Centrifugal Compressor failure & Performance Shortfall Case Study

Problem

A multistage integrally geared centrifugal compressor experienced a failure of an impeller causing major damage to the compressor, expensive down time, and costly repairs. In addition, the compressor had not been able to perform as designed since its installation. KHE was contracted to participate as a member of a failure analysis and troubleshooting team, consisting of personnel from the OEM, operating company and engineering company.

Solution

As part of its analysis, KHE considered the operating history and conditions, the performance test results, the events leading up to the failure, the changes made during several outages, the damage to the compressor components, and the changes implemented during the rebuild. KHE performed a critical speeds assessment, process analysis, surge/stall analysis, aerodynamic review of the impeller metallurgical review, corrosion assessment of all affected components, and a review of the inter-stage cooler design. It was determined that the blade failed due to surging of the failed stage which resulted from failed inlet guide vanes. The vanes failed due to corrosion of the control linkage which was caused by excessive water carry over and improper materials selection on some critical components. The performance shortfall was determined to be caused principally by poor design of the inter-stage coolers; however, inaccurate speed control and fouling were also identified as part of the performance problem. Not all factors contributing to the performance shortfall could be identified without additional analysis and research.

Results

The materials of all critical components were re-specified to a material suitable for the application, the inter-stage coolers were redesigned to eliminate the water carry over, and the compressor speed was raised to increase throughput.