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3710 and 3720 Positioners
SPOOL VALVE ASSY
SPOOL
FLEXURE
SUMMING
BEAM ASSY
SPOOL
FLEXURE
LARGER VIEW OF
SPOOL HEAD
A6044/IL
Figure 22. Spool Valve and Summing Beam
7. Be sure the spool head and summing beam
remain engaged, but do not bind up, over the entire
operating range of the input module.
Changing the Span Adjuster Assembly
(To Change Positioner Input Range)
WARNING
Refer to the WARNING at the
beginning of the Changing Positioner
Action section in this manual.
The span adjuster assembly (key 4) consists of the
span adjustment knob, span adjustment shaft
(threaded rod), range spring, and washer. The range
spring is welded to the washer and the washer is
welded to the span adjustment shaft.
To identify the span adjuster assembly for 0.4 to 2.0
bar (6 to 30 psig) input range, red color coding
appears on the range spring.
1. Unscrew the cam locknut (key 37) and remove
the cam (key 36).
26
SPOOL RELIEF
SPOOL
HEAD
SPOOL
HEAD
The zero adjustment locknut and zero
adjustment knob are identical parts,
key 35.
2. Loosen the zero adjustment locknut and turn the
zero adjustment knob (key 35) until the range spring
is free from the summing beam. Move the feedback
arm (key 21) until the range spring falls away from
the summing beam.
The feedback pivot cannot be removed
from the positioner base plate.
3. Remove the retaining ring (e-clip) (key 27) which
holds the feedback arm assembly (key 21) onto the
feedback pivot. Remove the washer under the
retaining ring and pull the feedback arm from the
pivot.
4. Remove the span adjuster assembly from the
feedback arm by removing the zero adjuster locknut
and sliding the span adjustment shaft (threaded rod)
from the zero adjustment pivot on the feedback arm.
5. Remove the zero adjustment knob from the span
adjuster assembly. Install the zero adjustment knob
on the new span adjuster assembly.
6. Inspect the zero adjustment pivot (key 32). Be
sure it rotates freely. If necessary, replace the zero
adjustment pivot. Also, if necessary, replace the
feedback arm assembly (key 21) and cam roller (key
23), following the instructions given in this manual.
7. Install the new span adjuster assembly by sliding
the span adjustment shaft (threaded rod) through the
zero adjustment pivot. Install the zero adjustment
locknut on the span adjustment shaft.
8. Install the feedback arm assembly with the new
span adjuster assembly by returning the feedback
arm assembly to the feedback pivot. Turn the zero
adjustment locknut and zero adjustment knob as
needed to fit the range spring to the summing beam.
Install the washer and retaining ring that hold the
feedback arm assembly in position.
9. Install the cam and cam locknut. Be sure the cam
roller on the feedback arm assembly is properly
positioned in contact with the cam.
10. Perform the calibration procedures in this
manual.
Instruction Manual
Form 5300
July 2005
Note
Note
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