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How To Use The Centrifugal Compressor Table
To utilize this table successfully, you must have
certain information available for your compressor
application. The most important is flow.
The table is sorted on ascending INLET FLOW as measured in
inlet cubic feet per minute. Inlet flow (ICFM) is
capitalized because there are several different
measurements of flow. If you use one other than the
inlet flow used in this table, your selection will be
incorrect.
Inlet flow is defined as the flow capacity of
the compressor at its design inlet temperature (in
Fahrenheit degrees) and design inlet pressure (in
pounds per square inch, absolute, not gauge). Do
not use standard cubic feet per minute (SCFM) as
there are several "standards", all of which are based
on arbitrary standard temperatures and pressures and which
may or, more likely, may not match your inlet conditions.
Once you have the correct flow, you will need the discharge
pressure in pounds per square inch absolute. This number
is used to check the discharge pressure rating of the
compressor. It represents the minimum design operating
pressure the compressor should be able to handle.
Don’t eliminate the unit if the discharge pressure rating
is higher than required. Staging can be removed to reduce
the discharge pressure. Even if the discharge pressure of
the compressor is lower than required, it may be possible to
re-hydrotest the compressor for an increased pressure rating.
However, don't arbitrarily assume that a
re-hydrotest is possible, as it may not be.
Impeller and diaphragm material
must be compatible with the new gas to be compressed. This
point is very important for both safety and reliability
considerations. Be sure to resolve all compatibility issues.
Casing material also must be checked for compatibility with the new
gas and with the inlet gas temperature. Low inlet temperature requires
special materials of construction. Try to find a compressor
that previously compressed a gas with a similar molecular
weight, although this point is not necessarily a major problem.
Different molecular weights might be tolerated by an existing
compressor.
Using the above discussion points to narrow the
selection of a compressor will help you choose one to focus on.
There are other points that must be checked before an ultimate
selection should be made but these checks will get you off to a
good start. If you have any questions, please contact
(Bill@eTurbomachinery.com)
or (Warren@eTurbomachinery.com).
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