3. Connect an adjustable current source to the terminal block on the circuit board. Apply the desired input signal to the
positioner at which the output pressure is to fall to approximately 1.7 psi
. This signal can range from factory setting of
3.7 to 8 mA.
4. Turn the minimum pressure cutoff pot clockwise until the output pressure drops off Turn the minimum pressure cutoff.
5. Fine-tune the pressure drop-off point by increasing the input signal and then decreasing it through the desired shut-off
signal. Observe the signal value at which the pressure drops off. If the pressure drops off at a lower mA signal than
desired, turn the MPC pot counterclockwise. If the pressure drops off at a higher signal than desired, turn the MPC pot
clockwise.
6. Repeat Step 5 until the pressure drops off at the desired input sign.
7. To disable the MPC feature turn the minimum pressure cutoff pot (marked “MPC”) 20 turns counterclockwise or until it
makes a clicking noise.
Positioner Maintenance:
NOTE: Refer to KM81 IOM for I/P module maintenance instructions.
For proper maintenance, proceed as follows:
1 Maintain a clean air supply, free of dust, oil and water. A coalescing air filter for I/P is required to ensure a clean air
supply. Check and maintain filter regularly.
2 Make sure all arms and levers move freely.
3 Check for loose parts.
4 Be sure there are no leaks in the air supply tubing fittings or connections.
5 Refer to the troubleshooting chart on page 9 in case of problems.\
Pilot Relay Disassembly and Reassembly:
The pilot relay is available as a complete unit and can be easily replaced (See Steps 2 and 18.) Before attempting to
correct any problem with the pilot relay assembly, obtain a positioner repair kit that contains the soft goods most
commonly required.
NOTE: Numbers in parentheses correspond to the numbers in Figure 8.
1 Remove the feedback spring (47) and rotate the span and zero arms (40, 46) out of the way.
2 Remove four screws (33) holding the pilot relay to positioner base (1). Remove relay from positioner.
3 Remove the nut (25) connecting the flapper assembly (21) to the signal capsule.
4 Remove four screws (32) holding the two halves of the pilot relay assembly together. Carefully pull the relay assembly
halves apart, making sure the flapper assembly
ٛ
(21) slides off the flapper adjustment screw (19) without damaging the signal diaphragm assembly (16). Pull the relay
diaphragm assembly (13) out of the other half of the relay body (9).
ٛ
5 With the relay assembly in two sections, remove two screws (22) holding flapper assembly (21) to the relay
diaphragm assembly (13). Remove the flapper.
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