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FDT-25 Handheld Ultrasonic Flowmeter
examples of optimum locations.
Principles to selection of an optimum location
(1) Install the transducers on a longer length of the straight pipe. The longer the better, and make
sure that the pipe is completely full of liquid.
(2) Make sure that the temperature on the location does not exceed the range for the transducers.
Generally speaking, the closer to the room temperature, the better.
(3) Take the pipe fouling into consideration. Select a straight length of a relatively newer pipe. If
the condition is not satisfying, consider the fouling thickness as part of the liner for a better result.
(4) Some pipes have a kind of plastic liner, and between the outer pipe and the liner there may be a
certain thickness difference that will prevent the ultrasonic waves from direct traveling. Such conditions
will make the measurement very difficult. Whenever possible, try to avoid this kind of pipes. If
impossible, try our plug-in transducers that are installed permanently on the pipe by drilling holes
on the pipe while liquid is running inside.
§2.8 Transducers Installation
The transducers used by the series ultrasonic flow meter are made of piezoelectric crystals both for
transmitting and receiving ultrasonic signals through the wall of liquid piping system. The
measurement is realized by measuring the traveling time difference of the ultrasonic signals. Since
the difference is very small, the spacing and the alignment of the transducers are critical factors to
the accuracy of the measurement and the performance of the system. Meticulous care should be taken
for the installation of the transducers.
Steps to the installation of the transducers
(1) Locate an optimum position where the straight pipe length is sufficient, and where pipes are in
a favorable condition, e.g., newer pipes with no rust and ease of operation.
(2) Clean any dust and rust. For a better result, polishing the pipe with a sander is strongly recommended.
(3) Apply adequate coupler to the spot where the transducers are to be installed and leave no gap
between the pipe surface and the transducers.
Extra care should be taken to avoid any sand or dust particles left between the pipe outer surface
and the transducers.
To avoid gas bubbles inside the upper part of the pipe, the transducers should be installed horizontally
by the side of the pipe.
§2.8.1 Transducers Spacing
The spacing value shown on menu window M25 refers to the distance of inner spacing between
the two transducers. The actual transducers spacing should be as close as possible to the spacing
value.
§2.8.2 V-method Installation
V-method installation is the moswidely used mode for daily measurement with pipe inner diameters
ranging from 20 millimeter to 300 millimeter. It is also called reflective mode or method.
