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Senin, 24 Mei 2010

Valve Testing Instruments

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DESCRIPTION

When valves leak or fail, it can be extremely costly in terms of product quality, safety and energy loss. Valve operation effects the way fluids will flow through a system. There are great differences in the way particular valves work (for example, control valve versus safety valve). The UltraProbe makes it easy to adjust for these differences and readily determine operating conditions while valves are on-line.


How Ultrasonic Leak Detection works

As fluid moves from the high pressure side of a valve through the seat to the low pressure side, it produces turbulence. This turbulence generates ultrasound which is detected by the Ultraprobe and translated, via heterodyning, down into the audible range. The translated ultrasounds are heard through headphones and seen as intensity increments, usually decibels on a display panel. High frequency tuning allows users to adjust for differences in fluid viscosity (i.e. water vs. steam) and reduce any interference from stray pipe noises.

Leak Detection Method

Inspection methods vary depending on the type of valve. Therefore the primary rule is to know the details of your system, for example the way a specific valve may work under specific conditions. In order to determine valve condition such as leakage or blockage: touch upstream of the valve and reduce the sensitivity of the instrument until the meter/display panel reads about 50% of scale. If the instrument has frequency tuning, you may also use this feature to hear the valve sound quality more clearly. Simply tune the frequency (usually 25 kHz) until the sound you would expect to hear becomes clear. It's that simple.
Next, touch downstream of the valve and compare intensity levels. If the sound is louder down stream, the fluid is passing through. If the sound level is low, the valve is closed. Ultrasonic valve inspection is considered a "positive" test in that an operator can instantly identify sound quality and intensity differentials and thereby determine operating condition accurately.
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