Quick Look

Mounting the New Class of High-Speed, Reciprocating Compressors to Reduce Sensitivity to Frame Bending and Cylinder Stretch Resonances, 18-9284

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Principal Investigators
Anthony J. Smalley
P. Joe Pantermuehl
Ralph E. Harris
J. Pete Harrell

Inclusive Dates: 12/04/01 - 04/04/02

Background - The expanding U.S. gas pipeline industry is adding a number of high horsepower (8,000 horsepower), high-speed (600 to 1,200 revolutions per minute) reciprocating compressors. The Institute has been heavily involved with the largest of these compressors and helped define and solve the vibration problems they have encountered. Recent data indicate that the compressor, its frame, and attachments can vibrate on their foundation severely enough to cause a trip and threaten production. This project sought to identify and quantify the nature and responsiveness of such vibration and to explore the potential to control it by stiffening the support structure.

Approach - A target compressor was chosen, for which significant vibration and operational data was available – a six-cylinder, 8,000-horsepower, motor-driven Ariel JGV compressor. The target compressor is shown in the illustration below. A detailed finite element model was built of the compressor, its mounting system, its cylinders, and close-in piping using data provided by the pipeline company, the compressor manufacturer, and the packager. Beam and plate elements were used for all the frame modeling. The model included the suction and discharge bottles, the cylinder supports, the I-beam support structure, and the chocks that mount the frame to the I-beams.

Accomplishments - The predicted vibration characteristics of the main system mode at 101 hertz closely matched the measurements of peak vibration at 100 hertz. Another important mode was predicted at 157 hertz – this involved lengthwise vibration of individual cylinders in a stretch mode, and the observed frequency was close (160 hertz). The influence of support structure stiffness on these modes was explored. To match vibration levels observed in the field at the main system mode, it was found that some traditional assumptions about excitation forces were no longer valid, and an alternative approach was hypothesized, which matched the data well. This discovery needs more specific definition, but is very significant to the understanding of high-speed compressor vibrations.

Timely execution of this quick-look project had a major influence on SwRI's success in being awarded a project to design the complete foundation of an 8,000-horsepower Ariel JGV6 compressor driven by a Caterpillar G16CM34 natural gas engine, as well as the piping pulsation and vibration control system.


 
This motor-driven reciprocating compressor is one of a new class being installed on US pipelines.

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