5.LOCATING FAULTY VALVES: Utilizing the contact (stethoscope) module in the Ultraprobe, valves can easily be monitored to determine if a valve is operating properly. As a liquid or gas flows through a pipe, there is little or no turbulence generated except at bends or obstacles. In the case of a leaking valve, the escaping liquid or gas will move from a high to a low pressure area, creating turbulence on the low pressure or "downstream" side. This produces a white noise. The ultrasonic component of this "white noise" is much stronger than the audible component. If a valve is leaking internally, the ultrasonic emissions generated at the orifice site will be heard and noted on the meter. The sounds of a leaking valve seat will vary depending upon the density of the liquid or gas. In some instances it will be heard as a subtle crackling sound, at other times as a loud rushing sound. Sound quality depends on fluid viscosity and internal pipe pressure differentials. As an example, water flowing under low to mid pressures may be easily recognized as water. However, water under high pressure rushing through a partially open valve may sound very much like steam. To discriminate:
1.Reduce the sensitivity. 2. Change the frequency to 25 kHz and listen.
A properly seated valve will generate no sound. In some high pressure situations, the ultrasound generated within the system will be so intense that surface waves will travel from other valves or parts of the system and make it difficult to diagnose valve leakage. In this case it is still possible to diagnose valve
PROCEDURE FOR VALVE CHECK
1.Use stethoscope module.
2.Touch downstream side of valve and listen through headset.
3.Start test at 40 kHz. If the sound appears weak or confusing, change the frequency. As an example, try to test at 30 kHz. then
20 kHz.
4.When necessary, if there is too much sound, reduce sensitivity.
5.For comparative readings, usually in high pressure systems:
a.Touch upstream side and reduce sensitivity to minimize any sound.
b.Touch valve seat and/or downstream side.
c.Compare sonic differentials. 'If the valve is leaking, the sound level on the seat or downstream side
will
be equal to or louder than the upstream side.
6.In some instances, such as in noisy background or low viscosity fluids, it will be helpful to adjust the frequency to adequately
interpret valve sounds. To do this:
a.Touch upstream of the valve and, in the Frequency Select Mode, gradually spin the Frequency until the stray signals are minimized or until the desired fluid flow is heard clearly.
b.Touch the upstream side, valve seat, downstream sides (as described above) and compare differences.
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