Page 226 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 3 .23 Compressor Best Practices

Fig 3.23.2 Typical gas seal system for
dry air and or inert gas (Courtesy of John
Crane Co.)

Referring back to the function definition of the gas seal
system, all requirements are met. ‘Continuously supplying fluid’
is met by utilizing the discharge pressure of the compressor. The
requirements for ‘specified differential pressure, temperature
and flow rate’ are met by the design of the seal itself, which can
accommodate high differential pressures, high temperatures,
and is sized to maintain a flow rate that will remove frictional
heat necessary to maintain seal reliability. The only requirement
not met is that of supplying a clean dry fluid, and this can be seen
in Figure 3.23.2. This requirement is met by using a dual system
coalescing filter.
When one considers all the advantages, the next question to
ask is; “Okay, what are the disadvantages?” Naturally, there are
disadvantages. However, proper design of the gas seal system
can minimize and eliminate many of them. Do not forget that
the requirements for any system mandate proper specification,
design, manufacture, operation and maintenance. One can never
Fig 3.23.3 Liquid seal flush (Courtesy of John Crane Co.) eliminate these requirements in any critical equipment system.

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