PRESENTER

Monroe Voyles

Monroe Voyles is a mechanical engineer with 23 years of experience; 7 in a chemical plant, 3 in a refinery, 9 as a pump improvement engineer for Flowserve, and 4 as a Solutions Engineer for ITT Goulds Pumps. Experience with large electric motors, gas turbines, centrifugal compressors, reciprocating compressors, steam turbines, large API pumps, ANSI pumps, high pressure boiler feed water pumps, non-contacting gas seals, high temperature bellows seals, mag-drive pumps, liquid ring compressors, cooling tower fans/gear boxes, and large compressor gear boxes. Work included RCFA, Vibration analysis, performance testing, and upgrading systems/equipment to resolve problems. Proficient with finite element modeling (CREO/Simulate).

SUMMARY

Most centrifugal pumps create vane-pass pressure pulsation and vibration as a normal reaction to head generation. In some cases the resulting vane-pass vibration amplitudes can be excessive. The cause of high vibration amplitudes can be related to large pressure pulsation forces; resonance can also amplify the vibration response in some cases.

This case study describes excessive vane-pass vibration amplitudes that were caused by structural and possibly acoustic resonance. The solution involved pump modifications to decrease vane-pass pressure pulsation amplitudes and a speed change to increase frequency separation margin between vane-pass frequency and natural frequencies. ODS and Modal data was used to evaluate the natural frequencies and mode shapes. Modal data was also used to calibrate a finite element model. Finite element analysis was used to evaluate the pump/piping system. Several previously planned (costly) actions were also shown to be ineffective; therefore, a planned outage scope was changed due to this analysis. The result was a dramatic reduction in vibration amplitudes and noise with minimal cost.