Keeping the World Flowing
15
12.4 Mechanical Manual Override
Single-Acting Actuator
The mechanical manual override can be of three types:
•
Type M: With a visible jackscrew
•
Type MH: With a jackscrew with protection pipe
•
Type MHD: With a jackscrew with protection pipe
and a declutch able handwheel
Type M mechanical manual override
Fig 12.5 Type M mechanical override
Type MH mechanical manual override
Fig 12.6 Type MH manual override
Fail to close, single-acting actuator:
•
Rotate the handwheel counter-clockwise to open
the valve
Fail to open, single-acting actuator:
•
Rotate the handwheel clockwise to close the valve
Instructions to engage or disengage the override are reported
on the plate installed on manual override:
Fig 12.7 Type MH manual override plate
Before re-starting the actuator with air supply,
rotate the jackscrew again to set the actuator in its
original position.
Type MHD mechanical manual override
Fig 12.8 Type MHD manual override
•
ENGAGE PROCEDURE: Pull disengaging knob and
handwheel at the same time; rotate the handwheel until
the manual override gets engaged
•
DISENGAGE PROCEDURE: Pull disengaging knob and
push the handwheel, at the same time
When the manual override is disengaged, the handwheel
operation is neutral and the actuator can be operated
pneumatically.
12.0 Operation
A4 US
US
A4
US
A4
A4 US
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