16
V1.4 March 15
5.2 Re
-
Pressurising the Cell contd..
However, it is also possible that the cell is already in good contact with the concrete, so
that crimping will immediately cause a pressure rise in the cell. If this is the case then
cease crimping immediately.
Continued crimping after the cell has made good contact could cause the concrete
around the cell to split open which is not desirable and could lead to erroneous readings.
A slight relaxation of the cell after the re
-
pressurization procedure is normal and should
drop the cell pressure to a value roughly equal to the concrete stress. From this point on,
the cell pressure should then be equal to the absolute concrete stress. Record the new
initial pressure after the cell has stabilized.
While the concrete is curing it will be a good idea to take simultaneous readings of
temperature and pressure for the purpose of developing a temperature correction factor.
See section 6.
5.3 Cable
5.3.1 Cable Installation
The cable should be protected from accidental damage caused by moving equipment.
This is best done by putting the excess cable inside a junction box (Cables may be
spliced to lengthen them, without affecting gauge readings. Waterproof splice kits are
available from
Geosense
®
.
5.3.2 Cable marking.
Cables should be marked with unique identification. Markings should be repeated at
regular intervals along the cable where multiple cables are to be grouped together, so
that in the event of cable damage, there may be a chance that the identification could be
exposed and the cables re
-
joined. Multiple cable marks are particularly important close
to the end of the cable. The spacing of markings can vary according to specific site
requirements but a guide of 5m to 10m is commonly applied (available on request).
5.4Tools.
5.4.1 Tools list
Obtain any tools necessary to carry out the installation. The following is a brief list of
tools typically used during the installation of
Geosense
®
NPC
-
3000 NATM Cells
:
-
•
NATM Crimper
-
to re
-
pressurise the cell.
•
Wire cutters and strippers
•
Vibrating Wire Readout unit
for checking the NATM cell function
•
Cable Marking
system / equipment ( eg coloured PVC Tapes )
•
Tie
wire/ Cable ties
-
for installing NATM cells and cable.
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