Table of Contents
Instruction Manual
Form 5755
September 2005
valves, use suitable gaskets between valve and
pipeline flanges.
5. If continuous operation is required during
maintenance and inspection, install a conventional
three-valve bypass around the valve.
6. Connect loading pressure for the Spring-to-Open
configuration to the 1/4-18 NPT connection in the
upper casing assembly (key 23) as shown in
figure 4. The Spring-to-Close configuration loading
pressure connection is in the lower casing assembly
(key 39) as shown in figure 3.
Spring Adjustment
The spring has a fixed pressure span over which
loading pressure will stroke the valve. Adjustment of
the spring compression shifts the span so that more
or less loading pressure is required to start travel.
Since the span does not change, there will be a
corresponding increase or decrease in the pressure
requirements at the end of the valve stroke.
In order to maximize shutoff pressure drop values,
the actuator spring must be accurately adjusted for
each Input Signal Pressure Range. If the actuator
has been disassembled or pressure conditions have
changed, the spring may require adjustment. Refer
to tables 2 and 3 to determine the Initial Spring Set
values based on the Input Signal range that is
available to the actuator. These values include
packing friction.
Spring-to-Close
Refer to figure 3.
1. Loosen the adjusting screw nut (key 44).
2. Turn the adjusting screw (key 31) clockwise to
compress the spring or counterclockwise to
decrease spring compression.
3. After adjustment, tighten the adjusting screw nut
(key 44).
Spring-to-Open
Refer to figure 4.
1. Unscrew the spring case assembly (key 27).
2. Turn the adjusting stem nut (key 44) clockwise to
compress the spring or counterclockwise to
decrease spring compression.
3. After adjustment, replace the spring case
assembly (key 27).
Maintenance
Refer to figure 3.
Valve parts are subject to normal wear and must be
inspected and replaced as necessary. The
frequency of inspection and maintenance depends
on the severity of the service conditions.
WARNING
Avoid personal injury from sudden
release of process pressure or
bursting of parts. Before performing
any maintenance operations:
D Always wear protective gloves,
clothing, and eyewear when
performing any maintenance
operations to avoid personal injury.
D Disconnect any operating lines
providing air pressure, electric power,
or a control signal to the actuator. Be
sure the actuator cannot suddenly
open or close the valve.
D Use bypass valves or completely
shut off the process to isolate the
valve from process pressure. Relieve
process pressure on both sides of the
valve. Drain the process media from
both sides of the valve.
D Vent the power actuator loading
pressure and relieve any actuator
spring precompression.
D Use lock-out procedures to be
sure that the above measures stay in
effect while you work on the
equipment.
D The valve packing box may
contain process fluids that are
pressurized, even when the valve has
been removed from the pipeline.
Process fluids may spray out under
pressure when removing the packing
hardware or packing rings.
D Check with your process or safety
engineer for any additional measures
that must be taken to protect against
process media.
D4 Valve
5
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