An air manifold is a large-diameter pipe that
transports compressed air from one or more
compressors over considerable distances without
friction line loss. In construction work, air manifolds
are usually constructed of 6-inch-diameter pipe with
check valves. A pipe of this size can carry 1,200 cfm of
air (output from two 600-cfm air compressors) at 100
psi with less than 0.035-pound pressure loss per 100
linear feet. One or more compressors pump air into the
manifold and then pressurize it at 100 psi. Air may
then be used at any point along the manifold by installing
outlet valves and connecting airlines to pneumatic tools.
Different types of compressors should not
be used on the same manifold. The difference
in pressure control systems of a rotary, a
reciprocating, and a screw compressor could
cause one compressor to be overloaded, while
the other is idled.
Any drop in pressure between the compressor and
the point of use is a permanent loss. Because of this, the
air distribution system is an important element of the
compressed air system. When planning the air system,
you should observe the following steps:
. Pipe size should be large enough to ensure the
pressure drop between the compressor and the point of
use does not exceed 10 percent.
. Extremely long distribution lines should have air
receivers near the far ends or at points of occasional
heavy use. Many peak demands for compressed air are
only for an instant, and storage capacity near such points
prevents an excessive drop in line pressure.
. Each header or main should be provided with
outlets as close as possible to the point of use to permit
shorter hose lengths and to avoid large pressure drops
through the hose. Outlets should always be located at
the top of the pipeline to prevent carry-over of
condensed moisture to the tool. Condensate drains
should be positioned correctly along the header or main
General safety precautions for air compressors are
. Be sure the intake air is cool and free from
flammable gases or vapors.
l Do NOT permit flammable materials to touch the
air discharge pipe.
l Never operate a compressor that has faulty
l Never kink a hose to stop the air flow, and keep
the hose clamps on tight.
. Before starting an air compressor, check the
safety valves, pressure valves, and regulators to see that
they are working properly.
. Do NOT leave the compressor after starting it
unless you are sure the control, unloading, and
governing devices are working properly.
. Do NOT run an air compressor faster than the
speed recommended by the manufacture.
l Use only the grade and amount of oil recom-
mended by the manufacturer. Use only high flash point
oils to lubricate the air cylinders of air compressors.
. Keep compressors, tanks, and accompanying
piping clean to guard against oil vapor explosion. Clean
intake air filters regularly.
l Use only soapy water or a suitable nontoxic,
nonflammable solution for cleaning compressor intake
filters, cylinders, or air passages. Never use benzene,
kerosene, or other light oils to clean these parts. These
oils vaporize easily and form a mixture that is highly
explosive under compression.
. Secure the engine before adjusting and repairing
an air compressor.
. Before working on or removing any part of a
compressor, make certain that the compressor is secured
and cannot be started automatically or accidentally and
that the air pressure in the compressor is relieved
completely. Also, ensure that all valves between the
compressor and receivers are closed.
l Be careful with compressed air. At close range,
it can put out eyes, burst eardrums, and cause serious
Always wear impact goggles or safety
glasses and dual-hearing protection when using
compressed air. NEVER use compressed air to blow
dust off clothing, skin, or hair.
l When transporting a compressor or any other
towed unit, ensure the pulling unit meets specifications.
This includes drawbar horsepower and height of towing
pintle (not too high or low because it can damage the