VEGA VEGAPULS 51K…54K 4 … 20 mA; HART compact sensor - Manual (Page 15)

VEGAPULS 51K … 54K 15
21750-EN-031222
Tube flange system as bypass tube
Make sure the required upper vent hole in
the surge pipe is aligned with the sensor
type label.
As an alternative to a surge pipe in the ves-
sel, a pipe antenna system can be installed in
a bypass tube outside the vessel.
With measurement in a surge or bypass
tube, the max. measuring range decreases
by 5 … 20 % (e.g. DN 50: 16 m instead of
20 m and with DN 100 only 19 m instead of
20 m) due to the change of running time of
the radar signal.
Align the sensor so that the type label lies on
the same axis as the tube holes or the tube
connection openings. The polarisation of the
radar signals enables a considerably stabler
measurement with this alignment.
When mounting a VEGAPULS 52 on a by-
pass tube (e.g. on a previous floating or
displacer unit), the radar sensor should be
placed approx. 500 mm or more from the
upper tube connection. If the tube has a
rough inner surface, the use of an additional
measuring tube (tube in tube) is recom-
mended, as poor surface quality of the meas-
uring tube hampers radar measurement
through an excessively high „noise level“.
Mounting and installation
100 %
0 %
> 500 mm
Extended bypass tube on a vessel with turbulent
product movement
Type label
75 %
0 %
100 %
100 %
0 %
> 500 mm
300 ... 800 mm
Tube flange system as bypass tube
Type label
For products with small dielectric values
(< 4), the bypass tube should extend below
the lower tube connection. Products with
small dielectric constants are partly pen-
etrated by the radar signals, which could
allow the tube bottom to deliver a stronger
echo than the product surface (when the
bypass tube is nearly empty). By extending
the lower end of the bypass tube, enough
liquid remains in the tube even when the
vessel i.e. emptied.