OPG1™ Operation and Maintenance Manual
Page 19
©2000
DH Instruments, Inc
.
3.
G
ENERAL
O
PERATION
3.1
OPERATING PRINCIPLE
Numerical references in this section refer to Section 3.1, Figure 5.
OPG1-30000-AF is a self-contained system designed to generate and adjust pressure from
atmosphere (zero gauge) to 200 MPa (30 000 psi) in and HGC-30000-AF Hydraulic Gauge
Calibrator System. OPG1 combines the capability to fill the system with oil and execute large
pressure changes very rapidly with very fine pressure adjustment around a point.
OPG1 uses two different techniques to generate and adjust pressure.
The first means of generating and adjusting pressure
is the hydropneumatic pump (2) combined
with the oil tank (3),
DRIVE SET regulator
(1),
INLET valve
(9)
and
OUTLET valve
(8).
This combination is used for filling the system under test, large pressure changes and rough
pressure control.
The valves are Belleville spring loaded, highly progressive, half-turn needle
valves. The pump is a pneumatically powered, gate valve controlled, piston pump similar to a
double-acting pneumatic cylinder. There is a ratio of 400:1 between the pneumatic piston and
hydraulic plunger. The pump will operate continuously until the pneumatic drive pressure on the
pneumatic piston is in equilibrium with the oil pressure on the oil plunger. For example, if the
pneumatic drive pressure is 500 kPa (75 psi), the pump will cycle until the oil pressure reaches
200 MPa (30 000 psi). The pump draws oil from the oil tank on top of OPG1. The
DRIVE SET
regulator
(1) is used to set the pneumatic drive pressure to the pump and thus the oil output
pressure. The pump oil output is connected to the
INLET valve
(9). Opening the
INLET valve
connects the pump output to the test system causing the pump (2) to cycle, drawing oil from the tank
as needed and pressurizing the system. Opening the
OUTLET valve
(8) returns oil to the tank (3),
depressurizing the system.
The second means of generating and adjusting pressure
is the Pneumatically Controlled Variable
Volume (PDVV) (10) combined with the
PDVV (+) valves
(12)
and
PDVV (-) valves
(11).
This combination is used for smaller pressure changes and fine pressure control.
The PDVV
is a pneumatically actuated variable volume. A piston or plunger in a cylinder is exposed to the
oil pressure. The other end of the plunger is connected to a dome loaded pneumatic actuator.
Changing the pneumatic pressure on the dome loaded actuator causes the plunger to move,
increasing or decreasing oil pressure. A spring returns the plunger to its minimum stroke position
when there is no pressure on it. A mechanical system tracks movement of the plunger and an
indicator (17) displays the plunger position on the front panel. The
PDVV (+) valves
(12)
and
PDVV (-)
valves
(11) are momentary, poppet valves that open when pressed. The
(+) valves
(12)
admit drive
air pressure to the PDVV actuator causing the PDVV piston to move forward compressing the oil and
increasing the pressure. The
(-) valves
(11)
have the opposite effect causing pressure to decrease.