1. Energy Efficient Compressed Air Systems

2. Compressed Air Fundamentals
dWelec = ∫V dP / [Effcompressor Effmotor Effcontrol]
V = volume flow rate
DP = pressure rise
Eff = efficiencies of compressor, motor, and control
Internal cooling decreases electrical power

3. Compressed Air Savings Opportunities
dWelec = ∫V dP / [Effcompressor Effmotor Effcontrol]
Reduce volume flow rate
Reduce pressure rise
Increase cooling during compression
Increase compressor efficiency
Increase motor efficiency
Increase control efficiency

4. Compressed Air System

5. Screw Compressor Operation

6. Compressed Air System Savings Opportunities
End use
Eliminate inefficient uses of compressed air
Eliminate air pumps, agitation, cooling and suction
Use blower for low-pressure applications
Install solenoid valves to shut off air
Install air saver nozzles
Install differential pressure switches on bag houses
Distribution
Fix leaks
Decrease pressure drop in distribution system
Compressor System
Compress outside air
Use refrigerated dryer
Direct warm air into building during winter
Use load/unload control with auto shutoff or VSD for lag compressor
Stage compressors with pressure settings or controller
Add compressed air storage to increase auto shutoff

7. Plant and Compressor Data For Calculating Example Savings
Plant operates 6,000 hours per year
Electricity cost including demand = $0.10 /kWh
Air compressor produces 4.2 scfm/hp
Air compressor motor is 90% efficient
Air compressor runs in load/unload control with FP0 = 0.50

8. Eliminate Inefficient Uses of Compressed Air

9. Replace Air Pump with Electric Pump
Air motors use 7x more electricity than electrical motors
Example
Replace 10 x 1-hp air pumps with electric pumps
Cost Savings = 10 hp / 0.90 x 6/7 x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $4,300 /yr 9

10. Replace Compressed Air with Mechanical Agitation
Compressed air agitation uses ~10x more electricity than mechanical agitation
Example
Replace air agitation from 0.5-in pipe at 50 psig with mechanical agitator.
Flow Savings = 11.6 (scfm/lbf) x [1 (in)]2 x 55 psia = 150 scfm
Power Savings = 150 scfm / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x (1-0.50) = 15 kW
Cost Savings = 15 kW x 6,000 hr/yr x $0.10 /kWh = $9,000 /yr

11. Replace Compressed Air Cooling with Chiller
‘Vortex’ coolers use 4x more electricity than electric chillers
Example
Replace 10,200 Btu/hr cooler using 150 scfm with chilled water
Cost Savings = 150 scfm / (4.2 scfm/hp x 90%) x 75% x 0.75 kW/hp x (1-0.50) x 6,000 hr/yr x $0.10 /kWh = $6,700 /year 11

12. Replace Air With Heat Pipe Cabinet Coolers
Air coolers use 8x more electricity than (heat pipe + small fan) coolers
Example
Replace 2,400 Btu/hr compressed air cooler with heat pipe cooler
Cost comp air = 2,400 Btu/hr / 80 (Btu/hr)/cfm / (4.2 cfm/hp x 90%) x 0.75 kW/hp x (1-0.50) x 8,760 hr/yr x $0.10 /kWh = $2,607/year
Cost heat pipe = 0.6 A x 120 V / 1,000 VA/kW x 8,760 hr/yr x $0.10 /kWh = $ 63 /year
Implementation Cost = $1,000
Source: and

13. Replace Pneumatic Suction Cups with Magnets
Suction cups use 6.0 scfm while holding while magnets use average of 0.3 scfm
Example
Replace cups with magnets if holding 3,000 hours per year.
Power Savings = 5.7 scfm / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x (1-0.50) = 0.57 kW
Cost Savings = 0.57 kW x 3,000 hr/yr x $0.10 /kWh = $167 /yr

14. Use Blowers for Low-Pressure Applications
Blowers generate 7.2 scfm /hp at 20 psig while compressors generate 4.2 scfm/hp at 100 psig
Example
Install low-pressure blower for application needing 140 scfm of 20 psig air
Power Savings = 140 scfm x (1/4.2 – 1/7.2) hp/scfm / x .75 kW/hp x (1-0.50) = 5.8 kW
Cost Savings = 5.8 kW x 6,000 hr/yr x $0.10 /kWh = $3,472 /yr

15. Reduce End Use Compressed Air Demand

16. Reduce Blow-off with Solenoid Valves
Flow from open tube (scfm) = 11.6 (scfm/lbf) x [Diameter (in)] 2 x Pressure (psia)
Example
Install solenoid to shut-off blowoff from 3/8-in pipe at 100 psig 80% of time
Flow Savings = 11.6 (scfm/lbf) x [3/8 (in)]2 x 115 psia x 80% = 150 scfm
Power Savings = 150 scfm / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x (1-0.50) = 15 kW
Cost Savings = 15 kW x 6,000 hr/yr x $0.10 /kWh = $8,933 /yr
Cost of 3/8-inch solenoid valve = $100

17. Reduce Blow off with Air-Saver Nozzles
Nozzles maximize entrained air and generate same flow and force with ~50% less compressed air
Example
Add nozzle to 1/8-in tube at 100 psig
Flow Savings = 11.6 (scfm/lbf) x [1/8 (in)]2 x 115 psia x 50% = 10.4 scfm
Power Savings = 10.4 scfm / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x (1-0.50) = 1.0 kW
Cost Savings = 1.0 kW x 6,000 hr/yr x $0.10 /kWh = $620 /yr
Nozzles cost about $10 each

18. Activate Bag House Air Pulses Using Pressure Differential Instead of Timer
Timers are designed for peak conditions, where demand-based control matches actual conditions
Example
Install differential pressure control to reduce timed pulse from 34 cfm by 60%
Flow Savings = 34 cfm x 60% = 20.4 cfm
Power Savings = 20.4 cfm / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x (1-0.50) = 2.0 kW
Cost Savings = 2.0 kW x 6,000 hr/yr x $0.10 /kWh = $1,214 /yr

19. Fix Leaks

20. Fix Leaks Leaks continuously drain power
Leakage rate increases exponentially with leak diameter
Example
Fix one 1/64” leak
Power Savings = .25 cfm / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x (1-0.50) = kW
Cost Savings = kW x 6,000 hr/yr x $0.10 /kWh = $15 /yr

21. Fix Leaks Many plants lose ~20% of compressed air to leaks Example
Fix leaks in plant with fully loaded 100-hp compressor and 20% leakage
Power Savings = 100 hp / 0.90 x x 0.75 kW/hp x (1-0.50) = 8.3 kW
Cost Savings = 8.3 kW x 6,000 hr/yr x $0.10 /kWh = $5,000 /yr

22. Identify Leaks Using Ultrasonic Sensor

23. Quantify Leakage By Logging Flow or Compressor Power

24. Fix Leaks Frequently Leak Loss = Rate x Time
Repairing leaks frequently cuts leak load at same implementation cost
Example
Fix leaks every 2 weeks instead of every 4 weeks if one new 1-cfm leak per week
Reduces leakage by 40%

25. Starve Leaks by Shutting off Branch Headers
Valve on branch header can starve all downstream leaks when area is not in use
Example
Install valve to shut off header with 200 cfm leak load for 4,000 hr/yr
Power Savings = 200 scfm x 50% / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x (1-0.50) = 9.9 kW
Cost Savings = 9.9 kW x 4,000 hr/yr x $0.10 /kWh = $3,969 /yr

26. Use Rubber In Place of Braded Hose
Braided hoses dry-rot and develop leaks that can’t be detected with ultrasonic sensors.

27. Reduce Distribution System Pressure Drop

28. Use Looped Piping System
If DP < 10 psi at farthest end use, use looped rather than linear design
Design Guidelines
Main line: size from average cfm to get DP = 3 psi
Branch line: size from cfm peak to get DP = 3 psi
Feed lines: size from peak cfm to get DP = 1 psi
Select hose with DP < 1 psi

29. Avoid ‘Collision’ Connections

30. Maintain Filters Place filter upstream of dryer to protect dryer
DP filter < 1 psi

31. Size Dryer for DP< 5 psi
Low Flow: DP = 1 psi High Flow: DP = 6 psi

32. Then, Reduce Compressed Air Pressure
Work = V DP, thus compressor requires less work to produce air at lower outlet pressure
Fraction savings from reducing pressure =
Fraction savings from reducing pressure = 1% per 2 psi pressure reduction
Example
Reduce pressure setting of fully-loaded 100-hp compressor from 110 to 100 psig
(P2high/P1)0.286 = [(110 psig psia) / 14.7 psia]0.286 = 1.84
(P2low/P1) = [(100 psig psia) / 14.7 psia]0.286 = 1.80
Fraction savings = (1.84 – 1.80) / (1.84 – 1) = 5.2 %
Cost Savings = 100 hp x 5.2% / 90% x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $2,582 /yr

33. Reduce Pressure To Maximum End Use Plus Friction Loss

34. Dry Air Efficiently

35. Refrigerated and Desiccant Dryers
Refrigerated dryer:
Dries air by cooling
Cools to Tdew-point = 35 F
Uses 6 W/scfm
Desiccant dryer:
Dries air by passing through desiccant, then purging desiccant of water
Cools air to Tdew-point = -40 F to -100 F
Uses 16 to 30 W/scfm
Desiccant dryers “should one be applied to portions of compressed air systems that require dew points below 35 F. Because desiccant dryers require a higher initial investment and higher operating costs, Kaeser strongly recommends using refrigerated dryers whenever practical.” Kaeser Regenerative Desiccan Dryers

36. Desiccant Dryer Purging
Three types of purge
Compressed air purge
Uses 15% of compressed air for purging
Total is about 30 W/scfm
Heated compressed air purge
Uses 7% of compressed air for purging
Plus 7 W/scfm for heating
Total is about 22 W/scfm
Heater blower air purge
Uses 3 W/scfm for blower
Plus 13 W/scfm for heating
Total is about 16 W/scfm
Purge cycle can be timed or demand-controlled
Source:

37. Use Refrigerated Rather than Desiccant Dryer
Example:
Replace desiccant dryer using compressed air purge with refrigerated dryer for 200 hp (840 scfm) compressor
Desiccant Power = 840 scfm x 15% / (4.2 scfm/hp x 90%) x 0.75 kW/hp x (1-0.50) = 12.5 kW
Refrigerated Power = (840 scfm x 85% x kW/scfm x (1-0.50) = 2.1 kW
Cost Savings = (12.5 kW – 2.1 kW) x 6,000 hr/yr x $0.10 /kWh = $6,215 /yr

38. Use Demand-Control Rather than Timed Purge
Summer air 4x wetter than winter air.
Timed purge set for peak (summer) conditions
Example
Switch from timed to demand-control purge and reduce purge by 50% on dryer for 200 hp (840 scfm) compressor
Timed-Purge Power = 840 scfm x 15% / (4.2 scfm/hp x 90%) x 0.75 kW/hp x (1-0.50) = 12.5 kW
Cost Saving = 12.5 kW x 50% x 6,000 hr/yr x $0.10 /kWh = $3,250 /yr
.016 lbw/lba
.004 lbw/lba 38

39. Replace Timed-solenoid with No-loss Drains
Winter air holds 50% less water than summer air
Timers designed for peak conditions, where demand-based control matches actual conditions
Example
Replace 3/8-inch timed-solenoid drain that opens 3 seconds every 30 seconds with no-loss drain that eliminates <90% of air losses.
Flow Savings = 11.6 (scfm/lbf) x [3/8 (in)]2 x 115 (psia) x 10% x 90% = 16.9 scfm
Power Savings = 16.9 scfm / (4.2 scfm/hp x 0.90) x kW/hp x (1-0.50) = 1.68 kW
Cost Savings = 1.68 kW x 6,000 hr/yr x $0.10 /kWh = $1,005 /yr
3/8-inch no-loss drains costs $600

40. Optimize Compressor Cooling

41. Compress Outdoor Air
Compressing cool dense air reduces compressor work:
Fraction Savings = (Thi - Tlow) / Thi
Fraction Savings = ~ 2% per 10 F
Example
Install PVC piping to duct outside air at 50 F to compressor rather than inside air at 80 F.
Fraction Savings = [( ) - ( )] / ( ) = 5.9%
Cost Savings = 20 kW x 5.9% x 6,000 hr/yr x $0.10 /kWh = $706 /yr

42. Direct Warm Air Into Plant During Winter
75% of compressor input power lost as heat
Example
Add duct work to direct warm air into plant during winter for compressors drawing 105 kW if heating system operates 2,000 hours per year and is 80% efficient
Heat Load Savings = 105 kW x 75% x 3,413 Btu/kWh x 2,000 hours/year = 537 mmBtu/yr
Cost Savings = 537 mmBtu/year / 80% x $10 /mmBtu = $6,719/year

43. Employ Efficient Compressor Control
FP = FP0 + (1-FP0) FC and P = Prated FP

44. Power Signatures from Modulation and Load/unload Control

45. Savings From Switching To Efficient Control
FP = FP0 + (1-FP0) FC
Typical Intercepts
FP0 bypass = 1.00
FP0 modulation = 0.70
FP0 load/unload = 0.50
FP0 variable-speed = 0.10
FP0 on/off = 0.00
Example
Switch 100-hp compressor at 50% capacity from modulation to variable-speed control.
FP (modulation) = ( ) .50 = .85
FP (variable-speed) = ( ) .50 = .55
Savings = 100 hp x ( ) / .90 x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $15,000 /yr

46. Savings Penalty for Inefficient Control
Consider savings from reducing fraction capacity (FC)
P1 = Prated x FP1 = Prated x [FP0 + (1-FP0) FC1]
P2 = Prated x FP2 = Prated x [FP0 + (1-FP0) FC2]
Psave = P1 – P2
Psave = Prated x [FP0 + (1-FP0) FC1] - Prated x [FP0 + (1-FP0) FC2]
Psave = Prated x (FC1 - FC2) x (1-FP0)
Psave = Unadjusted savings x (1-FP0)
Actual Savings = Unadjusted Savings x (1 – FP0)
Example
Calculate actual savings for reducing leaks by 100 scfm if compressor operates in modulation control.
Unadjusted savings = 100 scfm / (4.2 scfm/hp x 0.90) x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $11,905
Actual savings = $11,905 /yr x (1 – 0.70) = $3,571 /yr

47. Modulation to Load/Unload with Auto-shutoff
Reduced power 35% and saved $17,000 /yr

48. Centrifugal Compressor Control

49. Energy-Efficient Centrifugal Compressor Control
Minimize/eliminate by-pass using effective multi-compressor control
Operate compressor with throttling/unload control if available
Adjust throttling/surge pressure points to widen throttling range

50. Throttling/Surge Pressure Set Points Narrow or Widen Throttling Band

51. Poor Throttling/Surge Pressure Set Points
Inlet butterfly valve throttles to 95%, then bypass

52. Excellent Throttling/Surge Pressure Set Points
Inlet guide vane throttles to 65%, then bypass

53. Multi-compressor Control
Cascading pressure set-point control
Single-pressure network control
Smart PLC control

54. Cascading Pressure Set-Point Control
“Stage” compressors into lead and lag compressor(s) by sequentially reducing load/unload pressures.
Designate compressor with best control efficiency as final lag compressor
Staging allows Lead to run fully loaded and the Lag compressor(s) to turn off or run with smaller part-load penalty if they have better control efficiency.
Simple, effective, and inexpensive
However:
Increases pressure
Only applicable for compressors in same location 54

55. Single-Pressure Network Control
When compressors in different locations, staging compressors using cascading pressure set points doesn’t work, since the compressors see different pressures.
When more than three compressors are staged using cascading pressure set points, pressure increased and pressure range is large.
In these cases, use a sequencer with common pressure sensor to stage compressors. 55

56. Smart PLC Control Monitors pressure, flow and power
Most flexible (controls different compressor types, locations, manufacturers)
Trends data
Accommodates changes
Source: Taming Multiple Compressors, Niff Ambrosino and Paul Shaw,

57. Two Compressors Properly Staged

58. Savings From Staging Compressors
Example: Stage load/unload 100-hp and 50-hp compressors producing 400 scfm
Cr,100 = 100 hp x 4.2 scfm/hp = 420 scfm
Cr,50 = 50 hp x 4.2 scfm/hp = 210 scfm
Unstaged
FC = 400 scfm / (420 scfm scfm) = 0.63
P100 = Pr,100 x FP100 = 100 hp x [ ( ) .63] = 81.7 hp
P50 = Pr,50 x FP50 = 50 hp x [ ( ) .63] = 40.9 hp
Ptotal = P100 + P50 = 81.7 hp hp = hp
Staged with auto shutoff
FC 100 = 400 scfm / 420 scfm = 0.95
P100 = Pr,100 x FP100 = 100 hp x [ ( ) .95] = 97.6 hp
P50 = 0 hp (with auto shutoff)
Ptotal = P100 + P50 = 97.6 hp + 0 hp = 97.6 hp
Savings
Savings = (122.5 hp – 97.6 hp) / .90 x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $12,500 /yr

59. Savings From Staging Compressors
Before Staging After Staging
Example: Stage unstaged load/unload 100-hp and 50-hp compressors producing 400 scfm

60. Compressed Air Storage
Necessary for load/unload compressors
Lengthens load/unload cycle time:
Reduces compressor wear
Allows sump to completely blowdown, which reduces unloaded power
Increases auto-shutoff, which reduces unloaded power
Acts as additional compressed air capacity to meet demand spikes
Reduces pressure variation to process
Allows average pressure to be lowered, which reduces compressor energy use

61. Locating Compressed Air Storage
Locating storage after dryer protects dryer from compressed air demand spikes that can prevent dryer from effectively removing moisture.

62. Sizing Compressed Air Storage
Relationship between volume, flow and pressure from mass balance.
Mflowin – Mflowout = dM/dt
Vflowin r – Vflowout r = (RT/PV) / dt
2.7 gal/rated scfm (0.36 ft3/rated scfm) or 11.3 gal/rated hp (1.5 ft3/rated hp) of trim compressor guarantees load/unload cycle time > 1 minute with 10 psi pressure band
Example
Calculate storage for 100 hp compressor so load/unload cycle time > 1 minute with 10 psi pressure band.
100 hp x 4.2 scfm/hp x 2.7 gal/scfm =1,134 gal

63. Power During Load and Sump Blowdown
Initial rapid power increase when compressor loads
Subsequent slow power increase as pressure builds from load to unload pressure set points.
Initial rapid power decrease as compressor unloads
Subsequent slow power decrease as pressure in sump is bled down to near atmospheric pressure to reduce back pressure.
Blowdown time ~ 30 seconds

64. Add Storage to Lengthen Load/Unload Cycle and Enable Full Blowdown
Example
Adding storage reduces average power by 2.9%
If 100-hp compressor at 50% load, savings are:
50 hp / 0.90 x 2.9% x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $725 /yr

65. Power Savings From Adding Storage (to Achieve Full Blowdown)
For flooded compressor in load/unload mode at FC = 50% and blowdown = 30 sec

66. Add Storage to Enable Auto Shutoff
Example
Adding storage enables auto shutoff and reduces average power by 14.7%
If 100-hp compressor at 50% load, savings are:
50 hp / 0.90 x 14.7% x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $3,675 /yr

67. Add Primary Storage and Reduce Pressure
Plant requires 100 psig
Small storage doesn’t dampen L/UL swing
Pset =
Large storage dampens L/UL swing
Pset =

68. Add Secondary Storage and Reduce Pressure
Example
Adding secondary storage allows reducing pressure by 6 psi which reduces compressor energy by 3%
If 100-hp at 50% load, compressor savings are:
50 hp / 90% x 3% x 0.75 kW/hp x 6,000 hr/yr x $0.10 /kWh = $750 /yr

69. U.D. AirSim Software
AirSim simulates compressed air systems to understand the dynamics between compressed air control, capacity, storage and demand.
The software is available free of charge at:

70. D.O.E. AirMaster+ Software
AIRMaster+ provides a systematic approach for assessing the supply-side performance of compressed air systems.
AIRMaster+ evaluates the energy savings potential of any or all of the following eight energy efficiency actions:
Reduce air leaks
Improve end-use efficiency
Reduce system air pressure
Use unloading controls
Adjust cascading set points
Use automatic sequencer
Reduce run time
Add primary receiver volume

71. Summary of Key Equations and Relations
Input power (kW) = Voltage (V) x Current (A) x 1.73 x Power factor (kW/kVA) / 1,000 VA/kVA
Annual energy use (kWh/yr) = Input power (kW) x Operating hours (hr/yr)
Annual electricity cost ($/yr) = Annual energy use (kWh/yr) x Unit electricity cost ($/kWh)
Flow from open tube (scfm) = 11.6 (scfm/lbf) x Pressure (psig) x [Diameter (in)] 2
Input power from flow (kW) = Flow (scfm) x kW/hp / (Specific output (scfm/hp) x Motor efficiency) x (1-FP0 )
Typical compressor/blower specific output: 4.5 scfm/hp at 100 psig scfm at 20 psig
Savings from reducing operating pressure ~ 0.5% per psi
Savings from reducing intake air temperature ~ 2% per 10 F
Refrigerated dryer electricity use ~ 4-6 W/scfm Unheated desiccant dryer air use ~ 15% of flow
Recoverable heat from air compressors ~ 75% of electrical power (kW) x 3,412 (Btu/kWh)
Fraction Power = [(Fraction Capacity x (1 – Fraction Power at No Load)] + Fraction Power at No Load
Typical Fraction Power at No Load (Modulation Control) = 0.70
Typical Fraction Power at No Load (Load/unload Control) =
Typical Fraction Power at No Load (Variable Speed Drive) = 0.10
Typical Fraction Power at No Load (On/Off) = 0.0

72. Thank you!

73. Compressed Air Storage
Lengthens load/unload cycle time:
Reduces compressor wear
Allows sump to completely blowdown, which reduces unloaded power
Increases auto-shutoff, which reduces unloaded power
Reduces pressure variation to process
Allows average pressure to be lowered, which reduces compressor energy use
2.7 gal/rated scfm of trim compressor (1.5 ft3/hp) guarantees load/unload cycle time > 1 minute

74. Dryer Pressure Drop Low Flow High Flow
DPDRYER = 1 psi DPCOMP = 8 psi DPDRYER = 6 psi DPCOMP = 6 psi

75. Dryer Pressure Drop Causes Short Cycling
10 psi DP at compressor reduced to 5 psi “effective DP”

76. Locating Primary Storage
If DP across dryer is small, locate primary storage downstream of dryer to reduce flow variation through dryer and thoroughly dry air
If DP across dryer is large, locate primary storage upsteam of dryer to enable compressor to realize full load/unload pressure range

77. Inlet Guide Vane vs Inlet Butterfly Valve Throttling
Source: Ingersol Rand Centac Compressor Manual

78. Stage Compressors for Efficient Control
“Stage” compressors into lead and lag compressor(s) by sequentially reducing load/unload pressures of the lag compressors.
Designate compressor with best control efficiency as Lag compressor
Staging allows Lead compressor to run fully loaded and the Lag compressor(s) to turn off or run with smaller part-load penalty if they have better control efficiency. 78

79. Use Efficient Compressed Air Pumps
Some pumps use ~30% less air than others

80. DOE 16% of our industrial motor system energy use
DOE 16% of our industrial motor system energy use. Seventy percent of our manufacturing facilities use compressed air in their production process.
Compressed Air Audit
“Studies indicate that as much as 35% of the compressed air produced in the market today is wasted to leaks, and everyone has leaks.” Wayne Perry, technical director, Kaeser Compressors “It has been our experience that plants which have no formal, monitored, disciplined, compressed air leak-management program will have a cumulative leak level equal to 30% to 50% of the total air demand,” Henry van Ormer, Air Power USA
“The compressed air system had to run at 98 psi because the grinding area. The header pressure was lowered to 85 psi. Results after 18 months showed that tool repair went down for the grinders, production increased by 30% and total air demand fell from 1,600 to 1,400 cfm.“ Henry van Ormer, Air Power USA
“The easy answer to many system problems is to jack up the pressure. Unfortunately, the leaks will leak more, and unregulated users will waste more air and more energy.” Norm Fischer, Centrifugal Equipment Service
“More important, the back pressure sends a false unload signal to the controls, causing premature unloading or extra compressors to be on line,” van Ormer says. “Using a 30 degree to 45 degree directional angle entry instead of a tee will eliminate this pressure loss. The extra cost of the directional entry is usually negligible.”
Remember, pressure costs money in two ways — power to produce increased pressure costs one half of one percent per psi, and excess pressure produces excess flow that must be compressed. Van Ormer
Source: The top 10 targets of a compressed air audit, Rich Merritt,

81. “More important, the back pressure sends a false unload signal to the controls, causing premature unloading or extra compressors to be on line,” van Ormer says. “Using a 30 degree to 45 degree directional angle entry instead of a tee will eliminate this pressure loss. The extra cost of the directional entry is usually negligible.”
“Upgrading to copper or aluminum piping provides excellent value for money and ideal delivery characteristics,” Perry says. “When upgrading, ensure that the physical piping diameter is sized to deliver the required air flow with minimum pressure drop.”
“Open blow, refrigeration and vortex cooling may all be replaceable with heat tube cabinet coolers with a potential savings of 3.5 kW to 4 kW each on a 30- by 24- by 12-inch average cabinet,” van Ormer says. “The initial cost is usually in the $700 to $750 range with a potential resultant power savings of $1,000 to $2,000 per year each.”
14.2 at inlet

82. Use booster compressor for high-pressure applications

83. Single Pressure Network Control
Narrower pressure band
However:
Compressors from same manufacture
Compressors in same location
Source: Taming Multiple Compressors, Niff Ambrosino and Paul Shaw,

84. Cascading Pressure Set-Point Control
Simple, effective, and inexpensive
However:
Increases pressure
Only applicable for compressors in same location
Source: Taming Multiple Compressors, Niff Ambrosino and Paul Shaw,

85. Cascading Pressure Set-Point Control
“Stage” compressors into lead and lag compressor(s) by sequentially reducing load/unload pressures of the lag compressors.
Designate compressor with best control efficiency as Lag compressor
Staging allows Lead compressor to run fully loaded and the Lag compressor(s) to turn off or run with smaller part-load penalty if they have better control efficiency. 85

86. Sizing Primary Storage
Required Storage Per Blow Down Time (gal)
Compressor Size
Blowdown Time (sec)
(hp) 30 45 60 90 10
124
186
247
371 50
619
928
1,237
1,856
100
2,474
3,711
150
2,783
5,567
200
4,948
7,422
250
3,093
4,639
6,185
9,278
300
11,133
350
4,330
6,494
8,659
12,989
400
9,896
14,844
Volume Storage Required per Rated Scfm (gal/rated-scfm)
Pressure Band
Blowdown Time (sec)
(psi) 30 45 60 90 5
5.5
8.2
11.0
16.5 10
2.7
4.1 15
1.8
3.7 20
1.4
2.1