VEGA VEGAPULS 43 Profibus PA - Manual (Page 22)

22 VEGAPULS 43 – Profibus PA
0 %
~45ы
ш 100,8
0,0…0,4
1,5…2
3,6
0,0…0,4 150…500
5…10
3,6
ш 95 2
100 %
Flange DN
100
Connecting
sleeve
Welding neck
flanges
Welding of the smooth
welding flange
Welding of the connect-
ing sleeves
Meas. pipe fastening
Vessel
bottom
Deflector
Deburr the
holes
Welding of the welding
neck flanges
Mounting and installation
Guidelines for standpipe construction
The radar sensors with a DN 50 flange only
form a functioning measuring system in con-
junction with a measuring tube.
The measuring pipe must be smooth inside
(average roughness Rz
≤ 30). Use stainless
steel tubing (drawn or welded lengthwise) for
construction of the measuring pipe. Extend
the measuring pipe to the required length
with weld-on flanges or with connecting
sleeves. Make sure that no shoulders or
projections are created during welding. Be-
fore welding, join pipe and flange with their
inner surfaces flush and exactly fitting.
Avoid welding through the pipe wall. The pipe
must remain smooth inside. Roughness or
welding beads on the inner surfaces must be
carefully removed and burnished, as they
cause false echoes and encourage product
adhesion.
If the vessel contains agitated products,
fasten the measuring pipe to the vessel bot-
tom. Provide additional fastenings for longer
measuring pipes.
In products with lower dielectric values (< 4),
a part of the radar signal penetrates the
medium. If the vessel is nearly empty, echoes
are generated by both the product and the
vessel bottom. The echo from the vessel
bottom can in some cases be stronger than
the echo from the product surface. If a de-
flector is installed below the open end of the
measuring tube, the radar signals are scat-
tered and prevented from reaching the ves-
sel bottom. This ensures that, in nearly empty
vessels or with products of low dielectric
value, the product delivers a more distinct
echo than the vessel bottom.
Due to the deflector, the useful echo (and
thus the measured value) remains clearly
detectable in a nearly empty vessel, and the
0 % level can be reliably measured.