Environmental Engineering Reference
In-Depth Information
operating correctly (i.e., as per design) they must monitor its operation.
Again, they do this by monitoring the operation of the air compressor by
observing certain parameters.
Before starting any machine or system, however, we must first per-
form a prestart check to ensure that it has the proper level of lubricat-
ing oil, etc. Then, after starting the compressor, we need to determine
(observe) if the compressor is actually operating (normally, this is not
difficult to discern, considering that most air compressor systems make
a lot of noise while in operation). Once in operation, our next move is
to double check the system line-up to ensure that various valves in the
system are correctly positioned (opened or closed). We might even go to
a remote compressed-air service outlet to make sure that the system
is producing compressed air. (Keep in mind that some compressed-air
systems have a supply of compressed air stored in an air receiver; thus,
when an air outlet is opened, air pressure might be present even if the
compressor is not functioning as per design.) On the other hand, instead
of using a remote outlet to test for compressed-air supply, we could look
at the compressor air-pressure gauge. This gauge should indicate that
the compressor is producing compressed air.
Gauges are the main devices that provide us with the information
we need to evaluate equipment or system operation. With regard to the
air compressor, the parameter we are most concerned about now is air
pressure (gauge pressure). Not only is correct pressure generation by
the compressor important, but maintaining the correct pressure in sys-
tem pipes, tubes, and hoses is also essential. Keeping air pressure at
the proper level is necessary mainly for four reasons:
1. Safe operation
2. Efficient, economic conveyance of air through the entire system,
without waste of energy
3. Delivery of compressed air to all outlet points in the system (the
places where the air is to be used) at the required pressure
4. Prevention of too much or too little pressure (either condition can
damage the system and become hazardous to personnel)
We pointed out that, before starting the air compressor, certain
prestart checks must be made. This is important for all machinery,
equipment, and systems. In the case of our air compressor example, we
want to ensure that proper lubricating oil pressure is maintained. This
is important, of course, because pressure failure in the lubricating line
that serves the compressor can mean inadequate lubrication of bear-
ings, and, in turn, expensive mechanical repairs.
4.15.2 Pressure gauges
Many pressure-measuring instruments are called
gauges
. Generally,
pressure gauges are located at key points in piping systems. Usually
expressed in pounds per square inch (psi), there is a difference between
