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5
Technical Information
Routine Maintenance of the PHD-4
Management of Sampling Pump
The sampling pump is the device that makes it possible to move the
gas to be analyzed from the point where a leak is suspected to the
sensor inside the PHD-4.
This function is afforded by the micromembrane pump which, as it
sample the gas required for analysis (leak check), also allows any
impurities in the gas (dust, water, oils, etc.) to pass through.
These impurities tend to accumulate inside the pumping element
with a consequent gradual reduction in performance until a fault is
generated.
This phenomenon is effectively contrasted by the two filter elements
(see glass wool filter and sintered filter) and by the sampling auto-
adjust cycle (see the chapter on “Sampling auto-adjust”); however, it
is important to restrict flow of these materials inside the sampling
pump.
If sampling pump performance is inefficient (this condition is
notified during the initial automatic test) after use in a particularly
“dirty” environment or after many hours of operation, the pumping
block must be replaced.
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PHD-4 Portable Helium Detector User Manual / 87-900-120-01 (F )
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