Ross Controls 3_2 VALVES SERIES DM2 D - Manual (Page 3)

The ROSS DM 2® Series D double valves provide significant
features in response to the changing demands of the
mechanical press industry and its associated standards and
regulations regarding the control of pneumatically controlled
clutch and brake applications. The consensus requirements
of the regulations and good practices require that, in case of
a failure within the valve, the clutch and brake mechanisms be
quickly exhausted, a monitor takes action to prevent further
operation, and a method to alert personnel is incorporated.
These features also make the valve suitable for use in other
Category 3 & 4 safety-related applications.
A ROSS DM
2® Series D double valve has two valve elements
independently controlled by two solenoid pilots. The two
valve elements share common inlet, outlet, and exhaust ports.
When the pilot valves are simultaneously energized, the valve
elements operate so that the valve functions as a 3/2 normally
closed valve.
If one of the valve elements does not open or close synchronously
with the other, the valve goes into a faulted condition, exhausts
downstream air and keeps residual outlet pressure to less than
1% of inlet supply. This is an important safety characteristic of
the ROSS DM
2® Series D design.
Valve element redundancy provides an additional safety factor,
as the likelihood of a malfunction in both valve elements in the
same cycle is considered extremely remote.
DM
2® valves also have an internal monitor that is integrated
into the valve elements. Should the valve operate abnormally,
the monitor will lock-out the valve and prevent further operation
until corrective action is taken.
IMPORTANT NOTE:
Standards, regulations, and good practice all require that
mechanical power presses or other hazardous machines using
a pneumatically-controlled clutch and brake mechanism be
equipped with a double valve with a self-contained monitoring
device and/or an external monitoring system, which inhibits
further operation of the valve and machine in the event of a
failure within the valve. Of course, a double valve is just one
of the components in a press control system, and all other
elements of the system should be planned with safety as a
primary consideration.
DM 2® Series D Double Valves
Installation Example
Pressure regulator
Clutch and brake
combination
Filter and
water separator
Pressure gauge
Volume
DM 2® Series D Double Valve
(Status indicator – optional)
Lubricator
L-O-X ® - Valve
DM 2® Monitoring:
The DM 2® is a patented 3/2 normally closed valve (with an
intermediate, lockout position) distinguished by Crossflow TM
passages with poppet and spool valving on the main valve
stems. This arrangement provides the valve’s outstanding
flow characteristics and an integrated monitoring capability
with total memory. The valve provides dynamic monitoring
and dynamic memory.
Dynamic Monitoring means that all monitoring components
change state on every valve cycle. Should the valve elements
cycle asynchronously, the valve will exhaust downstream air
and lock-out, prohibiting further operation.
Dynamic Memory within a monitoring system indicates that
when a valve lock-out occurs, the valve will retain the fault
information regardless of air or electrical changes. The DM
2®
system can only be reset by a defined operation/procedure, and
will not self-reset (turning the valve off and on) or reset when
inlet air supply is removed and re-applied. Such automatic
resetting would conceal potential hazards from the operator.
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