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4. SETTINGS AND ADJUSTMENTS.
The positioner will have been factory set to the requirements given in the ordering code ( i.e. the direction of rotation for a rising pressure signal and the range and zero settings). However, if these settings need to be changed, the following section describes the procedure for achieving this.
4.1 Change of Direction for Rising Signal (direct mounting units only).
4.1.1 Move the actuator to approximately mid-position to avoid problems in correct orientation later. This is obviously not possible or necessary with spring return models because the position of the vane will be known. Reduce both main supply and signal pressures to zero.
4.1.2 Remove positioner cover and undo the two M4 screws retaining the red angle scale plate and remove, as shown in Figure 5. Loosen the central coupling screw sufficiently to draw the coupling off the actuator square.
4.1.3 Pull the two halves of the coupling apart sufficiently to allow the cam to be withdrawn from its location peg as shown in Figure 6. Flip the cam over and push it back into the slot between the two coupling halves and locate it back on the peg.
4.1.4 If when the coupling was removed, the collet was left behind on the actuator square, remove the collet from the square and push it into the lower half of the coupling ensuring that it locates in the semicircular 'pip'. Tighten the clamping screw by two turns before placing it back on the actuator square such that the cam follower is approximately half way up the rise of the cam and tighten the clamping screw. Replace the angle scale plate.
4.1.5 Undo the changeover block central screw and rotate it by a quarter turn and replace and tighten screw. For your convenience, the changeover block is marked 'A' and 'C' which refers to 'anticlockwise' and 'clockwise' respectively. Ensure the required letter is placed opposite the arrow marked on the top of the valve block.
4.2 Zero and Range Adjustment (refer to Figure 4).
4.2.1 Move the actuator/positioner to the zero end of the stroke (i.e. when the cam follower is at the beginning of its rise). This can be most easily achieved by pressurising the main air supply without any signal air pressure (spring return models
will already be at this position. Exhaust the supply air and move the internal indicator to indicate just below zero on the angle scale.
4.2.2 Set the coarse zero by slackening the coupling screw by approximately half of a turn until the top part of the coupling can be rotated by hand and rotate until the cam follower just starts to rise up the cam profile. Retighten the screw.
4.2.3 Turn on the main air supply and carefully increase the signal supply pressure to 3psi (0.2Bar). Slacken the fine zero adjustment clamp screw and rotate zero adjuster using thumb pressure so that the actuator moves to indicate zero on the internal indicator. Tighten clamp screw.
4.2.4 Increase the signal pressure to 15psi (1 Bar). Slacken the range adjuster clamp screw and rotate the adjuster knob between thumb and forefinger until the actuator moves to the desired end stroke position (normally 90 degrees) as indicated on the internal indicator. Re-tighten the clamp screw.
4.2.5 Reduce the signal air pressure again to 3 psi and check that the zero position has not changed.
4.3 Speed Control.
Maximum actuator speed can be regulated by the two following methods:
a.) Changing the valve spool/liner size. The valve size is normally specified at the point of ordering by the letters 'AP', 'MP' or 'HP'. This method, however, not only effects the actuator speed but also effects the 'gain' and therefore control stability of the unit and care must be taken not to specify a too high flow valve for a given size of actuator. Kinetrol Ltd has recommendations (shown in the AP literature) for each size of the actuator
b.) adjustment of the built in flow restrictors (shown in Figure 4) is achieved using a screwdriver. There are two restrictors, one for each direction of travel. Clockwise rotation, this will reduce the actuator speed. 'AP' and 'MP' size units with 1/8 or 1/4 ports are controlled in this way but 'HP' size units having 3/8 ports are fitted with external silencer/restrictors which are adjusted using an allen key fitted down the centre of the adjuster.