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Low Level Leaks
In ultrasonic inspection of leakage, the amplitude of the sound often depends upon the amount of
turbulence generated at the leak site. The greater the turbulence, the louder the signal, the less the
turbulence, the
lower the intensity of the signal. When a leak rate is so low that it produces little, if any
turbulence that is
"detectable", it is considered "below threshold". If a leak appears to be of this nature:
1. Build up the pressure (if possible) to create greater turbulence.
2. Utilize LIQUID LEAK AMPLIFIER. This patented method incorporates a UE Systems product called
LIQUID LEAK AMPLIFIER, or LLA for short. LLA is a uniquely formulated liquid substance that has
special chemical properties. Used as an ultra sonic "bubble test, a small amount of LLA is poured
over a suspected leak site. It produces a thin film through which the escaping gas will pass. When
it comes in contact with a low flow of gas, it quickly forms a large number of small "soda-like"
bubbles that burst as soon as they form. This bursting effect produces an ultrasonic shock wave
that is heard as a crackling sound in the headphones. In many instances the bubbles will not be
seen, but they will be heard. This method is capable of obtaining successful leak checks in systems
with leaks as low as 1 xl0-
6
ml/ sec.
NOTE:
The low surface tension of the LLA is the reason small bubbles form. This can be negatively
changed by contamination of the leak site with another leak fluid, which can block LLA or cause
large bubbles to form. If contaminated, clean the leak site with water, solvent or alcohol (checks with
plant regulations before selecting a decontaminating cleaning agent).
3. Use the UE-CFM-2 Close Focus Module. Specifically designed for low level leaks, the unique scanning
chamber is designed to receive low level signals with reduced signal distortion and provides easier
recognition of a low level leak. For more information, call the factory.
