Page 279 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Gear and Coupling Best Practices Be st Practice 4.7

Fig 4.6.16 Coupling guard dimensional design criteria (Courtesy of M.E. Crane, Consultant)
considering a retrofit, the following action should be taken to Critical speeds will not be affected
maintain or increase coupling system reliability: Coupling guard design is acceptable
Advise coupling vendor or any environmental considerations
Consult equipment or coupling vendor for proper selection of that may affect dry flexible element life (environmental
new coupling. gases, temperatures, excessive dust, etc.).
Consult equipment O.E.M.(s) (each affected vendor) to confirm:

Best Practice 4.7Practice 4.7Practice 4.7
Best
Best
Ensure liquid free start-ups with hydraulically fit couplings, Ensure that the procedure for draining compressor cases is prop-
to prevent coupling slip and costly long term shutdowns. erly written in the operations manual, and is implemented before each
Liquid in the compressor casing with hydraulic fit couplings (no start-up.
keys) can exceed the slip torque minimum safety factors and slip the Benchmarks
coupling hub, causing extensive damage to the coupling, rotor and This best practice procedure has been used since 1975, when I ex-
coupling guard.
perienced a catastrophic coupling slip incident. The coupling hub
Casing drains must be supplied with a means of confirming the
slipped, melted the hub and shaft, broke the coupling assembly and
compressor case is liquid-free prior to start-up.
left the coupling guard, whereupon it struck a small diameter gas line
Special care is required for motor driven compressors that will
and started a refinery fire.
accelerate to full load in less than 30 seconds.
Since that time, each compressor project has required the following
Lessons Learned plan concerning compressor casing draining:
The majority of hydraulic coupling slip incidents are Multiple case drains
caused by liquid inside the compressor casing at start-up. A means of assuring that the case was properly drained
Detailed compressor case draining procedure that is contained in
the plant operations manual and must be implemented properly by
all shifts.
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