Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery

6Assessing Reciprocating Compressors and Engines

By Robert X. Perez

Rotating Equipment professionals are frequently asked to guess the answer to challenging machinery condition questions such as:

• Can we make it until…?
• When should I plan for a major overhaul?
• Is this compressor safe to run?
• Should we go into the compressor during this outage or can we make it until the next one?

Deciding whether to repair a machine or keep it running can be a time of high anxiety, especially if limited information is available to decide. Fortunately, the right tools and training can now give you the ability to “see” inside your reciprocating compressors to make confident decisions on repairs.

Figure 6.1 Six throw reciprocating gas compressor coupled directly to 8000 Hp, 720 rpm synchronous motor.

Reciprocating compressors (see Figure 6.1) are unique in that they are the only compressor type I know whose thermodynamic cycle can be accurately analyzed in great detail using commercially available analysis equipment. Advances in portable reciprocating compression analyzers have made them capable of collecting, storing, and analyzing actual P-V plots. P-V plots are pressure-volume diagrams that are generated by measuring dynamic pressure data inside compressor cylinders and plotting them against the displaced volume of the cylinder. The displaced volume is calculated by correlating the crank ...