Siemens SITRANS LG250 Operating Instructions Manual page 19

Fasten
PBD-51041388
Microwaves can penetrate many plastics. This is why plastic tubes are
problematic for measurement applications. If durability is no problem,
we recommend the use of uncoated metal standpipes.
When the SITRANS LG250 is used in standpipes, contact with the
tube wall must be avoided. We recommend for this purpose a cable
probe with centering weight.
Caution:
When mounting, make sure that the cable is straight over its entire
length. A kink in the cable can cause measurement errors and contact
with the tube.
With rod probes, a spacer is generally not required. However, if there
is a risk of the rod probe being pressed against the tube wall by in-
flowing medium, you should mount a spacer at the probe end to avoid
contact with the tube wall. In the case of cable probes, the cable can
be strained.
Keep in mind that buildup can form on the spacers. Strong buildup
can influence the measurement.
Note:
Measurement in a standpipe is not recommended for extremely
adhesive products. In case of slight buildup, you should choose a
standpipe with bigger diameter.
Instructions for the measurement:
•
The 100 % point with standpipes should be below the upper
ventilation hole.
•
The 0 % point in standpipes should be above the gravity or center-
ing weight.
•
A false signal suppression with installed sensor is generally rec-
ommended to achieve the best possible accuracy.
If there is a risk of the cable probe touching the vessel wall during
operation due to product movements or agitators, etc., the measuring
probe should be securely fixed.
There is an inside thread (M8) in the gravity weight, e.g. for an eye-
bolt (optional).
Make sure that the probe cable is not completely taut. Avoid tensile
loads on the cable.
Avoid undefined vessel connections, i.e. the connection must be
either grounded reliably or isolated reliably. Any undefined change of
this requirement can lead to measurement errors.
If there is a danger of the rod probe touching the vessel wall, then the
probe must be fastened at the bottom end.
Keep in mind that below the fastening, a measurement is not possible.
SITRANS LG250 - Operating Instructions
19