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Appendices
226 UDA2182 Universal Dual Analyzer Product Manual January 2009
15.13 Appendix L – Leak Detection in PPB Applications
Before performing air leak detection, it is necessary to determine that both the probe and
analyzer are working properly. Refer to Probe and Analyzers tests in Section 15.9
1.
First, check to see that the probe contains an O-ring. Per the probe directions, an O-
ring must go into a probe that is used in ppb applications. This creates a tight seal
between the probe and flow chamber. MAKE SURE THIS O-RING IS IN THE
PROBE.
2.
Unless already in air, open the probe to air for 30 seconds.
3.
Put it back into the process again.
4.
Allow the DO to drift down to the 20-30 ppb range. The 20-30 ppb range was chosen
because the reading was low enough that the drift was small with respect to the
changes observed for various flow rates but high enough that changes could be
observed.
5.
At this range, vary the flow rate from 10 to 100 ml/min. These low flow rates were
selected for two reasons. The first, the tester may only have a 0 - 100 ml/min flow
indicator. The other reason is a leak that exists at this low flow, will cause a change in
the DO reading.
6.
If the DO value at 10 ml/min exceeds the DO value at 100 ml/min, a leak is present in
the sampling line.
7.
Fixing the leak may require plastic tubing to be replaced with metal tubing, tape to be
put on fittings, and/or fittings at the bottom of the probe to be tightened securely.
8.
Now, repeat Steps 2 - 6 until the flow can be changed from >100 ml/min to 10 ml/min
with no change in the DO value.