Tokyo Keiki UFL-30, Installation & Operation Manual

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4.9 What are ‘Z’ and ‘V’ methods of measurement?
These refer to transducer placements. The Z (through-transmission or single-traverse) method is
where the transducers are mounted diametrically opposite each other and the ultrasonic signal is
transmitted directly from one transducer to the other across the pipe. This method is used when
the pipe is of adequate diameter or for pipes where acoustic signals are greatly reduced.
With the V (reflection or double traverse) method transducers are mounted on the same side of the
pipe and the ultrasonic signal is bounced from one transducer to the other off the opposite pipe wall.
This method is devised to measure flows that are not linear with the pipe axis and which are not
affected by radial flow velocity components.
The applicable diameters for the V method depends
on pipe material but is generally less than ø2,000mm.
See Chapter III-3-2 for more detail on the through transmission and reflection methods.
4.10 What are single path and dual path methods of measurement?
Single path is the standard method of measurement. With the Z method, transducers are mounted
opposite side of the pipe as shown in Fig. 3-5-2.
With dual path measurement, two pairs of transducers (4 pcs) are mounted on the pipe as shown
in Fig. 3-5-3. Compared to single path measurement of flow velocity along 1 path (diametrical
axis), the dual path method measures flow velocity along 2 paths (diametrical axis) as shown in Fig.
9-3. The values of the two flow velocity measurements obtained are averaged to lessen the affect
of distortions in flow velocity distribution over the pipe cross section providing more stable
measurements.
With four path measurement, four pairs (8 pcs) of transducers are mounted on the pipe to provide
measurement along 4 paths (diametrical axis) and the average of each measuring velocity is taken,
the affect of flow velocity distribution distortions are further lessened.
Top
Bottom
Side
V
Opposite
Fig. 3-5-2
Opposite
V
Fig. 3-5-3
Top
Bottom