3 General principles
FLUXUS F501
3.4 Undisturbed flow profile
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UMFLUXUS_F501V1-3EN, 2020-06-30
Free inlet or outlet pipe section
Select the measuring point at a pipe section where the pipe cannot run empty, see Fig. 3.13 and Fig. 3.14.
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 disturbances. 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 distance to disturbances cannot be met for practical reasons (no ideal inflow, see section 16.5).
The recommended straight inlet and outlet pipe lengths for different types of flow disturbance sources are shown in the examples
in Tab. 3.1.
Fig. 3.13: Recommended transducer
mounting position
Fig. 3.14: Disadvantageous transducer
mounting position
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 × 90° elbows on different planes
inlet: l ≥ 40 D
outlet: l ≥ 5 D
l
l
l
l