6. 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: reduce the sensitivity, touch a steam
line and listen to the sound quality, then touch a water line. Once you have become familiar with the sound
differences, continue your inspection.
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 blow-through by
comparing sonic intensity differences by reducing the sensitivity and touching just upstream of the valve, at
the valve seat and just downstream of the valve.
PROCEDURE FOR VALVE CHECK:
1. Use stethoscope module.
2. Touch downstream side of valve and listen through headset.
3. When necessary, if there is too much sound, reduce sensitivity.
4. For comparative readings, usually in high pressure systems:
a. Touch uptream side and reduce sensitivity to minimize any sound (usually bring the meter to a mid-line
"50 %" reading).
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.
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. CONFIRMING VALVE LEAKAGE IN NOISY PIPE SYSTEMS
Occasionally in high pressure systems, stray signals occur from valves that are close by or from pipes (or conduits)
feeding into a common pipe that is near the down stream side of a valve. This flow may produce false leak signals.
In order to determine if the loud signal on the downstream side is coming from a valve leak or from some other
source:
1. Move close to the suspected source (i.e., the conduit or the other valve).
2. Touch at the upstream side of the suspected source.
3. Reduce sensitivity until the meter displays a mid-line ("50 %") reading.
4. Touch at short intervals ( such as every 6 - 12 inches (15-30.5 cm) and note the meter changes.
5. If the sound level decreases as you move towards the test valve, it indicates that the valve is
not leaking.
6. If the sound level increases as you approach the test valve, it is an indication of a leak in the
valve.
