Flowserve 3400IQ Digital Positioner - Manual (Page 59)


Logix 3400IQ Digital Positioner FCD LGENIM3401-00 – 06/06
flowserve.com
8.6 Stem Position Sensor
The position feedback assembly transmits valve positions information to the processor. This
is accomplished by means of a rotary position sensor that connects to the valve stem through a feed-
back linkage. To provide for accurate tracking of the pin in the slot, the follower arm is biased against
one side of the slot with a rotary spring. This spring also automatically moves the position feedback
assembly to its limit in the unlikely event of failure of any component in the linkage.
Stem Position Sensor Replacement
To replace the stem position sensor, refer to Figure 16, 19 and 22 and proceed as outlined below. The
following tools are required:
• Phillips screwdriver
c WARNING: Observe precautions for handling electrostatically sensitive devices.
1. Make sure the valve is bypassed or in a safe condition.
2. Disconnect the power and air supply to the unit.
3. Remove the main cover.
4. Remove the plastic board cover by removing the three retaining screws (see Figure 16).
5. Disconnect the position sensor wires from the main PCB assembly.
6. Remove the two rotary position sensor-retaining screws and lift the sensor out of the housing.
7. Turn the new position sensor shaft until the dot on the side of the shaft is aligned with the wires
on the side of the position sensor (Figure 19).
8. Insert the position sensor into the shaft with the wires pointing toward the main PCB assembly.
Turn the position sensor clockwise until bolting slots align with the housing screw holes and the
wires on the sensor protrude over the main PCB assembly.
NOTE: Do not mix the position sensor with those from older Logix positioners. Older models
contain sensors with different ranges that will not work in the Logix 3400IQ model. The wires on
the Logix 3400IQ position sensor are red, white and black.
9. Carefully center the position sensor on the shaft bore, insert and tighten the screws. Do not
overtighten.
10. Route the wires along the side of the position sensor and reconnect to the main PCB assembly.
11. Install the plastic board cover. Insert the three retaining screws through the plastic cover into the
threaded boss and tighten evenly, using a Phillips screwdriver. Do not overtighten (see Figure
16).
12. Reinstall all covers.
13. Reconnect power and air supply to the positioner and perform a stroke calibration.