15 - Compressor casings and stationary internals

Abstract

This chapter discusses the compressor case and the stationary internals. The major functions of any compressor case, regardless of type are to provide support of all bearing seals and stationary internals and provide positive containment of the process fluid. Excessive casing forces caused by the process piping or foundation can cause bearing, seal, and rotor failures. Positive containment of the process fluid is accomplished by the design and manufacture of leak tight joints. The available types of turbo-compressor casings are single stage radial split, single state integral gear, and multistage radial split. The advantage of a horizontally split casing is the ease of removing internal parts. During the compressor design phase the vendor issues an allowable piping forces and moments diagram which states the maximum values of external forces and moments to which the casing can be subjected. The piping systems are then designed to comply with these limits. The field piping fabrication methods, field foundation building, and improper spring support sizing can result in excessive case stresses even though the systems were properly designed.