3 General principles
3.4 Undisturbed flow profile
FLUXUS F60*
2017-10-16, UMFLUXUSF60xV5-0EN
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3.4
Undisturbed flow profile
Some flow elements (e.g., elbows, valves, pumps, reducers) distort the flow profile in
their vicinity. The axisymmetrical flow profile in the pipe needed for correct measurement
is no longer given. A careful selection of the measuring point helps to reduce the impact
of disturbance sources.
It is most important that the measuring point is chosen at a sufficient distance from any
disturbance sources. Only then it can be assumed that the flow profile in the pipe is fully
developed. However, measuring results can be obtained even if the recommended dis-
tance to disturbance sources cannot be met for practical reasons.
The recommended straight inlet and outlet pipe lengths for different types of flow distur-
bance sources are shown in the examples in Tab. 3.1.
Tab. 3.1:
Recommended distance from disturbance sources
D – nominal pipe diameter at the measuring point
l – recommended distance between disturbance source and transducer position
disturbance source: 90° elbow
inlet: l
≥
10 D
outlet: l
≥
5 D
disturbance source: 2 x 90° elbows on different levels
inlet: l
≥
40 D
outlet: l
≥
5 D
l
l
l
l