5 Selection of the Measuring Point
UMFLUXUS_G8V4-6-1EN, 2018-10-10
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5
Selection of the Measuring Point
The correct selection of the measuring point is crucial for achieving reliable measurement results and a high measurement
accuracy.
A measurement on a pipe is possible if
• the ultrasound propagates with a sufficiently high amplitude (see section 5.1)
• the flow profile is fully developed (see section 5.2)
• the influence of noise is sufficiently low (see section 5.3)
The correct selection of the measuring point and thus, the correct transducer positioning guarantees that the sound signal
will be received under optimum conditions and evaluated correctly.
Due to the variety of applications and the different factors that influence the measurement, there is no standard solution for
the transducer positioning. The correct position of the transducers is influenced by the following factors:
• diameter, material, lining, wall thickness and shape of the pipe
• fluid
Avoid measuring points in the vicinity of deformations and defects of the pipe and in the vicinity of welds.
Avoid locations with deposit formation in the pipe.
The ambient temperature at the measuring point has to be within the operating temperature range of the sensors (see
Technical Specification).
Select the location of the transmitter within the range of the cable of the measuring point.
The ambient temperature at the measuring point has to be within the operating temperature range of the transmitter and
the sensor (see Technical Specification).
If the measuring point is within an explosive atmosphere, the danger zone and gases that may be present have to be de-
termined. The transducers and the transmitter have to be appropriate for these conditions.
5.1
Acoustic Penetration
The pipe has to be acoustically penetratable at the measuring point. The acoustic penetration is reached when pipe and
fluid do not attenuate the sound signal so strongly that it is completely absorbed before reaching the second transducer.
The attenuation in the pipe and in the fluid depends on:
• kinematic viscosity of the fluid
• the proportion of liquids and solids in the fluid
• deposits on the inner pipe wall
• pipe material
The following requirements have to be met at the measuring point:
• no material deposits in the pipe
• no accumulation of liquid (condensate), e.g., before orifice plates or at pipe sections located lower
Observe the notes in the following table:
Attention!
Observe the "Safety Instructions for the Use in Explosive Atmosphere" (see document SIFLUXUS).
Tab. 5.1: Recommended transducer mounting position
horizontal pipe
Select a measuring point where the transducers can be mounted on the side of the pipe, allowing the sound waves to
propagate in the pipe horizontally. By doing this, the solid or liquid deposits on the bottom of the pipe or gas bubbles in
the pipe's upper part are prevented from influencing the propagation of the signal.
correct:
disadvantageous:
