5 Selection of the Measuring Point FLUXUS G80x
UMFLUXUS_G8V4-6-1EN, 2018-10-10 23
5.4 Selection of the Measuring Point Taking into Account the Flow Profile and the Influ-
ence of Noise
• Select an area on the pipe where the flow profile is fully developed (see section 5.2).
• Select the measuring point within this area so that the influence of noise can be neglected (see section 5.3).
Example:
fluid: natural gas
pipe material: stainless steel
c
P
: 3000 m/s
c
F
: 400 m/s
number of sound paths: 2
l
S
= 7.5 D
The range (7.5 ± 2) D is disadvantageous for the transducer installation.
example: fluid: natural gas
pipe material: stainless steel
length of pipe segment 1: 20 D
length of pipe segment 2: 20 D
number of sound paths: 2
• area with developed flow profile:
disturbance source: 90° elbow
recommended area for the measuring point: l ≥ 20 D (complete pipe segment 2) (see Tab. 5.2)
• area with low influence of noise:
reflection point: flange
recommended area for the measuring point: l ≥ 3 D and outside of l = (7.5 ± 2) D on pipe segment 2 (see Tab. 5.2)
Fig. 5.2: Area for the measuring point with a favorable flow profile and low influence of noise
Considering flow profile and influence of noise, the measuring point can be selected in the area 3...(7.5 - 2) D on the right
side of pipe segment 2 (with max. distance from the elbow).
In the example, a distance of 36 D from the elbow was selected.
Tab. 5.3: Measuring points to be avoided
20 D 20 D
36 D
(7.5 - 2) D
3 D
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