3. OPERATION
Page 9
© 2004-2008 DH Instruments, a Fluke Company
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3.1
GENERAL OPERATING PRINCIPLES AND INFORMATION
3.1.1
OVERVIEW
See Section 1.5, Figure 6
MPG2-H is used to manually generate and adjust liquid pressure from atmosphere to
200 MPa (30 000 psi) (limited to 100 MPa (15 000 psi) with MPG2-H-HV) or using a priming
pump, two valves and a variable volume. Fittings for connecting to a device or system under
test are located on the top and middle rear of the instrument housing. A reservoir holds a
supply of fluid.
3.1.2
VALVES
The reservoir shutoff and test shutoff valves are manually operated needle valves.
The reservoir shut valve isolates the reservoir from the pressurized circuit. It is opened use
the priming pump, to fill the variable volume with fluid and to open the pressurized circuit to
atmosphere (vent).
The test shutoff valve isolates the TEST1 and TEST2 ports from the rest of the MPG2 circuit.
It can be used to isolate the variable volume and reservoir from the pressurized test system,
for example, if it becomes necessary to refill the variable volume with fluid when it reaches
end of stroke.
As test shutoff the valve needle displaces fluid when it is operated, it can also be used as a
very fine variable volume for very fine pressure adjustment.
3.1.3
PRIMING PUMP
The priming pump is a syringe style fluid injector, built into the reservoir cover. On its plunger
upstroke, it draws oil from the reservoir into its barrel. On the down stoke, the barrel tip seals
with the connection on the bottom of the reservoir and the plunger pushes oil into the rest of
MPG2 and out the test port.
The priming pump is used to fill the MPG2 and system to which it is connected with hydraulic
fluid and then generate a low, starting pressure.
3.1.4
VARIABLE VOLUME (VV)
The variable volume (VV) is a piston-cylinder type screw press. Rotating the variable volume
handles, moves the piston in or out decreasing or increasing the volume and therefore
increasing or decreasing pressure.
The VV is used to generate and adjust pressure in the system to which MPG2 is connected
when the reservoir shut valve is closed and test shut off valve is open. The torque necessary
to rotate the VV handle is proportional to the pressure in the variable volume.
Generally, the starting position of the VV when beginning to generate pressure from
atmosphere is with the piston fully retracted (handles rotated maximum CCW) so that the full
stroke of the VV is available to fill the test system and generate pressure.
