VEGA VEGAPULS 51K…54K Profibus PA - Manual (Page 19)

VEGAPULS 51P … 54P 19
24890-EN-041227
Guide tube in existing surge or bypass tubes
Extended guide tube
Flange connections on bypass tubes
Use of guide tubes
In case of very rough inner surfaces in exist-
ing bypass tubes (e.g. due to corrosion), or
with large connection openings, the use of a
guide tube inside the existing bypass tube is
recommended. This reduces the noise level
and increases reliability considerably. The
flange of the guide tube can be easily
mounted as a sandwich flange between
vessel and sensor flange.
Mounting and installation
To increase the min. distance, the guide tube
can project out of the surge or bypass tube.
This can be done by welding a plain flange
can be welded at the required position on the
outside of the guided tube. In both cases, a
breather hole must be provided.
Seals on tube connections and tube ex-
tensions
Microwaves are very sensitive to gaps in
flange connections. If connections are made
without proper care, distinct false echoes as
well as increased signal noise can result.
Observe the following points:
• The applied seal should correspond to the
tube inner diameter.
• If possible, conductive seals such as con-
ductive PTFE or graphite should be used.
• There should be as few seal positions as
possible in the guide tube.
Guide tube