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ZERO and SPAN preset pots are accessible using a small instrument screwdriver through the two access holes in the positioner circuit (see Figure 6). Connect the air supply, positioner signal and angle retransmit reader supply. To set the ZERO, move the positioner to its minimum signal position (usually 4mA), and set the ZERO preset pot to give the desired retransmit current. Then set the SPAN by moving the positioner to its maximum signal position (usually 20mA), and adjusting the SPAN pre-set pot to give the desired retransmit current. Recheck and read just these two settings until both are correct – as the SPAN is adjusted, it has a small effect on the ZERO reading, and vice-versa, so a few readjustments may be necessary.
The angle retransmit circuit is fitted with a jumper, which should be fitted to bridge its two pins if you want the circuit to read 4- 20mA over 45 degrees or near, rather than the usual 90 degrees. The range adjustment pot is adjustable to give ranges in between these two values. To gain access to this jumper, it is necessary to remove the whole carrier plate assembly from the positioner – see Section 2.1 for instructions on this.
4.15 Adjustment of Position of Optional Clearcone Monitor.
If your positioner is fitted with a Clearcone position monitor, you may need to adjust its angle to read correctly after you have set up the positioner. The internal O-ring slides to give a coarse setting, and the shell mounting slots give a few degrees of fine adjustment.
To adjust the position of the angle scale, first unscrew the two self-tapping stainless mounting screws which hold the transparent outer shell to the lid, and lift off the shell complete with its black mask/pointer moulding. Don't lose the screws or the sealing O-ring which seals round the outside of the shell-lid interface.
If you have reversed the clockwise/anticlockwise sense of the positioner, you may at this
stage need to replace the self adhesive angle scale sticker with one marked in the opposite sense. Take care to stick it to the scale cone moulding accurately.
Rotate the scale cone by sliding it round on its internal O-ring against the coupling inside it, which is located on the positioner shaft square. This may take some effort if the O-ring has stuck on. Move it until it is reading as near correctly as you can achieve against the pointer on the mask/pointer moulding, which you should hold in position with the outer shell mounting slots centrally located above the screw holes in the lid. Refit the mounting screws, making sure that the mask moulding and the sealing O-ring are well located in the outer shell moulding. Adjust the pointer position to its final position by rotating the outer shell slots against the mounting screws, taking care to position the screws at equivalent positions in both slots so that the shell remains central relative to the rotating parts inside, then tighten the screws to clamp it into position.
5. MAINTENANCE AND TROUBLESHOOTING
The EL positioner is designed to be maintenance free during a long life, if it is supplied with clean, dry oil free air, and electrical signals free of noise and high voltage spikes.
When the lid is removed, take care not to wipe all grease from shaft lip seal.
Table 2 is a troubleshooting guide, which aims to assist only with simple easily remedied problems. If problems persist, contact Kinetrol or a Kinetrol distributor for further assistance.
TABLE 2. Troubleshooting Guide.
Failure to move when signal and air are connected:
- Check air pressure – must be above 50psi./3.5 Bar.
- Check signal is connected with correct polarity.
- Check signal is really above 4 mA
- Discrete units – is shaft connected in correct orientation? The feedback pot strap may need replacing if orientation is incorrect.