Vibration analysis pinpoints: valve noise source

Research engineer Daniel Eilers is responsible for noise and vibration testing, noise prediction development, and computational fluid dynamic simulations of flow-through control valves. He recently wrote an article for Valve Magazine highlighting findings from an oil refinery. For the full version of the article, click HERE.  

Since the exact noise source could not be identified using acoustic sound pressure level measurement techniques, which was the process used earlier by the consulting firm, the efforts to measure vibrations began with a survey of the quench valve area to determine where to begin testing.

Accelerometers were used to allow testers to isolate a specific component for analysis, which leads to a systematic evaluation and subsequent elimination of suspect piping and valves.

To determine whether the noise source in this case was upstream of the valves with noise then propagating through the system, the accelerometers were mounted upstream and downstream of the motor-operated valves that feed the quench valves. Following measurements taken at these locations, the sensors then were placed immediately upstream and downstream of each quench valve, as well as mounted on the stem of each valve.

The highest piping vibration levels were found next to the quench valves, with the highest overall reading being taken on the valve stems. This finding indicated that the source or cause of the noise was most likely the valve trim components.

Stroking the quench valves was shown to impact the tone of the noise. Depending upon the travel, the tones would disappear, increase or change frequency.

The quench valves were 25-year-old units that used post guiding of the valve plug. In such valves, if the tolerance between the plug and valve body is too large, the plug/stem assembly can vibrate. If the assembly is excited at the resonance of the plug/stem component, the vibrations can cause tones.

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