Document 560076
050216
DH Instruments, Inc.
4765 East Beautiful Lane
Phoenix AZ 85044-5318
USA
Tel 602.431.9100
Fax 602.431.9559
www.dhinstruments.com
Constant Volume Valve
P/N 402151
Installation Instructions
CONSTANT VOLUME VALVE, P/N 402151,
INCLUDES:
QTY
PART NO
DESCRIPTION
1
402177
Valve, constant volume
2
103686
DH500 F x DH200-2 M adaptor
1
102159
10-32 UNF M x 1/8 in. barb adaptor
1
103426
10-32 UNF M x 1/8 in. quick connector
1 560076
Instruction
Sheet
INTRODUCTION
The constant volume valve is a pneumatically
actuated needle valve with a return line connecting the
inlet to a coaxial compensator. Needle displacement is
matched by an equal and opposite volume
displacement on the compensator.
SPECIFICATIONS
Port A connection: DH200-2*
Port B connection: DH200-2*
Drive air connection (to open valve): 10-32 UNF F
Operating fluid: Oil
Maximum line pressure: 200 MPa (30 000 psi)
Maximum differential pressure on Port A or Port B:
200 MPa (30 000 psi)
Drive air pressure required to open valve:
- With zero differential: <500 kPa (70 psi)
- With 200 MPa differential, Port A:<400 kPa (60 psi)
- With 200 MPa differential, Port B: 750 kPa (110 psi)
Maximum drive air pressure: 850 kPa (125 psi)
Typical change in volume on port A or B when the
valve is opened or closed: <0.2 mm
3
* DH200-2 is equivalent to HIP HF2 for 1/8 in. OD, coned and
threaded stainless steel tube
INSTALLATION
Connect the valve between the two pressure
systems to be isolated using ports A and B. Use
the DH200-2 M x DH500 F adaptors supplied if
desired. To install the adaptors, remove the
DH200-2 glands and collars from the DH200-2
connections.
Connect a drive air supply to the drive air connection.
Use the 10-32 UNF M x barb adaptor or 10-32 UNF
M x quick connector supplied if desired.
Figure 1.
Constant volume valve cutaway view
APPLICATION NOTES
•
To open the valve, supply drive air pressure to the
drive air port. To close the valve, vent the drive air
pressure.
•
To reduce the opening/closing speed of the valve,
put an adjustable restriction or fixed orifice on the
drive air supply and exhaust. This can be useful
to reduce pressure perturbations from the valve
opening/closing.
•
To automate opening and closing of the valve, use
a three way, low pressure solenoid valve to control
drive air/vent supply to the valve actuator.
•
To reduce the relative effect of the small change in
volume due to deformation of the valve seat after the
valve closes, add volume to the pressurized system.
•
After the valve closes, a small volume change
occurs from elastic deformation of the seat. The
deformation can be reduced by special shimming
to reduce the force of the needle on the seat when
the valve is closed, but the maximum differential
pressure on port A is reduced.
