MPC1-1000 and MPC1-3000 User’s Manual
© 2001 - 2007
DH Instruments, a Fluke Company
Page 6
3.1.3
VARIABLE VOLUME (VV)
This is a vessel whose internal volume may be changed by rotating a knob that moves an
internal piston. Attached to the top of the VV is a push/pull equalize valve that is designed to
isolate the low and high sides of the piston, provide protection to the unit itself, and ensure
ease of operation.
The VV is used to adjust the pressure (and/or piston position when used with a piston gauge)
by rotating the knob in the proper direction when the equalization valve is closed.
Before using the test inlet or test outlet valve, open the equalization valve. To open the
equalization valve, pull it outward; to close, push it inward.
When using the VV, it is useful to put its piston in the optimum position based on the intent
of use. Under most operating conditions, the piston is placed in its mid-stroke position (about
16 rotations of the knob from either stop). This will allow for equal movement, forward and
backward, of the piston. When a maximum increase or decrease of pressure is required,
especially at low pressures, place the VV knob at the stop limit (either clockwise for
maximum vacuum or counter-clockwise for maximum pressure).
The VV is designed to operate with a maximum differential pressure of 150 psi (1 MPa)
across the piston. When differential pressures exceed 150 psi (1 MPa), the equalization
valve will automatically open reducing the differential pressure to zero. This is a safety
feature intended to prevent damage to the VV. The value of 150 psi (1 MPa) is factory set
and cannot be changed.
3.1.4
PRESSURE GAUGE
There is a zero to 1 000 psi (7 MPa) or zero to 3 000 psi (21 MPa) dial gauge connected to
the test pressure circuit which has a dual function.
•
As a safety device since it is important for the operator to know the value of system
pressure at all times
•
As a means for the operator to properly control pressure changes
3.2
SETTING ZERO GAUGE PRESSURE (VENTED)
n
Close test inlet valve (1).
o
Place outlet selection valve (6) to VENT position.
p
Open test outlet valve (4).
q
Open pressure equalization valve (3) (pull valve outward).