Lubricant Viscosity Control for Gas Compressors - Rob Kasameyer

If you’re running one of the 140 working refineries in the US, the last thing you need is an unplanned shutdown. But a production standstill is exactly what is at risk if you don’t keep an eye on the viscosity of the lubricating oil used in any of the rotary compressors in the plant, with the highest risk of these being the gas compressors. One minute all processes are up and running, and the next there’s a bearing failure and production stops.

It’s not just the cost of lost production, either - a compressor failure in a single part of the refinery can run in the tens of thousands a day in lost revenue, similar amounts to rebuild a compressor, and hundreds of thousands of dollars for a replacement - not to mention the sunk cost of maintaining spares.

Clearly managing lubricant viscosity is critical to maintaining compressor health, yet it is common practice to monitor lubricant viscosity in each major compressor once a month by sending a sample to a lab for testing. For compressors where lubricant comes in contact with methane and other light hydrocarbon gases, the lubricant’s viscosity can break down much more quickly, increasing the risk of failure. Through hard luck, refiners also have found that real-time temperature monitoring is inadequate to monitor lubricant viscosity.

A major Gulf Coast refinery engineer indicates they solved the problem by moving to real-time monitoring of lube oil viscosity in the critical compressors. “We recognized that in-line viscometers are the best way to know what is happening to the lube oil in our large screw compressors,” says the plant manager. “Further, we have found in-line lubrication viscosity monitoring offers a cost-effective way to keep track of compressor health.”

The true measure of the health of a lubricant’s viscosity can only be gauged when measured in situ with gas vapors dissolved in the lubricant. Further, monitoring lubricant temperature isn’t sufficient to protect compressor bearings, especially in applications where process starts and stops can occur.

What’s needed is in-line viscosity monitoring to help provide plant operators with real time data on lubricant viscosity. There is a solution for refinery managers working to keep plants online and producing. New, inexpensive and rugged in-line viscometers are able to monitor real-time changes in lubricant viscosity, offering a cost-effective way to keep track of compressor health in real time.