OPG1™ Operation and Maintenance Manual
©2000
DH Instruments, Inc
.
Page
24
For the PDVV (+) valves (6) and PDVV (-) valves (7) to have an effect, the PDVV plunger
must have stroke available. If the PDVV is at its end of stroke (Figure 7, Ref 1 or 3), the
plunger cannot move to change pressure. The recommended PDVV START position
(Figure 8, Ref 2) puts the plunger at the middle of its stroke so 50 % of PDVV displacement is
available in either direction. The PDVV plunger can be positioned without affecting oil
pressure using the
and
valves when the OUTLET valve is open (oil pressure vented).
The plunger is returned to minimum end of stroke position by a spring. The PDVV plunger is
usually set to the desired position at the start of a calibration or test.
If the PDVV plunger reaches end of stroke during a calibration or test, used the INLET valve
and/or OUTLET valve to increase or decrease the pressure, as needed.
The PDVV (+) valves (6),
generate pressure indefinitely when opened.
Use caution not
to generate more pressure than desired when using these valves.
3.2.4
CONNECTING A DEVICE UNDER TEST (DUT)
See Section 2.3.1.4.
OPG1 covers a very wide range of pressures all the way up to 200 MPa (30 000 psi). It is the
user’s responsibility to assure that fittings and devices connected to OPG1 are rated for the
pressures at which they will be used.
If the DUT connection is lower than the OPG1 oil tank, when the OUTLET valve is open and the
DUT connection is open, oil will run out of the tank through the DUT connection.
3.2.5
PURGING AIR FROM THE DUT/SYSTEM UNDER TEST
Air is highly compressible. Oil is not. To the extent possible, air should be purged from the
system and devices that are connected to OPG1 prior to applying pressure to them.
Leaving air in the DUT reduces OPG1 efficiency, increases the time required to generate
pressures, increases the dangers associated with high pressure operation and makes it more
difficult to set a valid zero point.
The system and/or DUTs that are connected to OPG1 can be filled with oil prior to connecting
them or they can be purged using OPG1. To purge air using OPG1, open the system or DUT
at the highest point possible. Close the OPG1
OUTLET valve
. Then carefully open the
INLET valve
causing oil to be drawn from the tank and pumped into the system. Observe
the oil level at the purge point. Close the
INLET valve
when oil is present at the purge point.
While purging, watch the tank oil level carefully to be sure it is filled. Do not run the
hydropneumatic pump without oil in the reservoir.