GPC1-10000 / GPC1-16000
™
OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company
Page 22
3.2.5
PURGING LIQUIDS FROM THE DUT/SYSTEM UNDER TEST
GPC1 includes a sump to collect liquids that may return from the device or system under test
to which it is connected. However, the amount of liquid that the sump can handle without
liquids entering other GPC1 internal circuitry is limited. Excessive fluids in GPC1 and test
connections can cause erratic pressure control and introduce unexpected uncertainty in
measurements. DUTs and the system under test should be cleaned of liquids to the extent
reasonably possible before being connected to GPC1. Also, see Section 2.3.4.3 for
information about the appropriate GPC1 TEST port connection to use.
The procedure to purge the GPC1 sump and/or a DUT connected to GPC1 is:
Use GPC1 to pressurize the system, including the DUT, to approximately
3 500 kPa (500 psi) (or maximum pressure of the DUT if less than 3.5 MPa (500 psi)).
Open
DRAIN port
. Use the 5/8 in. open end wrench supplied in the GPC1 accessories to
slowly and then more fully open the port allowing gas to exhaust as quickly as is safe and
practical.
Observe whether the gas coming out of the
DRAIN port
contains liquid or liquid vapor.
Repeat
steps through until there is no evidence of liquid in the gas escaping from the
DRAIN port
.
3.3
TYPICAL OPERATING SEQUENCE FOR A COMPLETE
CALIBRATION OR TEST
GPC1 is most often used to set and adjust pressure to a reference measuring device and a DUT when
performing a test or calibration. The reference measuring device may be a pressure monitor such as a
digital indicator or a piston gauge or deadweight tester. The typical operational sequence is as follows:
Connect the DUT
to the appropriate GPC1
TEST port
or to a test port on the external system to
which GPC1 is connected (see Sections 3.2.4, 2.3.4.3).
Set the TEST INLET SET regulator
(see Section 3.2.1)
Position the PDVV plunger
(see Section 3.2.3).
Purge the DUT (if necessary)
(see Section 3.2 5).
Take the starting zero reading on the DUT:
With the
OUTLET valve
open, and the
INLET valve
closed, the pressure in the test system is zero gauge.
Set ascending test pressures:
Carefully open the
INLET valve
and control the gas input to set the
pressure in the test system just under the desired test point (see Section 3.2.2). Pause a moment.
Then use the
PDVV (+)
and/or
(-) valves
to adjust the pressure to the exact test pressure desired or,
if the reference is a piston gauge, to float the piston gauge piston (see Section 3.2.3). Repeat this
process for all of the ascending increments. If the increments are small enough for the PDVV
displacement to generate the pressure, only the
PDVV (+) valves
may be needed to reach the next
pressure. If the PDVV runs out of stroke, use the
INLET valve
to generate pressure and reposition
the PDVV plunger.
Set descending test pressures:
Very carefully open the
OUTLET valve
and control the gas
exhaust to set pressure in the test system just over the desired test point (see Section 3.2.2). Then
use the
PDVV (+)
and/or
(-) valves
to adjust the pressure to the exact test pressure desired or, if the
reference is a piston gauge, to float the piston gauge piston (see Section 3.2.3). Repeat this process
for all of the descending increments. If the increments are small enough for the PDVV displacement
to generate the pressure, only the
PDVV (-) valves
may be needed to generate the next pressure. If
the PDVV runs out of stroke, use the
OUTLET valve
to reduce pressure.
Vent the system and disconnect the DUT:
Open the
OUTLET valve
fully and check that the DUT
reads near zero. Disconnect the DUT.
