VEGA Capacitive electrodes EL … - Manual (Page 25)

Capacitive electrodes EL … 25
Mounting
Fig. 2.1 Lateral load
2 Mounting
2.1 Mounting instructions
General
The different mediums and the requirements to
the measurement require different installation
positions. Hence note the following instructions.
Length of the level electrode
Note when ordering the electrodes, that the
electrode must be sufficiently covered at the
requested level according to the electrical
features of the medium (DK-value).
E.g. an electrode for level detection in oil
(
ε
r
~ 2) requires a considerably higher covering
than in water (
ε
r
~ 81).
Lateral load
Note that the electrode is not subjected to
strong lateral forces. Mount the electrode in a
position in the vessel where no interfering
influences such as e.g. stirrers, filling openings
etc. occur. This is mainly valid for very long rod
and cable electrodes.
Plate electrode
Mount the plate electrode such that the
electrode must be flush to the vessel wall. The
wall thickness of the vessel should not exceed
20 mm. Chamfer the inner edge of the hole so
that no build-up is caused on the edge.
Extracting forces
In case of strong extracting forces e.g. due to
material inflow, high tensile loads can be
caused.
In these cases use for short meas. distances a
rod electrode, as generally a rod is more
stable. If due to the length or the installation
position a cable electrode should be
necessary, the electrode should not be fixed
but just provided with a gravity weight as the
cable can more easily follow the product
movements. Note that the electrode cable does
not touch the vessel wall.
Pressure
In case of gauge or low pressure in the vessel,
the mounting boss on the thread must be
sealed. Use the attached seal ring. Check
whether the seal ring is resistant against the
medium.
Isolating measures such as e.g. the covering of
the thread with Teflon tape, can interrupt the
necessary electrical connection in metal
vessels. Hence earth the electrode on the
vessel.