RST Instruments VW2100, Инструкция по эксплуатации, Страница: 16 / 34

VW2100 Vibrating Wire Piezometer
Instruction Manual
ELM0005P RST Instruments Ltd. Page 16
3
Re-assemble the filter housing into the piezometer body under the surface of de-
aired water, while keeping the piezometer oriented with the diaphragm pointing
upward. Take care to ensure that no air is trapped in the transducer cavity.
4
Vibrating wire readings must be taken with a VW2106 readout unit while the filter
housing is being pushed slowly into place. Allow any over-range pressures to
fully dissipate before pushing the filter on any further.
5
The vibrating wire piezometer with a high air entry filter installed must be stored
in de-aired water until the unit is installed.
CAUTION: V
IBRATING WIRE PIEZOMETERS CANNOT BE ALLOWED TO FREEZE WHEN
FULLY SATURATED
,
OTHERWISE DAMAGE WILL OCCUR TO THE TRANSDUCER
DIAPHRAGM
,
WHICH WILL INVALIDATE THE TRANSDUCER FUNCTION AND
CALIBRATION
.
5.3.2 Two Bar (or Higher) High Air Entry Filters
The proper procedure for de-airing and saturating two bar (or higher) high air entry
filters is complex and difficult to complete properly. It is recommended that it be
performed either at the factory or by carefully following the instructions below:
1
Place the assembled piezometer, with the filter housing facing downward, at the
bottom of a vacuum chamber. The vacuum chamber is to have an inlet port at
the bottom to later allow introduction of de-aired water into the chamber.
2
Close the valve for the de-aired water inlet and evacuate the chamber. The
piezometer should be monitored with a VW2106 readout unit while the chamber
is being evacuated.
3
When the maximum vacuum has been achieved in the vacuum chamber, use the
VW2106 readout unit to read the piezometer until it has also reached the same
maximum vacuum pressure.
4
Open the de-aired water inlet valve to allow de-aired water to enter the bottom of
the chamber and reach an elevation of approximately 50 mm above the top of
the piezometer high air entry filter.
5
Close the de-aired water inlet valve when the de-aired water has reached the
required height.
6
Release the vacuum, allowing the chamber to return to atmospheric pressure.
7
Observe the transducer output on the VW2106 readout unit. Up to 24 hours may
be required for the (5 bar high entry) filter to completely saturate and for the
piezometer pressure to return to zero. The saturation of the high entry filter is
considered to be completed at this point.
8
After saturation, the transducer must be kept in a sealed container of de-aired
water until ready for installation. If de-aired at the factory, a special plastic cap is