KATflow 150
3 Installation
3.2
Clamp-on sensor installation
The correct selection of the sensor location is crucial for achieving reliable meas-
urements and high accuracy. Measurement must take place on a pipe in which
sound can propagate (see Acoustic propagation) and in which a rotationally sym-
metrical flow profile is fully developed (see Straight pipe lengths).
The correct positioning of the transducers is an essential condition for error-free
measurements. It ensures that the sound signal will be received under optimal con-
ditions and evaluated correctly. Because of the variety of applications and the differ-
ent factors influencing the measurement, there can be no standard solution for the
positioning of the transducers.
The correct position of the transducers will be influenced by the following factors:
diameter, material, lining, wall thickness and general condition of the pipe,
the medium flowing in the pipe,
the presence of gas bubbles and solid particles in the medium.
Check that the temperature at the selected location is within the operating temper-
ature range of the transducers (see Specification).
After the sensor location has been selected, make sure that that supplied cable is
long enough to reach the flow transmitter mounting location. Ensure that the tem-
perature at the selected location is within the ambient operating temperature range
of the flow transmitter (see Specification).
Acoustic propagation is achieved when the flowmeter is able to receive sufficient
signal from the transmitted ultrasonic pulses. The signals are attenuated in the
pipe material, the medium and at each of the interfaces and reflections. External
and internal pipe corrosion, solid particles and gas content in the medium contribute
heavily to signal attenuation.
Sufficient straight lengths of pipe on the inlet and outlet of the measuring location
ensure an axi-symmetrical flow profile in the pipe, which is required for good meas-
urement accuracy. If insufficient straight lengths of pipe are available for your ap-
plication measurements are still obtainable, but the certainty of the measurement
can be reduced.
3.3
Installation location
Select an installation location following the recommendations in Table 1 and try to
avoid measuring
in the vicinity of deformations and defects of the pipe,
near welding seams,
where deposits could be building up in the pipe.
For a horizontal pipe:
Select a location where the transducers can be mounted on the side of the pipe, so that the sound waves emitted by
the transducers propagate horizontally in the pipe. In this way, the solid particles deposited on the bottom of the pipe
and the gas pockets developing at the top will not influence the propagation of the signal.
Correct
Incorrect
10
Acoustic propagation
Straight pipe lengths
