Failure of Cryogenic Gas Expander Thrust Bearings PDF Print E-mail
Written by Stephen H. Shakeshaft   
Wednesday, 10 March 2010 21:01
Article Index
Failure of Cryogenic Gas Expander Thrust Bearings
Initial investigations
Further investigation
Conclusion
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Introduction

An Oxygen production plant inside a steelworks is using a gas liquefaction plant to take Oxygen gas produced during low gas usage periods and liquefy it for use during high gas demand periods.

Machinery details

The liquefaction of Oxygen is a cryogenic process.

The refrigeration for the liquefaction of the gas is provided largely by gas expansion turbines (expanders).

The energy extracted by the expansion turbines from the gas as it expands and cools is used to drive a compressor.

If the expander and compressor share opposite ends of the same shaft, the unit is known in the industry as a "compander".

This plant has two companders operating in parallel on a gas liquefier.

The companders are high speed rotating machines, running in this case at around 46000 rpm.

The machines have oil lubricated bearings of the tilting pad white metal type, with the lubricating oil fed by an electric pump on a separate skid assembly.

The plant is located in an area that is subject to periodic losses of power from the public electricity supply completely without warning.

Of course, when the plant loses power, the liquefier is instantly tripped and the companders run down without a supply of oil from the electrically operated lubrication pump.