First encounters
Engaging the hole lock
To extend the jaw of the hole lock:
1. Hold the switch on the hole lock control unit in the EXTEND JAW or +
position. If you are using a deep-borehole control unit, there will be an
additional dial compared to the unit pictured; turn this until the built-in
ammeter reads around 0.1 A.
2. When the arm makes contact with the borehole casing, the current will drop
slightly. Continue holding the switch in the EXTEND JAW position.
3. When the lock arm reaches its fully extended position, the motor will
automatically stop and the current will drop to zero. If using a deep-borehole
unit, return the dial to zero.
4. If the current has not dropped quite to zero after 30 – 40 seconds of operation,
release the switch, wait a few seconds, and push it back to the EXTEND JAW
position briefly. If the arm is not completely extended, you will see a surge of
current. If the current remains constant, the jaw is at its maximum reach.
5. Once the sensor is locked in place, it is recommended that you remove the
hole lock power cable and control unit from the site. Without power, the hole
lock will not be able to retract, and the sensor will be secure.
3.4.1 Disengaging the hole lock
To retract the jaw of the hole lock:
1. Tension the load bearing cable, to take up any slack.
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Issue G - November 2019
