Introduction
The motor has a power system separate from that of the sensor, and can be
controlled from the surface using a hole lock control unit. Once the sonde is
installed, the hole lock control unit may be removed. Without power, the hole lock
will not be able to retract, and the sensor will be secured.
2.3.2 The three-jaw hole lock
A three-jaw hole lock is available which
gives better grip on the borehole casing, but
is bulkier and heavier than the single-arm
lock. This is the standard option for
uniaxial instruments; it can be installed in
boreholes between 99 mm (≈3.9 “) and
203 mm (≈8 “) in diameter.
The three-jaw hole lock consists of a set of
three active clamp arms attached to a
compression spring, which forces them to
swing out from the sonde and wedge
themselves against the borehole wall.
Serrated steel jaws at the end of each arm
provides maximum grip against the
borehole casing. This configuration
ensures that the sonde body is held parallel
to the axis of the borehole and prevented
from twisting or slipping under the
influence of ground vibrations.
10
Issue G - November 2019
