Xylem DH-21 - Manual (Page 13)

Chapter 2
Installation
DH-21
Installation 2-1
2.1 Installing the “ W ATER LOG”
This chapter covers installation techniques for the “ W
ATER LOG”. For proper installation, you
will need the following:
1. The Owner's Manual
2. Your “
W
ATER LOG” instrument
3. A fresh 7.2 Volt battery pack
4. RS-232 Cable
5. (Optional) Well head compression seal or stream installation package
6. (Optional) Stainless steel drop cable
7. (Optional) Cable clamps for fastening the drop cable
8. IBM compatible computer (usually a laptop computer) for programming and setup of
the “ W ATER LOG”
2.1.1 Sensor Deployment
There are many ways to deploy the “W ATER LOG”. However, there are some site preparations
and maintenance that must be considered.
If the sensor is to be clamped or tied down at a fixed location, the sensor must be where there is
no velocity flow. The “W
ATER LOG” contains a pressure sensor and changes in flow correlate to
changes in pressure. Thus, if the sensor is subjected to open flow, there is a good chance your
readings will be inaccurate. Key point: Use stilling wells, sand points, or other “no flow”
installation techniques. The result will be very accurate, reliable data.
The “W ATER LOG” can be hung in well bores and float type stilling wells or conduits. If this is
the type of installation that is being done, the “W ATER LOG” should be installed by suspending
the sensor not by its polyethylene vent cable, but by using a stainless steel drop cable and by
using a weighted ballast or sinker, such as the one that has been provided. The ballast will cause
the sensor to sink to the desired depth and will help the sensor to hang straight down. Adjust the
cable such that the weight of the sensor is entirely on the steel cable, not the vent tube. Allow a
small service loop in the vent tube to allow for future expansion and contraction of the plastic
tubing. The stainless cable and the miscellaneous hardware can be purchased from Design
Analysis Associates.
The polyethylene vent cable has an extremely large thermal coefficient of expansion. This
coupled with the fact that the polyethylene tubing will stretch with applied weight, make the use
of the stainless steel drop cable a must. Use of the stainless steel drop cable will insure long
term stability. THIS IS A MUST!!!