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Rockford Systems, LLC—www.rockfordsystems.com
Call: 1-800-922-7533
DM
2
Series D Dual-Solenoid Valves
SECTION 4—VALVE FUNCTION
EXHAUS
S
T
T
T
T
T
T
T
T
INLET
OUTLET
EXHAUST
OUTLET
INLET
A
B
EXHAUS
S
T
T
T
T
T
T
T
T
INLET
OUTLET
EXHAUST
OUTLET
INLET
A
B
A
B
EXHAUS
S
T
T
T
T
T
T
T
T
INLET
OUTLET
EXHAUST
OUTLET
INLET
A
B
Status indicator (optional)
in normal ready-to-run position
Size 12 & 30 pilots
VALVE DE-ACTUATED (READY-TO-RUN)
The flow of inlet air pressure into the
crossover passages is restricted by
the size of the passage between the
stem and the valve body opening.
Flow is sufficient to quickly pres-
surize pilot supply/timing chambers
A and B. The inlet poppets prevent
air flow from crossover passages
into the outlet chamber. Air pressure
acting on the inlet poppets and re-
turn pistons securely hold the valve
elements in the closed position. (Air
passages shown out of position and
reset adapter omitted for clarity.)
VALVE ACTUATED
Energizing the pilot valves simul-
taneously applies pressure to both
pistons, forcing the internal parts to
move to their actuated (open) posi-
tion, where inlet air flow to crossover
passages is fully open, inlet poppets
are fully open and exhaust poppets
are fully closed. The outlet is then
quickly pressurized, and pressure in
the inlet, crossovers, outlet, and tim-
ing chambers is quickly equalized.
De-energizing the pilots quickly
causes the valve elements to return
to the ready-to-run position.
VALVE LOCKED OUT
Whenever the valve elements operate in a sufficiently asynchronous manner, either on actuation or
de-actuation, the valve will move to a locked out position. In the locked out position, one crossover
and its related timing chamber will be exhausted, and the other crossover and its related timing cham-
ber will be fully pressurized. The valve element (side B) that is partially actuated has pilot air available
to fully actuate it, but no air pressure on the return piston to fully de-actuate the valve element. Air
pressure in the crossover acts on the differential of side B stem diameters creating a latching force.
Side A is in a fully closed position, and has no pilot air available to actuate, but has full pressure on
the inlet poppet and return piston to hold the element in the fully closed position.
Inlet air flow on side A into its crossover is restricted, and flows through the open inlet poppet on side
B, through the outlet into the exhaust port, and from the exhaust port to atmosphere. Residual pres-
sure in the outlet is less than 1% of inlet pressure.
The return springs are limited in travel, and can only return the valve elements to the intermediate
(locked out) position. Sufficient air pressure acting on the return pistons is needed to return the valve
elements to a fully closed position.
RESETTING THE VALVE
The valve will remain in the locked out position, even if the inlet air supply is removed and re-applied. A
remote reset signal (air or electric), or a manual push button actuation must be applied to reset the valve.
Reset is accomplished by momentarily pressurizing the reset port. Actuation of the reset piston physi-
cally pushes the main valve elements to their closed position. Inlet air fully pressurizes the crossovers
and holds the inlet poppets on seat. Actuation of the reset piston opens the reset poppet, thereby,
immediately exhausting pilot supply air, thus, preventing valve operation during reset. (Reset adapter
added to illustration.)
De-actuation of reset pistons causes the reset poppets to close and pilot supply to fully pressurize.
Reset air pressure can be applied by a remote 3/2 normally closed valve, or from an optional 3/2 nor-
mally closed solenoid, or a manual push button mounted on the reset adapter.
STATUS INDICATOR
The status indicator pressure switch will actuate when the main valve is op-
erating normally, and will de-actuate when the main valve is in the locked
out position or inlet pressure is removed. This device is not part of the valve
lockout function, but, rather, only reports the status of the main valve.
Size 12 and 30 valves require relatively large pilots to actuate and de-actuate
the main valve elements. In order to achieve extremely quick valve response
for such large pilots, a two-stage solenoid pilot system is incorporated into
the design. This keeps the electrical current required to operate the pilots to
a minimum.
Valve ready-to-run
Valve actuated
Valve locked out
EXHAUST
OUTLET
INLET
A
B
Resetting the valve
