14
Section 3
Model 580A Differential Pressure Switch
2.
Lightly tap the pointer hub with a hand-set or other flat-end tool. Use
perpendicular blows to avoid bending the shaft.
3.
Check the calibration of the indicating switch over its entire range (refer
to
Indicator Calibration, page 15
). If the indicating switch is correctly
calibrated, secure the pointer to the movement shaft by tapping the hub
with a hand-set or other flat-end tool.
4.
Test the pointer for tightness by moving the pointer from the zero to the
50% position manually, and then letting the pointer return freely to zero.
If the pointer indicates a shift, tap the pointer hub to tighten it to the
shaft.
Pointer Removal
The pointer is removed with a pointer puller shown in
Figure 3.3
. This tool is
included in the calibration toolkit, Part No. 9A-0288-1032B.
To remove the pointer, perform the following steps:
1.
Slide the pointer puller along the pointer until the pin protruding from the
tip of the screw in the pointer puller is directly over the movement shaft
and the arms of the pointer puller are directly under the pointer.
2.
Gently turn the knurled head of the screw clockwise, pushing the pin
against the movement shaft and lifting the pointer with the arms. Finger
pressure should be sufficient to pull the pointer free. If more pressure is
required, an Allen wrench (inserted into head of the screw) can be used.
However, care should be exercised to avoid breaking the pin.
HUB
MOVEMENT SHAFT
POINTER
HUB
POINTER PULLER
Figure 3.3—Pointer puller (Part No. 9A-0163-0005B)
Scale Plate Installation and Removal
During adjustments and calibration of the unit, it may be necessary to remove
and reinstall the scale plate. The scale plate is split to allow removal without
pulling the pointer. It is held in place by five screws (Item 40 in
Figure A.1,
page A-2
) and two mounting tabs at 12 o'clock and 6 o'clock positions. The
scale plate halves rest against the top tab (12 o'clock), and slide beneath the
bottom tab (6 o'clock).
