*TM 5-810-4/AFM 88-8, Chap. 3
CHAPTER 8
PIPING
8-1.
Materials.
pressor and after cooler or receiver, a safety valve or valves
will be placed in the pipeline between them. The safety valve
a. Steel compressed air piping will be Schedule 80 for
or valves will have a total capacity sufficient to handle the
sizes 2 inches and smaller and Schedule 40 for sizes over 2
entire output of the compressor. (If no safety valve is used,
inches and will be galvanized or black steel or stainless steel.
and the isolation valve is closed upon starting, or anytime
Copper compressed air piping or tubing will be Type K or
during compressor operation, sufficient pressure may be built
Type L. Fiberglass reinforced plastic (FRP), as specified in
up which could cause injury or damage.) A strainer or filter
Mil. Spec. MIL-P-28584, may also be used within the
and a lubricator must be provided in piping that serves tools.
following limitations:
Flexible connectors, such as flexible metal hose, will be used
(1) 150 psig maximum pressure, up to 200 degrees F.
to connect the discharge piping system to the air
(2) 75 psig maximum pressure, up to 250 degrees F.
compressors. Where air quality downstream of the
Pipe fittings will be galvanized or black steel or stainless
compressor. receiver, and dryer is not assured for the end
steel, to match piping used. When copper pipe or tubing is
use, the required additional filtration will be provided at the
used, brazed joints will he used for connections. Brazing
point of use.
filler metals with melting temperatures between 1 ,000 de-
grees F and 1 ,600 degrees F will be used. Soldered joints
should not be used.
b. Thermoplastic piping systems for transport or storage
of compressed air will not be allowed. Safety records show
that leaks in these types of pipe (when used for compressed
air service) have caused the pipe to rupture, causing serious
injury to personnel and/or property damage.
8-2.
Loss of air pressure due to friction.
The loss of pressure in piping is caused by resistance in pipe,
fittings, and valves, which dissipates energy by producing
turbulence. The piping system will be designed for a
maximum allowable pressure drop of 5 percent from the
compressor to the most distant point of use. The Darcy
formula and nomograph shown in the Crane Co. Technical
Paper No. 410 may be used to determine pressure drop
through pipe, valves, and fittings.
8-3.
Piping layout.
Where possible the piping system should be arranged as a
closed loop or "ring main" to allow for more uniform air
distribution to consumption points and to equalize pressure
in the piping. Separate services requiring heavy air consump-
tion and at long distances from the compressor unit should
be supplied by separate main airlines. Pipis to be installed
parallel with the lines of the building, with main and branch
headers sloping down toward a dead end. Traps will be
installed in airlines at all low points and dead ends to remove
condensed moisture. Automatic moisture traps used for this
purpose are effective only when the air has been cooled and
the moisture has precipitated. Branch headers from compres-
sed air mains will be taken off at the top to avoid picking up
moisture. When an isolation valve, or other flow restricting
device, is placed in the discharge line between the com-
8-1
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