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The operator connects the hook to a survey tape and
lowers the hook into the inclinometer casing. When the hook reaches the
approximate depth of the first coupling, the operator pulls up, causing the
arm of the hook to catch on the bottom edge of the casing section. The
operator notes the depth and then repeats the procedure for the next section
of casing. When the hook contacts the bottom of the casing, a mechanical
action locks the arm in the closed position so it can be withdrawn.
Settlements are calculated by comparing the current depth of each casing
section with its initial depth. Note that settlement hooks are used with
telescoping casing which provides edges for the hook to grab. The hooks do
not work with casing that has flush interior joints.
Simple Hook: This hook
has a swing-out contact arm or hook. It works to depths of 30 m (100 ft).
USBR-Type Hook: The USBR-type
hook has two spring-loaded arms. Guide wheels keep the arms positioned for
easy "hooking."
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