Is That a Screwdriver in Your Ear?

Advanced Inspection of Reciprocating Compressors with Ultrasound

We’ve known for more than twenty years that ultrasound provides the earliest warning signals for mechanical failure. If you can hear compressor valves knocking with a screwdriver you are too late. But, there is a fundamental difference in philosophy between what ultrasound inspection proposes to accomplish and what one can hope to achieve with his screwdriver.

Ultrasound monitors the condition of that compressor valve from the time it is new until the time it is ready to be replaced, all the while providing feedback about subtle changes in its operational condition. The screwdriver method presumably is used “to find the source of the problem” which suggests the knocking is already perceivable to the human ear and it is only a matter of days, hours, or minutes before the compressor will fail. We call this firefighting. It is certainly not condition-based monitoring and it leaves no room for planning the repair.

The reason machine systems fail “without warning” is because no warning system is in place. Using a predictive technology such as ultrasound condition-based monitoring to indicate subtle changes in machines over time allows industry to avoid firefighting catastrophes.

Advanced Valve Testing

A huge benefit of ultrasound is its ability to record dynamic wave files on reciprocating compressors. By using a free and simple time waveform analysis software such as UAS Lite, it is easy to expand 1/10th or even 1/100th of a second of data to see a valve open, exhaust and close. During that blink of an eye, we can see if there is complete sealing of the valve seat and we can even assess the strength of the valve spring. All of this data can be printed out into a logical report which serves as a summary for management to decide if further action is yet necessary. Because the document becomes historical archive, the next action set decision will have a basis of comparison.