Chapter 3 Measurements site selection
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Chapter 3 Measurement site selection
When selecting a measurement site, it is important to select an area where the
fluid flow profile is fully developed to guarantee a highly accurate measurement.
Use the following guidelines to select a proper installation site: Choose a section
of pipe that is always full of liquid, such as a vertical pipe with flow in the upward
direction or a full horizontal pipe. Ensure enough straight pipe length at least equal
to the figure shown below for the upstream and downstream transducers
installation.
Select a fluid-filled section, such as a vertical section of the line (upward flow
is preferred) or a horizontal section filled with fluid.
The measuring point should be within 10 diameters (10D) of the upstream
and 5 diameters (5D) of the downstream, without any devices such as valves,
elbows and diameters interfering with the flow field.The length of straight pipe
is recommended as shown in FIG. 6.
On the horizontal pipe section, the sensor should be installed at 9 o 'clock
and 3 o 'clock of the pipe and should avoid the position at 6 o 'clock and 12 o
'clock, so as to avoid the attenuation of the signal caused by the sediment at
the bottom of the pipe or the bubbles and cavitation at the top of the pipe.
Make sure the temperature at the measuring point is within the working range.
Full consideration should be given to the condition of scale formation on the
inner wall of the pipe, and the tube section without scale should be selected
for measurement as far as possible. If it cannot be completely satisfied, the
scale formation should be considered as the lining in order to obtain better
measurement accuracy.
Select the tube segment with uniform density and easy ultrasonic
transmission.
Ensure that the pipe surface temperature at the measuring point is within the
transducer temperature limits. Consider the inside condition of the pipe carefully. If
possible, select a section of pipe where the inside is free of excessive corrosion or
scaling.
