DH Instruments PPCH, Руководство по эксплуатации и обслуживанию

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PPCH™ OPERATION AND MAINTENANCE MANUAL
© 2009 DH Instruments, a Fluke Company Page 160
Use
[LEAK CK]
to run a leak test (see Section 3.3.9). Set the leak check time to at least
120 seconds and allow the leak check to complete. Repeat the process once or twice to
verify repeatability of the measurement.
Evaluate the leak rate. Calculate the leak rate relative to the measured pressure. For
example, if the rate is 0.007 MPa/second and the measured pressure 70 MPa, the rate of
change of pressure is 0.01% of the measured pressure per second (0.007 / 70 * 100).
- A negative or positive rate of less than 0.001% of measured pressure per second:
there is no significant leak present.
- A negative rate of 0.001% to 0.005% of measured pressure per second: there is
probably a leak in the system but it should not significantly affect PPCH pressure
control. It may, however, cause an excessive piston drop rate if the PPCH is being
used with a PG7302 piston gauge.
- A negative rate greater than 0.005% of measured pressure per second: there is a leak
that is likely to cause the PPCH to be unable to operate reliably (and will be messy in
terms of lost fluid). The leak should be corrected. If the leak is internal to the PPCH (leak
check was performed with PPCH plugged), see Section 5.11.2 to localize the leak.
- A positive rate consistently greater than 0.001% or reading per second: there is a leak
in the PPCH inlet control valve that may interfere with pressure control (see Section
5.12.2).
5.11.2 LOCALIZING A LEAK WITHIN THE PPCH
To determine if there is a leak in the PPCH, first leak check the complete PPCH by running a
pressure decay leak test with the PPCH
TEST
port plugged (see Section 5.11.1).
If there is a positive leak in the PPCH (leak test rate result is always positive), there is a leak
in the PPCH inlet control valve and the control valve needs service (see Section 5.12.2).
If there is a negative leak in the PPCH, the leak could be in a shutoff valve, in the outlet
control valve or in another component.
First check for a leak in a shutoff valve. PPCH has up to three shutoff valves (see Section
3.2.1, Figure 9). All PPCHs have a high pressure vent valve (see Section 5.11.2.1 to localize
a leak to the high pressure vent valve). PPCHs that are equipped with a Lo Q-RPT also have
a low pressure isolation valve and a low pressure vent valve. Check the low pressure
isolation valve for a leak (see Section 5.11.2.2), then check the low pressure vent valve (see
Section 5.11.2.3). Shutoff valves are user replaceable (see Section 5.12.1).
If the leak is not in a shutoff valve, check the PPCH internal components. Access the PPCH
mechanical module (see Section 5.9) and examine it for collected fluid at fittings and internal
collection point. Wipe away the fluid, be sure pressure is vented and then tighten the fitting
(never tighten a fitting without first removing pressure)
. Leak test again to determine
whether the leak has been corrected (see Section 5.11.1).
If the leak internal to the PPCH is not in a shutoff valve or a visible internal connection that
can be tightened, it is probably in the outlet control valve (see Section 5.12.2) or another area
that is not user serviceable.