Hazardous Area Operation
Purge Operation
A-14
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
Thermo Fisher Scientific
The above inspection procedure should always be carried out
prior to leak testing. Testing will not, for example, detect a
failure of one of the “back to back” sample tube seals.
Warning!
This test involves pressurizing the RMS and appropriate
precautions should be taken to avoid over pressurisation.
Correct fittings and blanks must be used.
Read this section in full and ensure that all the required parts
are available before commencing.
Remove the transfer line and blank the port with a 1/8” Swagelok
plug. The RMS exhaust and all but one of the inlet ports must be
blanked. If shutoff valves have been fitted in the sample lines
these may be used if the pressure rating is appropriate.
Otherwise, the individual ports must be blanked. Check that all
the main RMS cover plate bolts are in place and tight.
Connect a supply of a clean gas (e.g. nitrogen or helium) to the
remaining RMS port via a suitable shutoff valve. Also, fit a
pressure gauge (0 to 1 bar(g)) between this valve and the RMS
(or use another blanked inlet port if this is easier). Pressurise the
assembly to 0.5 bar(g). Close the isolation valve and disconnect
the gas supply. Monitor the pressure. The test is passed if the
pressure falls by no more than 0.05 bar in one hour. If a leak is
suspected, search with a leak detector such as Snoop.
If it is suspected that leaks have developed in the enclosure, a search
can be carried out during normal CPD operation. The enclosure
pressure should be checked to verify that there is at least 2 mbar of
over pressure; otherwise leaks will be difficult to locate. If required,
the enclosure pressure can be increased by carefully restricting the
purge vent from the system. Avoid pressures above 30 mbar as this
can cause distortion of the enclosure and cause leaks that would not
otherwise be present. Do not adjust the purge air inlet pressure or
flow as a way of increasing enclosure pressure; this requires
calibrated test equipment to allow it to be reset.
External leaks can be located either by feel in the case of major
leaks, or by using a bubble type leak detector such as Snoop.
At the end of this test, remember to remove any purge outlet
restriction.
Enclosure Leak
Testing
