VEGA Capacitive electrodes EL Profibus PA - Manual (Page 16)

16 Capacitive electrodes EL - Profibus PA
Mounting
Lateral load
2 Mounting
2.1 Mounting instructions
General
Different mediums and measurement require-
ments make different installation positions
necessary. Please note the following points.
Lateral load
Make sure that the electrode is not subjected
to strong lateral forces. Mount the electrode
in a position in the vessel where no disturbing
factors, e.g. stirrers, filling openings etc. are
present. This is especially important for very
long rod and cable electrodes.
In such cases, use a rod electrode for short
meas. distances, since a rod is usually more
stable. If, due to the length or the installation
position, a cable electrode is necessary, the
electrode should not be fixed but simply
provided with a gravity weight to allow the
cable to more easily follow the product move-
ments. Make sure that the electrode cable
does not touch the vessel wall.
Pressure
If there is pressure or underpressure 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.
Insulating measures, such as e.g., covering
the thread with Teflon tape, can interrupt the
necessary electrical connection. For this
reason, ground the instrument on the vessel.
Shortening the electrode
Fully insulated electrodes have fixed dimen-
sions which must not be modified in any way.
Any modification will destroy the instrument.
Partly insulated cable or rod electrodes can
be shortened if necessary. The basic capaci-
tance of the electrodes is compensated auto-
matically at adjustment time. Because of this,
the electrodes can be shortened by any
desired amount.
Cable electrode EL 31 can also be short-
ened. Loosen the two pins on the gravity
weight (hexagon socket) and remove them.
Pull the cable out of the gravity weight.
Extracting forces
In case of strong extracting forces, e.g. due
to material inflow or material slide, high tensile
loads can occur.