Converting A 3570 Valve Positioner To A 3570C Valve Positioner - Fisher 3570 Instruction Manual

Instruction Manual
D200137X012
8. Mount the relays in their respective positions on the positioner pedestal, making certain that the relay gasket
(key 30) is in good condition and is in place.
9. If the positioner operation is still sluggish, a slight adjustment of the bias spring post (see figure 2) might be
necessary. Loosen the locknut and rotate the post in half‐turn increments, checking after each half turn for proper
operation. Rotate the post no more than two turns from the position shown in figure 2. Refer to the adjustment
procedures after rotating the post to check the position of the post and beam assemblies.

Converting a 3570 Valve Positioner to a 3570C Valve Positioner

If desired, tire valves can be substituted for pressure gauges. Also, locking relay nozzles can be added on any 3570
positioner. This provides the construction that is standard with 3570C and 3570PC positioners.
Key numbers used in this procedure are shown in figure 10 except where indicated. When reassembling, coat all pipe
threads with a good quality pipe thread compound.
1. Isolate the control valve from the line pressure and release pressure from both sides of the valve body. If using a
power actuator also shut‐off all pressure lines to the power actuator and release all pressure from the actuator. Use
lock‐out procedures to be sure that the above measures stay in effect while you work on the equipment.
2. Loosen the knurled screws (key 38) and remove the cover (key 39).
3. Disconnect the tubing assemblies (keys 28 and 45) from the base and from the gauges (keys 24 and 25). Unscrew
the hex nuts (key 27) from the back of the gauges and remove the gauges (keys 24 and 25).
4. Unscrew the pressure gauge (key 54) from the gauge adaptor (key 29U).
5. Unscrew and remove the nozzle and spring (keys 29Q and 29P) from each relay.
6. The gauge bracket (key 5) can be removed if desired. To remove it, loosen the locknut (key 7) and remove the bias
spring post and cap screw (keys 6 and 32). When replacing the bias spring post, be sure that the bottom of the post
thread is positioned as shown in figure 2 for proper positioning of the E‐ring travel stops. This alignment can be
verified visually through the vent port.
7. Use compression plugs (key 52) to plug the holes opened in the base when the tubing is removed.
CAUTION
Never rotate the nozzle (key 29Q) when the locknut (key 29P) is tight, or damage to the relay diaphragm will result. Always
use a wrench on the nozzle to prevent it from turning while loosening or tightening the locknut.
8. Install the locknut and nozzle (keys 29P and 29Q) on each relay.
9. Install the tire valve (key 26, figure 11) into the gauge adaptor (key 29U).
10. Install the service tee and tire valve adaptor (keys 49 and 53, figure 11) into the CYLINDER connection. Connect the
pressure line that runs to the lower part of the cylinder to the service tee.
11. Install the pipe nipple, pipe tee, and tire valve adaptor (keys 50, 51, and 53, figure 11) into the INSTRUMENT
connection. Connect the input signal line to the pipe tee.
12. Refer to the adjustment procedures.
3570 Positioners
September 2015
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