Page 246 - Intro Predictive Maintenance

Process Parameters 237

Table 10–10c Common Failure Modes of Reciprocating Compressors

THE PROBLEM

Air Discharge Temperature Above Normal Carbonaceous Deposits Abnormal Compressor Fails to Start Compressor Fails to Unioad Compressor Noisy or Knocks Compressor Parts Overheat Crankcase Oil Pressure Low Crankcase Water Accumulation Delivery Less Than Rated Capacity Discharge Pressure Below Normal Excessive C

THE CAUSES Motor Over-Heating Starts Too Often
Location Too Humid and Damp
Low Oil Pressure Relay Open
Lubrication Inadequate
Motor Overload Relay Tripped
Motor Rotor Loose on Shaft
Motor Too Small
New Valve on Worn Seat
“Off” Time Insufficient
Oil Feed Excessive
Oil Filter or Strainer Clogged
Oil Level Too High
Oil Level Too Low
Oil Relief Valve Defective
Oil Viscosity Incorrect
Oil Wrong Type
Packing Rings Worn, Stuck, Broken
Piping Improperly Supported
Piston or Piston Nut Loose
Piston or Ring Drain Hole Clogged
Piston Ring Gaps Not Staggered
Piston Rings Worn, Broken, or Stuck H L H L H H
Piston-to-Head Clearance Too Small

compressors because they rely on the lubrication system to provide a uniform oil film
between closely fitting parts (e.g., piston rings and the cylinder wall). Partial or com-
plete failure of the lube system results in catastrophic failure of the compressor.

Pulsation
Reciprocating compressors generate pulses of compressed air or gas that are dis-
charged into the piping that transports the air or gas to its point(s) of use. This pulsa-
tion often generates resonance in the piping system, and pulse impact (i.e., standing
waves) can severely damage other machinery connected to the compressed-air system.
Although this behavior does not cause the compressor to fail, it must be prevented to
protect other plant equipment. Note, however, that most compressed-air systems do
not use pulsation dampers.