DH Instruments PPCH, Руководство по эксплуатации и обслуживанию

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3. OPERATION
Page 57 © 2009 DH Instruments, a Fluke Company
Changing the pressure in a test system causes adiabatic temperature change in the
pressurized liquid that need to have dissipated before a valid leak measurement can be made. In
general, a 2 to 3 minute wait before running a leak check is adequate to allow the adiabatic
temperature change to dissipate and valid leak measurements to be made. However, stabilization
time may be much longer with liquid test media, as volume and/or pressure increases.
 OPERATION
To run a leak check, first set the pressure to the desired leak check pressure using the direct
pressure control keys (see Section 3.1.3) or automated pressure control (see Section 3.3.10).
The effect of the thermal pressure control unit (TPCU) can make it difficult to run a reliable
leak test when the PPCH is in dynamic control mode. Before leak testing, change the control mode
to a mode other than dynamic and wait at least 5 minutes for the TPCU to cool down and
stabilize (see Section 3.4.6.2).
To access the LEAK CHECK function, press
[LEAK CHECK]
from the MAIN RUN screen.
Select
<1run>
to run a leak test. The display is:
1. Edit field for the time over which the leak check pressure
change will be measured, in seconds.
Set leak check time:
15 s
Edit the leak check time if desired (minimum 1, maximum 999) and press
[ENT]
.
Press
[ENT]
again when ready to start the leak test. The leak test display is:
1. Standard MAIN RUN screen first line showing measured
pressure.
2. Active RPT position indicator
3. Indication that leak test is running and countdown of time
remaining.
70.089 MPa a HI
Leak testing 13 s
[ESC]
can be used to abort the running leak test.
[ENT]
while the leak test is running
restarts the leak check timer. When the leak check timer countdown has completed PPCH
beeps three times and the leak check results screen is displayed:
1. Total pressure change from start to finish of leak check time.
2. Indicator of RPT used to run leak check.
3. Average rate of change of pressure over the leak check
time period.
∆ P 0.61 MPa HI
Rate 0.04 MPa/sec
From the leak check results screen, press
[ENT]
to repeat the leak test.
Press
[ESC]
to return to leak check main menu and exit to the MAIN RUN screen.