HALO Users Manual
Revision G
17
3.6 Leak-Testing the Sample Line
The procedure for leak-testing the sample line is in Table 3-3. Helium is required for leak-testing.
The leak-testing procedure should be done prior to connecting the sample line to the unit.
Table 3-3 Procedure for Leak-Testing the Sample Line
Step
Action
1
Pressurize the sample line with helium to approximately 20 psig. Close
the helium tank, back off the regulator and close the regulator valve.
Wait until the pressure re-equilibrates in the system. If losing pressure
rapidly, perform a quick visual check to make sure all the fittings have
been tightened and there are no valves that are opened to vent.
Repressurize by repeating this step.
2
If pressure is holding steady for several minutes, proceed. Carefully
leak-test all the welds and fittings with a helium leak detector from the
sample source to the analyzer fittings.
ATTENTION
Do not put Snoop® on fittings to be helium leak-tested since it can cause high
erroneous readings. A helium leak detector such as a portable
thermoconductivity detector (TCD) or quadrupole mass spectrometer is
recommended. Watch for drafts since they also cause high or off scale
readings while using the helium probe.
ATTENTION
A fitting that leaks is a major source of contamination and can cause
persistent high analyzer readings. Do not use compression fittings. Tighten
VCR-type fittings using the manufacturer’s specifications for a sufficient seal.
Use metal gasket seals between the fitting and tubing flange. Do not over-
tighten the fitting. Replace the gasket seal if fitting was loosened.
3
Tighten or replace any bad fittings or welds. Repressurize system as
often as necessary as described in Step 1 until system pressure holds
for a few minutes.
4
Tag the sample line or record the best leak rate, and date.
