(3a) Rotordynamic Considerations of Large Frame Centrifugal Compressors for Ethylene Service

To achieve improved economies of scale, ethylene plant sizes have increased to as large as 1000 KTA.  Building compressors of this scale requires careful rotordynamic design due to the high flow rate requirement and large size.  Maintaining good rotordynamic stability and critical speed separation margin is key to reliable equipment operation.  This paper summarizes unique considerations in the compressor design to maintain acceptable rotordynamic performance.  The influence of labyrinth seals, impeller secondary flow cavities, damper seals, swirl brakes, gas seals, and bearings on the rotordynamic behavior will be investigated.  API rotordynamic requirements will also be discussed.