Ross Controls SERPAR AND CROSSFLOW DOUBLE VALVES SERIES 35 - Manual (Page 7)

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A B
1
3
2
S
Pb Pa
A B
1
3
2
C D
S
Pb Pa
A
B
1
3
2
C D
S
Pb Pa
Conditions at start:
Normal operation:
Detecting a malfunction:
Conditions at start:
Inlet 1 is closed to outlet 2 by both
valve elements A and B. Outlet 2
is open to exhaust 3. Pilot air is
ported from inlet 1 and through
the center section of spool S to the
normally closed pilots Pa and Pb.
Monitoring pressure signals at both
ends of spool S are exhausted.
Normal operation:
Simultaneously energizing both
solenoids actuates both pilots and
causes valve elements A and B to
shift. Inlet 1 is then connected to
outlet 2 via crossflow passages
C and D. Exhaust 3 is closed.
Monitoring pressure signals go to
each end of spool S and become
equal to inlet pressure.
Completition of normal cycle:
Simultaneously deenergizing both
solenoids returns the valve to the
“Conditions at Start” described at
left.
Detecting a malfunction:
A malfunction in the system or
the valve itself could cause one
valve element to be open and the
other closed. Air then flows past
the inlet poppet on valve element
A, into crossflow passage D, but is
substantially blocked by the spool
portion of element B. The large size
of the open exhaust passage past
element B keeps the pressure at
the outlet port below two percent of
inlet pressure. Full monitoring air
pressure from side A goes to the
right end of spool S, and a reduced
pressure goes to the left end. This
pressure imbalance causes the spool
to shift to the left. This shuts off and
exhausts pilot air to both solenoid
pilots, and allows valve element A to
return to the closed position.
L-G monitor locked-out:
When the L-G spool shifts it is held
by a lockout pin (not shown). Pilot
air is then exhausted to atmosphere
via port YB, and pilot supply air is
diverted to atmosphere via port YA.
The lockout mechanism must be reset
before the valve can return to normal
operation. During and following reset,
the pilot solenoids must be kept
deenergized to prevent inadvertent
and possibly dangerous cycling
of the press. The reset function is
either manual or remote-pneumatic
depending on valve model.
A B
1
3
2
S
Pb Pa
YA YB
L-G monitor locked-out:
Series 35 SERPAR ® Double Valves with L-G Monitor
Overview of Valve Function
For accessories please see page 17.
Double Valves with Internal Monitoring & Lockout feature:
Internal monitoring – requires no additional monitoring circuitry •
Automatic lock-out/inhibit upon detection of a malfunction •
Default to de-energized position upon fault detection •
Dedicated reset function •
No undesired automatic reset upon removal of electrical or pneumatic energy sources •
Built-in non-clogging silencers on Sizes 4, 8, 12 and 30. •