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Compressed Air Piping System:
The purpose of the compressed air
piping system is to deliver compressed air to the points of usage. The
compressed air needs to be delivered with enough volume, appropriate
quality and pressure to properly power the components that use the
compressed air. Compressed air is costly to manufacture. A poorly
designed compressed air system can increase energy costs, promote
equipment failure, reduce production efficiencies and increase
maintenance requirements. It is generally considered true that any
additional costs spent improving the compressed air piping system will
pay for themselves many times over the life of the system.
Compressor Discharge Piping:
Discharge piping from a compressor
without an integral after cooler can have very high temperatures. The
pipe that is installed here must be able to handle these temperatures.
The high temperatures can also cause thermal expansion of the pipe,
which can add stress to the pipe. Check the compressor manufacture's
recommendations on discharge piping. Install a liquid filled pressure
gauge, a thermometer and a thermowell in the discharge airline before
the after cooler. Proper support and flexible discharge pipe can
eliminate strain.
Condensate Control:
Condensation control must be considered when installing a compressed
air piping system. Drip legs should be installed at all low points in the system. A drip leg is an extension of pipe below the
airline, which used to collect condensation in the pipe. At the end of
the drip leg a drain trap should be installed. Preferably an automatic
drain will be used (see drain valves section for a complete description
of the type of drain valves available).
To eliminate oil, condensate, or cooling water (if water-cooled after
cooler leaks), a low point drain should be installed in the discharge
pipe before the after cooler. Be sure to connect the after cooler
outlet to the separator inlet when connecting the after cooler and the
moisture separator together. If they are not connected properly, it
will result in either poor after cooling or poor separation.
The main header pipe in the system should be sloped downward in the
direction of the compressed air flow. A general rule of thumb is 1" per
10 feet of pipe. The reason for the slope is to direct the condensation
to a low point in the compressed air piping system where it can be
collected and removed.
Make sure that the piping following the after cooler slopes download
into the bottom connection of the air receiver. This helps with the
condensate drainage, as well as if the water cooler develops a water
leak internally, it would drain toward the receiver and not the
compressor.
Another method of controlling the condensation is to take all branch
connections from the top of the airline. This eliminates condensation
from entering the branch connection and allows the condensation
continue to the low points in the system.
Pressure Drop:
Pressure drop in a compressed air system is a critical factor. Pressure
drop is caused by fiction of the compressed air flowing against the
inside of the pipe and through valves, tees, elbows and other components
that make up a complete compressed air piping system. Pressure drop
can be affected by pipe size, type of pipes used, the number and type
if valve, couplings and bends in the system. Each header or main should
be furnished with outlets as close as possible to the point of
application. This avoids significant pressure drops through the hose
and allows shorter hose lengths to be used. To avoid carryover of
condensed moisture to tools, outlets should be taken from the top of
the pipeline. Larger pipe sizes, shorter pipe and hose lengths, smooth
wall pipe, long radius swept tees and long radius elbows all help
reduce pressure drop within a compressed air piping system
In recent years we have developed piping systems especially for
compressed air. These compressed air piping systems typically have
smooth walls, are lightweight and reduce the installation costs
associated with copper and threaded pipe. Follow our recommendations
for installing these systems.
Loop Pipe System:
The layout of the system can also affect the compressed air
system. A very efficient compressed air piping system design is a loop
design. The loop design allows airflow in two directions to a point of
use. This can cut the overall pipe lenght to a point in half and that
reduces pressure drop. It also means that a large volume user of
compressed air in a system may not starve users downstream since they
can draw air from another direction. In many cases a balance line is
also recommended which provides another source of air.
Reducing the velocity of the airflow through the compressed air piping
system is another benefit of the loop design. In cases where there is a
large volume user, an auxiliary receiver can be installed. This reduces
the velocity, which reduces the friction against the pipe walls and
reduces pressure drop. Receivers should be positioned close to the far
ends or at points of infrequent heavy use of long distribution lines.
Many peak demands for air are short - lived and storage capacity near
these points helps avoid excessive pressure drop and may allow a
smaller compressor to be used. |
