VEGA VEGAPULS 43 Profibus PA - Manual (Page 19)

VEGAPULS 43 – Profibus PA 19
Welding beads too large
Tube connection protrudes
Additional connection in the bypass tube in one plane
Use of guide tubes
In case of very rough inner surfaces in exist-
ing bypass tubes (e.g. due to corrosion),
large connecting tube openings, as well as
bypass tubes with more than 100 mm inner
diameter, the use of a guide tube inside the
existing bypass tube is recommended. This
reduces the noise level and increases meas-
urement reliability considerably. The flange of
the guide tube can be easily mounted as a
sandwich flange between vessel and sensor
flange.
Connections to the bypass tube
The connections to the bypass tubes must
be fashioned in such a way that only minimal
reflections are caused by the walls of the
connecting tubes. This is especially important
for the breather connection in the upper part
of the tube. Observe the following points:
• Use small openings for the connection.
• The diameter of the connecting tubes
should not exceed 1/3 of the bypass diam-
eter.
• The tube connections must not protrude
into the bypass tube.
• Large welding beads in the tubes should
be avoided.
• Additional connections to the bypass tube
must lie in the same plane as the upper
and lower vessel connection (above each
other or displaced by 180°).
Mounting and installation
Optimum connection to the bypass tube