*TM 5-810-4/AFM 88-8, Chap. 3
CHAPTER 1
GENERAL
1-1. Purpose.
b. After cooler with separator.
This manual provides guidance for designing low pressure
(1) Aftercooler selection should be based on degree of
compressed air systems with a maximum design operating
drying required downstream of the aftercooler. Final
pressure of 125 psig. including piping, compressors,
discharge air temperature of the aftercooler will affect dryer
aftercoolers and separators, air receivers, and air dryers.
sizing and can reduce both initial and operating costs of
Methods for sizing piping are included.
compressed air dryers.
(2) Duct air from air-cooled aftercoolers to provide
1-2. Scope.
space heating in winter and to remove heat from the plant in
The intention of this manual is to provide criteria to achieve
summer. Pipe coolant water to recycle heat waste.
economical, durable, efficient, and dependable compressed
c. Filters and dryers.
air systems to support Army and Air Force facilities. Where
(1) Improve air quality only to the degree required at
special conditions and problems are not covered in this
the point of use. If air quality requirments differ at various
manual, industry standards will be followed. Modifications
points of use, specify appropiate filters or dryers in
or additions to existing systems solely for purpose of meeting
applicable branch lines.
criteria in this manual are not authorized. Figure 1-1 shows
(2) Accurately determine the dew point required at each
the arrangement of a typical compressed air system.
point of use. The type and size of dryer selected will affect
operating cost. If the dryer must prevent condensation of
1-3. References.
moisture in air systems, determine lowest temperature to
Appendix A contains a list of references used in this
which piping will be exposed and select dryer to achieve a
document.
system pressure dew point 20 degrees F below that lowest
temperature. If seasonal temperatures vary widely as from
1-4. Energy conservation.
freezing to temperate, select a dryer which allows dew point
In selecting the type and number of compressors. the
adjustment.
daytime. nightime, and weekend compressed air demands of
(3) Room air temperatures will affect drying efficiency.
the facility must be determined. A single, large air
If practicable, locate dryers where ambient temperature will
compressor is more efficient and less costly than several
not exceed 100 degrees F.
smaller units if the demand is fairly constant. If the nightime
a(4) Select dryer in conjunction with aftercooler so inlet
or weekend demand is considerably less than the daytime
air temperature to the dryer can be as low as feasible. Keep
demand, however, the use of several compressors should be
inlet pressure as high as possible. Accurately determine
considered to handle the total load. At night and on
operating temperature and pressure, since even minor
weekends one unit could serve the load with the second as a
changes in either can result in substantial operating costs.
standby, thereby saving energy. Other energy-saving methods
d. Air leakage.
include the following:
(1) Maximum acceptable air leakage rate for a compres-
a. Compressors.
sed air system should not exceed 10 percent of the installed
(1) Install a speed modulator to increase or decrease
system flow rate. Air leaks occur most often at pipe joints.
compressor speed according to compressed air demand when
hose connections, and equipment connections; and are usu-
applicable,
ally a result of poor maintenance practices and/or in-
(2) Shut down idling air compressors.
adequately trained maintenance personnel.
(3) Where possible, locate air-cooled compressors
(2) Specification of quality materials and workmanship
where room temperature will not exceed 100 degrees F.
are a major contribution the designer of a compressed air
Utilize heat from compressors to provide space heating in
system can provide for a safe and relatively leakfree air
winter and provide ventilation to remove heat from the plant
system. In addition, designing the compressed air system
in summer.
with minimum piping and pipe joints, will reduce potential
(4) Select an air compressor with a pneumatic load-
leakage sources.
unload feature that, when fully unloaded, consumes
approximately 15 percent of the base load horsepower.
1-5. Electrical work.
(5) Use waste heat from the oil cooler to heat makeup
Work will be designed in accordance with TM 5-81 1-2/
air, or for building space heating in the winter.
AFM, 88-9. Chapter 2.
(6) When economically justifiable, use multistage
compression with intercoolers.
1-6.
Foundations.
1-1
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