TL04 - Stability Considerations of Centrifugal Compressors Equipped with Active Magnetic Bearings 

LectureMany centrifugal compressor rotordynamic stability investigations have been performed over the last 40 years. Rules, based on the large experience and knowledge are defined to ensure compressor stability in operation. The API 617 standard describes a standardized procedure valid for all compressors, manufacturer type or size independent. Up to the 7th edition these rules did not account for compressors equipped with bearings than other conventional oil bearings. The 8th edition added a separate procedure for AMB equipped compressors. Centrifugal compressors with AMB are used for various applications. In the last decade they have been implemented in new areas (upstream, subsea). Therefore, AMB compressor technical challenges are increasing because the AMB load capacity is lower than a comparable oil bearing and causes the rotordynamic stability to become a crucial issue. This paper describes a standardized procedure (based on API) for reliable stability determination. A comparison between conventional and AMB equipped compressors is drawn and the main differences are highlighted. This paper shows that the API 617 procedure to assess stability is appropriate for oil bearing machines. However this procedure is not sufficient to determine the stability threshold of AMB compressors. An AMB machine stability analysis shall also include radial force variation