Owners and Engineering Companies Often Require a Dynamic Analysis of FPSO Production Structures When High Horsepower Reciprocating Compressors are Employed to Mitigate Damage and Safety Issues Caused by Vibration
By Kelly Eberle and Chris Harper
Editor’s Note: This article has been extracted from a paper given by theauthors at the Fifth European Forum for Reciprocating Compressors, March 21-23, 2007, Prague, Czech Republic. For further information or list of references, contact the authors at the following e-mail addresses: firstname.lastname@example.org; email@example.com
Introduction A growing number of reciprocating compressors are being used on Floating Production Storage and Offloading vessels (FPSO)for many applications. These compressors are significant sources of vibratory forces and can cause high vibrations of the compressors and FPSO module, resulting in costly and premature machine failures as well as safety concerns to operators in work areas. Owners and en-
Kelly Eberle graduated from the University of Saskatchewan with a Bachelor of Science in Mechanical Engineering in 1986. He hasbeen a professional member of APEGGA since 1991. He has worked with Beta Machinery Analysis, Calgary, Alberta, Canada, since 1988 and is presently in the role of principal engineer. He has accumulated a wide range of design and field experience, particularly in the area of pressure pulsation analysis and mechanical analysis of reciprocating compressor and pump installations. The scope of hisdesign experience includes acoustical simulations, thermal flexibility studies, dynamic finite element analysis, structural analysis and foundation analysis. He also directs development of new analysis tools and techniques. He has co-authored numerous papers and presentations including the articles: Cylinder Stretch in Reciprocating Compressors; Acoustic Modeling of Stepless Valve Unloaders; API 618Forced Response Studies; and Guidelines in Pulsation Studies. Chris Harper graduated from the University of Alberta with a Bachelor of Science in Mechanical Engineering in 1996. He has been a professional member of APEGGA since 2003. He has worked with Beta Machinery Analysis since 2000. In his present position as principal engineer, he works on digital acoustic simulation, thermal analysis anddynamic finite element analysis of reciprocating compressor packages and structural steel for onshore and offshore applications. Field troubleshooting experience includes solving vibration and pulsation problems on reciprocating gas compressors and engines. He also manages the internal training department. He has co-authored two papers presented at the Southern Gas Association, Gas MachineryConference: API 618 Forced Response Studies — They Can Be Done; and Vibration Related Failures of Small-Bore Attachments.
gineering companies often require a dynamic analysis of the production structure when high horsepower reciprocating compressors are employed to mitigate these issues. Based on our experience with over 60 offshore reciprocating projects, this paper discusses new analysistechniques to calculate the amplitude and location of high vibrations on the module deck and to optimize the topside module design. An example is included that reviews an integrated design approach, combining the topside module structural model with the mechanical model of the compressor packages. A summary of the recommended specifications for performing dynamic analysis studies is included. Examplesare included from recent projects, including a large FPSO project where three compressor packages were mounted on the topside module. Compressors used in FPSO applications range from small vapor recovery units — typically 500 hp (370 kW) — to large, multistage compressors used in high-pressure injection service that can range over 3000 hp (2240 kW). The reciprocating compressor, driver (engine or...