Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery

15Reliability Improvement Ideas for Integrally Geared Plant Air Compressors

By Abdulrahman Alkhowaiter

Integrally Geared Plant Air Compression Packages

The heart of most packaged plant air compressors covered by the American Petroleum Institute (API) 672 standard (Packaged, Integrally Geared Centrifugal Air Compressors for Petroleum, Chemical, and Gas Industry Services, Fifth Edition) is the integrally geared compressor (see Figure 15.1). An integrally geared compressor is a multi-shaft design where each stage utilizes a three-dimensional (3D) impeller running at its optimum rotational speed. Typically, this compressor type consists of a gear unit with a central bull gear and different gear pinions driving a number of impeller stages (see Figure 15.2).

Refer to Figure 15.3 as I explain the basic operation principles of packaged air systems utilizing integrally geared compressors: (Note the system described here has four stages of compression, but three stages of compression are common.)

1. Atmospheric air enters the first stage impeller where it is compressed and discharged into the first intercooler system. The intercooler system must cool the first stage, discharge air, and remove any liquid water or scale in the air before it enters the second stage of compression.
2. Air exiting the first intercooler system enters the second stage impeller, where it is compressed and discharged into the second intercooler system. Again, the intercooler system must cool the second stage, discharge ...