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ForSevere ServiceControl Solutions, Turn to Fisher Technology and Innovation

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MODIFIED VALVE-PLUG DESIGNSOLVES PIPING VIBRATION PROBLEMS

In the early 1990s, a gas producer in the jungles of Indonesia required more pressure to draw natural gasfrom an underground geological formation. This gas-production complex includes 40 wells, a LiquefiedNatural Gas (LNG) plant, and a 30-kilometer pipeline, which transports LNG to the coast. For this booster-compression project at the site, the customer planned to install million-dollar compressors, driven by20,000-horsepower gas turbines.

Project managers hired a Japanese contractor to design and build the new booster compression facility.They also asked Fisher to design and build control valves for the demanding, anti-surge applications that

would help protect their valuable new compressors. Fisher supplied a dozen valves for the project,including six 12X8-inch Design EWNT globe-style valves with Whisper TrimIII.

Fisher has hundreds of anti-surge valves like these installed around the globe. What made this projectunique and challenging was an unfortunate piping design. During the first startup on site, the piping aroundthe compressor began to vibrate violently and threatened to bring production to a halt. Desperate to avoid apiping re-design, compressor damage, and/or lost production, the customer and contractor came to Fisher-Marshalltowns Engineered Products team for help.

Fisher engineers determined that the piping between the compressor discharge and the anti-surge valveinlet had an acoustic resonance (similar to the vibrations of a pipe organ making sound). This resonance

matched the frequency of the pipes natural pattern of motion. In other words, pressure waves excited thestructural resonance or motion of the pipe itself.

Following some on-site work and extensive laboratory testing, including computational fluid dynamicsimulations, Fisher demonstrated that the EW valve installed had a hydraulic flow pattern in its inlet cavity,aggravated by this pipe-organ effect. They modified the valves plug design, adding a diverter cone(normally used to boost capacity in Whisper III trim) and thereby modified the flow pattern in the EW inlet.This eliminated the path of flow energy driving the vibration (acoustic-hydraulic excitation). Once the newvalve plugs with diverter cones were installed, the severe piping vibration stopped, even when thecompressor was at full speed.

For more severe service solutions see us at www.fishersevereservice.com.

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