TECHNICAL INFORMATION
20
87-900-120-01 (A)
3. Using a tool, unscrew the sintered filter
C
located
inside the cone.
4. Clean the filter with a grease remover and dry with
dry compressed air. Check the connections and
inspect the flexible tube for any damage.
5. Retighten the sintered filter and the sampling cone
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.
To replace the pumping block, proceed as follows:
1. Remove the housing as described above.
2. Place the inside block of the PHD-4 on a flat
surface able to support its weight, positioning the
device so that the lower part (sampling/filter zone)
is accessible
3. Disconnect both air tubes
A
(inlet and exhaust of
the sampling pump).
4. To remove the delivery tube, press down ring
B
so
as to free the tube to be removed.
5. Disconnect the two-pin pump power supply
connector
C
.
C
B
A
C
