Engineer's Notebook

Meeting compression train base package design requirements for service on floating production, storage and offloading vessels

Editor’s Note: Reproduced with permission of the Turbomachinery Laboratory from Proceedings of the Asia Turbomachinery and Pump Symposium, Singapore, February 22 – 25, 2016 (http://atps.tamu.edu/proceedings).

ABSTRACT
Typical floating production, storage and offloading (FPSO) compression applications are presented, including drivers and auxiliary equipment, and typical compressor operating conditions. Base packages consisting of centrifugal compressor(s), gear, motor or gas turbine driver, lube oil tank, and auxiliary equipment require extensive analyses to validate design requirements for service on FPSO vessels. Finite element analyses (FEA) are performed to insure that stress and displacement criteria are met. This paper discusses loading conditions that are evaluated including package lifting, transportation loads, short circuit torque, and upset loads. Operating load cases are also analyzed, which include dead weight, FPSO motion, rotor unbalance, torque, nozzle, and wind loads. Modal analyses are performed to ensure that predominant package modes do not lie in the run speed range. Rotor unbalance forced response analyses can be performed to ensure that amplitudes at key locations remain within allowable vibration criteria. Typical FEA models and analytical procedures are presented.
The use of the analytical results to assist in selecting design modifications is discussed. The paper emphasizes the importance of gathering information early in the design cycle. This includes ship structural stiffness at the anti-vibration mount (AVM) locations, AVM stiffness, and load specifications including wind, wave, upset, and transport loading, and coupling capability. Finally, the paper presents a design change that allows for significant footprint reduction of the overall package.

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other articles from insights issue 12.2016