Users’ Manual
Uplift pressure measurement system
Page 5-2
Rev. 0
sions after due regard to corrections made for difference in temperature, barometric pressure,
height above sea level and actual cell position (whether standing up or lying down).
For example in test certificate (see § 3.4), the zero reading in frequency
2
at the time of dispatch is
6917 (x 10
3
Hz
2
). In case the temperature and the barometric pressure is the same at the place
and time of installation and the sensor is placed lying down, the reading in frequency
2
should be be-
tween 6867 and 6967 (x 10
3
Hz
2
).
5.1.3
Connect the required length of cable to the sensor as suggested in the operating manual on
cable jointing - 6002.11/Rev 03/98.
WARNING!
Take precautions while handling the epoxy system so that skin contact is minimal. The
epoxy components should never come in contact with eyes or other sensitive body parts.
Wash hands very thoroughly with soap immediately after work is over.
5.1.4
Check the working of the sensor again following the procedure described in § 5.1.2.
NOTE:
Remember to add the cable resistance when checking the resistance between the leads
after the cable jointing. For the model ERC-10/11 cable, the resistance is 26 Ohm/km and
for the model ERC-12-15 cable, the resistance is 84 Ohm/km. (x 2 for both leads). In
case any other cable is used, make the necessary addition in the resistance value.
5.1.5
Record the initial readings including offset, barometric pressure and temperature in the field
book in the format provided in
§ 6.
5.1.6
Cable should be carefully marked. Cable should be marked with permanent markers every 5m
by the use of stainless steel tags tied by stainless steel wire stamped with appropriate con-
crete pressure cell numbers. Alternatively, plastic tabs are also available. Temporary identifi-
cation is possible by writing serial number of the sensor, its code number and the location at
which it is installed, on a strip of paper, placing the strip on the cable and covering it with a
transparent plastic cello tape. Permanent identification is necessary for proper connections in
the junction box and to insure correct splicing if cable is cut or broken.
CAUTION:
The single most important factor leading to loss of worthwhile data from sensors is
losing track of identification of the cable ends. Proper identification and marking of the
cables is generally taken most casually. Care should also be taken to put an identifi-
cation tag at the point where the cable comes out of the structure such that cable
identity is not lost if the cable gets accidentally cut.
5.2.
In st allin g t h e u p lif t p ressu re m et er
The installation procedure comprises of the following steps:
5.2.1
A system of piping is installed at several stations in the dam with the top of any uplift pressure
measuring pipe ending in the gallery.
5.2.2
Remove the plug on the pipe coming into the gallery from foundation and check the threads.
5.2.3
Ensure before starting the installation that the pipes are not choked. If so clean them.
5.2.4
Make the connections as illustrated in figure 3.1. Use Loctite or the teflon tape to make them
water tight.
5.2.5
Connect the leads of the jelly filled cable to the respective connector pins in the junction box.
NOTE:
For transmitting the signals to the observation room from the junction box, 10 core (5
pairs) or 20 cores (10 pairs) jelly filled cable, standardized by TRITECH may be used.
