Confi rming a leak exists, Pressure & air flow information – GxT Ferret 21 Smoke User Manual

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Confi rming a Leak Exists

This feature incorporates a highly accurate fl ow gauge, which is used with one of the two internal
automated pressure limiters to assess the suspected leak. Once the CoolSmoke is hooked up to the
system or component to be tested, the technician simply selects the appropriate pressure level and
applies pressure using the foot switch or the timer.

When the selected limit pressure is reached, the application of pressure is automatically cut out, indicating
that the system has reached the target pressure.

Any leak will lower the pressure that is trapped in the system. When this occurs, the sensitive pressure
switch cuts the fog / air supply back in. As the system cuts back in, the ball in the fl owmeter is blown
high up in the fl owmeter display, indicating that there is in fact a leak. This may be repeated as often as
you wish. The more frequently the ball bounces the larger the leak.

Pressure & Air Flow Information

The following information is an outline of the relationships between the fl ow of air, the pressure applied
and the size of a leak that infl uences them.

In all cases, we must assume that any leak size we
describe, is the equivalent area of the diameter of the
leak. Of course few leaks are round, but all have an open
area of leakage.

This Leak Chart will provide you with a better idea of how
air fl ow and pressure are infl uenced by the size of the
leak you are looking for.

The fi rst chart represents a 0.020” diameter leak, which
is so small, it will not register on the Flow Gauge until
we apply 4psi of smoke. At this point it registers just 1
SCFH (Standard Cubic Feet per Hour). As we increase
the applied pressure, so do we increase the air fl owing
through the leak.

Leak Chart 2 shows the increase in air fl ow for a 0.040”
leak.

Note the large difference in air fl ow, even though the
diameter of the leak is just doubled. The actual fl ow has
increased dramatically.