DH Instruments MPC1-1000, Руководство пользователя

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MPC1-1000 and MPC1-3000 User’s Manual
Page 17
© 2001 - 2007 DH Instruments, a Fluke Company
5.2.2 PRESSURE DECREASE LEAK (ABOVE ATMOSPHERE)
This is the most common leak condition and can be caused by a variety of components
and fittings. The first step is to isolate the leak to a particular area within the MPC1.
Establish the conditions under which the leak occurs. After doing so, close the test
outlet valve, position the outlet selection valve to VENT and open the equalization valve
(pull out). Wait for the pressure to stabilize (about 1 to 5 minutes). Close the equalization
valve (push in). If the indication of the leak is gone, see Steps
n
through
p
below. If the
leak is still present, go to Section 4.
n
If the pressure drop is gone, the leak is downstream of the equalization valve stem seal.
Possible sources include the low pressure side of the VV, low pressure side of the
equalization valve, the test outlet valve and the fittings between the two valves.
To check the test outlet valve for a leak past the seat, look for gas at the vent fitting on
the unit's back panel using a leak detection fluid. If a leak is present, the test outlet valve
is not properly closed or is damaged. Tighten, repair or replace the valve as needed.
o
If the leak is not found at the vent port, check the fittings between the equalization valve
and the outlet valve. Remove the top cover of the MPC1 and check the appropriate
fittings using a leak detection fluid. If a leak is present, carefully tighten or replace the
leaky fitting(s). Refer to Section 5.2 for information about tightening a leaky fitting.
p
If the leak is not present at the fittings, it is most likely in the VV. To confirm that the leak
is in the VV, remove it from the MPC1 and connect all tubing together. Repeat leak
check on the MPC1. If leak is gone, the VV needs to be repaired.
q
Most leaks are located in either the VV, gauge, filter and/or in the connecting tubing
including the test inlet and equalization valve. It is also possible, though unlikely, for the
leak to be in the test inlet valve. This can only happen if the supply pressure is below the
test pressure. To check, reduce the test pressure to below the supply pressure. If the
leak is gone or if the leak reverses direction, then the problem is in the test inlet valve.
Tighten, repair or replace the valve as needed.
r
Remove the top cover. Check all the fittings within the suspected circuit using a leak
detection fluid. If a leak is present, carefully tighten or replace the leaky fitting(s).
Refer to Section 5.2 for information about tightening a leaky fitting.
If no leaks are found, depressurize the system and disconnect the gauge tube at the tee
located near the test port and plug the tee (refer to Section 6.1). Repeat the leak check.
If the leak is gone, the leak is in the gauge or the disconnected fitting. Replace the fitting
and/or repair or replace the gauge.
If the leak is still present, depressurize the system and remove the VV. Connect the test inlet
valve to the tubing that was connected to the rear of the VV. Repeat the leak check. If the
leak is gone, the leak is in the VV or the disconnected fittings. Replace the fittings and/or
repair the VV.
The above steps have resulted in the checking of all items within the MPC1 that could cause
a leak. If you have not located the leak, repeat the steps or contact
DHI Technical Service
for additional assistance.