only need to be programmed properly The cost of a new name brand controls system could be as high as 140 000 Although the actual cost should be quoted it is estimated that the cost of a new system would be 100 000 If the current system can be used as a network controls system in the same manner as an automatic sequencer programming the controls and training facility personnel to operate the controls the implementation of this measure would cost much less than a brand new system The project could incur a low implementation cost should the issue require a simple programming fix If the issue is deeper and a decent amount of time is required to resolve any problems the implementation cost could be as high as 10 000 An estimate of 10 000 will be assumed for simple payback calculations Figure 94 illustrates the general data tab of
3. After entering the Energy Efficiency Measures module a new scenario was created to calculate savings by reducing the system pressure while only considering the 600 hp compressor The module screen is shown below 5 Efficiency File Calculators Help Dllvulgl ele Copy EEM Scenario f Life Cycle Results Close Facilty 600 hp Compressor e System 600 hp compressor v EEM Scenario Sample Pressure Reduction x SUPPLY SIDE Data Entry Description Sample Pressure Reductiorl DEMAND SIDE Improve End Use Efficiency Reduce System Air Pressure Adjust Cascading Set Points Use Automatic Sequencer Add Primary Receiver Volume Savings Summary Reduce An Leaks IT Use Unloading Controls Reduce Run Time Indude Order ll Edit Data Needs Review Review r Available only if air storage capacity was entered in the system module Visit the system module to edit this value Only lubricant injected rotary screw compressors with unloading controls will benefit from adding receiver volume Figure 92 Sample Pressure Reduction Simulation 15 The results of this measure can be found in the table below Table 7 600 hp System Pressure Reduction Results Daytype Baseline Average Airflow acfm Peak Demand kW Annual Energy kWh 2 971 579 Annual Energy Cost 127 481 Demand Cost 70 587 After Pressure Reduction 2
4. LIST OF TABLES Table 1 Inappropriate Uses of Compressed Air and Alternative Methods i e 5 Table Ze Facility Compressors eege use eege Seen 50 Table 32 Motor Efficiencies ee 59 Table 4 100 hp Compressor Power Pactor 61 Table 5 Full Load Amperage and Power Factor ecceesscccesseecesececeeceeceseeeceseeecsneeeeeaeees 63 Table 6 System Profile TOtal six jccassicasaacs Wogsdecssdeeedavas i eine a EREN 129 Table 7 600 hp System Pressure Reduction Results 133 Table 8 Savings from Reducing Compressor Pressure 134 Table 9 AIRMaster Baseline Operating Results eee eeecceessececeseeeceeeeeceeeeeceeeeeesteeeesaes 142 Table 10 AIRMaster Use Automatic Sequencer Results cceeeceeceeeeeceeeceeeeeeeeeteeeenaes 142 Table 11 AIRMaster Savings Resulting from Automatic Seduencer 143 Table 12 AIRMaster Reduce Air Leaks Results 147 Table 13 AIRMaster Reduce Air Leaks Savings ceccecesccecssececeeeeeceeceeceeeeceeeeenteeeesaes 147 Table 14 AIRMaster Savings Summa ry cc ceeeecsseeceeeeeceseeeceeeeececeecssececseeeeeteeeesaes 148 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 xii LIST OF FIGURES Percent of Energy Generation for Various Sources OI 2 Compressor Subsets 2 csi sccesetvcssccesnszeatareuscdauadeacia
5. 100 Pressure Figure 46 Plot of Compressor Power and Pressure 79 When the facility returns to operation after the weekend on January 20 all of the compressors turn on but only the 600 hp compressor remains operating From January 20 to the morning of January 21 the 600 hp compressor is the only compressor running until the 100 hp compressor is used to trim for increased compressed air demand From Figure 46 the 100 hp compressor is seen to operate in load unload cycles during periods of increased demand and remain unloaded during periods of low demand The system pressure is expected to drop during high demand periods and rise during low demand periods This is clearly seen from the morning of January 21 to the morning of January 24 Data from the morning of January 24 indicates that the 100 hp compressor shuts down but the 600 hp compressor remains on until January 25 The 600 hp compressor power trends lower from approximately 640 hp to 530 hp until the morning of January 25 when it shuts down During the period when the 600 hp compressor power trends lower a pressure run up is observed in the data The pressure rises from approximately 110 psig to 120 psig This trend of lowering compressor power and increasing pressure indicates that the compressed air system is producing too much compressed air implying less compressor power is required to satisfy the compressed air demand The final segment of data Januar
6. 2 647 131 892 0 65 062 2 647 196 954 According to the system baseline simulation the compressed air system uses 3 749 849 kWh yr resulting in a total of 241 880 yr in operating costs The introduction of the automatic sequencer results in an annual energy consumption of 3 074 665 kWh which yields a total of 196 954 in yearly operating costs The savings are shown in the Table 11 below Daytype Table 11 AIRMaster Savings Resulting from Automatic Sequencer Operating Hours Average Airflow Reduction acfm Peak Demand Reduction kW Annual Energy Savings kWh Annual Energy Cost Savings Demand Cost Savings 143 Total Cost Savings Production 628 058 26 944 15 949 42 893 38 582 1 655 0 1 655 8 798 377 0 377 28 976 15 949 44 925 Saturday Sunday 675 438 The implementation of an automatic sequencer results in substantial savings The energy savings is 675 438 kWh yr and the peak demand reduction is 114 kW This results in a total annual operation cost savings of 44 795 representing a savings of 18 5 2 3 Reduce Air Leaks By reducing the compressed air volumetric flow through leaks in the compressed air system the compressors will consume less power and energy Air leaks cause unnecessary compressed air demand which causes the compressor to run longer or at a higher power The compressed air volumetric rate associated w
7. N e O oo 0 0123 45 67 8 9 101112131415 161718 192021 22 2324 Hour of Day Production Saturday Sunday Figure 78 Plot of 100 hp Compressor Daytypes Since the 150 hp compressor rarely runs on an average production day the production daytype was chosen from a day in which the compressor did not run The compressor does run on Saturdays and Sundays thus appropriate days were chosen for the daytype Friday January 24 was chosen for the production daytype followed by January 25 and 26 for the Saturday and Sunday daytypes In Figure 79 the chosen daytypes for the 150 hp compressor can be viewed Figure 80 is a plot of the 150 hp daytypes 121 System NotAssigned Period Baseline Current Amps Right click on data points to select day type Left click to highlight the trace 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Hour of the Day Plot Day Type Remove Day Type Caution Day profiles can be similar even though fAlbas lf different equipment e g compressors is operating Day Type All Days x ZJ Use Trend Plots to examine the details of equipment Excluded Days operation before determining whether days should be assigned to the same daytype ExcludedDays sf Eesen Create System Copy Plot to f Copy Profiles to Excluded Days DayType Profiles ClipBoard L Excluded Days S stem Da Type Profiles Exc
8. Se Saree Savings Summary April 7 2014 By Your Name Page 1 of 1 Facility Textile Manufacturer System Textile Manufacturer EEM Scenario Textile Manufacturer efficiency measures Savings Summary Energy Energy Energy Demand Demand Installed Total Simple Savings Savings Savings Savings Savings Cost Savings Payback Description kWh kw years Automatic Sequencer 675 438 28 976 18 0 1143 15 950 10 000 44 926 0 2 Reduce Air Leaks 128 998 5 534 3 4 137 1 917 4 000 7 451 0 5 TOTALS 804 436 34 510 21 5 128 0 17 866 14 000 52 377 0 3 D 1 AIRMaster Energy Efficiency Measures Savings Summary
9. 23 The lubricant free rotary screw compressor works in the same fashion as the oil flooded screw compressors As the name would suggest there is no lubrication injected in the compression chamber Additionally there are two distinct types of oil free rotary screw compressors dry type and water injected type Figure 12 illustrates an oil free rotary screw system with the distinct lubricated timing gears Figure 12 Oil free 4 A dry type oil free screw compressor uses lubricated timing gears which are external to the compression chamber to keep the intermeshing rotors from touching These types of compressors do not have coolant injected into the compression chamber and therefore may require two stages of compression with an intercooler between stages and an after cooler 24 after the second stage to compress air to higher pressures This is similar to a reciprocating compressor Teflon may be used to help seal the rotors and limit friction between moving parts A one stage dry type compressor can operate up to 50 psig whereas a two stage may operate up to 150 psig Similarly the water type lubricant free rotary screw compressor uses timing gears However in this type of compressor water is injected into the compression chamber This acts to remove the heat of compression and seal any internal clearances An oil free screw compressor can be expected to operate at an efficiency of 18 to 22 kW 100 CFM Although these types o
10. various energy efficiency measures one of which is using an automatic sequencer An automatic sequencer is essentially system master controls which help operate lager compressed air systems efficiently To understand how multiple compressors operate together first a familiarity of different types of compressors and an understanding of various methods of single compressor and multiple compressor controls must be realized Through the simulation of the implementation of an automatic sequencer using AIRMaster the potential energy and cost savings associated with sophisticated compressed air system controls can be conveyed to the subject facility Chapter 2 Compressed Air Modern manufacturing facilities utilize multiple types of air compressors to meet the compressed air demand for their processes Currently the most common compressors used in the industrial world are reciprocating compressors rotary screw compressors and lastly centrifugal compressors Based on the application and compressed air demand of the manufacturing facility a type of compressor is chosen Each compressor has its own benefits and drawbacks which must be considered before purchase and installation This chapter will discuss compressed air terminology common compressed air components and types of compressors 2 1 Important Compressed Air Terminology In order to gain a better understanding of compressed air systems it is important to become familiar with
11. 749 906 117 971 64 949 133 134 After reducing the pressure there are reductions in average airflow demand and energy The following table details savings Savings Table 8 Savings from Reducing Compressor Pressure Average Airflow Reduction acfm Peak Demand Reduction kW Annual Energy Savings kWh 221 673 Annual Energy Cost Savings Demand Cost Savings Total Cost Savings 15 148 The measure reduces the average air flow by 151 acfm the peak demand by 49 4 kW and the yearly energy use by 221 673 kWh This results in a total cost savings of 15 148 yr This represents a cost savings of 7 5 The next step is to validate these findings To verify whether the AIRMaster calculations are accurate an alternate method of calculating savings from dropping pressure will now be performed Demand Reduction is given by DR 1 FR x kW x loaded Efficiency Equation 7 FR is the ratio of proposed power consumption to current power consumption based on operating pressure no units FR is based on an analysis using the ideal gas law and isentropic compression power The average power of the 600 hp compressor is approximately 500 kW with an efficiency of 94 5 The following equation can be used to 135 estimate the horsepower reduction factor FR based on current and proposed operating pressures N k 1 k E 4 P FR SCHU
12. Combin d Analysis EE 76 4 3 7 Volumetric DEE 81 43 8 Pressure Analysis siorino eare ia nisi erein rrai ae ENE Aa e ii 95 Chapter 5 AIRMaster System Modeling detresse ege Eecher 100 5 1 Modeling the Compressed Air Zeta Eege dee 100 5 1 1 Company Module i acccccsssessrtieaosscedsseseecsiavasaiarte soacsateavactesevsaceaauacedte R EN a nai 102 S2 E NV EE 103 Sel gt aert eene ota teas dun eege Ee 104 S LLA System WOM rte koores tie Doten ren Eed sted dacs aee geor a a 105 S ENTENTE 107 SL GLO ST OOM vi estate erster a a EES ENEE Seed 116 sel7 Erres 124 5 2 Enersy Efficiency Meastre Ss orines rene T E dquteaaasanles T k 130 5 2 1 Reduce System Air Pressure AIRMaster Naldaton cee ceeeeeseesseceteeeees 131 5 2 2 Automatic SEQUENCER snenia i sunina sa degsaanasds sad tuuneceds EE EEN 137 5 2 0 Reduce Air eener eege ett 143 52 Total Say Oss enee leegen ee 147 Chapter EEN 149 6 1 Data Analysis ee TEE 149 6 2 AIRMaster Conclusions e aer ENEE 152 6 3 Further Opportunities saisicigscets nstigis aeia EEEE E R asad nue eege 154 REFERENCES acest eet was Eege 155 PUP PEEING TS oes EE acu Sea Sa Ss sad Sh aes a se rank Ya Ge 157 Appendix A AIRMaster Automatic Sequencer Existing and Proposed Scenarios 158 Appendix B AIRMaster Automatic Sequencer Results 162 Appendix C AIRMaster Reduce Air Leaks Input 166 Appendix D AIRMaster Savings Summary 0 0 0 0 cee eeseeseeceseeeeeeeeneeceaeceaeesseeesaeeesaeens 167 xi
13. Data Facility name Textile Manufacturer Utility Duke Power v Address 1 Rate Schedule Average Energy Rate 7 Address 2 Season 1 Season 2 City Start month day 04 01 10201 Demand rate State Zip Raro 11 63 11 63 Contact Block 1 0 04290 ye 0 04290 ve Energy Phone I I 2 Rate Block 2 0 04290 m 0 04290 7 kWh Annual plant bare aca eet 12 606 000 Block 3 0 04290 7 0 04290 Figure 63 AIRMaster Facility Information 15 105 File Calculators Help oza eg Model Manufacturer Compressor Type Compressor Control Ty Inlet mode Inlet mode DD hp 75 k Sullair Corporati Single stage lubricant injected rot 100 hp compress Load unlc IBU hp 375 Sullair Corporatic Two stage lubricant injected rotai 500 hp compress Inlet mad e GEE PSRs Ee System Totals Be ee ee ees Deeg Facility Totals 4 Figure 64 AIRMaster Facility Compressor Summary 15 5 1 4 System Module The System Data tab within the System module allows the user to input the nominal system pressure elevation of facility and air storage capacity The user can also enter sequencer data should the system utilizes a sequencer The Daytypes tab allows the user to define the types of days in which the compressors operate Each daytype is assigned a number of operating days Examples of daytypes could 106 be production days or weekends For this project Production Saturdays an
14. Demand CFM 83 System Compressor Power NH ss oe So o oO Nn LA 2 2 e v Da n v Ben a Q T T 2 22 2 23 2 24 2 25 Date Figure 49 System Compressor Power February 21 to February 27 EH Qa 5 z A Ss a a DI a Se SA N Volumetric Flow and System Compressor Power a 2 24 Date System Hp Flow Figure 50 Compressed Air Demand and Compressor Power Compressed Air Demand 84 85 Seen in Figure 50 the volumetric flow seems to correspond to the overall system compressor power As the compressor power increases the volumetric flow also increases Similarly as the compressors draw less power the volumetric flow will also lower and sometimes dramatically The dramatic drops in compressed air flow despite minor drops in the compressor power is related to the individual compressor controls The larger compressors utilize modulating controls and therefore still use a considerable percentage of the compressor s power at low capacities To accurately estimate a volumetric flow a curve fit was performed on a plot of volumetric flow against compressor power from February 21 to February 28 A linear regression was performed and the corresponding linear equation was added This equation can be used to calculate
15. Equation 8 E A 1 P Where Pap proposed discharge pressure 93 psig 107 7 psia Pac current discharge pressure 103 psig 117 7 psia Pi inlet pressure 14 7 psia N compression factor for two stage screw 2 k ratio of specific heat for air 1 4 no units The FR ratio will be calculated with a proposed discharge pressure and current discharge pressure of 93 psig and 103 psig respectively After entering the values into the above equation FR is equal to FR 0 9288 Therefore the demand reduction is DR 1 0 9288 x 500 kW x 100 loaded 94 5 Efficient 37 64 kW The Energy savings are therefore Energy Savings 37 64 kW x 6 000 hours yr 136 225 845 kWh yr The overall cost saving CS from the demand and energy reduction are given below CS 225 845 kWh yr x 0 043 kWh 37 64 kW x 11 63 KW x 12 14 942 yr AIRMaster gives hour by hour results in which the pressure may differ from than the average pressure This is in contrast to calculating savings in the simplistic manner shown above The formulas offer assumptions as to what the pressure is at all times and to what pressure the system will be reduced which also remains static Despite the inherent differences in complexity the results are quite similar The hand calculations result in overall savings that are 205 yr less than the results from AIRMaster and are about 1 4 less than the AI RMaster results The two calculations are fair
16. as opposed to 7 8 1 11 This is illustrated in Figure 17 34 Atmospheric Pressure 14 7 psia Compressor lt Inlet Valve 40 Open Inlet Pressure 5 88 psia Figure 17 Compressor Inlet Butterfly Valve 40 Open The result is that a modulating rotary screw compressor will require approximately 88 of the total kW input to produce 50 of its capacity 4 11 The energy savings come from the reduced mass of the air being compressed The following curve in Figure 18 illustrates the relationship between percent kW input power and percent capacity for a rotary screw compressor utilizing modulating controls 35 Percent kW Input Power Percent Capacity Inlet modulation no blowdown m Inlet modulation with blowdown Figure 18 Percent kW Input Power vs Compressor Capacity for Modulation 11 Modulating controls might be appropriate if a rotary screw compressor is operating with little to no storage at higher capacity Generally rotary screw compressors can be switched to run on either load unload or modulating controls Some compressors may allow modulation with blowdown which is a control method that allows the compressor to unload at some low capacity From Figure 18 above a compressor using inlet modulation with blowdown would use modulating control until about 40 percent capacity at which point the compressor begins using load unload control 36 3 1 4 Dual Auto and Variable Displacement The next
17. control type is the Dual Auto which is for either small reciprocating compressors or rotary screw compressors For reciprocating compressors dual auto dual allows the compressor to select either start stop or load unload Dual Auto Dual controls allow oil flooded rotary screw compressors to select between modulating and load unload controls Furthermore if unloaded for a long duration this control type will shut down rotary screw compressors Another control type available for rotary screw compressors is variable displacement Variable displacement effectively shortens the length of the screws by using a turn valve spiral valve or a poppet valve This allows a decrease in the amount of air flowing through the inlet and in turn decreases the amount of power needed to compress air This is an effective way to increase and decrease compressor capacity Variable displacement is generally more efficient at running partially loaded compressors than even load unload controls with high storage Figure 19 below illustrates the relationship between percent kW input power and percent capacity for a rotary screw compressor with variable displacement control 4 11 37 Percent kW Input Power 40 100 60 80 Percent Capacity Rotary Compressor Performance with Variable Displacement Figure 19 Variable Displacement Control 8 3 1 5 Variable Speed Drive Control The most effective control method for operating at partial loads is
18. excellent way of setting which compressor room will have base compressor duties and which will have trim duties For example in a two compressor room system with outputs of 125 psig and 100 psig respectively the Pressure Flow controller can allow the 100 psig room to be the base and have the 125 psig room trim while decreasing pressure to a standard facility pressure 11 Pressure flow controllers respond very quickly to demand events which allows for stable pressure output The pressure flow controller will respond much quicker to demand events than standard compressor controls With properly sized storage upstream the pressure flow controller will react quickly enough to a demand event to avoid the need to start another air 48 compressor Below is a schematic of a pressure flow controller in a single room compressed air system Figure 25 Pressure Flow Controller with One Compressor Room 11 Pressure flow controllers can be vital to operating a compressed air system with both positive displacement and dynamic compressors A centrifugal compressor s performance can be influenced in several ways by positive displacement compressors with varying discharge pressure An example of this influence is when a load unload or modulating compressor s pressure band overlaps the throttling line of the centrifugal compressor the centrifugal will blow off any excess compressed air to atmosphere Additionally if a multiple compressor syst
19. method of networking positive displacement and dynamic compressors System master controls are required for more complex compressor systems such as these 3 3 3 System Master Controls For facilities with complex compressed air systems consisting of both positive displacement and dynamic compressors and remote compressor rooms system master controls can safeguard against compressors coming online when they are not needed In addition to running a more efficient compressed air system such as monitoring and controlling all 46 components in the system system master controls can trend data to better help with maintenance thereby reducing overall operation costs 11 The simplest system master controls will utilize cascading set point logic to control air compressors within the system High tech system master controls utilize a technique called single point control logic This uses rate of change dynamic analysis to decide how compressors will react in regard to changes whether it be from the supply side demand side or atmospheric conditions Compressor demand is influenced by what are termed end use events Events influence system demand either positively or negatively and the control system must react accordingly 11 A few examples of events include shift change line purge dense phase transport and compressor failure 11 A system master control can perform many different and complex functions However the number of func
20. minimum and maximum pressures for an air compressor Also referred to as load no load pressure ranges Rated Pressure The ideal pressure for optimal compressor performance Receiver A pressure vessel used to store compressed gas or air 12 Surge A dangerous and destructive operating condition for centrifugal air compressors This occurs when a reduced flow rate results in backwards flow The compressor can no longer overcome backpressure 2 2 Types of Compressors Industrial compressors are divided into two main types of compressors which are positive displacement and dynamic For the positive displacement compressor a finite quantity of air or gas enters into a compression chamber and the volume of the chamber is mechanically reduced thereby increasing the pressure of that gas before discharge 4 Dynamic compressors such as centrifugal compressors and axial flow compressors operate much differently By means of impellers rotating at an extraordinary speed a dynamic compressor imparts kinetic energy to continuously flowing air The kinetic energy of the air or gas is changed into potential energy pressure by the impellers and diffusers 4 Below is a figure that further breaks air compressors into subcategories Compressors z Centrifugal Axial Double Acting Liquid Ring Sliding V ane Res Figure 2 Compressor Subsets 2 13 14 2 3 Positive Displacement Compressors Positive displacement compressors are
21. percentage of its full load power even when it is producing no compressed air Because the 150 hp 500 hp and 600 hp compressors all use modulating controls it is reasonable that their performance curves would be similar 114 Performance Profile 500 hp compressor Power Full Load Airflow Capacity Performance Profile 600 hp compressor Power Full Load 40 50 Airflow Capacity Figure 74 600 hp Compressor Performance Profile 15 115 5 1 5 1 Compressor Pressure Performance Control Points Another important aspect to setting up an adequate model is to specify the compressor pressure control range Each compressor has a pressure band which it adheres to in order to meet demand This compressor system likely cascades the compressors with different pressure performance points for each compressor The 600 hp compressor and the 100 hp compressor currently operate together to meet compressed air demand The 600 hp compressor is the base load compressor and the 100 hp is the swing compressor to meet any additional demand Using modulating controls the 600 hp compressor controls between 110 psig and 120 psig where the compressor is fully loaded when the system air pressure is 110 psig or below and is completely modulated when the system air pressure reaches 120 psig Thus if the system air pressure is below 110 psig the 600 hp compressor is fully loaded all the time The 100 hp compressor likely has a contr
22. represents the best estimation of savings 148 resulting from the implementation of these two measures The total savings summary is detailed below Description Automatic Sequencer Energy Savings kWh 675 438 Table 14 AIRMaster Savings Summary Annual Energy Cost Savings 28 976 Demand Savings Demand Cost Savings 15 950 Total Savings 44 926 Implement Cost 10 000 Simple Payback months Reduce Air Leaks 128 998 804 436 5 534 34 510 1 917 17 867 7 451 52 377 4 000 14 000 149 Chapter 6 Conclusions 6 1 Data Analysis Conclusions An important analysis performed in this study was determining a method to calculate power factor which is an important factor when calculating compressor power When a compressor is operating around full load amperage the power factor is likely between 0 85 and 0 9 but the power factor can be much lower when the compressor is operating at part load For example when a load unload flooded oil rotary screw compressor is fully unloaded it may have a power factor as low as 0 3 Conversely at full load amperage the same compressor might have a power factor of 0 87 Consequently power factor greatly affects the actual compressor power and therefore is important to have a means to quickly estimate the power factor AIRMaster has a compressor power calculator which it uses during its simu
23. system pressure reaches a set minimum allowable pressure For larger rotary screw compressors load unload and modulation are commonly employed Using load unload controls will track system demand and help save energy while unloaded This will also ensure that the compressor does not turn on and off in short cycles which can destroy larger motors from locked rotor current Load unload controls allow the compressor to unload when the system pressure reaches a predetermined maximum Modulation controls are typically found in rotary screw and dynamic compressors Modulation follows system demand by restricting the flow of air to the compressor through the use of an inlet valve such as a butterfly valve As less air flows through the inlet less power is required to compress that air However the main drawback of using modulation is that it reduces the pressure of the inlet air causing the compression ratio to increase For flooded oil rotary screw compressors utilizing modulation the percent kW input at 50 percent capacity will likely be approximately 85 which is rather inefficient Allowing less air through the inlet increases the compressor efficiency but the decreased pressure at the inlet is akin to taking a step backward Variable frequency drives are generally found in rotary screw compressors The variable frequency drives allow the motor to track system demand by altering the speed of the electric motor by varying voltage frequency
24. the automatic sequencer set up 140 S Teen Soquel Se File Calculators Help ta ig Results _ Ghose Data View Facility Textile Manufacturer System Textile Manufacturer Existing Restore Ze Proposed General Data Hourly Data m Measure Description Proposed Sequencing Options Description Automatic Sequencer Target pressure 95 0 psig TTT C Cascade pressures Measure cost S e S Target pressure Variance 3 0 psia NOTE All pressures measured at the sequencer pressure tap Figure 94 AIRMaster Use Automatic Sequencer Measure 15 It is correspondingly important to properly set up the inputs for each daytype in the hourly data tab All compressors are made available for each hour of the day and shut down timers are added to the control This allows the sequencer to choose the best combination of compressors for operation and the shut down timers allow the compressors to turn off if they remain unloaded for a period of time In Appendix A the complete set up and savings report will be detailed Figure 95 shows the hourly data set up tab 141 l EM Ue Astor Seoane File Calculators Help Za eg _Pesuts ges Data View Facility Textile Manufacturer System Textile Manufacturer C Existing Ze Proposed General Data m Proposed Sequencing Data Daytype Production X Comp S00 hp compres
25. the volumetric flow for periods without given values of compressed air demand Figure 51 is a plot of the volumetric flow against system compressor power The data indicates that there is a strong positive linear correlation between compressor power and the compressed air demand Using the Pearson product moment correlation equation the correlation coefficient was found to be 0 968 The Pearson product moment correlation coefficient is found with the following equation Zeck p Equation 5 ex Eho Led E S 8 E lt 3 Ka Ke D S F S n CFM vs HP T T T T T 100 150 200 250 300 350 400 450 500 550 600 650 700 Hp oe CFMvs HP Linear CFM vs HP Geer Figure 51 CFM vs hp with Linear Regression 750 800 86 87 The linear regression results in a trend line formula of y 4 44 X This means that the linear regression predicts that for every one system compressor horsepower 4 44 CFM will be produced by the air compressors This is a reasonable estimate as the CAGI reference for the 600 hp unit gives 4 4 CFM per horsepower at full package load 13 Figure 51 shows an interesting relationship between compressor power and compressed air volumetric flow rate Generally at high system compressor power between 700 hp and 750 hp the volumetric flow rate ranges from 2 700 CFM to 3 500 CFM The modulating con
26. up and initiated to monitor amperage and pressure Additionally volumetric flow data was requested for this second period of data collection On February 11 2014 the five programmed data loggers for the compressor and pressure monitoring were dropped off at the facility to be installed by the maintenance manager The IR data loggers collected data from the 11 of February to the 27 of February Volumetric flow data from February 21 to February 28 was provided by the facility The flow data was 58 1 to February OT sik recorded every 30 minutes Upon viewing the data from February 1 was determined that the data logger monitoring system pressure malfunctioned and did not record the pressure Therefore it was decided to use the first set of data for analysis and to estimate a volumetric flow for this period 4 3 Data Analysis The amperage was recorded every 5 seconds but to analyze multiple compressors at once the data was averaged over 1 minute periods This means that 12 five second amperage recordings were averaged into one data point First the compressor horsepower for each compressor is plotted and then the power for each compressor pressure and volumetric flow will be integrated To calculate the compressor power in kW the following formula is used Pies kw _ Amperage x ee aL x PowerFactor Equation 1 The voltage to the compressor is 460 volts The electric motors in each of the air compres
27. when the facility first starts up and the compressors must pressurize the system for production At that moment the system turns all compressors on to fulfill the demand to pressurize the system However this may incur a large billing demand Thus a solution to this issue might be to control which compressors turn on while pressurizing the system 74 The compressor has an average power of 87 hp during the entire logging period and an average of 462 hp while producing compressed air Figure 43 is a plot of the compressor power utilizing averaged amperage data to smooth out the data and exclude large spikes in amperage during initial compressor startup 500 hp Compressor Power CH cn Aa N Compressor Power bhp D 0 1 14 1 16 1 18 1 20 1 22 1 24 1 26 1 28 1 30 Date Figure 43 500 hp Compressor Power 4 3 5 600 hp Air Compressor Data Analysis The 600 hp compressor is the primary compressor which satisfies the greater part of the compressed air demand when in operation The compressor operates with modulating controls to match compressed air demand During the data collection period the compressor 75 had an overall average power of 317 hp While the compressor was in operation the average power draw was 601 hp The large spike in the amperage is likely due to locked rotor amperage during the initial startup of the electric motor
28. 0 21 22 23 24 Hour of the Day Click a date to highlight profile in graph Plot Day Type Remove Day Type Caution Day profiles can be similar even though All Days EN different equipment e g compressors is operating Day Type Use Trend Plots to examine the details of equipment operation before determining whether days should be d Jan 16 2014 Excluded Days A assigned to the same daytype Jan 17 2014 Excluded Days Create System Copy Plot to Copy Profiles to Hel Jan 18 2014 Excluded Days DayType Profiles ClipBoard ClipBoard F Jan 19 2014 Excluded Days denetaik Encuuded Dave a EC EE BEER ChannelName DC Jan 21 2014 Excluded Days p Not Assigned za Baseline Production 100 75 26 74 7 gt Not Assigned Current Baseline Saturdays 100 ooo O E SEH __ Not Assigned Current Baseline Sundays 100 mem 115 Jan 23 201 4 Excluded Days Jan 24 2014 Excluded Days Jan 25 2014 Saturdays Jan 26 2014 Sundays Jan 2 7 2014 Excluded Days Jan 28 201 4 Excluded Days gt Figure 77 100 hp Compressor Daytypes 16 The user must then copy profiles to the clipboard and then paste into a spreadsheet All daytpes will be pasted into the same spreadsheet to easily transfer the daytpes into AIRMaster Figure 78 is a plot of the three daytypes for the 100 hp compressor 120 100 hp Compressor Daytypes oo N oo EI Sr S im EI C lt
29. 1 Startup periods account for approximately 4 4 days per year During the times of low capacity but high compressor power the average percent difference is 57 The system operates at low capacity but high power approximately 2 days per year However the percent difference during periods of high capacity and high compressor power is only 3 E 2 8 E lt 3 Ka Ke D S a S ks an Actual CFM and Predicted CFM Acai 2 25 Date Time ActualCFM Estimated CFM Percent Difference Figure 52 Actual CFM and Predicted CFM Difference 89 90 Now the volumetric flow will be estimated for the system compressor power data from January 14 to J anuary 30 using the linear regression analysis previously performed Although this will not accurately reflect the volumetric flow during shutdown startup and low compressor capacity it will adequately estimate the volumetric flow during normal compressed air demand periods Figure 53 is a plot of the predicted volumetric flow from January 14 to J anuary 30 The plot shows large spikes in volumetric flow when all of the compressors turn on during production startup or during increased demand The volumetric flow estimates during this time are likely inaccurate because of the time it requires for a compressor to actually start producing compressed air The system almost
30. ABSTRACT PAPROCKI DANIEL A Quantitative Analysis to Determine Methods to Improve an Industrial Compressed Air System Under the direction of Dr Stephen Terry Compressed air systems are an integral part of many manufacturing facilities Compressed air is used for many things including pneumatic controls manufacturing equipment air motors air tools and blow off nozzles Despite the versatility of compressed air it comes at a great cost as approximately 80 percent of the energy used by the air compressor is rejected as heat The remaining 20 percent of the energy is converted to compressed air Thus it is important to produce and use compressed air as efficiently as possible which controls can help accomplish The subject facility has a compressed air system that consists of four rotary screw type compressors Currently this system of compressors is not using system master controls which would help sequence the compressors according to compressed air demand After collecting amperage and pressure readings through data logging several analyses were carried out First a method to estimate power factor was created then compressor power for each compressor was calculated using amperage power factor and compressor motor efficiency Additionally a technique to calculate volumetric flow using compressor power was developed The estimation of power factor and volumetric flow are essential when determining compressor power and analyzin
31. Centrifugal Compressor Performance Curve 12 40 The opposite of surge is choke or stonewall This occurs at flow rates that are above the design rate which should not occur until the velocity at the impeller inlet reaches the speed of sound As the compressor exceeds the capacity limit the performance enters the choke area At this point any increase in flow rapidly decreases the pressure being produced 11 Centrifugal compressors are designed to operate at pre determined tip speed which is usually between Mach 0 85 and Mach 0 9 Thus to increase and decrease the flow rate an inlet throttle valve is utilized Additionally the throttle valve reduces the pressure and air density at the inlet before the impeller which reduces the head produced by the impeller Throttle valves can usually control capacity of centrifugal compressors from 100 to about 70 of full capacity Properties such as air density can affect the capacity of the air compressor For example higher density cool air will effectively increase the volumetric flow rate at any compressor capacity Though the capacity can be increased with cooler inlet temperatures this also results in an increase in power consumption 11 In Figure 22 the effect of inlet air temperature on capacity is illustrated 41 Figure 22 The Effect of Inlet Air Temperature 11 3 3 Multiple Compressor Control Multiple compressor systems are quite common in larger facilities It is of pa
32. First controls for individual compressors will be discussed followed by multiple compressor system controls 3 1 Basic Individual Compressor Controls For smaller single compressor compressed air systems controls are contained to the compressor itself Individual compressor types to be discussed are start stop load unload modulating dual auto variable displacement and variable frequency drive control 3 1 1 Start Stop Control For reciprocating compressors and rotary screw compressors under 25 hp a simple Start Stop control scheme would be a satisfactory control method The compressor motor turns off as a specified pressure set point is reached and then turns back on when the pressure drops below a given lower pressure set point 27 A simple example of start stop control is a home thermostat During the winter as the temperature in a space dips below a set point temperature the heating system will turn on to supply heat The temperature in the space will rise until it reaches another set point at which point the heating system will shut off In this manner an average temperature is maintained The difference between the cut on point and cut off point is the deadband The system will operate between the two setpoints in this deadband region Depending on storage capacity the pressure range or deadband needed for this control method can be as high as 35 psi This is a fairly simple control scheme needing only a pressure sw
33. Including demand reduction cost savings the total savings from this simulation is 44 926 annually The implementation of this measure should require minimal involvement The facility already owns a control system thus the cost will likely only originate from reprogramming which is estimated to cost no more than 10 000 The second efficiency measure that AIRMaster simulated is the reduction in air leaks This measure requires finding and fixing compressed air leaks as they occur which will reduce compressor power The recommendation offers an energy savings of 128 998 kWh per year resulting in a total operational cost savings 7 451 per year The combination of the implementation of an automatic sequencer and the reduction of air leaks results in a reduction of 804 436 kWh per year and a total annual savings of 52 377 representing 21 4 reduction in compressor electrical costs Ensuring that the compressor controls are operating properly will help to improve the compressor system operation The system pressure will be reduced and controlled to a tighter pressure band both reducing compressor power and improving overall system operation The compressors will have the capability to quickly respond to demand events and avoid 154 operation leading to inefficiencies such as pressure run up Additionally while reducing air leaks is not a complicated measure any reduction in operation cost will directly influence the facility prof
34. Logging Interval _iminute e Sampling Interval 1 second Logging Duration 126 5 days Start Logging On Date Time x 02 25 14 Lel 01 00 00 Pm Stop Logging When memory fills Never wrapping E Skip launch window next time Cancel Delayed Start Figure 31 Launch Logger Interface After the sensors to log are selected they must be scaled to match the CT For example if the CT measures 0 mV the corresponding amperage would be 0 Likewise if a CT measures a maximum of 333 mV this would correspond to the maximum amperage that CT is valid for This means that for a 200 amp CT if the CT measures 333 mV the amperage through the wire is 200 amps These points must be configured to accurately measure amperage The interface to scale parameters is shown below in Figure 32 56 r Configure Sensor Sensor Information Module Port Name FS TRMS AC1 Firmware Version 2 8 Serial Number 9926612 Sensor Number 1 Sensor Name Current w Scaling Parameters Raw RMS 0 33315 k Figure 32 Configure Sensor After configuration the launch time is set There are two options the first is to simple launch the logger immediately but if multiple loggers are being used to monitor a compressed air system a delayed launch time can be chosen for all loggers Because this project dealt with four compressors and it is ideal for all loggers to begin logging at the same time de
35. The motor speed and percent power have approximately a one to one ratio meaning that at half the fully rated revolutions per minute the motor will draw half the fully rated power input Compressor capacity and motor speed also have a one to one ratio which implies that at half capacity the compressor will only require half of its fully rated power This is a rather efficient method of controlling a single compressor As compressor systems grow larger it is important for compressors to communicate with each other helping to ensure compressors only turn on when necessary Generally network controls are utilized to make certain compressors communicate with each other More complicated systems such as those with multiple compressor rooms consisting of both centrifugal and positive displacement compressors require System master controls System master controls allow for the control of large compressed air systems through measurement of system parameters pressure for instance Further description of each of the aforementioned control methods is detailed in Chapter 3 1 4 Main Project Objective The main objective of this study is to collect data from a subject facility s compressed air system using data loggers analyze data and then to model the compressed air system using AIRMaster which is a free software package made available by the Department of Energy After the compressed air system is modeled in AIRMaster the software will simulate
36. This can be seen in Figure 44 below Figure 45 focuses and depicts the 600 hp compressor s power during the logging period of January 14 to J anuary 30 The 600 hp compressor typically supplies the majority of the compressed air demand therefore the 500 hp compressor does not operate in conjunction with the 600 hp compressor However both the 500 hp and 600 hp compressor turn on when the facility initiates startup after a weekend When this occurs the 500 hp compressor almost immediately shuts off and the 600 hp air compressor remains on 600 hp Compressor Amperage 2500 N fom 1500 1000 500 Compressor Amperage Amps 0 T T T T bk AP ai A wb ai ci AW dk di ab ei OO ZZZ EZE AA AAT AE d N e gt A AW MP Date Figure 44 600 hp Compressor Amps 76 600 hp Compressor Power I aN A A i gt N 5 l wa a Q S Q 0 q T T T T T 1 14 1 16 1 18 1 20 1 22 1 24 1 26 1 28 1 30 Date Figure 45 600 hp Compressor Power 4 3 6 Combined Analysis To gain a better picture of how the system is operating as a whole all of the air compressors power and system pressure is graphed in Figure 46 below Pressure is indicated by the light blue curve on the top of the graph followed by 600 hp compressor power trend in dark
37. a higher rise in pressure as flow is decreased When operating centrifugal compressors it is important to control for surge and choke Surge which is harmful to the machine occurs when flow reverses in the diffuser after the air leaves the impeller This is possible because of an increased flow path length in the diffuser 39 causing the flow to dissipate due to friction and ultimately the flow reverses 11 The aerodynamic instability within the system is to the extent that the compressor can no longer deliver the necessary pressure to produce flow downstream 12 To avoid the destructive surge condition centrifugal compressors may use discharge bypass or blow off control To avoid surge enough compressed air is discharged to atmosphere to keep the unit at some minimum load while the required capacity is delivered to the facility For example if the facility needs only 45 capacity the compressor will produce approximately 70 of its capacity and blow off the extra 25 of the compressed air For this reason blow off is quite wasteful and expensive and therefore should be avoided Figure 21 depicts the surge line in a centrifugal compressor performance curve SURGE 19 AREA 550 2 5007 100 sQ 450 Eq A J39 400 eet 7 men a B D i vw amp 40 vU ze 3 STONE WALK N AREA X See E Oy CONSTANT v APPROX x ak a Lem RRE LE ELE RR T 0 20 40 60 80 100 120 140 PERCENT INLET FLOW Q ACFM Figure 21
38. a plot of volumetric flow against compressor power Through this analysis it was determined that there is a strong linear correlation between compressor power and volumetric flow and that volumetric flow in cubic feet per minute is equal to approximately 4 44 multiplied by the compressor horsepower This estimation is quite accurate at full load power but during facility shut down start up and periods of part load operation the estimation lacks accuracy The compressor system is fully loaded approximately 97 of the time and therefore the volumetric flow estimation is only about 3 different than the actual value 97 of the time The estimation of 4 44 CFM per horsepower is likely translatable to other compressed air systems and verification of this could be an area of future work Additionally observations were made regarding the relationship between pressure and compressor power It was shown that pressure is difficult to predict based on compressor 152 power This is because pressure can decrease when compressor power increases increase when power increases decrease when power decreases and finally pressure can increase when power decreases As seen in Figure 59 in section 4 3 8 pressure can decrease as the compressor power increases This is a typical and expected trend associated with using modulating compressors as compressed air demand increases At low demand pressure is high and the compressors can operate at a higher
39. age 2 of 3 D 0 113 7 1137 754 754 100 0 1000 1 1 B 2 AIRMaster Automatic Sequencer Results Page 2 Textile Manufacturer efficiency measures Automatic Sequencer Daytype Sunday cont 1 Saturday Sunday System Totals Total Demand Cost 65 062 Total Operating Costs 196 954 165 Energy Efficiency Measure Parameters Report REES Results Cont Page 3 of3 Annual Energy Energy Cost KWh 2 721 122 116 736 291580 12509 61 708 2647 3 074 411 131 892 B 3 AIRMaster Automatic Sequencer Results Page 3 166 Appendix C AIRMaster Reduce Air Leaks Inputs Energy Efficiency Measure Parameters Report AIR Mas ter For Company Name Reduce Air Leaks April 2 2014 By Your Name Page 1 of 1 EEM Scenario Textile Manufacturer efficiency me Description Reduce Air Leaks Facility Textile Manufacturer Measure cost 800 System Textile Manufacturer 4 000 Measured data Airflow capacity Compressor Operations to Feed Leaks Compressor Units Airflow 600 hp compressor Cap 0 0 150 hp compressor Cap 0 0 100 hp compressor Cap 50 0 500 hp compressor Cap 0 0 Lowest hourly system airflow acfm 3103 Leak Airflow Values Leaks acfm Peak system requirement Leaks 3103 Leaks 251 Peak system requirement 2852 Reduce leaks by 251 acfm C 1 AIRMaster Reduce Air Leaks Inputs 167 Appendix D AIRMaster Savings Summary aR Energy Efficiency Measure Parameters Report AIRMas ter
40. air Figure 3 Reciprocating Compressor Cross Section 9 The single acting reciprocating compressor is distinguished by a piston and cylinder similar to that of an internal combustion engine which is driven by a connecting rod from the crank 4 The reciprocating compressor is essentially a piston cylinder device with an inlet and exit valve The compression cycle starts when the piston is at top dead center when the piston volume is zero not including the clearance volume 16 KZ HOTU Waw Iuav 90T Ta MOTS Sim CAR Figure 4 Piston at Top Dead Center As the crank shaft turns the piston moves down in the cylinder thereby increasing the piston volume and creating a vacuum The intake valve allows atmospheric air to enter the chamber during this process 3 hi osma E Figure 5 Air Intake At the intake valve atmospheric pressure is higher than the pressure in the cylinder therefore air enters the cylinder At bottom dead center the intake valve is closed and the piston is driven back up the cylinder by the crank shaft 3 17 Figure 6 Piston at Bottom Dead Center The volume in the cylinder decreases as the piston moves towards top dead center which increases the pressure At the desired gauge pressure the exhaust valve opens and the compressed air is released from the cylinder The desired compressor pressure is often controlled by a spring which will force the exhaust valve shut The sp
41. air compressors Table 2 Facility Compressors Rated Rated Model Voltage Pressure Volumetric psig Flow 2 530 ACFM 3 000 ACFM 20 150 100 110 750 CFM 20 1001 100 110 500 CFM Compressor TS 32S 500 100 150 TS 32S 600 100 150 To gain a better understanding of how the system is operating collection of pertinent data is required Parameters required for proper analysis are the compressor power trending over time for each compressor pressure trending over time and total system capacity in cubic feet per minute over time The facility monitors compressed air flow continuously but not 51 amperage to the compressors or system pressure Thus installation of data loggers is required to acquire amperage and pressure readings As a note about the facility the facility uses compressed air 24 hours per day but typically does not require compressed air on Sundays 4 1 Measurement Equipment Onset Hobo data loggers and Onset HOBOware software is used to collect data regarding amperage and system pressure The H22 data logger was chosen for this project The H22 system consists of a HOBO H22 Data Logger a FlexSmart TRMS Module and the necessary HOBOware Pro Software Additionally a current transducer and a pressure logger will be required for data collection These items are depicted in the figures below FlexSmart TRM Active Figure 26 FlexSmart TRMS Module 52 The FlexSmart An
42. alog Module is a DC signal conditioning module for the H22 HOBO Energy Logger It is equipped with two channels which accepts a wide range of sensors and transducers The next item is the logger itself the HOBO H22 Data Logger which is a 15 channel system The H22 can monitor many different measurement types including gauge pressure AC current and compressed air flow Figure 27 below depicts the HOBO H22 Data Logger onset Push to Start Delayed Start Logging Memory Low Battery Low Sensor Fail Figure 27 HOBO Energy Logger The modules connect to one of the three ports and the sensor to record measurements connects to the module by means of a detachable screw terminal connector For this study 200 and 1500 amp current transducers were used to monitor AC current flowing to the electric motors of the compressors A CT senses voltage through a wire and then scales it to a matching amperage Figure 28 is a close up of a 200 amp Current Transducer CT 53 MAGNELAB scT 1250 200 200Amp To 0 333 Volt 4725 015 TAL 96927 HOS CE Figure 28 200 AMP Current Transducer Figure 28 shows the CT connected to the FlexSmart module which is connected to the HOBO H22 Energy Logger Before data logging can commence the logger must be programmed and launched Figure 29 Data Logger Setup 54 To launch the data logger one must first open the HOBOware program and connect the data logger to the computer using
43. an interface cable When the program is started the user can launch the device by clicking Launch under the Device tab This is shown in Figure 29 HOBOware Pro File Edit View Tools Window Help et Launch Ctrl L CH gt gt al a e A a2 E E SG SIE Ge SS KZ IS CRW ES Readout ZE Status Ctri 1 amp Stop Ctrl K Manage Shuttle Manage HOBO Data Node Network Ctrl Shift H Configure Modules Ports Ctrl Shift C Manage U30 Lab Calibration Select Device Ctrl N Default Action Utilities Figure 30 Launching a Device HOBOware then recognizes the device to be launched By moving forward the data logger can be programmed The Launch Logger screen allows the user to add a description configure sensors and select a launch time If logging a compressor the description may simply be the number of a compressor in a system of air compressors Choosing the required sensors for logging is also required The most pertinent data needed when logging an air compressor is the amperage so this may be selected Figure 31 displays this interface 55 HOBO Energy Logger gS Description Compressor 4 Serial Number 9920604 Status Deployment Number 3 Battery Level LA 70 Akaine Sensors Configure Sensors to Log FS TRMS AC1 S FS TRMSA S N 9926612 1 Current lt Enter label here gt Enable disable logging for this sensor 7 Logger s Battery Voltage Deployment
44. and System Dressumg 80 Compressed Air Demand CEM s cccscccssssecetssetsancacsseceaasteccdaser sactssontenss lecedatasetaas 82 System Compressor Power February 21 to February 2 83 Compressed Air Demand and Compressor Bower ssssssssssessseeessetesstesseesseessee 84 CFM vs hp with Linear Keren acc cececehest oncdataasuedsnas daveandaaeaeenaleactanesaaeeeadies 86 Actual CFM and Predicted CPM iie ccnsc2bsieeda wane EEN ech 89 Estimated Volumetric EE 91 Estimated Volumetric Flow Excluding Outliers 20 0 0 cecececeeneeceececseeeeeeeeeeesaes 93 Estimated Volumetric Flow and System Pressure cessceceeeeeeeeeeeeeeeeeeeseeeees 94 System Pressure Varying with Compressor Power 95 Pressure vs Power 60 hp 120 lp EE 96 System Pressure vs Compressor Power 210 hp to 270 Bp sssessssssesssessseeessees 98 Pressure vs Compressor Power 500 hp to 800 bp 99 AIRMaster Home Screen CI31 E a E NNE aT 101 AIRMaster Company Screen EE 102 ALI Masters ET EEN 103 Figure 63 Figure 64 Figure 65 Figure 66 Figure 67 Figure 68 Figure 69 Figure 70 Figure 71 Figure 72 Figure 73 Figure 74 Figure 75 Figure 76 Figure 77 Figure 78 Figure 79 Figure 80 Figure 81 Figure 82 Figure 83 XV AIRMaster Facility Information 131 104 AIRMaster Facility Compressor Summary 51 105 AIRMaster System Module 15 ceessccssscecsscecssececssccessscceensecessseeeenseeeees 106 AIRMaster System Module Da
45. and for a few hours into the morning on Saturdays Thursday January 26th was chosen as a typical production day January 25th and January 26th were chosen to represent typical Saturdays and Sundays Current Amps Click a date to highlight profile in graph System Not Assigned Period Baseline Right click on data points to select day type Left click to highlight the trace 12 13 14 15 16 17 18 19 Hour of the Dan 2 3 4 5 6 8 9 10 11 20 21 22 23 24 Caution Day profiles can be similar even though different equipment e g compressors is operating Use Trend Plots to examine the details of equipment operation before determining whether days should be assigned to the same daytype Create System Copy Plot to Copy Profiles to Hel DayType Profiles ClipBoard ClipBoard P Plot Day Tupe Remove Day Type D fades z Excluded Days Excluded Days Excluded Days Excluded Days Excluded Days Excluded Days Production Excluded Days Saturdays System DayType Profiles L System Type Period DayTypeName Gerda Hi 01 gt Baseline Production 600 694 76 696 ___ Not Assigned Baseline Saturdays 600 635 67 631 ___ Not Assigned Baseline Sundays 600 0 00 0 Current Current Sundays Figure 82 600 hp Compressor LogTool Daytypes 16 800 700 600 o 500 400 300 200 100 0 Ampera 600 hp Co
46. anufacturer At X Desired full load SE x pressure psig m Search results 127 records found Scroll right for more details Compressor Details Comp Type Manufacturer Model Single stage lubricant injected rotary screw lt Generic 5 hp 3 kw 5 Inlet modulation without un Single stage lubricant injected rotary screw lt Generic gt 5 hp 3 7 kw 5 Inlet modulation without un Single stage lubricant injected rotary screw Shp 3 7kwW Slinlet modulation without un Single stage lubricant injected rotary screw 7 5 hp 5 5 kw Inlet modulation without un Inlet modulation without un Inlet modulation without un Single stage lubricantinjected rotary screw lt Generic gt 10 hp 7 5kW 10 Inlet modulation without un Single stage lubricantinjected rotary screw lt Generic gt 10 hp 7 5kW 10 Inlet modulation without un Single stage lubricant injected rotary screw lt Generic gt 10 hp 7 5kW 10 Inlet modulation without un Single stage lubricantinjected rotary screw lt Generic gt 10 hp 7 5 kW 10 Inlet modulation without un w 4 Figure 68 AIRMaster Compressor Module Compressor Catalog 15 For example if one wanted to add a 150 hp single stage lubricant injected rotary screw compressor using modulating controls the search and results would be as shown in Figure 69 For this project an entry was made for each of the facility s compressors Each compressor was chosen from a generic entry which clos
47. ary 30 This data comes from the raw amperage data which was recorded every 5 seconds 65 100 hp Compressor Amperage 350 wo N A N n ji Compressor Amperage Amps n 1 14 1 19 1 24 1 29 Date Figure 36 100 hp Compressor Amps from Raw Data The compressor is utilizing load unload controls which is seen clearly during the period of January 21 to January 24 The spikes in the data in which the compressor power spikes close to 300 amps come from when the compressor first starts up This likely caused by locked rotor current which occurs due to high initial inductance requiring high amperage to turn the motor During the data collection period the average power from this compressor was 47 hp Figure 37 is a plot of the 100 hp compressor power using averaged data points Averaging data points together will smooth out the data thereby precluding high amperage readings from locked rotor amperage The power factor is calculated based on the percent full load amperage for each data point 66 been E 5 S Ba 5 aA v DI a Q 0 100 hp Compressor Power 1 14 1 16 Figure 37 100 hp Compressor Power from Averaged Data Points 67 68 The following Figure details the load unload cycle of the 100 hp compressor 100 hp Compressor Power _ 130 120 j kt
48. available in two distinct categories which are reciprocating and rotary screw compressors Reciprocating compressors are divided further into single acting and double acting both of which operate similar to that of a bicycle pump to compress air Industrial facilities also commonly use rotary screw compressors which compress air by trapping air inside the rotors and compress the air as it travels down rotors to the discharge point 4 Rotary screw compressors are often oil flooded to lubricate the rotors but oil free is also available 2 3 1 The Reciprocating Compressor Typically the modern reciprocating compressor used in manufacturing facilities are between 5 hp and 30 hp Single acting reciprocating compressors are generally available up to 150 hp and can produce higher than 175 psig compressed air 8 For a single acting reciprocating air compressor the operating efficiency is between 22 and 24 kw 100 CFM In general a double acting reciprocating compressor can achieve an operating efficiency of 15 to 16 kW 100 CFM Reciprocating compressors are often staged to improve efficiency with an intercooler between stages Most reciprocation compressor systems have two stages to produce 100 psig 15 air Three or more stages may be used where high pressure greater than 150 psig is needed such as in blow molding operations Figure 3 below is a cross section of a reciprocating compressor with three pistons to produce compressed
49. ay simply disable the control system or notch up the pressure band of each compressor which leads to inefficiency Tighter overlapping pressure bands may also be chosen as a solution but this will cause unnecessary starts leading to the purchase of another compressor The real issue with cascade systems is that time is rarely considered If enough storage is installed the compressors will have plenty of time to react to demand changes Instead of the purchase of an additional compressor which will likely only match demand efficiently 15 of operation storage should be considered Even more complex control systems exist for controlling multiple compressor systems Mainly this consists of Network and System Master Controls 11 3 3 2 Network Controls Network controls are used for larger systems of compressors and are better suited for avoiding part loading of compressors Network controls use the already existing control microprocessors to link together multiple compressors This forms a chain of communication that makes it easier to decide when to stop start load unload modulated vary displacement or vary speed for a compressor Generally in a system of compressors one compressor is the 44 lead compressor which operates constantly Other compressors in such a system would be subordinate to the demands of the lead compressor Traditionally network controls will have all necessary compressors except one fully loaded The
50. blue the 500 hp compressor power trend in red the 150 hp compressor power curve in green and finally the 100 hp compressor power trend in purple As shown the facility tends to operate multiple compressors simultaneously During standard operation hours which excludes weekends the facility tends to run either the 600 hp or the T11 500 hp compressors in conjunction with either the 150 hp compressor or the 100 hp compressor On Saturdays the plant typically operates the 150 hp compressor and the 100 hp compressor to fulfill compressed air needs while on Sundays the facility does not have a need for compressed air During the data collection period the 500 hp compressor supplied compressed air to the facility from January 15 to January 8 To fully meet the compressed air demand during this period the 150 hp compressor was also turned on From the 17 to the 18 of J anuary the 500 hp compressor power trended downwards while the 150 hp compressor utilizing modulating controls maintained power In the course of these operating conditions the system pressure drifted upwards to 110 psig from 100 psig 78 Combined Analysis Ki System Pressure Ei 5 S Ba S a v DI a Q E T C r O 0 0 1 14 1 15 1 16 1 17 1 18 1 19 120 1 21 1 22 1 3 1 24 1 25 1 26 1 27 128 1 9 130 181 Date 600 500 150
51. but at around 8 am the 100 hp compressor and the 150 hp compressor begin to supply compressed air to satisfy demand Although the 600 hp compressor is operating from hour 1 to hour 7 the compressor capacity is low This indicates that the compressor is operating inefficiently for a modulating compressor still requires a high percentage of its power at lower capacity 127 System Profile Data System Profile Data Saturday 2000 1800 1600 1400 1200 Airflow acim 1000 800 600 400 200 0 yo as GP by de re E G e afl aes UEP UR Ter Des ag TEP TE eal a aes a ot Hour Air Flow acm Print 2 Scale Compressor lt System gt v C Power kw yI Adjust Se C Capacity Figure 87 Saturday Profile Volumetric Flow 15 wm p FE System Profile Data x System Profile Data Saturday 500 7 E 600 hp compress 450 7 M 150 hp compress 100 hp compress 400 7 E 500 hp compress 350 4 300 4 Power kw 2504 200 4 150 4 i 100 4 50 4 0 2 e ER ty tyr EP SS Un PARE GEE aby GI EP Rea keet Hour C Air Flow acfm Print Scale c raven E Fee Acust compressor lt Sy fe wer E cI C Capacity osa Figure 88 Saturday Profile Data Power 15 H 4 128 Figure 88 is a plot of power over the Saturday daytype As expected the power is highest when the 600 hp compressor is operating Sundays are the final daytype to be profiled After inputting data the pr
52. c motor at specific amperages The calculation assumes a power factor and calculates the 60 power in kW See the AIRMaster power calculator in Figure 33 below The voltage used in the calculator is 460 volts and the electric motor is three phase File Calculators Help m WA i Eki Copy Compressor Query Inventory Copy From Catalog Cancel Facility v Compressor fio hp compressor v GE PN Power Calculator x ge Rotary Screw 501 acfm J User Enter average amps and average 7100 psig PRAT assigned ID volts to calculate power Compressor Description 100 hp compressor Details Average amps Nameplate Average volts 460 l Totals from Profile module Inlet Conditions Calculated power kw 82 5 Airflow Power Avg temperature F 85 DI acfm Df kw Atmos pressure psia 14 4 OK Cancel Vv l 501 m 827 J Iw l 498 Iv l 87 1 EI Y Unloading Blowdown Time n El o w E For lubricant injected rotary screws sec 40 Pressures are referenced from the compressor discharge Performance Profile Figure 33 AIRMaster Power Calculator Using the 100 hp compressor the next step is to tabulate power calculations starting with 0 amps all the way to 135 amps which is the full load amperage The power is then calculated with a power factor of 1 To calculate the power factor the AIRMaster power calculation
53. compressor that is not fully loaded is the trim compressor which is operated partially loaded to meet fluctuations in demand 11 The system can be dynamic in that as pressure increases to a point above the unload pressure or below the load pressure changes in the system operating can be made For example if the system pressure increases even after the trim compressor unloads one of the base load compressors will begin to unload When this happens the system pressure will likely begin to fall and the former base loaded compressor can begin to trim The former trim compressor can be shut down after a set run time and cool down timers are finished The former trim compressor will turn back on and continue to trim during high demand periods 11 The pressure sensor is typically downstream from the lead compressor to a central point where all compressed air meets 11 An example of network controlled system can be viewed in Figure 24 45 Figure 24 Network Controls There are potential pitfalls with network controls Using a pressure downstream of air treatment equipment could result in higher compressor discharge pressure due to increased pressure drop over time through equipment Measures must be made to ensure compressors are not compressing air above maximum allowable discharge pressures Typically network controls only work with compressors of the same brand and cannot be networked with remote compressor rooms Also there is no
54. ctricity rate is an important step in calculating cost savings from energy efficiency recommendations For this step the average energy and demand rates were used as inputs The electricity rates are divided into two seasons but as the electricity rates were averaged over a 12 month period both seasons are equivalent Energy costs 0 0429 kWh and demand costs 11 63 kW File Calculators Help D A T E a Close Utiity Duke Power d Rate Schedule WEE Rate Schedule Description Average Energy Rate Season 1 Season 2 Start Month Day 04 01 10 01 Demand rate u me 11 63 11 6 Block 1 0 04290 0 0429 Energy Rate k Wh Block 2 0 04290 0 04291 Block 3 0 04290 0 0429 TER Figure 62 AIRMaster Utility 104 5 1 3 Facility Module There are two main tabs within the Facility setup Facility Information and Compressor Summary from Compressor module The Facility Information tab includes input for the electricity rates facility name and annual plant electrical use in kWh The utility information fills in automatically when the facility name is chosen from the drop down menu on the top left corner of the screen The second tab Compressor Summary is automatically filled in after the compressor information is recorded in the Compressor module Sang ar Facility IESEL Facility Information Compressor Summary from Compressor module Facility Data Utility Rate
55. d Sundays were used as daytypes These daytypes are used later to input averaged logger data for specific periods of operation e x File Calculators Help m emm e LDllol9l eis Facility Textile Manufacturer DI System Textile Manufacturer DI System Data Sequencer Data Daptypes Calculated airflow capacity 6700 Textile Manufacturer System name WEE SL sum of compressors acfm Contact Nominal system pressure psig 103 0 Phone I E System elevation feet 633 Ar storage capacity receivers Sequencer used distribution pipe IO 414 0 S C Cascade pressures Air Storage equencer type E Targel presse Capacity Calculator Air storage capacity refers to unregulated primary storage This field is required to run Add Receiver Volume efficiency measure Figure 65 AIRMaster System Module 15 107 L File Calculators Help Daag Se Facility Textile Manufacturer DI System Textile Manufacturer DI Daytypes Season 1 demand months Season 2 Producion 125 demand months Study Sundey Dee e RE Total down days 1 Figure 66 AIRMaster System Module Daytypes 15 The System module also allows the user to qualify compressed air end uses however this project is not concerned with end use 5 1 5 Compressor Module The Compressor module is used to add compressors to the system Once the compressors are added to the system the controls and t
56. deavecaasesiandoaasasadentaeseumstunsaceesntee 13 Reciprocating Compressor Cross Section 9 oo ceescescsseeesseecsseceseeeseeeeseeesaeenseesees 15 Piston at Top Dead Gente EE 16 Ee 16 Piston at Bottom Dead Center ic i c dcesieseieci teen i tecsdeeleeinesiea listless 17 Top Dead Center EE 17 Compression TEE 18 Double Acting Reciprocating Compressor 1 19 Rotary Screw Compressor 3 eeessiisrernsssis sieisen erir si i a e iea 20 Oil flooded Screw Compressor 10 EE 22 OTIS AD as EE 23 Impeller of Centrifugal Compressor i e 25 IERT 29 CHE 31 Average kW vs Average Capacity with Load Unload Capacity Controls 11 32 Compressor Inlet Butterfly Valve 40 Open 34 Percent kW Input Power vs Compressor Capacity for Modulation 11 35 Variable Displacement together dee 37 VSD CUVE Sherehe ao a A 38 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 Figure 31 Figure 32 Figure 33 Figure 34 Figure 35 Figure 36 Figure 37 Figure 38 Figure 39 Figure 40 Figure 41 xiii Centrifugal Compressor Performance Curve 12 e cccesscecseceeceeececeeeeeeeteeeesaes 39 The Effect of Inlet Air Temperature 11 ssssesssesssseeesseesssessessseeessetessresseesseessee 41 Compressors in Cascade 11 csccgicscccsesctansaccssetsisantavivnvacrssecuedsaanssaceetedeneentonsasterednncs 42 Network e EE 45 Pressure Flow Controller with One C
57. e blowers and mixers Aspirating Atomizing Low pressure blowers Padding Low to medium pressure blowers Vacuum generator Dedicated vacuum pump or central vacuum system Personnel cooling Electric fans Open tube compressed air operated vortex coolers without thermostats Air to air heat exchanger or air conditioner add thermostats to vortex cooler Air motor driven mixer Electric motor driven mixer Air operated diaphragm pumps Proper regulator and speed control electric pump Idle equipment Put an air stop valve at the compressed air inlet Abandoned equipment Disconnect air supply to equipment 1 3 Introduction to Compressor Controls Compressor controls can vary from compressor to compressor and can be unique to a compressor system based on the number and types of compressors the system is comprised of As the number of compressors in a system increases so does the complexity of the required controls Single air compressor systems can consist of two distinct compressor types those being positive displacement and dynamic compressors Typically positive displacement machines are controlled by on off load unload modulation or VFD control types On off controls are generally found in smaller reciprocating compressors When the desired system pressure is reached the reciprocating compressor simply shuts down The compressor will subsequently turn back on when the
58. eaks After simulating this scenario AIRMaster calculated a new annual energy usage and total electricity cost The new annual energy usage is 2 945 413 kWh which is a reduction of 128 998 kWh per year The results from reducing air leaks are listed in Table 12 Daytype Production Table 12 AIRMaster Reduce Air Leaks Results Operating Hours Average Airflow acfm Annual Energy kWh 2 638 725 Annual Energy Cost 113 201 Demand Cost 63 145 147 Total Cost 176 346 Saturday 258 320 11 082 0 11 082 Sunday 48 367 2 945 412 2 075 126 358 0 63 145 2 075 189 503 The savings from reducing air leaks are detailed in Table 13 The total annual cost savings is 7 451 This represents a savings of 3 4 of the operational costs Daytype Production Table 13 AIRMaster Reduce Air Leaks Savings Operating Hours Average Airflow Reduction acfm Peak Demand Reduction kW Annual Energy Savings kWh 82 397 Annual Energy Cost Savings Demand Cost Savings Total Cost Savings Saturday 33 260 Sunday 5 2 4 Total Savings 13 342 128 999 The two measures result in a total annual savings of 52 377 representing 21 4 reduction in compressor electrical costs It should be noted that the actual savings could be lower or higher than the simulated savings This model
59. easing the amount of energy consumed by the air compressor This operating trend occurs again from January 24 to January 25 93 5 a 2 im EI i gt KI kl Ke L i a Figure 54 Estimated Volumetric Flow Excluding Outliers emand NNN 2 e Li aon oe Zi ii Compressed Air Dem 0 Estimated Volumetric Flow and System Pressure II mn dp nh Ohean JI Wa WWW TT VTT Ia 1 VIER We pl rr besa ee H 4 WITZ SC pt 1 14 1 16 1 18 1 20 1 22 1 24 1 26 1 28 1 30 Date Compressed Air Volumetric Flow System Pressure psig Figure 55 Estimated Volumetric Flow and System Pressure System Pressure psig 94 95 4 3 8 Pressure Analysis The pressure varies greatly depending on the system compressor power and compressed air demand Figure 56 is a plot of pressure in psig against the combined compressor power System Pressure vs Compressor Power Ze S a Band Gd EI a e x Ba 2 e Ce L i P 400 600 800 1000 1200 Total Compressor Power bhp Figure 56 System Pressure Varying with Compressor Power There are some interesting observations regarding Figure 56 At zero hp the pressure ranges from 110 psig to 0 psig This is due to pressure bleed down after the compressors are shut down for Sundays The next grouping of data points in Figure 56 sh
60. ectrical energy consumed by air compressors is converted to heat and not compressed air Thus the use of electricity instead of compressed air is much more efficient To illustrate this issue we will compare the operating cost of a one hp compressed air motor to a standard one hp electric motor A typical one hp compressed air motor requires 30 scfm at 90 psig which requires approximately 7 hp at the compressor shaft Therefore the compressed air motor will require 7 times as much electrical input and money to produce the same amount of work as a standard one hp motor This indicates that one should be judicious when determining whether or not compressed air should be used for a certain task at a manufacturing facility 1 2 1 Inappropriate Compressed Air Use Considering the expensive and inefficient nature of compressed air as a utility inappropriate compressed air uses must be kept to a minimum An inappropriate compressed air use is defined as any application that can be done more efficiently by a method other than compressed air 5 Provided below is a table from the Industrial Technologies Program which lists potentially inappropriate uses and a suggested alternative to that use Table 1 Inappropriate Uses of Compressed Air and Alternative Methods 5 Potentially Inappropriate Uses Suggested Alternatives Actions Clean up Drying Process Cooling Low pressure blowers electric fans brooms nozzles Sparging Low pressur
61. ely resembled the actual compressor specifications The chosen compressors are shown in Figure 70 below 5 Compressor Catalog Search _Select_ Clear Add Copy ka Cancel r Search Criteria M U otor power ser Compressor type IESEL T rating E S scil 150 110 DN E created only Desired capacity 5 Control type Inlet modulation without unloading D P ad ES p 8 Desired full load s Manufacturer Al e Ee Di EN m Search results 11 records found Scroll right for more details Compressor Details 150 Inlet modulation without un 150 Inlet modulation without un Single stage lubricant injected rotary screw lt Generic gt 150 hp 110 kW 150 Inlet modulation without un lt Generic gt Inlet modulation without un lt Generic gt 150 hp 110 kw 150 Inlet modulation without un lt Generic gt 150 hp 110 kW 150 Inlet modulation without un lt Generic gt 150 hp 110 kW 150 Inlet modulation without un lt Generic gt Inlet modulation without un lt Generic gt 150 hp 110 kw 150 Inlet modulation without un Generic gt 150 hp 110 kW 150 Inlet modulation without un v Figure 69 AIRMaster Compressor Catalog Search 15 110 amp Compressor Inventory Query 111 x Search _Select Clear air e m Search Criteria Compressor All type Control type At X Manufacturer Al Y Motor power rating hp kw Desired capacity acfm Desired
62. em cascades compressors and system pressure drops as compressors come online a centrifugal compressor will begin to operate in a condition known as stonewall This occurs when the compressor experiences less than design pressure at high flow rate The compressor pressure will plummet and lose the ability to produce additional flow While this is not harmful to the compressor the compressor does not realize its full potential To avoid these 49 issues a pressure flow controller can operate in back pressure mode for the dynamic compressor while operating with a forward pressure flow controller for the positive displacement side of the system The back pressure pressure flow controller has a pressure set point above the choke point and below the set point of the dynamic compressor which ensures the dynamic compressor will not be subject to surge or choke 11 50 Chapter 4 Data Collection The subject facility is a textile manufacturer in central North Carolina Large volumes of compressed air are used throughout the manufacturing of their high quality product The facility s compressed air system consists of four compressors flooded oil screw compressors Compressor 1 is a 500 hp Sullair TS 32 compressor 2 is a 600 hp Sullair TS 32 compressor 3 is a Sullair 150 hp rotary screw utilizing modulating controls and the final compressor is a Sullair 100 hp rotary screw utilizing load unload controls The table below lists the facility
63. ement Compressors iviseisssesicsssavessiseesactadeacevabecesacnaseceeeusdecedenasevaavabensass 14 2 50 The Reciprocating le 14 2 3 2 R tary Screw e ET 19 2A Dynamic OT 24 Chapter 3 Compressor Controls 1a vessasaiiig seeds sicseacnasgedieaysussadeusosdantscosbadessnbodavanueoadecaesdcatansbaas 26 3 1 Basic Individual Compressor Control 26 3 1 1 Start Stop Control sinnini ean e a AEN EEN 26 3 1 2 L oad Unload Contr l 42 05 22 Baad a e E a a e e E AE 27 Sols Mod latng ER eg eene deeg e R E E E 33 3 1 4 Dual Auto and Variable Displacement cc ceesceceeccecesececeeececeeeeecseeeecseeeessaeees 36 3 1 5 Variable Speed Drive Control ves jsicissecccieianjeacessziarssdesegaaasussaaevenadendansasaacedasdaceasnceae 37 3 2 Centrifugal Compressor Operation and Control 38 1X 3 3 Multiple Compressor Eemol casniscss eect ed cade tices Ss cglcseaetuacatvantes Zeg e sures dtvetccsaueeaban tee 4 3 3 1 Cascade E E 42 Ee e Ee 43 D5 F SV SUID Master E 45 3 3 4 Pressure POW e EE 47 Chapters Data Collect EE 50 41 Measurement Equipment sinsero E E Ee 51 4 2 Measurement Procedure and Data Collectnon 56 4 3 Data Analysis E 58 eS PO WEL Factor Analysis Ee 59 4 3 2 100 hp Air Compressor Data Analys 64 4 3 3 150 hp Air Compressor Data Analysis REENEN 69 4 3 4 500 hp Air Compressor Data Analysis 0 ccceeescccsseeeceeececeeececeeceeceseeeenneeeesaes 12 4 3 5 600 hp Air Compressor Data Analysis REENEN 74 A356
64. energy kWh and annual energy cost are located in Table 6 System Profile Totals below Table 6 System Profile Totals Peak Load Annual Annual Daytype Demand Factor Energy Energy kW kWh Cost Production 3 349 180 143 680 Saturday 330 162 14 164 Sunday 70 507 3 025 3 749 981 160 869 130 5 2 Energy Efficiency Measures AIRMaster calculates the savings from several energy efficiency measures On the demand side of the compressed air system the user can calculate savings from reducing the system air leak load improving end use efficiency and reduce system air pressure The software also offers a number of supply side efficiency measures Savings can be calculated from using unloading controls adjusting cascading set points the use of automatic sequencers reducing compressor run time and adding primary receiver volume This project will use AIRMaster to simulate savings from the controlling pressure and compressor operation with the use of an automatic sequencer and the reduction of air leaks The order of implementation of these recommendations does matter Decreasing the system air pressure will naturally decrease the leak load To validate the AIRMaster simulation a simplified model will first be made to calculate the savings from reducing system air pressure and then savings will be calculated by an alternate method 131 5 2 1 Reduce System Air Pressure AIRMaste
65. f compressors produce oil free compressed air they have a higher initial cost are generally less efficient and require higher maintenance costs than their oil flooded counterparts 4 2 4 Dynamic Compressors The most common and widely used compressor used for large industrial applications is the centrifugal compressor Centrifugal compressors operate by converting the high velocity of air flowing through an impeller to pressure energy The impeller accelerates the continuously flowing air stream to a high velocity and then the compressor converts the kinetic energy to pressure energy as the speed is reduced by means of a diffuser 4 Interestingly as the system pressure decreases the compressor capacity to produce compressed air increases 4 A centrifugal compressor will operate at an efficiency of 16 20 kW 100 CFM 4 Also it 25 should be noted that a centrifugal compressor will produce oil free compressed air Figure 13 depicts an impeller accelerating the flow of air through a compressor Gas out Gas in Figure 13 Impeller of Centrifugal Compressor 4 26 Chapter 3 Compressor Controls The purpose of compressor controls is to match the compressor output with the facility compressed air demand This is done by sustaining the compressor discharge pressure between a specified range Developing a control strategy whether for one compressor or multiple air compressor systems is vital to saving energy and money
66. full load pressure psig AL x Facility All E E Description E m Search results 4 records found Comp ype Manufacture gle stage lubricant injected r Sullair Corpor ingle stage lubricant injected r Sullair Corpor Textile Manufacture Textile Manufacture Two stage lubricant injected rot Sullair Corpor Textile Manufacture Textile Manufacture Two stage lubricant injected rot Sullair Corpor Figure 70 Compressor Inventory 15 Once the compressors are chosen the individual compressor controls and performance can be modified further to match the actual compressor The performance curves for each compressor are shown below The performance profile indicates the percent full load power the compressor uses at a certain percent capacity 112 Power Full Load Figure 71 100 hp Compressor Performance Profile 15 Figure 71 is indicative of an air compressor using load unload controls Because the compressor is allowed to unload one can expect to see a low percentage of full load power when no compressed air is being produced 113 Performance Profile 150 hp compressor GEN Ki D O I 3 ir ES wo a ao 30 40 50 Airflow Capacity Figure 72 150 hp Compressor Performance Profile 15 The performance curve in Figure 72 is a classic curve seen with compressors utilizing modulation controls The compressor tends to use a high
67. full load amperage to equal a power factor of 0 87 See Table 5 for power factor values at corresponding percent full load amperages 63 Table 5 Full Load Amperage and Power Factor Trend Line Power Factor Calculated Full AIRMaster Load Power Amperage Factor The power factor calculated using the trend line equation is fairly close to the AIRMaster power factor calculations therefore it is reasonable to use the trend line equation in subsequent analysis The trend line is eh order polynomial The trend line equation is given by PF 1 4059088822E 10x 4 5145915214E 08x 5 4563692241E 06x 3 0324285292E 04x3 7 5529979405E 03x 7 9049331517E 02x Equation 4 64 Power Factor vs Full Load Amperage 40 60 Full Load Amperage Figure 35 Power Factor vs Percent Full Load Amperage When calculating compressor power the collected amperage data will first be divided by the full load amperage to calculate percent full load amperage Next Equation 4 is used to calculate an estimated power factor This power factor will be used to calculate power in kW which is then converted to horsepower This method is used to calculate power for each of the compressors in the subsequent sections 4 3 2 100 hp Air Compressor Data Analysis Below in Figure 36 is a plot of the 100 hp compressor amperage from January 14 to Janu
68. g compressed air systems as a whole The free software package AIRMaster made available by the Department of Energy allows the modeling of a compressed air system and the simulation of energy efficiency measures Using this program the subject facility s compressed air system was modeled and then energy efficiency measures were simulated First an automatic sequencer was simulated to control the system air pressure to a reduced pressure of 95 psig and to decide which combination of compressors will adequately meet compressed air demand The second measure was to reduce the air leak load The reduction of air leaks will reduce the compressor capacity which then reduces compressor power The measures result in cost savings of 52 377 per year a 128 kW demand reduction and 804 436 kWh per year in energy reduction The total project cost is estimated to be 10 800 giving a simple payback of approximately three months Copyright 2013 by Daniel Paprocki All Rights Reserved A Quantitative Analysis to Determine Methods to Improve an Industrial Compressed Air System by Daniel John Paprocki A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Mechanical Engineering Raleigh North Carolina 2014 APPROVED BY Dr Stephen Terry Dr Herbert M Eckerlin Committee Chair Dr Alexei Saveliev DEDICATION I w
69. he compressors and creating a profile based on data acquired by data logging After opening the AIRMaster program the 101 user 1s presented with buttons to input review and edit the required information The figure below depicts the home screen of the program S AIRMaster fo amp s3 Inventory System Enhancements Calculators Help Maintenance Catalog Life Cycle Print Data Compressor Input Forms Profile Kayser Rath CAUSERS DJPAPROC DOCUMENTSI AIRMASTERAC Version 1 27 03 21 14 1 21PM Figure 60 AIRMaster Home Screen 15 102 5 1 1 Company Module After clicking on the company button the user is presented with several inputs After indicating the name of the company the industry type SIC description the units and the currency type the user can save and move forward to the next step File Calculators Help D A oa H Edit Currencies Company TextleCompary 2 Bowe Units Name Textile Company Ce English C Metric Industry type Manufacturing X E ey Tee SIC description Apparel and Other Textile Products A bar Address 1 as C kPa Sa m Metric Airflow Units City Cenal liters sec State Zip NC D cu meters hr Contact Phone Currency US Dolas o y File name C USERS DJPAPROC DOCUMENTS AIRMASTER COMPANY1 MDB Figure 61 AIRMaster Company Screen 15 103 5 1 2 Utility Module Determining the ele
70. he performance can be modified for each compressor 108 File Calculators Help im Bl ele Lepp Compressor Query Inventory Copy To Catalog Close Facility Textile Manufacturer e Compressor 600 hp compressor DI System Textile Manufacturer D 600 hp Two Stage Rotary Screw 2975 acfm User IT Compressor discharge T00 1200 cen GT control range 110 0 120 0 psig Geer Description e00 hp compressor Sequencer used l Details cen Full load operating Compressor type Two stage lubricant injected rotary screw GE 100 0 Rated capacity full Manufacturer Sulair Corporation load operating 3000 pressure acfm Model e00 hp 450 kw Serial nny Installation date 0371 7 2014 el Zeie E 450 e Compressor location Figure 67 AIRMaster Compressor Module 15 The first step is to add a new compressor to the system which is accomplished by clicking Add New Record on the top left corner of the screen under the File tab This will bring up a screen in which the user can search for a compressor by compressor type control type or power rating The compressor catalog is shown in Figure 68 109 DN Compressor Catalog Sc Search _ Select Clear Add Copy ele Cancel m Search Criteria Se Motor power a E User Compressor type RIF ERE ee Y rating hp kW created only aE Desired capacity S Control type Inlet modulation without unloading D M
71. icates the meshing rotors and bearings and serves to intercool the air during compression The lubrication also performs much like oil in an automobile piston and cylinder system would in that it acts as a clearance between the meshing rotors Thus the rotors never touch greatly reducing friction and heat 4 Commonly oil flooded rotary screw compressors are available from 3 hp to 900 hp with discharge pressures from 50 psig to 250 psig 4 Figure 11 is a schematic of a generic oil flooded screw compressor package 22 1 Air filter 2 Intake valve 3 Airend 4 Coupling 5 Motor 6 Minumum pressure valve 7 Separator elemet 8 Blow down valve 9 Receiver tank 10 Ball valve drain 11 Oil filter 12 Thermal valve 13 Oil cooler 14 After cooler 15 Ball valve service line 16 Fan 17 Pressure transmitter 18 Temperature sensor 19 Moisture separator Figure 11 Oil flooded Screw Compressor 10 Advantages of oil flooded rotary screw compressors include relatively compact sizes for high horsepower systems low vibration and accurate part load capacity control systems Disadvantages of an oil flooded rotary screw compressor include the fact that lubricant can carry over into the compressed air flow and the system efficiency can vary depending on the chosen control mode One can expect to achieve operating efficiencies of 17 to 22 kW 100 CFM for single stage compressors and 16 to 19 kW 100 CFM for two stage compressors 4
72. immediately turns the redundant compressors off before they can start to produce compressed air 91 Estimated Volumetric Flow 1 17 1 19 1 21 1 23 1 25 Date Estimated Volumetric Flow Figure 53 Estimated Volumetric Flow 92 Because the large spikes in the estimated volumetric flow plot are unlikely and similar spikes in actual volumetric flow are not seen these points will be removed These changes are reflected in Figure 54 on page 93 Figure 55 on page 94 is a plot comparing the system pressure in psig to the estimated volumetric flow Pressure and volumetric flow are depicted in red and blue respectively Generally as the volumetric flow in a compressed air system increases the system pressure will reduce indicating a demand event This is seen from January 20 to J anuary 24 as the pressure drops when the compressed air demand increases This trend is normal and expected but another trend emerges in the data which is concerning From January 17 to January 18 the pressure rises while the volumetric flow decreases which is known as pressure run up This occurs during periods of low demand meaning that compressor power and capacity are decreasing while the pressure continues to increase Ideally the pressure would remain at a set point of around 95 psig Operating the compressors at 120 psig uses an unnecessary amount of compressor power and wastes money by incr
73. in both Mechanical Engineering and German Studies Daniel applied to N C State s Mechanical Engineering graduate program under the direction of Dr Stephen Terry Daniel s concentration within Mechanical Engineering is Thermal Sciences Daniel has attended approximately 40 energy surveys as a member of the IAC and has been the lead graduate student on several reports Outside of school Daniel enjoys lifting weights running and going to the gym Daniel also enjoys collecting and listening to vinyl records Additionally Daniel loves spending time with friends and family playing card and board games and playing fetch with Seamus vi ACKNOWLEDGMENTS I would like to thank and recognize several people that helped make this work possible I would first like to thank my parents Gerald and Cathi Paprocki for their endless support and patience during my pursuit to earn undergraduate degrees in Mechanical Engineering and German Studies and a Master s degree in Mechanical Engineering Undoubtedly it required a great deal of patience during this length of time I would also like to thank my brother Nathan and sisters Katie and Jennifer for their show of support and love during this process I would like to thank all good friends including but not limited to Connor McDonald Patrick Murray Sam Gates Jackson Wooten Kiran Thirumaran and Taylor Atkins for their encouragement throughout the process Additionally I would like to thank Laura f
74. ing discipline to succeed in and with a second major in German Studies Daniel had his work cut out for him With the double major graduating in the standard four years would be next to impossible The German Studies iv major required a semester studying in Germany which would take a whole semester and summer away from engineering Daniel spent the spring and summer of 2009 in Europe to study in Germany The semester abroad in Germany proved to be trying but eye opening Immersing in another culture and language is a rare and excellent way of expanding one s horizons but can be exhausting While in Germany Daniel spent time with old friends met many new and interesting people saw beautiful cities artwork and landscapes Once back at N C State Daniel continued to march through his Engineering and German courses Of the topics within Mechanical Engineering the thermal sciences interested Daniel the most During the fall of 2011 Daniel decided to apply for the State Energy Internship Program which was headed by Dr Stephen Terry of the Mechanical Engineering Department This Internship offered Daniel his first hands on engineering experiences Daniel worked on several measurement and verification projects and was able to attend four energy surveys through the Industrial Assessment Center at N C State After the internship ended Dr Terry offered Daniel a position within the IAC After graduating in December of 2012 with degrees
75. ing with heat recovery to the steam system Raleigh North Carolina North Carolina State University 2013 3 Hunt David George An experimental and quantitative analysis to determine the effect of changing inlet air temperatures on the performance of an oil injected electrically powered twin screw air compressor for industrial process Raleigh North Carolina North Carolina State University 2012 4 Fundamentals of Compressed Air Systems Raleigh s n 2013 Compressed Air Challenge 5 Energy Tips Compressed Air EERA Online August 2004 https www l eere energy gov manufacturing tech_assistance pdfs compressed_air2 pdf 6 Pre Workshop Assignment The Compressed Air Challenge 1999 7 Terry Dr Stephen MAE 403 540 Chapter 3 Psychrometrics and HVAC Processes 8 Lawrence Berkeley National Laboratory Resource Dynamics Corporation Improving Compressed Air System Performance a sourcebook for industry Office of Energy Efficiency and Renewable Energy Online November 2003 Cited February 18 2014 156 http www l eere energy gov manufacturing tech_assistance pdfs compressed_air_sourceboo k pdf 9 Tawil Elie Miscellaneous Mechanical Equipment CED Engineering Online http www cedengineering com upload Miscellaneous 20Mechanical 20Equipmentpdf 10 Poona Pneumatic Rotary Compressor Division Poona Pneumatic Company Online Cited January 24 2014 http www poonapneumatic com rotary compressors html 11 Adva
76. isndcsisassuseedevsaieaerasersnassdcaddecasdsead etenedaetssotian E 129 600 hp Compressor Production Profile 15 oo eeeceeeeseceeececeeeeeceeeeeeeteeeenteeeees 131 Sample Pressure Reduction Simulation 131 133 Energy Efficiency Measures Cl 3 ic igsicecsanceceastestonstataasveecaassaveasdaaeaceaolenctasesaaeceats 138 AIRMaster Use Automatic Sequencer Measure 131 140 AIRMaster Automatic Sequencer Hourly Data l 141 ATRMaster Reduce Air Leaks 146 Chapter 1 Introduction Industrial manufacturing a vital component to the United States economy requires a significant amount of energy during production The energy consumed by industry is distributed to a diverse number of end users which may include ovens electric boilers robotics manufacturing machinery HVAC lighting and lastly air compressors Utilities must provide the energy to manufacturing facilities to run all of these systems but this comes at a large cost The substantial energy consumption comes at a price which cuts directly into profit margins Compressed air which is often a necessity to manufacturers comprises a significant segment of energy consumption in the average manufacturing facility For the reason that energy costs can directly influence profits and compressed air encompasses a large percentage of the energy use in a manufacturing facility finding any means to increase efficiency of compressed air systems should be a high priority This project wi
77. isting and Proposed Data 160 Energy Efficiency Measure Parameters Report Sg 2014 Use Automatic Sequencer Cont Page 2 0f3 10 1 12 Of Off Of 1 1 1 2 2 2 of Off Of 1245 1245 1245 1133 1152 nyu 205 3 207 1 2064 A 2 Automatic Sequencer Saturday Existing and Proposed Data 161 Energy Efficiency Measure Parameters Report April 2 2014 Use Automatic Sequencer Cont Page 3 of3 A 3 Automatic Sequencer Sunday Existing and Proposed Data 162 Appendix B AIRMaster Automatic Sequencer Results 163 a55 Energy Efficiency Measure Parameters Report AlRMaster For Company Name Results April 2 2014 By Your Name Page 1 of 3 Profile Summary EEM Scenario Texte Manufacturer efficencymessures EEM Automatic Sequencer Daytype Production 2 3 4 5 4464 2550 846 1 09 0 09 2 09 H 00 3 00 0 09 4 4464 2550 Daytype Saturday 1 2 3 4 5 6 7 8 9 10 WI 12 B 14 15 16 17 18 19 20 21 22 foo hp compressor CatPower KW 4005 398 3 3973 3989 396 9 3964 3854 0 0 00 00 0 0 00 00 0 0 00 00 0 0 00 00 0 0 00 09 0 0 bo CalcAirfow acm 1712 1672 1655 1683 1647 1638 1438 0 0 0 0 H 0 H 0 0 0 0 H 0 0 H 0 p Cab Capacty 568 555 549 558 546 43 477 0 0 00 09 0 0 00 bb 0 0 00 00 0 0 090 00 0 0 0 0 00 0 0 p o Sequence 1 1 1 1 1 1 1 0 H 0 0 0 0 H 0 0 0 0 H 0 0 0 0 P 150 hp compressor B 1 AIRMaster Automatic Sequencer Results Page 1 164 Energy Efficiency Measure Parameters Report eg sang Results Cont P
78. it 6 3 Further Opportunities While this project is associated primarily with improving the overall compressor system controls part load control is an area of possible improvement From data analysis there is often a smaller compressor that is partly loaded using a high percentage of full load power at lower compressor capacities If the facility were to purchase a variable speed drive for one of the smaller compressors the part load efficiency would increase A variable speed drive has approximately a one to one ratio between percent compressor capacity and percent full load compressor power Hence if the variable speed drive compressor is at 50 percent capacity the compressor will use 50 percent of its full load power A compressor using load unload or modulating controls cannot achieve this ratio and therefore are more expensive to operate at part load While this opportunity could offer significant energy and cost savings the implementation of a variable speed drive is quite costly therefore only a complete analysis could determine the practicality of such a project 155 REFERENCES 1 Electricity Explained Electricity eia U S Energy Information Administration Online April 25 2012 Cited January 16 2014 http www eia gov energyexplained index cfm page electricity_home tab2 2 Cranford Elton Dale A quantitative investigation to improve industrial reciprocating and centrifugal air compressor performance via inlet air cool
79. itch Furthermore this method can save energy as the motor and compressor operate only when required However the frequent full load amp starting can wear down a motor and can only be used with smaller motors 3 1 2 Load Unload Control Load Unload controls are a common control scheme for oil flooded rotary screw compressors but can be used for larger reciprocating and centrifugal compressors As the predetermined pressure set point is reached the compressor is allowed to unload which uses a lower power setting and saves energy To unload means to close the inlet air damper ceasing the production of compressed air and slowly depressurizing the compressor During this process the compressor is still pushing against the pressure in the sump which requires power but the sump pressure is allowed to slowly decrease Once the sump reaches about 15 28 psig the compressor operates at fully unloaded conditions and draws 30 to 40 of its full load power Decreasing the oil pressure too quickly would be analogous to shaking up an unopened soda bottle Shaking the soda bottle causes dissolved carbon dioxide in the liquid to be released thus increasing the pressure If opened too quickly the soda will foam and result in a mess The same phenomenon will occur in an oil flooded rotary screw compressor Oil is compressed along with air and gas is dissolved in the lubricant If the pressure is reduced too quickly the oil will foam and lose i
80. ith the leak depends on the system air pressure and the size of the leak The formula to calculate volumetric flow of free air associated with an air leak is given below E RCRD SE 460 C x P x T 460 Vf Equation 9 Where 144 Ve volumetric flow of free air CFM Ci choked flow constant 1336 ft min oR 5 Po compressor operating pressure Ca discharge coefficient for orifice 0 6 no units D leak diameter inches Ti inlet temperature C2 conversion constant 144 in ft P inlet atmospheric pressure 14 7 psia To average line temperature The compressor power required to supply the compressed air for each leak is given in the formula below k 1 k P kxN P xC xV x _ x N xC x 1 k 1 P H Power Re quired E x E where L power loss hp C2 conversion constant 144 Ir k specific heat ratio of air 1 4 no units N factor based on type of compressor considered 1 25 for single stage flooded oil screw 2 for two stage C3 conversion constant 3 03 x 10 hp min ft 1b 145 Ey air compressor volumetric efficiency 85 no units Em compressor motor efficiency Because of the way typical compressors operate even if all leaks are eliminated the entirety of the power required to satisfy those leaks will not be saved Typically a modulating compressor still uses 65 to 70 percent of its full load power at zero percent capacity Thus only 30
81. lations Using the 100 hp compressor the power was calculated with input amperages from 0 to its full load amperage of 135 amps The calculated compressor power was divided by the power at the same amperage assuming a power factor of one resulting in the AIRMaster calculated power factor The calculated power factor was then plotted against the calculated compressor power which was then used to perform a 6 order polynomial regression The resulting polynomial equation could be used to determine the power factor at a specific compressor power reading This first trendline equation is only useful for the 100 hp compressor 150 Therefore to form a power factor equation that is applicable to all compressors the input amperage was divided by the full load amperage to give the percent full load amperage Then a plot of power factor against percent full load amperage was made resulting in a 6 order polynomial trendline equation This equation is particularly useful as the power factor can now be calculated for any sized motor based on the percent full load amperage Furthermore this equation can be utilized during any future compressor power analyses It can be quite worthwhile to collect data about the compressed air demand Knowing information about a facilities demand for compressed air can help determine periods of the production day in which compressed air demand is high Volumetric flow can also help determine inefficiencies in the opera
82. layed start was used 4 2 Measurement Procedure and Data Collection The initial phase in the experimental analysis of the compressed air system operation involved collecting data regarding the amperage draw of each compressor the system pressure and system volumetric flow rate There were two separate visits to collect two sets of data 57 An initial facility visit on January 14 2014 was setup to become familiar with the compressed air system and program data loggers to monitor amperage and system pressure The data loggers for amperage readings were programmed to record a reading every 5 seconds whereas the pressure transducer recorded readings every minute For the 100 hp and 150 hp air compressors 200 amp current transducers were used whereas 1 500 amp current transducers were utilized for the larger 600 hp and 500 hp compressors To indicate the air compressor to which each data logger would be installed a specific label was attached to each data logger The data loggers were left with the maintenance manager to be installed These loggers remained logging until January 30 2014 for a total of 17 days of data collection On January 30 2014 the loggers were retrieved to analyze the data Additionally volumetric flow data for this time period was requested for a complete overview of the system operation Unfortunately the total volumetric flow was unavailable for this time period thus a second data collection period was set
83. ll analyze an actual compressed air system and attempt to identify methods to increase the overall efficiency with a focus on compressor controls and how to operate a system of compressors efficiently and to meet compressed air demand 1 1 Electrical Energy and Compressor Use in the United States The United States relies on several sources of energy for the production of electricity This includes coal natural gas nuclear hydro oil and finally renewables The percent of generation for each energy source for 2011 is shown in Figure 1 below 1 Ge Percent Energy Generation Oil Petroleum and other 1 Figure 1 Percent of Energy Generation for Various Sources 1 As shown above coal represents the largest percentage of electricity generation followed by natural gas and nuclear In 2011 the total U S electrical energy consumption was 3 882 billion kWh 1 In addition to electricity natural gas is also commonly used in manufacturing facilities U S Manufacturers consume nearly 26 of all electrical energy consumed in the United States 2 Approximately 10 of electricity consumed in manufacturing facilities is from compressed air Thus 2 6 of all energy consumed in the United States is consumed by air compressors in an industrial setting 3 This represents a staggering 101 billion kWh per year To put this into perspective 101 billion kWh could power the average American home using 1 200 kWh per month for o
84. luded Days System Tye Period Day TypeName ame Name eo Tg Excluded Days p Not Assigned Current Baseline Production 0 00 Excluded D Not Assigned Curent Baseline Saturdays e 0 00 Ge __ Not Assigned Curent Baseline Sundays 150 173 75 1 Excluded Days i are Figure 79 LogTool 150 hp Compressor Daytypes 16 150 hp Compressor Daytypes Koch nN Amperage nn 0 01234567 8 9 101112131415161718192021222324 Hour of Day Production Saturday Sunday Figure 80 Plot of 150 hp Compressor Daytypes 122 The 500 hp compressor is not a primary compressor and does not ordinarily operate Generally the 600 hp compressor is the base compressor operating in conjunction with a smaller compressor Thus the 500 hp compressor is considered off at all times during modeling simulations Nevertheless daytypes were created but the average amperage values for each daytype were zero As seen in Figure 81 the 500hp compressor rarely turned on but operated at close to full load on 3 days The effect of setting the daytypes to zero for the 500 hp compressor is that A RMaster will model the 600 hp compressor as the base compressor System NotAssigned Period Baseline AY ES a i Se ee S 4 Hourofthe Day Figure 81 500 hp LogTool Daytypes Plot 16 The 600 hp compressor operates all hours from Monday to Friday
85. ly close accordingly it is reasonable to utilize the AIRMaster simulation for forthcoming recommendations 137 5 2 2 Automatic Sequencer Aligning with the main objective of this thesis an automatic sequencer which is a form of system master controls could create a better compressor control system Controls would allow the compressors to operate more efficiently thereby saving both energy and money An automatic sequencer allows the compressed air pressure to be controlled to a lower set point adhering to a smaller control band At the same the sequencer decides based on pressure and compressed air demand which compressors are needed or unnecessary First reducing the compressed air system pressure will greatly reduce the demand for compressed air consequently the compressors will see a reduction in power Secondly the sequencer might decide to turn off the 600 hp compressor and use the 500 hp compressor with the 100 hp compressor to meet demand In turn the operating demand will further reduce leading to energy and cost savings Employing an automatic sequencer makes sense for a large compressed air system such as this AIRMaster will simulate the use of an automatic sequencer hour by hour first reducing the pressure to the desired set point then choosing which compressors make sense to operate In addition to operating an automatic sequencer savings will be shown from decreasing the air leak load in section 5 2 3 For larger co
86. modulating percentage As the compressed air demand increases the butterfly valve begins to open up and the compressor power increases The pressure continues to decrease until the compressors are at full capacity and the demand is met This indicates a negative correlation between pressure and brake horsepower Ultimately observations such as these help to illustrate compressor operation and help determine any potential issues with the subject compressed air system 6 2 AIRMaster Conclusions As aresult of data collection analysis and modeling with the AIRMaster the operation cost of the facility s compressed air system can be greatly reduced by the implementation of network controls and the possible reduction of air leaks The automatic sequencer will first act to reduce the system air pressure to 95 psig with a variance of 3 psig This would control the system pressure within 92 psig and 98 psig Secondly the sequencer would determine which compressors are to operate based on compressed air demand During data collection all of the compressors turned on during operation start up which is not necessary and could set a high billing demand An automatic sequencer would avoid this type of operation 153 After modeling the facility s compressed air system in AIRMaster the first energy efficiency measure to be simulated was the implementation of the automatic sequencer This measure offers an energy savings of 675 438 kWh annually
87. mpressed air systems fixing air leaks could realize significant savings Entering the Energy Efficiency Measures module in AIRMaster the user is given the opportunity to employ the use of an automatic sequencer It was decided that an appropriate pressure set point would be 95 psig with a variance of only plus or minus 3 psig The facility 138 might have the ability to further decrease the pressure but this would need to be accomplished in small pressure increments to ensure no production issues occur at the lower pressure The Energy Efficiency Measures screen is shown in Figure 93 below File Calculators Help D FAIK ele Copy EEM Scenatio Life Cycle Results Close Facility ENEE EEM Scenario Textile Manufacturer efficiency me D System Textile Manufacturer e Data Entry Savings Summary Acht j e Edit Data Needs Description extile Manufacturer efficiency measures Indude Order eae diss DEMAND SIDE Reduce Air Leaks 2 DI xI Improve End Use Efficiency Reduce System Air Pressure SUPPLY SIDE Use Unloading Controls Adjust Cascading Set Points Ra ll bal Use Automatic Sequencer 5 Reduce Run Time 4 Add Primary Receiver Volume Available only if air storage capacity was entered in the system module Visit the system module to edit this value Only lubricant injected rotary screw compressors with unloading controls will benefit from adding receiver volume
88. mpressor Daytypes 0123 45 67 8 9 101112131415161718192021222324 Hour of Day Production Saturday Sunday Figure 83 600 hp Compressor Daytypes 123 124 5 1 7 Profile Module After the daytypes have been have been defined they can be applied to AIRMaster The voltage and average amperage for each compressor for all three daytypes are pasted into AIRMaster to create the system profile In the System Profiles module first the daytype is chosen the cascade order is or an on off position is chosen and then the voltage and averaged amperage data is entered Figure 84 is the system profile for the production daytype File Calculators Help lgl ale r Select Facility Textile Manufacturer D Daytype Production z System pressure THON 120 0 psig System Textile Manufacturer z control range Profile Summary Cascade Order click cell to toggle staget off Copy Prev Col Graph Compressor 2 3 d 5 6 7 1 1 5 Data Entry 150 Fp compressor vots Oo oof oof ool oof oof D oof oo _ Amps oof oof oof oof ooj oof ooj ooj oo Figure 84 System Profile Module Production Daytype 15 125 The system profile data for the production daytype is plotted below The plots include volumetric air flow ACFM and power kW Figure 85 shows the volumetric flow by the hour for the average production day The peak air flow is a
89. nced Management of Compressed Air Systems Raleigh The Compressed Air Challenge 2014 12 Boyce Meherwan et al et al Practical Apsects of Centrifugal Compressor Surge and Surge Control Turbolab tamu edu Online Cited 1 27 2014 http turbolab tamu edu proc turboproc T12 T12147 173 pdf 13 CAGI Compressor Data Sheet Compressed Air and Gas Institute Online Cited March 19 2014 http www sullairinfo com Downloads CAGI 20Data 20Sheet_TS32S 600LWC pdf 14 AIRMaster User s Manual energy gov Online 2000 Cited March 21 2014 https www 1 eere energy gov manufacturing tech_assistance pdfs airmaster_user_manual pd f 15 Program Washington State University Energy AIRMaster Software sl Developed by WSU for the Department of Energy 2000 16 LogTool Software s l SWB Consulting INC Compressed Air Challenge 157 APPENDICES 158 Appendix A AIRMaster Automatic Sequencer Existing and Proposed Scenarios 159 APB Energy Efficiency Measure Parameters Report AIRMas ter For Company Name Use Automatic Sequencer April 2 2014 By Your Name Page 1 of 3 EEM Scenario Textile Manufacturer efficiency measures Description Automatic Sequencer Facility Textile Manufacturer Measure cost 10 000 System Textile Manufacturer Target Sequencing Data Target Pressure Varance 1 1 Of Off 2 2 Of Off UT WIT 3008 2385 575 6 5741 A 1 Automatic Sequencer Production Ex
90. nd the compressor power increases The pressure continues to decrease until the compressors are at full capacity and the demand is met Figure 59 indicates a negative correlation between system pressure and total compressor power at higher percentages of compressed air system power 100 Chapter 5 AIRMaster System Modeling AIRMaster is an energy efficiency tool used to model compressed air systems and then create energy efficiency recommendations It can help to maximize compressed air system efficiency AIRMaster allows the user to manage multiple facilities and compressed air systems cataloging an inventory of generic or name brand air compressors The software simulates the existing compressed air system and any modifications The software will model part load system operation for any combination of compressors AIRMaster will allow the modeler to consider a number of efficiency measures including reducing air system air leaks improving end use efficiency reducing the compressor air pressure adjusting cascading set points implement unloading controls when applicable implement an automatic sequencer programming compressors to run less or more depending on compressed air demand and finally add receiver volume if necessary 14 5 1 Modeling the Compressed Air System Modeling a facility s compressed air system involves entering factual information about the company utilities facility compressed air system operation t
91. ns between 103 psig and 105 psig The pressure range is higher during high loads typically remaining between 100 and 105 psig Pressure against compressor power is shown in Figure 58 98 System Pressure vs Compressor Power S a Z Gd EI a a Q Ba ZS e SA L i 230 240 250 Total Compressor Power bhp Figure 58 System Pressure vs Compressor Power 210 hp to 270 hp The final grouping of data points from 325 hp to 825 hp shows a few different combinations of compressors It includes the 600 hp compressor operating alone the 600 hp compressor operating with the 100 hp compressor and the 500 hp compressor operating with the 150 hp compressor The most notable trend occurs between 500 hp and 800 hp 99 System Pressure vs Compressor Power jnd n S a Z Gd EI a a Q DI Ba ZS e SA N y 0 0502x 136 08 R2 0 2981 600 650 700 Total Compressor Power bhp Figure 59 Pressure vs Compressor Power 500 hp to 800 hp Figure 59 shows pressure decreasing as the compressor power increases This is a typical trend seen with modulating compressors as compressed air demand increases At low demand pressure is high and the compressors can operate at a lower power percentage As the compressed air demand increases the butterfly valve begins to open up a
92. ofile indicates that the 100 hp compressor and the 150 hp compressor are the only compressors to operate and only from hour 1 to hour 7 Figure 89 is a plot of air flow for the Sunday system profile The peak air flow is just under 1200 ACFM After hour 7 the compressors turn off and the system compressed air demand remains at 0 ACFM until production resumes on Mondays pj System Profile Data System Profile Data Sunday 2000 E 600 hp compress 1800 E 150 hp compress 100 hp compress 1600 E 500 hp compress 1400 1200 Airflow acim 1000 800 600 400 200 0 1223 EE er eyy PR wW nd et Gy AE e TA A eee ath Hour Air Flow Lech Print Cen Compressor lt System C Power kW e C Capacity Figure 89 Sunday Profile Volumetric Flow 15 Figure 90 illustrates the compressor power for each hour of the Sunday profile The peak power is just over 200 kW 129 System Profile Data System Profile Data Sunday 500 7 E 00 hp compress 450 150 hp compress 100 hp compress 400 4 Ben hp compress 350 4 300 7 Power kw 250 4 200 4 150 4 100 4 50 4 1234566 oe tS ie ail Wee iis VAY ite E ily asl Ue al 2 oes A Hour C Ait Flow acm Print eae Compressor lt System gt I G Bower It C Capacity _ Cose Figure 90 Sunday Profile Power 15 The profile totals generated in AIRMaster for average airflow ACFM peak demand kW annual
93. ojoo C ben Current _ Amps x Baseline v Not Assignec 1 14 2014 13 00 00 1 30 2014 16 51 20 5 Data giel Tele C 500 Curent v fAmps v f Baseline w Not ssignec e 1714 2014 13 00 00 1 30 2014 16 51 20 5 Data miimi mjm O 600 Current y Amps v Baseline w NotAssignec e 1 14 2014 13 00 00 1 30 2014 16 51 20 5 Uncheck Trend Scatter DayType Figure 76 LogTool Imported Loggers 16 To create a daytype for a compressor click check box next to the compressor for a particular compressor and then press the DayType button above The program will output the average amperage hourly for each day of data collection The user must choose a day that most resembles the daytype that is desired For example the user would choose a typical operating day for a production daytype and an average Saturday and Sunday for those daytypes respectively Daytypes for the 100 hp compressor will be chosen first followed by the 150 hp compressor 500 hp compressor and 600 hp compressor Wednesday January 22 was 119 chosen as a Production day The chosen dates for the daytypes for Saturdays and Sundays are January 25 and January 26 respectively br DayType Analysis ez System Not Assigned Period Baseline Current Amps 1407 120 4 Right click on 100 data points to select day type on Left click to highlight the en trace 407 207 0 e g gt 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2
94. ol band from approximately 100 psig to 113 psig At 113 psig the compressor unloads which is called the cut out pressure When the pressure drops under 100 psig the compressor cuts back in at maximum power To further illustrate the operation of the compressors if the system air pressure is 108 psig the 600 hp compressor will be fully loaded and the 100 hp compressor will be partly loaded Should the system air pressure drop below 100 psig both compressors would be fully loaded to meet increased demand 116 The performance points entered into AIRMaster for each compressor are as follows The 600 and 500 hp compressors are fully loaded at 110 psig and fully modulated at 120 psig As the trim compressor the 100 hp compressor has a cut in pressure of 100 psig and a cut out pressure of 113 psig The 150 hp compressor is the base compressor during operation on Saturdays and Sundays therefore the compressor is fully loaded at 110 psig and fully modulated at 120 psig 5 1 6 LogTool The next step is to add operation profiles for each compressor This is to indicate when and how the compressors operate Using data acquired by data logging the user can indicate how each compressor operates within the compressed air system The first step is to input logged data into a program called LogTool which is a public domain tool made available from SBW Consulting Inc and the Compressed Air Challenge The program allows the user to create a da
95. ompressor Room OI 48 FlexSmiart RMS Module ee erer 51 HOBO Energy Loe Ser onene aoii edel Eed Edge 52 ZOO AIP Current Transducer e ni a gabe Sadun E paneer west 53 Data Logger EE 53 AUF RE 54 Launch Logger Interface censent Iddee aE E EE E 55 Contie re SENSOR Ee 56 AIRMaster EE 60 Power Factor Vs Ampera dee 62 Power Factor vs Percent Full Load Amperage nssesseessssssessseeesseeessresseesseessee 64 100 hp Compressor Amps from Raw Data sseseseeeeeeseeseesereresreeseesresreeseesresrresee 65 100 hp Compressor Power from Averaged Data Ponts 67 100 hp Compressor Load Unload Cycle A 68 150 hp Compressor Amperage ccceccsccsseecssccecssececssececsseeecssccecsseceesscceeseeeesaes 69 150 Hip EE 71 Illustration Of Modulation oo ceccccecccccccesssssssceccccceeesssssscsscecsssesneaeeeseeseeees 72 Figure 42 Figure 43 Figure 44 Figure 45 Figure 46 Figure 47 Figure 48 Figure 49 Figure 50 Figure 51 Figure 52 Figure 53 Figure 54 Figure 55 Figure 56 Figure 57 Figure 58 Figure 59 Figure 60 Figure 61 Figure 62 XIV 200 hp Compressor Amperage EE 73 SOO hp Compressor POW x eeler eege ee ee 74 600 hp Compressor AMPs iscsieaysccis ceeciassaveisatsgeacseavacaeensecyadeasnesudeetntcecentecsacnenenines 75 GOO ip Compressor POWET atir aa a E E E vo E ais Gees E E 76 Plot of Compressor Power and Pressure cccessceceescecesececeecceceeeeeceeeeeeeeeeeesaes 78 System Compressor Power
96. or her encouragement during the writing process I would like to state my utmost appreciation to the subject facility for access to their compressed air system their cooperation throughout the process and assistance in collecting all necessary data I would also like to thank Dr Stephen Terry whose support and guidance has not only made this work possible but has made a Master s degree a realistic possibility for me I will be forever thankful for the many invaluable opportunities provided to me vii I would also like to thank Dr Herbert Eckerlin and Alexei Saveliev for serving on my graduate committee advisory committee I greatly appreciate your participation in this project viii TABLE OF CONTENTS Eeer eeh A a a A TS EN SSA xi TTS POP BIGUIRES eege Ehe xii Chapter 1 Introduction eiee iinne ESE a E aE a EEGEN 1 1 1 Electrical Energy and Compressor Use in the United States 2 1 2 Compressed Air Benefits and Drawbacks 0 0 0 ceccceessecessceceeneeceseeeceeeeeceeeecseeeeceteeeesaeees 3 1 2 1 Inappropriate Compressed Air Use vic c2sc5 Si Aad ce tees bated ede ee ens 4 1 3 Introduction to Compressor Control 5 AL Mam Project e 7 Chapter 2 Compressed AI csscansseisgessetaseuccavesedenstesnscbeuus tsuucanasavadeubageaesaseaeesslsgeeadeassaeeaeateaseaues 9 2 1 Important Compressed Air Terminology ceescccesscecescecssececeeececeseeececeecesececseeeeenaeees 9 22 TYPES OPC OMIT ESSN EE 12 2 3 Positive Displac
97. ould like to dedicate this work to my parents Gerald and Cathi for showing me their support during my extensive stay as a student at North Carolina State University ii iii BIOGRAPHY Daniel John Paprocki was born in the year of our lord 1988 in Durham North Carolina shortly after Daniel s parents relocated from Milwaukee Wisconsin At the age of two Daniel s family made the decision to move 20 miles from Durham to the burgeoning suburban community of Cary North Carolina During Daniel s elementary school years he gained an interest in mathematics and sciences which only grew stronger as he got older Daniel acquired an appreciation for hands on skills during his formative years Gerald Daniel s father would frequently have a home improvement project to work on and would inevitably recruit Daniel to help out Additionally instead of taking the family cars to the shop Gerald would routinely change the oil and make simple repairs and always would have Daniel pitch in to acquire these valuable skills This gave Daniel an appreciation for hard work the satisfaction of saving money by being self reliant During Daniel s senior year of High School he applied to North Carolina State University in Raleigh North Carolina In the fall of 2007 his first year at N C State he decided to study Engineering and German and was able to matriculate into Mechanical Engineering after his first year Mechanical Engineering is a demand
98. ows the system pressure 96 when the 100 hp compressor is the only compressor running which is between 70 hp and 130 hp on Figure 56 The power ranges from about 71 hp to 125 hp The pressure reaches about 105 psig and the minimum is roughly 100 psig It appears that during high demand periods the pressure remains between 100 psig and 105 psig but during low demand periods the will rise above 105 psig This is seen in Figure 57 below The data points reading zero psig corresponding to positive power likely is when the compressor first turns on System Pressure vs Compressor Power 115 110 E 105 EE A ne att g S A Lei w Af we a Tno Matus H g 100 S Ex N 95 90 60 70 80 90 100 110 120 130 Total Compressor Power bhp Figure 57 Pressure vs Power 60 hp 120 hp 97 The third grouping of data points between 210 hp and 370 hp in Figure 56 is likely the system pressure when the combination of the 150 hp compressor and the 100 hp compressor are operating A similar pattern to the pressure vs 100 hp compressor occurs in when this combination of compressors are running This operating condition is regularly seen on Saturdays when the demand for compressed air is lower The lowest pressure recorded while the compressors were producing compressed air is 97 psig at 258 hp while the maximum is 111 psig at 249 hp During low loads the pressure remai
99. pproximately 3103 ACFM at 8 AM System Profile Data x System Profile Data Production 5000 7 E 00 hp compress 4500 7 E 150 hp compress 1100 hp compress 4000 7 E 500 hp compress 3500 4 3000 4 Airflow acim 2500 1 2000 4 1500 4 1000 4 500 4 iow eh tho i re 21 bla Veh aS Ve GI ah VBP mal 231 ped ex 2 Hour Air Flow actm Print REE Compressor lt System gt X C Power kw C Capacity Figure 85 Production Profile Compressor Volumetric Flow 15 Figure 86 is a plot of compressor power by the hour of day for the average production day The peak power occurs at 8 am with a power of 580 5 kW 126 System Profile Data k System Profile Data Production 1000 7 E 600 hp compress 300 7 150 hp compress 100 hp compress 800 7 E 500 hp compress 700 4 600 4 Power kw 5004 400 4 300 4 200 4 100 4 EE Ee UU Ra S E m EE Hour C Air Flow acim Print Ss Compressor lt System gt e Bower Di C Capacity Close Figure 86 Figure 85 Production Profile Compressor Power 15 The next daytype to consider is the Saturday daytype Two compressors generally operate on Saturdays the 100 hp compressor and the 150 hp compressor Thus less power is expected to be required for this daytype and the compressed air demand will be much lower As seen in Figure 87 the 600 hp compressor operates briefly in the early hours of the daytype
100. pressor which is depicted in Figure 41 below The compressor clearly responds quickly to changes in compressed air demand through modulating controls 71 150 hp Compressor Power 5 S Ba S e v DI S Q 1 14 1 16 1 18 1 20 1 22 1 24 1 26 1 28 1 30 Date Figure 40 150 hp Compressor Power 12 150 hp Compressor Power Koch Nn _ 5 S Ba 5 A a Q km S Q 1 16 1 16 1 17 1 17 Date Figure 41 Illustration of Modulation 4 3 4 500 hp Air Compressor Data Analysis The larger air compressors supply much of the compressed air demand for the facility The TS 32S 500 hp compressor produces 2 530 ACFM at full load power The amperage flowing to this compressor over two and a half week data logging period is graphed below in Figure 42 73 500 hp Compressor Amperage N ei L a a Ep SI Pa S i E ken S 3 Pad S E Q 0 1 14 1 16 1 18 1 20 1 22 1 24 1 26 1 28 1 30 Date Figure 42 500 hp Compressor Amperage Interestingly we see large spikes of current which to indicate the amperage to the electric motor power to be above 2 000 amps The compressor turns on has a large inrush of current and then almost immediately turns off This occurrence should not happen as a compressor should only turn on when it is absolutely needed It is likely arising
101. r Validation A simplified AIRMaster model using only the facility s 600 hp compressor must first be created The utility information is the same as described in section 5 1 2 Using LogTool the compressor profile for the production daytype was created then pasted into AIRMaster The compressor pressure control range is modeled to be 103 psig at full load and 120 psig at no load The compressor profile is shown below E System Profile Data p System Profile Data Production 1000 E 00 900 800 700 600 Power kw DO 400 300 200 100 ors eth Te EN EY GED a Vs Tie aca ke es ry 18 19 val a ead uty re Hour C Air Flow actm Print eae Compressor Em e Power kw l C Capacity Close Figure 91 600 hp Compressor Production Profile 15 132 Reducing the system air pressure can result in considerable savings The current average system air pressure is approximately 103 psig and it is recommended that the air pressure be dropped to 93 psig or by roughly 10 psig Although the average system air pressure is 103 psig the system pressure is sometimes much higher or lower than 103 psig For example pressure rises up to 120 psig when the compressed air demand is low The compressor power would drop considerably if the average pressure were to be reduced by an average of 10 psig Reducing the pressure would decrease compressor power because it takes more power to compress air to higher pressure
102. ramount importance that multiple compressors are controlled to ensure compressors are not operating when they are not needed As more compressors are added to a system the complexity of the control scheme increases 42 3 3 1 Cascade Control Traditionally cascading controls were used to start compressors in a predetermined order as compressed air demand increases and system pressure falls To get a sense of what is happening with one compressor the unload set point and the full load set point will be discussed As the pressure in the system increases and exceeds a compressors set point the compressor will unload to save energy If the system pressure falls below the lower pressure set point after the compressor unloads the compressor will reload 11 Cascade control is illustrated in Figure 23 below Figure 23 Compressors in Cascade 11 The top of the each bar represents the pressure at which the compressor unloads Conversely the bottom of each bar represents the pressure at which the compressor is fully loaded The 43 issue with this type of control scheme is that the last compressor in the cascade will potentially allow the system pressure to dip below the production minimum requirement There is always a lag between when a compressor starts up and when it begins to deliver compressed air thus the system pressure could fall below the minimum pressure before demand is met 11 To avoid this problem a facility employee m
103. ressor power during the period from February 21 to February 27 The linear regression will form a trend line with a corresponding equation for CFM per hp which will be applied to total compressor power from January 14 to J anuary 30 to estimate volumetric flow First a brief description and analysis of the volumetric flow and system compressor power is needed Volumetric flow data was recorded every 30 minutes whereas the amperage recordings were every 5 seconds To match volumetric flow readings with compressor power the 5 second amperage readings were averaged over 30 minute periods This means that 360 amperage data points were averaged together to create one 30 minute data point 82 Figure 48 shows the compressed air flow in CFM from February 21 to February 28 This data was measured and supplied by the facility During the seven day period the averaged compressed air demand was 2201 CFM However during production periods the compressed air demand was 3075 CFM The maximum compressed air demand was 3 783 CFM Figure 49 is a plot of the system compressor power during this period Figure 50 depicts both the compressed air volumetric flow and system compressor power on the same plot Compressed Air Volumetric Flow 4000 LA L 3000 2500 2000 1500 Compressed Air Demand CFM T T 1 2 21 2 22 2 23 2 24 2 25 2 26 2 27 2 28 Date Figure 48 Compressed Air
104. ring may be adjusted to allow for different pressure settings 3 A Fee ee Figure 7 Top Dead Center 18 At the end of the cycle the compressed air is released and both the intake and exhaust valves are closed The cycle repeats until the demand for compressed air is satisfied at which point the compressor will shut off Commonly the power to drive this cycle is derived from an electric motor Figure 8 below details the complete compression cycle 3 H H D g D g g g g g 8 D D H g g VA g DH D H 4 D g H f 4 5 g AA Een Le Figure 8 Compression Cycle The double acting reciprocating compressor is similar to the single acting reciprocating compressor but with one exception Double acting means that the compressor uses both sides of the piston and cylinder for air compression effectively doubling the capacity for a giving cylinder size This type of compression is particularly efficient with multi stage compressors 4 19 Figure 9 Double Acting Reciprocating Compressor 4 Using a reciprocating compressor to produce compressed air can have advantages Generally reciprocating air compressors are small in size and weight and therefore can be located close to the point of use This would avoid long lengths of compressed air piping and potential pressure drops Also reciprocating compressors generally require simple maintenance procedures Unfortunately reciprocating compressors are associa
105. s are divided by the power with a power factor of one The results are listed in Table 4 61 Table 4 100 hp Compressor Power Factor Trend AIRMaster Line Power Power Factor Factor Calculated Air Amperage Master Input Power The AIRMaster power factor is graphed against amperage input and a polynomial trend line is created See Figure 34 for the plot of power factor against amperage The trend line resulted in the following equation PF 2E 11x 1E 08x 2E 06x 0 0001x 0 0041x 0 0586x Equation 3 Above 90 amps the power factor levels out to approximately 0 87 This is reflected in the Trend Line Power Factor Calculated column in Table 4 above 62 Power Factor vs Amps 10 20 30 40 50 60 70 80 90 100 110 120 130 Amps Figure 34 Power Factor vs Amperage To calculate a corrected power factor for all compressors percent full load amperage is plotted against the AIRMaster calculated power factor A trend line equation is computed for calculating power factor for a percent of full load amperage for any compressor Each amperage input from Table 4 is divided by 135 amps to calculate percent full load amperage and the corresponding AIRMaster power factor is carried over When using Excel to calculate power factor with the trend line equation an IF statement is used to qualify everything above 88
106. s will not need to be turned on in a large demand event Figure 16 plots the efficiency of running a load unload control scheme for a rotary screw compressor at gallon of storage per CFM to 10 gallons of storage CFM 4 11 32 ynduy MJ Waad Percent Capacity 1 gal cim 3 gal cfm 5 gal cfm 10 gal cf m Figure 16 Average kW vs Average Capacity with Load Unload Capacity Controls 11 33 3 1 3 Modulating Control Modulating controls are often used in industry for rotary screw and centrifugal compressors Modulation restricts the air flow through the inlet valve of the compressor to reduce the production of compressed air This allows for tighter pressure control and continuous motor operation reducing wear Modulating also allows for accurate matching of capacity production to compressed air demand The main issue with modulation is that the pressure ratios increase as the inlet valve is restricted causing inefficient operation As the inlet valve closes the pressure at the inlet decreases accordingly For example a compressor using modulating controls with an inlet valve 40 percent open will experience an inlet air pressure of 40 percent of standard atmospheric pressure Atmospheric pressure at sea level is approximately 14 7 psia therefore the inlet air pressure for the aforementioned operating condition will be 5 88 psia If the compressor is producing compressed air at 100 psig the new compression ratio is 17 5 1
107. savings may be reduced Compressed air storage is key to running an efficient load unload control scheme The compressor will be more efficient with increased storage For example if a compressed air system has one gallon CFM of storage and is operating at 50 capacity the compressor will still be using approximately 84 of its kW input on average This operating condition the result of low air storage arises because the compressed air is depleted at a quick rate and the compressor will need to load before the sump fully depressurizes and it is fully unloaded The compressor will begin to unload and decrease compressor power However before the compressor can completely unload at 30 to 40 of its power the compressor will reload due to the fast depletion of compressed air in the system Consequently the compressor will operate at a higher average percentage of its full load power during operation 31 Loaded Loaded Actual power with low storage Ideal power with good storage Fully Unloaded Reloads Short Cycle Figure 15 Short Cycle Conversely should a rotary screw compressor using load unload controls have 5 gallons CFM the compressor would be consuming approximately 68 of its kW input With more storage the compressed air in the system will deplete at a slower rate and the compressor will have more time to remain unloaded and therefore will use less energy Storage should be sized to ensure additional compressor
108. sor _ _ 2 978 W5Ohp compressor IT we 22 fj 2 Deen tac a a O E 500hp compressor 2479 H je ja e e o e a WH E E a I Available Airflow acfm Ces ee ei ei el 6787 en 6787 6787 Required Airflow acfm CS 2562 zen 2553 2576 2616 2737 2912 286 Power kw 446 0 447 0 446 4 446 5 447 8 450 0 456 6 466 2 463 6 4 b Figure 95 AIRMaster Automatic Sequencer Hourly Data 15 The measure is now ready for simulation By exiting to the main Energy Efficiency Measure module screen and pressing the results button on the top right of the screen the simulation results can be viewed The baseline results are listed below in Table 9 followed by the automatic sequencer results in Table 10 Daytype Production Table 9 AIRMaster Baseline Operating Results Operating Hours Average Airflow acfm Annual Energy kWh 3 349 180 143 680 Annual Energy Cost Demand Cost 81 011 142 224 691 Saturday 330 162 14 164 0 14 164 Sunday Daytype Production 70 507 3 749 849 160 869 3 025 0 81 011 Table 10 AIRMaster Use Automatic Sequencer Results Operating Hours Average Airflow acfm Annual Energy kWh 2 721 122 Annual Energy Cost 116 736 Demand Cost 65 062 3 025 241 880 181 798 Saturday 291 580 12 509 0 12 509 Sunday 61 709 3 074 411
109. sors is three phase To convert kW to brake horsepower the following formula is used kW 0 746 nad hp Power hp x MotorEffic iency Equation 2 Power factor varies depending on percent load on the compressor motor An analysis to determine the power factor at percent of full load amps follows The motor efficiency 59 depends on the size of motor and is fairly constant for motors that are at least 50 loaded For this study we assumed the motor efficiency to be that of a standard efficiency motor These values are taken from AIRMaster modeled compressors for consistency throughout the study All subsequent horsepower values are in brake horsepower Table 3 Motor Efficiencies Compressor Model Motor Efficiency TS 32S 500 TS 32S 600 20 150 20 1001 4 3 1 Power Factor Analysis Depending on the loading of the compressor the motor power factor can vary between 0 3 and 1 0 This would greatly reduce the compressor power during periods of unloading despite the current remaining high Thus it is especially important to quantify an accurate power factor for compressors that utilize load unload controls although the power factor may vary slightly for a compressor uses modulation The Department of Energy software program AIRMaster which will be used to model the compressed air system to determine and quantify efficiency measures has a feature that determines the calculated power of an electri
110. ted with a high initial cost and high vibrations which require a thick foundation 4 2 3 2 Rotary Screw Compressors Oil flooded rotary screw compressors and oil free rotary screw compressors are two common types of rotary screw compressors The more common air compressors found in industry 20 today is the oil flooded rotary screw compressor due in part to its versatility 4 The operation of the screw compressor is distinctly different than the aforementioned reciprocating compressor The rotary screw compressor mechanically compresses air with two screws one of which the male screw is driving the female screw These screws are meshed together in a stator and rotate Air flows through the inlet port and becomes trapped between the meshing screws As the screws rotate the point of intermeshing where the air is trapped moves gradually along the axial length of the rotors As this occurs the space occupied by air reduces in volume resulting in an increase in pressure Air compression follows until the air reaches the discharge port and the air is released to the demand side of the compressed air system 4 Figure 10 depicts the two screws meshed together Atmospheric Air low pressure Compressed Air high pressure Power In Figure 10 Rotary Screw Compressor 3 21 Lubrication is vital to health and longevity of the oil flooded rotary screw compressor The lubrication serves three basic functions The oil lubr
111. terminology related to compressed air Capacity Capacity is the amount of air delivered under specific conditions This is usually measured in cubic feet per minute or CFM 6 Cubic Feet Per Minute CFM This is the volumetric flow rate 6 Actual CFM ACFM Flow rate of air at a certain point at the actual temperature and pressure at that point When this is used for the capacity of an air compressor it is measured at prevailing ambient conditions of temperature pressure and relative humidity 6 10 Inlet CFM ICFM The volumetric air flow rate through the compressor inlet valve under the prevailing ambient conditions For positive displacement machines ICFM and ACFM should be identical but could be different in some centrifugal air compressor designs due to air losses through shaft seals 6 Standard CFM SCFM The volumetric flow of free air measured and converted to a standard set of reference conditions The International Standards Organization ISO defines standard air as 14 5 psia 68 F and 0 relative humidity 6 This is equivalent to specifying mass flow rate since a volume at a given temperature and pressure has a specific density Demand The CFM of air required by a specific point in a facility or by the entire facility This is generally referenced to scfm Humidity Relative Relative humidity is the ratio of the actual vapor pressure to the vapor pressure if the air were completely saturated 7 Dew Point The de
112. tion of the compressed air system in relation to system pressure For example during the transition from normal compressed air demand periods to low demand periods one would expect lower compressor capacity and the pressure to remain relatively static One can find issue with the way the compressed air system is operating if the pressure rises significantly above the desired setpoint Additionally during the transition to high compressed air demand periods one can expect the compressor capacity to increase until demand is met and the pressure will likely decrease to below setpoint By knowing more about the operating parameters of the compressed air system one can begin to make better judgments about the system However it is not always possible to collect all of the data necessary for instance volumetric flow For this reason it could be 151 greatly important to accurately estimate a volumetric flow for a given compressed air system which was necessary during this study During the first data collection period volumetric flow was not obtainable but was for the second data collection period Likewise pressure data was collected during the first data collection period but due to data logger error pressure was not collected during the second period of data collection Therefore it was required to estimate the compressor capacity for the first set of data Using data from the second data collection a linear regression was performed on
113. tions a particular system will have is given to practicality and cost For example if the dewpoint of the compressed air must be controlled to a tight band it would make sense to install a sensor after the air dryer to communicate with the System Master control Some examples of the possible functions of a System Master control are send receive communications communicate with plant information systems monitor weather conditions adjust pressure flow controller set points monitor filter differential pressure start stop and load unload compressors change base trim duties and select the appropriate mixture of compressors to optimize efficiency 11 The purchase of sensors may cost as little 47 as 300 or as high as 1 500 depending on the application 11 Another potentially important controller is a pressure flow controller 3 3 4 Pressure Flow Controllers If a facility requires tight pressure bands for production a Pressure Flow controller might be considered Typically in a multi compressor system the multiple pressure control bandwidths will overlap which could cause large variance in pressure Also facilities with only one modulating rotary screw compressor will have an approximate pressure band of 3 to 10 psi which may be undesirable A pressure flow controller will control the pressure and flow coming from a single compressor or a multiple room compressor system and drop the pressure to the desired facility pressure It is an
114. to 35 of that power required to supply the air leaks will be realized in savings AIRMaster will calculate savings from the elimination of a designated volumetric flow of compressed air Typically a facility can expect 10 percent of compressor capacity to be leak related AIRMaster requires that the user specify the percent capacity of a compressor that is dedicated to supplying leaks As the 100 hp compressor is the trim compressor any reduction in compressed air leaks will affect its percent capacity and power It was approximated that 50 of the 100 hp capacity is given to leaks that can be eliminated resulting in 251 CFM of compressed air blowing to atmosphere The Reduce Airleaks set up is shown in Figure 96 below 146 ba EEM Reduce Air Leaks e File Calculators Help A E el Results Close Facility i extile Manufacturer System Textile Manufacturer Description Reduce Air Leaks Measure cost 4000 Measured data Airtlow capacity v Compressor Operations To Feed Leaks r Leak Airflow Values Airflow actm ZC Peak system 600 hp compressor j requirement leaks 2312 42 150 hp compressor i Leaks 251 3 100 hp compressor l Faak aaen 500 hp compressor requirement al 38 SESS Ee Maximum hourly system airflow actm Ge according to entered profile values 2312 Reduce leaks by 251 acfm 100 0 Compressor Figure 96 AIRMaster Reduce Air L
115. trols used for the 500 hp and 600 hp compressors help to explain the dips in volumetric flow at high compressor power which is seen at around 650 hp and 700 hp With modulating controls the compressor requires a high percentage of its full rated power to produce a lower compressed air capacity Additionally we would expect lower compressed air flow at lower compressor power which is clearly displayed in Figure 51 The prediction of 4 44 CFM per horsepower will be more accurate at higher compressor capacities and less accurate when the larger compressors are modulating to a lower compressor capacity or during start up and shut down This can be seen in Figure 52 below The predicted volumetric flow in red generally trends with the actual volumetric flow except for when the compressors are shutting down after production turning on during production startup or when the compressors modulate to a lower compressor capacity but still use a high compressor power To determine how similar the predicted volumetric flow is to the 88 actual volumetric flow the percent difference was found for each point The formula for percent difference is given by E1 E2 difference x 100 Equation 6 z El 2 The predicted volumetric flow during the shutdown on February 22 had an average percent difference of 109 Shutdown periods account for approximately 2 1 days per year The startup on February 24 had an average percent difference of 10
116. ts ability to lubricate the rotors For this reason the compressor is blown down slowly Figure 14 depicts the load unload cycle of a real 100 hp compressor In Figure 14 below the compressor is fully loaded until approximately 13 38 10 at which point the compressor unloads because the maximum system pressure set point is reached From 13 38 10 to 13 39 40 the compressor blows down and gradually uses less power At approximately 13 39 40 the compressor reloads when the system pressure falls to the minimum pressure set point At this point the compressor demand rapidly increases until it has reached full load The compressor remains fully loaded until the desired system pressure has been reached _ Rei m A 8 ka L CH 3 Z a CH g a E S U 8 100 hp Compressor Load Unload Cycle Compressor Unloads Figure 14 Load Unload Cycle 29 30 Thus some period of time is required to fully unload a rotary screw compressor As the pressure in the system drops to a fixed lower pressure the compressor reloads This method of controlling higher powered compressors is advantageous compared to start stop controls because there is less stress on the electric motor increasing the longevity of the compressor package However if the compressed air system does not have enough storage short cycles may occur Short cycles may cause premature wearing and energy
117. using a variable speed drive VSD The variable frequency drive adjusts the compressor capacity by changing the speed of the electric motor as compressed air demand in the system changes The compressor capacity is proportional to the speed of the male rotor but due to the design of variable displacement drive package at full load capacities the male rotor is rotating above the optimum rotor speed Thus a compressor with a VSD will require more power at full load than otherwise but a VSD offers significant power reduction and energy savings at lower loads Figure 20 illustrates the relationship between percent kW input power and percent capacity for an oil flooded screw compressor with a variable speed drive 11 38 Total kW input and or specific power over the full operating range must be analyzed for a proper comparison with other types of capacity control LTT UU kW input vs capacity With unloading With stopping Figure 20 VSD Curve 8 3 2 Centrifugal Compressor Operation and Control The operation characteristics of centrifugal air compressors are complex and affected by inlet air density and intercooler cooling water temperature The basic compressor performance curve pressure against flow is determined by the design of the impeller An example of this is that an impeller with radial blades will yield a low rise in pressure as flow is decreased and backward leaning blades will create
118. ver 84 million years At an average energy price of 0 062 kWh the total electrical cost to run industrial air compressors is 2 6 billion per year 1 Considering the high energy consumption and energy cost of operating compressed air systems it would behoove manufacturers to attempt to increase the efficiency of their systems to capture significant savings 1 2 Compressed Air Benefits and Drawbacks It is important to understand why we use compressed air Compressed air is a fundamental utility at many industrial sites and manufacturing facilities just as important as power and fuel Compressed air can have many important uses including operating pneumatic tools motors pneumatic cylinders automation equipment conveyors and controls schemes There are also many specific compressed air uses in manufacturing processes including oxidation fractionation cryogenics refrigeration filtration dehydration and aeration 4 A facility may also use compressed air for an application as opposed to electricity in a combustible environment such as a chemical plant Although compressed air has many appropriate uses inappropriate uses in which a more efficient method could be used can have high costs Despite the effectiveness and flexibility of compressed air unfortunately the overall efficiency of a typical compressed air system is only 10 to 15 This is due to losses from the heat of compression meaning that approximately 80 of the el
119. w point is the temperature at which water vapor will begin to condense out of air if the air is cooled at constant pressure Specific Humidity The mass of water vapor in an air vapor mixture per mass of dry air Power Power is work over a period of time Power is often measured in measured in kW or brake horsepower Brake Horsepower bhp This is the horsepower required at the compressor shaft to produce compressed air 11 Load Factor Load factor is the average compressor load divided by the maximum rated compressor load over a period of time Full Load When the air compressor is operating at full speed with a fully open inlet and delivering maximum air flow Specific Power A method of measuring compressor operating efficiency usually in the form bhp 100 ACFM or kW 100 ACFM Total package Input Power This is the total power used by the air compressor including the drive motor fans motors and controls Pressure Pressure is defined as force per unit area This is commonly measured in pounds per square inch psi Atmospheric Pressure This is the naturally occurring pressure in the atmosphere The atmospheric pressure at sea level is approximately 14 7 psi Gauge Pressure Pressure determined by instruments which are calibrated so that atmospheric pressure is zero psi Gauge pressure is expressed as psig Pressure Drop Pressure drops occur in compressed air systems due to friction or restrictions Pressure Range The range between
120. y 27 to J anuary 30 shows the 600 hp air compressor and the 100 hp air compressor meeting the compressed air demand It must be noted that during the compressor startup all of the compressors were initiated but only the 600 hp and 100 hp compressors remained operating System Compressor Power and System Pressure es E S g Bo S pa S S E N WM 0 1 15 1 17 1 23 1 27 Date Total System Hp Pressure Figure 47 System Compressor Power and System Pressure 1 29 t 1 31 80 60 40 20 0 System Pressure Psig 80 81 Figure 47 shows the total system compressor power and the corresponding system pressure During the full production week Monday through Friday the average compressor power is 625 hp On a typical Saturday the plant averages 337 hp of compressor power 4 3 7 Volumetric Flow Analysis Due to the failure of the pressure data logger during the period of data collection from February 11 to February 27 it was decided to use the amperage and pressure readings from the data collection period from January 15 to J anuary 31 The volumetric flow data from February 21 to February 27 will be utilized to predict to predict a volumetric flow for the data collection period From January 14 to J anuary 30 This will be accomplished by preforming a linear regression of a plot of volumetric flow against comp
121. ytype which is collected data averaged over one hour periods for an entire day The LogTool opening screen is shown below Tt Logtoot vz k gt a File Tools Help Open Create Database file to store logger data Open an Existing Database MDB File Create a New Database MDB File Help File Folder Import Logger Data Trend Scatter DayType Logger Data in no MDB selected Uncheck Trend Scatter DayType Figure 75 Log Tool Opening Screen 16 From the opening screen the user should create a new database The database allows data loggers to be uploaded and daytypes to be created The amperage data from the facility s four compressors were uploaded to the database Three daytypes including Production Saturdays and Sundays were created for each compressor 117 118 r al E LogToo v2 Lo 15 eee File Tools Help Open Create Database file to store logger data Open an Existing Database MDB File Create a New Database MDB File Help File LogToolattempt 4 mdb Folder Daniel Thesis Data Loager Data 2 4 14 Import Logger Data Trend Scatter DayType Logger Data in Log oolattempt 4 mdb Trend Scatter DayType LD f Include Name Type Units Period System oe End Interval sec Data FIEIEIE Vv 100 Current e Amps el Baseline y NotAssignec 1 14 2014 13 00 00 1 30 2014 16 51 20 5 Daer
122. ytypes 13 107 AIRMaster Compressor Module OCI 108 AIRMaster Compressor Module Compressor Catalog 131 109 AIRMaster Compressor Catalog Search i 110 Compressor Inventory LKE ee 111 100 hp Compressor Performance Profile CU 112 150 hp Compressor Performance Profile 51 113 500 hp Compressor Performance Profile OI 114 600 hp Compressor Performance Profile OI 114 Log Tool Opening Screen LEE egene ege tee EE aaah 117 LogTool Imported Leet TT eege eer 118 100 hp Compressor Daytypes pi 119 Plot of 100 hp Compressor Dayty pes vcd sss iat inietiateldeestininendinen teas baa aentos 120 LogTool 150 hp Compressor Daytypes Op 121 Plot of 150 hp Compressor Daytypes cccceessecesseeceeneeceeneeceeneeceeeeeceeeeeeeteeeees 121 500 hp LogTool Daytypes Plot oi 122 600 hp Compressor LogTool Daytypes pi 123 600 hp Compressor ETag gester AER 123 Figure 84 Figure 85 Figure 86 Figure 87 Figure 88 Figure 89 Figure 90 Figure 91 Figure 92 Figure 93 Figure 94 Figure 95 Figure 96 xvi System Profile Module Production Daytype l 124 Production Profile Compressor Volumetric Flow i 125 Figure 85 Production Profile Compressor Power l 126 saturday Profile Volumetric Flower eer Eder Watewesee 127 Saturday Profile Data Power 15 sssssssessssssssssessssssessseressseessresseesseeeseeesseeesseeso 127 Sunday Profile Volumetric Flow ID 128 Sunday Profile Power 15 c
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