KROHNE UFM 600T EN - Manual (Page 22)

C.1.1 Installation of mounting rails
Mounting Considerations:
The pipe section on which the transducers will be clamped
must always be completely filled with liquid, even if there is
no flow.
The transducers can be fitted on both horizontal and vertical
pipe sections (or any other elevation).
On horizontal pipes the transducers should be fitted such
that the ultrasonic pulse travels approximately horizontally
through the pipe since gas/vapour at the top of the pipe or
any contamination at the bottom can cause an obstruction to
the ultrasonic pulses.
The solid or gas content of the liquid must not exceed 1 per-
cent by volume.
Note that, due to cavitation, bubbles can appear behind
valves, pumps etc., so the transducers should not be
installed too closely to these positions.
The absolute minimum distances are given in the table
below.
Highly distorted flow profiles may require significantly longer
straight upstream lengths.
Upstream straight length
- when mounted behind a pump
≥ 15 x DN
- when mounted behind a fully opened valve
≥ 10 x DN
- when mounted behind one or more elbows
≥ 10 x DN
- when mounted behind a reduction
α/2,7° ≥ 5 x DN
Downstream straight length
≥ 5 x DN
(DN: Nominal Diameter)
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