PPCH™ OPERATION AND MAINTENANCE MANUAL
© 2009 DH Instruments, a Fluke Company
Page 164
Before going to the trouble of disconnecting the low pressure vent valve to leak
check it specifically, the PPCH low pressure circuit can easily be leak checked if
the low pressure isolation valve is known not to leak. To leak check the low
pressure circuit, just compare the results of a pressure decay based leak test
(see Section 5.11.1) with the Hi Q-RPT active and the Lo Q-RPT active. If the
leak is greater with the low Q-RPT active, there is a leak in the Lo Q-RPT circuit
and the low pressure vent valve is the most likely source.
To localize a leak to the low pressure vent valve, proceed as follows:
If the PPCH
TEST
port is not already
plugged, plug it with a DH500 gland and
plug.
Vent the PPCH and disconnect electrical
power and drive air supply.
Open the PPCH chassis to gain access to
the mechanical module (see Section 5.9).
Loosen the low pressure vent valve
bracket retaining hardware (two button
head bolts).
Disconnect the 1/8 in. swage and DH200
connections on the pressure tube
between the 1/8 in. swage tee and the
inlet of the low pressure vent valve.
Place a 1/8 in. swage cap (not supplied)
on the open port of the 1/8 in. swage tee.
Reapply drive air supply, connect
electrical power and power on the
PPCH.
Use
[RANGE]
to make the Lo Q-RPT
active (see Section 3.3.1).
With the Lo Q-RPT active, perform a
pressure decay based leak check (see
Section 5.11.1).
If the leak is no longer present then the
low pressure vent valve is the cause of
the leak and the valve should be
replaced (see Section 5.12.1).
If the leak is still present, there is a leak
that is not in the low pressure vent valve.
Reconnect the original vent valve and
proceed with additional leak testing to
localize a leak within PPCH (see Section
5.11.2).
Step 4
Step 5
