FLOW 32 manual
Page 4 (total 18)
COMAC CAL s.r.o.
Installation in pipeline
Important information for selection of location
Outdoor conditions
It is necessary to ensure that the flow sensor is not exposed to weather effects and that the
measured medium cannot freeze in the flow sensor as it would damage the measuring tube.
In case of outdoor location of the flow meter, the manufacturer recommends using a
protective box or a roof to avoid direct solar exposure so that the meter cannot get overheated.
Sources of disturbances
The following items rank among the most frequent sources of disturbances to the steady flow
of liquid:
•
Abrupt changes in pipe cross-section if not performed as a cone with an angle of
7°
(where
is the angle made by bevelled walls of the pipe reduction).
•
Incorrectly centred sealing, low ID sealing or sealing made of soft elastic materials
which are pushed out into the interior pipe cross-section after flanges are tightened.
•
Anything interfering in the flow of liquid, for example thermowells, branch pipes, T-
pieces, bends, elbows, slide valves, cocks, flap valves, shut-off valves, control valves,
butterfly valves and check valves. Pipe outlets from tanks, heat exchangers and filters.
•
No intensive magnetic fields in the proximity of the induction flow sensor (detector)
must be present.
No sources of disturbances
affecting the steady flow must be present in the straight pipeline
sections. They must be located in the piping after the flow sensor or at the farthest distance
before it. Sources of disturbances may substantially reduce the measuring range and accuracy
of the flow meters.
Vibration
We recommend supporting the connecting pipes on both sides of the meter for partial
elimination of vibrations. Levels and range of vibrations must be under 2.2 in the frequency
range of 20 ÷ 50 Hz according to IEC 068-2-34.
Actual location
The flow sensor (detector) must not be at the top position of the pipe which may be airlocked,
or in declining or even in horizontal pipelines with open ends in which air may penetrate.
Impurities may accumulate during long-term measurement of very low flow rates Q < 0.1
m/sec. There must be a sufficient pressure in the place of flow sensor installation so that the
expulsion of gas or vapour bubbles from the liquid is avoided. Little bubbles that always
occur in liquids may accumulate at any of the electrodes and this may result in incorrect
operation of the meter. Gas bubbles are expelled also at an abrupt pressure drop. Therefore,
butterfly valves and similar elements should be located
after the flow sensor
. For the same
reason, the flow sensor should not be placed at the suction side of the pump. To prevent the
bubbles from accumulation at a low flow in the flow sensor, it is suitable, e.g. that the pipe is
slightly ascending or that the flow sensor is located in the vertical section of the pipeline.
