*TM 5-810-4/AFM 88-8, Chap. 3
CHAPTER 4
AIR DISCHARGE PIPE
4-1.
Critical pipe lengths.
Consideration must be given to critical pipe lengths of the air
discharge pipe, and certain lengths must be avoided to
prevent resonance. The critical lengths vary with the type and
size of air compressor, and can be determined from air
compressor manufacturers.
4-2.
Surge volume.
Consideration will also be given to surge volume between
reciprocating compressors and aftercoolersm to minimize
vibration and wear in the tubes and tube supports or baffles
in the aftercoolers. Pulsation dampers or surge bottles at the
compressor discharge will increase the installation cost,
however, they may reduce maintenance costs because at-
tenuation of discharge pulsations reduces wear and the po-
tential of tube failures.
4-3.
Safety provision.
A safety valve must be provided between a positive displace-
ment compressor discharge and any block valve or other flow
restricting device, as well as between the compressor and an
internally finned tube after cooler. This is particularly true
with lubricated compressors. If deposits should clog the after
cooler, proper protection would be afforded. Safety valves
should be connected directly into the piping at the pressure
point it is sensing, without unnecessary additional piping or
tubing. Safety valve discharge should be directed away from
personnel areas and traffic lanes.
4-1
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