MPG2-H OPERATION AND MAINTENANCE MANUAL
© 2004-2008 DH Instruments, a Fluke Company
Page 12
Opening the reservoir shut off valve while the MPG2 is under pressure will very rapidly drop
the pressure. Generally, it is not recommended to drop the pressure applied to pressure
measuring devices very rapidly. To reduce pressure slowly, use the variable volume and only open
the reservoir shut off valve to open the system to atmosphere.
3.2.3
REFILLING OR EMPTYING THE VARIABLE VOLUME
WITHOUT RELEASING TEST PRESSURE
When working to high pressure with large test volumes or test volumes that are not fully
purged of air, the volume displaced by a single stroke of the variable volume may not be
sufficient to generate the maximum pressure desired. Conversely, when lowering pressure
the variable volume may run out of stroke before it is desirable to use the RESERVOIR
ISOLATION valve to release pressure rapidly. In these cases, the variable volume can be
backed off and refilled without releasing the pressure in the test system.
To refill or empty the variable volume without releasing test pressure, proceed as follows:
Close the test shut off valve. This isolates the system connected to the TEST port(s)
from the variable volume and the reservoir shut off valve. Note that after refilling the
variable volume, the test shut off valve will be opened again. At that time, the pressure
on both sides of the valve will not be perfectly equal so the pressure in the system
connected to the TEST port(s) will change. Consider this possibility before closing the
test shut off valve. For example, if using a piston gauge, put the piston gauge piston at
its bottom stop before closing the test shut off valve.
Open the reservoir shut off valve. This vents the pressure in the variable volume and
connects it to the reservoir.
Back out the variable volume (CCW) to fill it or screw it in (CW) to empty it, as desired.
Close the reservoir shut off valve.
DO NOT OPEN THE TEST ISOLATION VALVE YET.
Operate the variable volume as needed to generate a pressure equal to the pressure in
the system connected to the TEST port(s). This is the pressure that was present on the
variable volume before the test shutoff valve was closed in . The pressure may be
reasonably approximated by the feel (torque) on the variable volume.
Slowly open the TEST ISOLATION valve to equalize the pressure. Proceed to generate
and adjust pressure as desired (see Section 3.2.2).
