3570 Series
19
valve assembly out of service. To avoid
personal injury or property damage
caused by uncontrolled process pres-
sure, provide a temporary means of con-
trol for the process before taking the as-
sembly out of service.
Before removing the input signal and
supply pressure connections from the
positioner, remove the input signal and
supply pressure sources from the con-
nections. The sudden release of pres-
sure can cause personal injury or prop-
erty damage.
1. Bypass the control valve and shut off the input sig-
nal and the supply pressure lines to the positioner.
2. Remove the positioner cover (key 39).
3. Loosen the spring lock (see figure 3) that holds the
range spring (key 18) to the beam.
4. Disconnect the other end of the range spring by
performing one of the following steps:
D For Type 3570, 3570C, 3572, and 3573 posi-
tioners, use a screwdriver to remove the spring re-
tainer (key 19, figure 3) from the piston rod extension.
D For Type 3570P and 3570PC positioners (see
figure 12), remove the screws (key 87), from the cap
(key 86) and rotate the cap clockwise to remove all
torsion spring force. Disconnect the actuator cable
(key 92) from the cable strap (key 93). Unhook the
positioner cable (key 91) from the cable spool (key
96).
D For Type 3571, 3576, and 3577 positioners,
loosen the set screw found in the spring retainer (key
56A, figure 14) and remove the spring wire (key 56D)
from the retainer.
5. Remove the range spring from the beam by
rotating the range spring counter clockwise.
Assembly
1. Install the new range spring. For Type 3570,
3570C, 3572, and 3573 positioners, also install the
spring retainer. See figures 3 or 11.
2. Reconnect the range spring to the piston rod exten-
sion (Type 3570, 3570C, 3572, and 3573 positioners)
or the feedback wire (Type 3571, 3576, and 3577 po-
sitioners, figure 14). For Type 3570P and 3570PC po-
sitioners, install the positioner cable (key 91, figure 13)
in the range spring so that the large ball on the cable
seats in the conical portion of the spring.
3. Install the spring lock (key 20, figure 11). Adjust the
positioner per instructions in the adjustments proce-
dures.
The action of the positioner can be reversed in the
same manner as described in the changing positioner
action procedures. However, before attempting to re-
verse the action, see table 4 or consult your Fisher
sales office or sales representative to determine if any
different parts are required.
Bias Spring
Disassembly
1. Refer to figure 3. Remove the top E-ring travel
stop.
2. Loosen the locknut securing the bias spring seat in
place. Then rotate the adjusting screw until the spring
force is at a minimum.
3. Loosen the locknut that secures the bias spring
post to the positioner base. Using a screwdriver in the
slot in the top of the post, unscrew the post from the
base.
4. Tilt the bottom of the post out and remove the post
from the beam.
5. Remove the locking nuts and the spring seat from
the bias spring post.
Assembly
1. Install the new bias spring, spring seat, and locking
nuts on the bias spring post.
2. Replace the bias spring post into the beam and
install the top E-ring travel stop.
3. Install the bias spring post into the base. Be certain
that the bottom of the post thread is positioned as
shown in figure 3. Ensure that the beam does not rub
on the post.
4. For Type 3570P and 3570PC positioners, go to the
initial range spring extension procedures for Type
3570P and 3570PC positioners.
5. Adjust the positioner as described in the adjust-
ments procedures.
The action of the positioner can be reversed in the
same manner as described in the changing positioner
action procedures. However, before attempting to re-
verse the action, see table 4 or consult your Fisher
sales office or sales representative to determine if a
different retainer, different range springs or different
bias springs are required.
Parts Ordering
A serial number is assigned to each positioner. The
serial number is stamped on the nameplate. Always
refer to the serial number when corresponding with
your Fisher sales office or sales representative regard-
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