Case Study: Resolving Vibration Issues at Cryogenic LNG Submersible Vertical Pump

Ahmad Fadzli Ismail, Principal Engineer, PETRONAS

Description

Three units of cryogenic submersible vertical pump for new LNG tank project underwent Factory Acceptance Test (FAT) at Original Equipment Manufacturer (OEM) shop test bench. Each of this pump equipped with four accelerometers installed at upper and lower bearings. These three pumps could not meet the vibration limit as per project specification. Two dominant peaks were observed at running frequency and vane pass frequency. These pumps later were dismantled for inspection and further checks. Re-balancing were done at rotor assembly, impeller and balanced drum which the only component not underwent component balancing prior assembly. Computed Flow Dynamic (CFD) analysis were also done to verify series of combination between impeller and diffuser vanes. The presentation will cover vibration signature plots, diagnostic done to determine the faults and actions taken including improvement done to permanently resolve the high vibration issue.

Takeaways

(1) Vibration Signature and Analysis to resolve the issue
(2) Detail analysis to resolve high amplitude at Vanes Pass Frequency
(3) Effects of Accelerometer mount type on vibration value

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