Tokyo Keiki UFL-30, Руководство по установке и эксплуатации

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III- 47
III-5-2. Measured fluids
2.1 Measured fluids
In principle, any liquid, which allows stable propagation of ultrasonic waves, can be measured.
However in liquids where large amounts of air bubbles or solid particles are present, problems such
as mis-measurements or non-measurable conditions may occur. As high temperature and high
pressure liquids (oil, etc.) cannot be described categorically, consult manufacturer or local
representatives when measuring such liquids.
2.2 Can raw water be measured?
River water and raw water can be measured in addition to clean water.
2.3 In the case of raw water, how does turbidity affect measurement?
Two separate questions arise with regard to this.
(1) Do changes in turbidity produce measurement error?
(2) Does high turbidity attenuate acoustic signals creating non-measurable conditions?
Regarding (1), if the penetration of acoustic signals is adequate, changes in turbidity does not
normally cause errors.
Regarding (2), although related to attenuation of acoustic signals by solid particles in the liquid,
exceedingly high levels of turbidity does cause reduction in signal. Tokyo Keiki specifies turbidity
levels up to 10,000 in the case of a pipe diameter of 1m. (Note: turbidity of 1g of refined Kaolin
clay in 1 litter of water is 1,000.)
Turbidity of 5,000 is quite severe, but as turbidity of river water rarely exceeds 1,000, there should
be no problem for all practical purposes.
2.4 How is measurement affected if air enters the pipe?
(1) Compared to water, air is a very difficult medium for the transmission of acoustic signals.
Therefore when pumps continuously draw air into the piping, air bubbles will pass through the
acoustic signal transverse path resulting in measurement swings or mis-measurements.
(2) Also in cases where the depth of the tap from the water surface to the top
of the pipe at the intake location is insufficient, air will be sucked into the pipe and may cause
mis-measurements or create non-measurable conditions.
(3) If air accumulates at the upper part of the pipe
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although flow measurement can
be carried out, the flow indicated will be larger than the actual flow. (Note: If the sensors are
located vertically on the pipe, measurement cannot be done if there is a layer of air in the
pipe.) Thus, in cases where there may be accumulation of air in pipes, air bleed valves
should be installed fore and aft of the measurement position.