VEGA VEGACAP 82-98 - Manual (Page 19)

VEGACAP 19
Mounting
Metal vessels
Make sure that the mechanical connection of
the instrument to the vessel is electrically
conductive, in order to ensure sufficient
grounding.
Use conductive seals such as e.g. copper,
lead etc. Isolating measures such as cover-
ing the thread with Teflon tape can interrupt
the necessary electrical connection. In this
case use the earth terminal on the housing to
connect the instrument to the vessel wall.
Non-conductive vessels
In non-conductive vessels, e.g. plastic tanks,
the second pole of the capacitor must be
provided separately, e.g. by a concentric
tube or earth rod.
Under ideal ground conditions (e.g. short
electrodes) the earth plates or concentric
tube can be omitted.
When using a standard electrode, a suitable
earth plate is necessary. For this purpose
provide the largest possible earth plate, e.g.
wire braiding laminated into the vessel wall or
a metal foil glued to the vessel. Connect the
earth plates with the earth terminal on the
instrument housing (or on the hexagon).
Fig. 2.5
If the filling medium has not been grounded
separately (VEGACAP 27 and 35) and the
electrode is covered with a conductive. adhe-
sive medium (up to the mounting boss), the
full signal is triggered only when the medium
touches the threaded mounting boss and
gets grounded. With vertically installed sen-
sors therefore, a provision for grounding the
filling medium should be made.
Filling opening
Install the electrode such that it does not
protrude directly into a strong filling stream.
Should such a mounting location be neces-
sary, mount a suitable sheet metal cover
above or in front of the electrode e.g. L 80 x 8
DIN 1028, etc. (see fig. 2.4 a).
In abrasive solids, mounting acc. to fig. 2.4 b
has proven to be a good solution. A material
cornice forms on the concave protective
sheet, thus preventing unnecessary wear of
the sheet.
Mounting boss
Install the rod electrode (VEGACAP 11, 21,
26, 97) such that the electrode protrudes into
the vessel. When installed in a tube or a
socket, build-up can be caused which can
influence the measurement. This is particu-
larly true for viscous or adhesive products
(see fig. 2.6).
In case of longer sockets, use an electrode
for adhesive products (VEGACAP 26, 27, 35,
97, 98) or a screening tube.
Fig. 2.6
0
1
max. 80 mm