Page 395 - Reciprocating Compressors Operation Maintenance

38O Reciprocating Compressors: Operation and Maintenance

bustible. For example, coal, flour, or paper dust and other finely divided
solids are often present. These contaminants are held together by oil and
oil oxidation products.
Oxygen from the air is also present. At temperatures below autoignition
of compressor lubricating oil, but nevertheless abnormally high, it is
believed that oxidation of combustible contaminants can proceed within a
layer or mass of deposit and that the attendant generation of heat can cause
a portion of the deposit to glow. A portion of glowing deposit, however
small, is often sufficient to start a serious compressor fire or explosion.
Under certain conditions, a considerable mass of deposit may reach
glowing temperature in the manner just described, and the heat generated
within this may so weaken the walls of a discharge pipe or some other
part of a discharge system that an explosive rupture may occur.
In some cases, fires or explosions occur at points remote from the
compressor discharge area, for example, in an intercooler or receiver. It
is probable that these fires or explosions originate near the compressor
discharge area in the manner previously described. A fire, once started,
may follow along the discharge pipe, or a fragment of glowing deposit
may be carried by the gas stream to a point where a combustible mixture
exists. In this connection, it should be noted that aftercoolers, because of
their cooling effect, have considerable ability to prevent the starting and
spreading of fires.
Fires or explosions have sometimes occurred shortly after compressors
were cleaned with kerosene or other light cleaners. Combustible products
such as these should never be used to clean compressors. Instead, a
strong soap solution or other noncombustible cleaner should be used.
Measures that should be taken to prevent fires or explosions are identi-
cal to those that should be taken to prevent abnormally high operating
temperatures. In addition, on air machines, adequate filters should be
provided to assure clean suction air. It is possible that compressed air
may contain traces of inflammable gases, which may collect in a small
area and become a fire hazard. Fumes or vapors coming off an oil may
sometimes cause the same risk.

CONSIDER SAFETY DEVICES

For extra safety, a high air discharge temperature alarm and shutdown
switch may be necessary. These would be in addition to the low water
pressure shutdown switch.