Varian 948, Operation And Service Manual

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Models 947, 948 and 960 Leak Detectors Operations and Service Manual
4-6
4.1.1.2 General Suggestions for Leak Checking
The following suggestions apply whether leak checking components, systems, or the leak
detector itself:
1. When spraying suspected leak locations:
❑ Always apply helium sparingly.
❑ Since helium rises, start at the highest points first.
❑ Apply helium downstream from the source of a draft first, or deflect the draft until
leak checks are completed.
2. If vent grooves exist at flanges or other assembled seals, apply helium to these points
(rather than spraying a general area) to:
❑ Obtain the most positive response.
❑ Minimize the use of helium.
❑ Save time in checking.
3. Locate and repair large leaks before attempting to locate extremely small leaks.
4. Limit the search to a general area of the test piece by isolation methods to shorten the
time required to locate both large and small leaks. Isolation methods include:
❑ Bagging
❑ Masking
❑ Shielding with tape, plastic film or duct seal (if applied properly)
5. Use only enough helium to reach the leaks. Do not flood the area.