GF PORTAFLOW 330, Инструкция по эксплуатации

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Instrction manual Installation
13
Diagonal mode
This mode might be selected by the instrument
where relatively large pipes are concerned. In
this mode the transducers are located on
opposite sides of the pipe but the separation
distance is still critical in order for the signals
to be received correctly. This mode might be
used with the standard ‘A’ & ‘B’ transducer
sets but for really large pipe installation the
optional transducer set ‘D’ might be
recommended.
6 Installation
6.1 Transducer Positioning
In many applications an even flow velocity profile over a full 360° is unattainable due, for
example, to the presence of air turbulence at the top of the flow and possibly sludge in the
bottom of the pipe. Experience has shown that the most consistently accurate results are
achieved when the transducer guide rails are mounted at 45° with respect to the top of the
pipe.
The Portaflow equipment expects a uniform flow profile as a distorted flow will produce
unpredictable measurement errors. Flow profile distortions can result from upstream
disturbances such as bends, tees, valves, pumps and other similar obstructions. To ensure a
uniform profile the transducers must be mounted far enough away from any cause of
distortion such that it no longer has an effect. Montage
To obtain the most accurate results the condition of both the liquid and the pipe wall must be
suitable to allow the ultrasound transmission along its predetermined path. It is important
also that the liquid flows uniformly within the length of pipe being monitored and that the flow
profile is not distorted by any upstream or downstream obstructions. This is best achieved by
ensuring there is a straight length of pipe upstream of the transducers of at least 20 times
the pipe diameter and 10 times the pipe diameter on the downstream side. Flow
measurements can be made on shorter lengths of straight pipe, down to 10 diameters
upstream and 5 diameters downstream, but when the transducers are positioned this close to
any obstruction the resulting errors can be unpredictable.