3 General principles
3.6 Selection of the measuring point taking into account the flow profile and the influence of noise
FLUXUS G809
2020-06-25, UMFLUXUS_G809V2-2EN
20
Example
fluid: natural gas,
c
γ
= 400 m/s
pipe material: stainless steel,
c
β
= 3000 m/s
length of pipe segment 1: 20 D
length of pipe segment 2: 5 D
number of sound paths: 2
l
s
= 7.5 D
• area with developed flow profile:
disturbance source: 90° elbow
recommended area for the measuring point: l ≥ 10 D (complete pipe segment 2)
• area with low influence of noise:
reflection point: flange
recommended area for the measuring point: l ≥ 3 D and outside of l
S
= (7.5 ± 2) D on pipe segment 1
Fig. 3.13: Area for the measuring point with low influence of noise and not fully developed flow profile
In the example, there is no area where both demands are met at the same time. The measuring point has to be selected
as far as possible from the elbow, at a point where the influence of noise can be neglected: 3...(7.5 - 2) D on the right
side of pipe segment 1. In the example, a distance of 16 D from the elbow was selected.
20 D
5 D
16 D
(7.5 - 2) D
3 D
disadvantageous measuring range
10 D
