Chlorine Compressor Failure Analysis Case Study

Problem

A chemical plant experienced a major failure of a high-speed chlorine compressor. It had been experiencing many operational problems with the compressor since its installation. The failure resulted in significant damage to the compressor and a significant outage of the process line. KHE was contracted to perform a failure analysis to determine the root cause of the failure.

Solution

KHE performed process, process control, mechanical, and metallurgical reviews of the application as well as interviews with operational and maintenance personnel. KHE took a comprehensive look at the problem and conducted a root cause failure analysis to determine the possibility of liquid slugging the compressor, fatigue failure of the high speed shaft, bearing failure, seal failure, and seal pressure control system failure. It was determined that the seal system between the gear box and compressor, including the controls for the pressurized seal zone, were inadequately designed to prevent manual override of the system. Operator personnel unwittingly lowered the nitrogen supply to an insufficient level, causing chlorine gas to leak from the compressor through the seal zone to the gearbox. The gas contaminated the lubricant causing the bearings to fail. This provided adequate heat to initiate a chlorine metal fire that consumed aluminum and carbon steel components, including a portion of the shaft.

Results

The controls to the supply of buffer gas for the seal system were modified to ensure an appropriate supply of seal gas in the event of a train shut down on low pressure in the seal zone.