-6-D. 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 1x10-6 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 (check with plant regulations before
selecting a decontaminating cleaning agent).
E. TONE TEST (Ultratone )
The Tone Test is an ultrasonic method for non-destructive testing which is used when it is difficult to pressurize
or draw a vacuum in a system. This ultrasonic test is applicable to a wide range of items, including:
CONTAINERS, TUBES, PIPES, HEAT EXCHANGERS, WELDS , GASKETS, SEALS, DOORS, WINDOWS,
OR HATCHES.
The test is conducted by placing an ultrasonic transmitter, called TONE GENERATOR, inside (or on one side) of
the test item. The warble pulse-signal from the TONE GENERATOR will instantly "flood" the test item and
penetrate any existing leak hole. Depending on configuration and material, even thin spots in certain metals can be
vibrated by the signal. By scanning for sonic penetration on the exterior surface (or opposite side) of the test item
with the Ultraprobe, the leak will be detected. It will be heard as a high pitched warble, similar to bird chirping.
LLA