VEGA VEGAPULS 45 4 … 20 mA; HART compact sensor - Manual (Page 18)

18 VEGAPULS 42, 44 and 45 – 4 … 20 mA
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.
Flange connections on bypass tubes
Adhesive products
In non-adhesive or slightly adhesive prod-
ucts, use a surge pipe with a nominal width of
e.g. 50 mm. VEGAPULS 42 and 44 radar
sensors with 26 GHz technology are for the
most part insensitive to buildup in the meas-
uring tube. However, buildup should not
block the measuring tube.
For products with heavier buildup, the use of
a DN 80 to max. DN 100 standpipe or surge
pipe can make the measurement possible
despite buildup. With products that are ex-
tremely adhesive, measurement in a stand-
pipe is not possible at all.
Mounting and installation
Guide tube in existing surge or bypass tubes
Extended guide tube
Guide tube
To increase the min. distance, the guide tube
can protrude out of the surge or bypass
tube. For this purpose, a plain flange can be
welded at the required position on the out-
side of the guide tube. In both cases, a
breather hole must be provided.