Design, Testing, And Field Experience Of A High-Pressure Natural Gas Reinjection Compressor.

Abstract

This paper explains the design and testing of a high-pressure centrifugal compressor. It also covers commissioning and field experience. Importance issues for high-pressure compressors are highlighted in the paper in general terms and for a specific design. Included are the mechanical impeller design, seal clearance control, and rotor stability. The impeller integrity is ensured by means of finite element analysis and supported by experimental modal analysis. During full load testing, a unique measurement was also carried out in order to verify the relative rotor displacement in the balance drum labyrinth under transient conditions. Special consideration is given to the verification of analytical rotor stability predictions, which is of major importance for high-pressure applications. The forces originating from the labyrinth seals tend to destabilize the rotor. The rotordynamic analysis is presented for a 418 bar (6061 psi) natural gas reinjection compressor. The predictions from this analysis were verified during an ASME/PTC-10 Class I (1997) test on the test stand. The compressor was tested with and without labyrinth swirl brakes installed resulted in reliable, trouble-free operation. This has been confirmed by actual field data from a floating production, storage, and offloading (FPSO) vessel in the North Sea.