PPCH™ OPERATION AND MAINTENANCE MANUAL
© 2009 DH Instruments, a Fluke Company
Page 152
5.10
HYDROPNEUMATIC PUMP
5.10.1
PRIMING THE PUMP
PURPOSE
To run an automated routine that reprimes the PPCH’s on-board, hydropneumatic pump
when it has pumped air instead of liquid.
PRINCIPLE
A pump that has lost its prime cycles rapidly and continuously while attempting to
generate pressure. To stop the pump immediately, cycle PPCH power. This interrupts the drive air
supply to the pump until a new pressure generation attempt. The pump can also be stopped by
venting the PPCH using [VENT].
The PPCH on-board hydropneumatic pump is an air driven hydraulic pump. The hydraulic
side of the pump must be continuously supplied with liquid. If significant amounts of gas are
drawn into the pump, the pump will lose its prime. A pump that has lost its prime pumps
rapidly (more than once per second) without generating significant pressure.
Once the pump has lost its prime, oil must displace the gas in the pump before the pump will
operate normally again. This requires forcing oil into the pump.
The PPCH pump priming routine uses the drive air supply to pressurize the reservoir, forcing
oil into the pump. This makes recovery from accidentally introducing gas into the pump, for
example if the pump was run with the reservoir empty, relatively convenient.
If the on-board prime routine is unable to prime the pump, the check valve prime procedure
may be necessary (see Section 5.10.1.1).
PROCEDURE
The pump priming routine will generate pressure of mid-scale or more of the active pressure
range. Before running the priming routine, plug the TEST port
To reprime the on-board hydropneumatic pump, proceed as follows:
Fill the reservoir (see Section 5.6) to at least the point at which the MAIN RUN screen
<Low fluid level>
goes off (see Section 3.5.7.3).
Close the
RESERVOIR FILL/DRAIN
valve. Failure to close this valve will cause liquid to
be forcibly ejected from the
FILL/DRAIN
port when attempting to prime!
Set the range to default, internal high (DF IH) (see Section 3.3.1).
Assure that the
TEST
port is NOT open. Plug the
TEST
port. Liquid will be driven out
the
TEST
port during priming if it is open.
Press
[SPECIAL]
,
<7internal>
,
<3pump>
,
<1prime>
.
