The generation of heat always accompanies the
compression of air.
In most low-pressure air
compressors, the heat from compression is dissipated
before the temperature gets too high. Aluminum
cylinders have cooling fins, and a fan forces cooling air
past the cylinders. In most medium-pressure and high-
pressure air compressors, the compressor has to be
cooled with pump-circulated water. The cooling water
is circulated in much the same fashion as in an
automobile engine with the coolant passing through
jackets in the cylinder walls, cylinder heads, and so on.
In addition, compressors are fitted with other cooling
devices, known as intercoolers and aftercoolers.
Generally, these devices consist of a series of tubes,
either air-cooled or water-cooled, through which the
compressed air charge flows after leaving the
These devices cool the compressed air.
INTERCOOLERS are placed between the stages or
cylinders of multistage compressors. Thus they cool
the compressed air charge before it is drawn into the
next cylinder. The AFTERCOOLERS cool the final
discharge of air from the compressor. Both the
intercoolers and the aftercoolers are of the same
general construction, except the aftercoolers are
designed to withstand a higher working pressure.
Perhaps the most important advantage of these
coolers is they aid in keeping the air charge in a
In other words, hot air has a
tendency to expand, and if the compressed air charge is
not cooled, it, too, tends to expand and thereby liberate
much of its pressure or energy.
Locate the compressor unit so that it is reasonably
level. The design of this unit permits a 15-degree
lengthwise and a 15-degree sideways limit on out-of-
level operation. The engine, not the compressor, is the
limiting factor. When the unit is to be operated out of
level, keep the engine crankcase oil level near the high
level mark (with the unit level) and have the
compressor oil gauge show nearly full (with the unit
level). The mechanical parking brake lever is near the
bumper. Set the brake by pulling or pushing the lever
as directed by a decal or a stencil located beside the
lever on the unit. The parking brake should always be
set once the air compressor is on location to prevent
accidental rolling of the unit, which could cause not
only mechanical damage but also possible injury to
personnel. As an added precaution, the wheels should
be chocked when possible.
Open the side curtains on both sides of the
enclosure and leave them open whenever the unit is in
operation. When the side curtains are closed and the
engine running, the flow of air through the oil cooler
and engine radiator is restricted. The curtains may be
left closed for a few minutes during starting procedures
in cold weather to ease engine warm-up. However,
when the compressor goes to work, open the side
curtains. For specific operating instructions, check the
instruction plate attached to the unit being used.
The heart of the compressor is the engine that
furnishes power for the compressor and produces air
for the pneumatic tools used during drilling. Know
how to start, operate, and maintain the compressor
engine properly. In most cases, the general operating
procedure is similar to that given below. Check the
engine oil level. If necessary, add oil as recommended
in the engine manual. Do not overfill.
Check the engine cooling system. The radiator
should be filled to the bottom of the filler neck. If
necessary, add soft, clean water until full. In cold
weather, use a permanent antifreeze with a rust
inhibitor. Ethylene glycol solutions are recommended
because they do not evaporate and only water is added
to maintain a full system. Two fuel tanks are
furnished-one on each side. The two tanks are cross-
connected to permit filling from either side of the unit.
Clean fuel is vitally important. Ensure clean fuel is
poured or pumped into the tanks. Be sure no
condensate (water) lies in the bottom of the fuel tanks.
Drain off any water that may be there. Clear away
obstructions in the vents of the fuel tank.
Lubricate all parts of the engine as recommended
in the manufacturers engine manual. Make periodic
checks of the oil filter, the fuel filter, and the fuel oil
pump screen. Ensure the rain cap on the exhaust pipe
swings freely,, so a back pressure on the engine exhaust
cannot be created. Check the battery cells for the
proper liquid level. A pair of two-stage dry-type air
cleaners filters the intake air for the compressor
suction and engine air-intake manifold. Both cleaners
are under the canopy at the compressor end of the unit.
The first stage of the air cleaner uses centrifugal
precleaning which rotates the intake air and separates a
large portion of the dust collected in the dust cup. The
dust cup should be checked and emptied daily.