Siemens SITRANS LG270 Operating Instructions Manual page 18

Standpipes
18
Fig. 9: Position of the spacer or centering weight
1 Rod probe with spacer (steel)
2 Cable probe with centering weight
h Measurable tube section
Note:
Measurement in a standpipe is not recommended for extremely adhe-
sive products. In case of slight buildup, you should choose a bypass
tube with bigger diameter.
Instructions for the measurement:
•
The 100 % point in bypass tubes should be below the upper tube
connection to the vessel.
•
The 0 % point in bypass tubes should be above the lower tube
connection to the vessel.
•
A false signal suppression with installed sensor is generally rec-
ommended to achieve the best possible accuracy.
Standpipes or surge pipes are normally metal tubes with a diameter
of 30 ... 200 mm (1.18 ... 7.87 in). Up to a diameter of 80 mm (3.15
in), such a pipe corresponds to a coax measuring probe. It does not
matter if the standpipe is perforated or slotted for better mixing.
Measuring probes can be mounted in standpipes up to DN 200.
For standpipes, select the probe length such that the upper blocking
distance (dead band) of the probe is above the upper ventilation hole.
This allows you to measure the total level range of the medium in the
SITRANS LG270 - Operating Instructions
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PBD-51041064