Reliability: Piping Distribution & Storage Matter Instructor: Kurt Thielemann Principal
What is the Supply Side? Supply Side Demand Side
Supply-side System - Best Practices Comp #1 100 HP Wet Receiver (5 Gals / HP) 2 Coalescing Pre-filter Air Dryer Particulate After-filter To Plant Comp #2 100 HP OEM s Solenoid Drain Valve 2 Rotating Ball Drain Valve (>1/2 ) No Air Loss Drain Valve (>1/2 ) Dry Receiver (15 Gals / HP) 2 Manual Drain Valve (>1/2 )
Storage Tanks The basic purpose of an air receiver is to store a volume of compressed air for use when needed. Storage can be used to: control peak demand periods by reducing the rate of pressure decay, protect critical pressure applications from other events in the system, Fundamental best practices about primary air receiver(s) 1. Wet receivers are installed upstream of air treatment equipment to provide radiant cooling and drop out moisture, thereby benefiting the air treatment equipment. Additionally, allows compressor time to react appropriately to changes in the system (condensate blow down valves, desiccant air dryer tower switch, compressor loading/unloading). 2. Dry receivers are located after air treatment equipment to provide an immediate response of clean, dry air to any sudden demand event. The air treatment equipment will not be overloaded, as the maximum flow rate will be the compressor output, therefore, the pressure dew point will not be affected.
Correctly Sizing Storage Tanks Compressor room or primary storage should be sized based on: Supporting peak or large demand periods with storage in lieu of starting the next compressor Minimizing compressor cycling (ie. best practices recommends 3-5 gallons per total compressor acfm), Providing enough time to start of the next compressor in the event the primary unit fails without production noticing a change in pressure. The size of a primary air receiver can be calculated as follows: V = T x C x P a P 1 - P 2 where: V = Receiver volume, ft3 T = Time allowed (minutes) for pressure drop to occur. C = Air demand, cfm of free air P a = Absolute atmospheric pressure, psia P 1 = Initial receiver pressure, psig P 2 = Final receiver pressure, psig
Correctly Sizing Primary Storage Tanks Problem: What control storage is required to support the failure of a 490 scfm compressor and the automatic start of the backup 490 scfm compressor? What else do you need to know? What pressure is the back up compressor is set to start? Answer = 95 psig. What is the permissive start time for the next compressor? Answer = 30 sec. Solution: The formula: V = T x C x P a P 1 - P 2 where: V = Receiver volume, ft3 T = Time allowed (minutes) for back up unit to start & load (.2 min). C = Air demand of free air lost when compressor shutdown (750 acfm) P a = Atmospheric pressure, (14.4 psia) P 1 = Initial receiver pressure (starting pressure of back up unit = 95 psig) P 2 = Final receiver pressure, (lowest operating pressure for the plant = 85 psig) V =.5 min x 490 scfm x 14.4 psia = 353 ft 3 x 7.48 gals / ft 3 95 psig - 85 psig = 2,640 gals 6
Benefits Of Storage High demand, short duration critical pressure user requires 80 psig to but pressure fluctuations to a low of 56 psig was creating dangerous conditions, poor quality cuts, and destroying saw blades. Retrofitting the system by closing the main header piping grid and installing 20 gallons/hp of storage capacity, and one (1) regulator, the air pressure stabilized to 87 +/-4 psig.
What is the Demand Side? Supply Side Demand Side
Main Header Piping Distribution - Best Practices Closed Ring Header From 200 HP Compressor Area 2 Sub-header Cross-ties 2 Dry Receiver (15 Gals / HP)
Distribution Piping A good distribution system delivers the supply of clean, dry air to the points of use with minimal pressure loss. Loss of air pressure is due to friction which is a function of cfm, pipe ID, pipe length and pressure. Pressure drop increases as the square of the rate of flow (ie. doubling the flow rate means four times the pressure drop) Running another compressor or adding a pressure/flow controller will not cure an inadequately sized distribution piping system. A properly designed system should have a pressure loss of much less than 10% of the compressor s discharge pressure, measured from the receiver tank output to the point-of-use.
Compressed Air System Pressure Profile 110 psig Supply operating range of compressors 100 psig 90 psig pressure drop on dryers and filters Distribution desired header pressure 85 psig Demand system droop Where is the greatest opportunity to reduce system pressure? pressure drop on regulators and filters 70 psig article pressure pressure fluctuations inadequate capacitance 70-50 psig 11
Distribution Piping NPS Pipe Size 1/2 3/4 1 1 1/2 2 2 1/2 3 4 (cfm) (kg/cm2) (psi) (kg/cm2) (psi) (kg/cm2) (psi) (kg/cm2) (psi) (kg/cm2) (psi) (kg/cm2) (psi) (kg/cm2) (psi) (kg/cm2) (psi) 4 7 0.02 0.24 11 0.04 0.52 0.01 0.13 14 0.06 0.88 0.02 0.22 18 0.02 0.32 0.01 0.10 21 0.03 0.46 0.01 0.14 25 0.04 0.61 0.01 0.18 28 0.05 0.78 0.02 0.23 32 0.07 0.96 0.02 0.29 35 0.02 0.35 42 0.03 0.49 49 0.05 0.65 0.01 0.08 56 0.06 0.84 0.01 0.10 64 0.01 0.12 71 0.01 0.15 78 0.01 0.18 85 0.01 0.21 92 0.02 0.24 99 0.02 0.28 0.01 0.08 106 0.02 0.31 0.01 0.09 124 0.03 0.42 0.01 0.12 141 0.04 0.53 0.01 0.15 159 0.05 0.66 0.01 0.19 0.01 0.08 177 0.06 0.81 0.02 0.23 0.01 0.10 194 0.07 0.96 0.02 0.28 0.01 0.11 212 0.02 0.32 0.01 0.13 229 0.03 0.38 0.01 0.15 247 0.03 0.43 0.01 0.18 265 0.03 0.49 0.01 0.20 282 0.04 0.55 0.02 0.23 0.01 0.08 300 0.04 0.62 0.02 0.25 0.01 0.09 318 0.05 0.69 0.02 0.28 0.01 0.10 335 0.05 0.76 0.02 0.31 0.01 0.11 353 0.06 0.84 0.02 0.34 0.01 0.12 530 0.05 0.73 0.02 0.25 706 0.03 0.42 0.01 0.11 883 0.04 0.63 0.01 0.16 1059 0.06 0.88 0.02 0.23 1236 0.02 0.30 1412 0.03 0.39 1589 0.03 0.48 1765 0.04 0.59 1942 0.05 0.70 2118 0.06 0.82 2295 0.07 0.95
Distribution Piping Good Rules of Thumb Increasing the size of distribution piping to increase storage capacitance is ill advised and a very expensive. Piping Distribution System (Demand Side) Pipe Size Linear Lengths cu. Ft/100' cu. Ft/psia Gals 16" 1000 139.56 94.94 10439 14" 1000 106.85 72.69 7992 12" 1000 78.50 53.40 5872 10" 1000 54.51 37.08 4078 8" 1000 34.89 23.73 2610 6" 1000 19.63 13.35 1468 5" 1000 13.63 9.27 1019 4" 1000 8.72 5.93 652 3" 1000 4.91 3.34 367 2 1/2" 1000 3.41 2.32 255 2 1000 2.18 1.48 163 1 1/2" 1000 1.23 0.83 92 1" 1000 0.55 0.37 41
Distribution Piping Good Rules of Thumb Closed Ring main header with piping sloped toward the compressor room to allow drainage of condensate. Piping drops from the main header to end users should connect to the top of the header to avoid being filled with moisture. All drip legs to catch condensate should be piped from the bottom of the header. Size all piping where the pressure drop <.5 psig / 100 linear feet or < 5% of applied pressure.
Inadequate Secondary Storage Typical Baghouse or Dust Collector filter regulator cranked open 6 scf per pulse = >1,000 scfm rate of flow for 0.1 sec from air supply 4" or 6" x 6' manifold solenoids with 0.1-0.25 sec open time 15
Inadequate Secondary Storage 16
Proper Application Of Secondary Storage Proper Installation of Dedicated Storage for Baghouse or Dust Collector 6 cf per pulse = >36 scfm rate of flow for 10 sec restricting needle valve slows recovery of pressure in tank regulator 70 psi typical check valve needle valve 6 cf per pulse = >1,000 scfm rate of flow for 0.1 sec from air supply 4 X 6 manifold 0.1-0.25 sec solenoids must be min. 2" for peak rate of flow minimize this distance must be within 25 ft of manifold for 0.1 sec pulse 30-60 gallon typical 70 psi drain D 60 psi service valve 17
Benefit Of Secondary Storage 18
Supply-side System - Best Practices Comp #1 100 HP Wet Receiver (5 Gals / HP) 2 Coalescing Pre-filter Air Dryer Particulate After-filter To Plant Comp #2 100 HP OEM s Solenoid Drain Valve 2 Rotating Ball Drain Valve (>1/2 ) No Air Loss Drain Valve (>1/2 ) Dry Receiver (15 Gals / HP) 2 Manual Drain Valve (>1/2 )
Main Header Piping Distribution - Best Practices Closed Ring Header From 200 HP Compressor Area 2 Sub-header Cross-ties 2 Dry Receiver (15 Gals / HP)
Effect Of Storage On Part Load Efficiency Per cent kw Input Average kw vs Average Capacity with Load/Unload Capacity Control 1 20 1 00 80 60 40 20 0 0 20 40 60 80 10 0 1 20 Per cent Capacity 1 gal/cfm 3 gal/cfm 5 gal/cfm 10 gal/cfm
Main Header Piping Distribution - Best Practices
Where To Find Help? Location: 22113 Satilla Drive, Cornelius, NC 28031 Phone: (704) 806-4559 Email: energy-group@att.net 23