Siemens SITRANS FUH1010PVDX, Руководство по эксплуатации, Страница: 92 / 308

4-2
CQO:1010PVXFM-3 Section 4
4.3 PIPE CONSIDERATIONS FOR CLAMP-ON TRANSDUCER
Clamp-on flow transducers operate on any round pipe that conducts sound. Suitable pipe materials
include most metals, plastics, glass and mandrel wound FRP. Pipes with a fine grain structure (e.g.,
carbon and stainless steel) conduct sound more freely than cast iron, ductile iron or copper pipes. Nev-
ertheless, all are usually acceptable. Unsuitable pipes include concrete or other non-homogeneous
materials. Pipe liners are acceptable if they are sonically conductive and bonded solidly to the inner wall
of the pipe. The system operates successfully on pipes with cement liners that are “spun” onto the pipe
interior to exclude any air bubbles. Pipes with smoothly applied bituminous and epoxy coatings are also
acceptable. Plastic liners are universally acceptable, if they are in intimate contact with the inner wall and
not merely slipped within the pipe.
4.3.1 PIPE DIMENSIONS
Siemens manufactures transducer assemblies to service pipes from 0.25" to 360" in outer diameter.
During the transducer install procedure, the flow computer will recommend transducer sizes based on
the site data that you enter. Pipes with OD-to-Wall thickness (OD/W) ratios greater than 10 to 1 are ideal
applications. Operation on pipes with OD/W ratios of 7 to 1 (or less) are acceptable, but may exhibit
reduced stability and linearity. Generally, higher OD/W ratios provide better stability. If a pipe has a low
OD/W ratio, you should use the smaller of the recommended transducer sizes (if the flow computer
recommends two transducer sizes).
4.3.2 PICKING THE APPROPRIATE TRANSDUCER
To ensure that you select the appropriate transducers for your application, consider the pipe outer diam-
eter, temperature range and degree of precision required. Decide whether you need two independent
flow channels or if you have to operate the system in dual-path configuration for greater accuracy and
flow profile aberration immunity.
Initial transducer size recommendations are based on your pipe outer diameter, wall thickness and pipe
material entries. However, you can override the meter recommendations to accommodate specific situ-
ations. For example, you may own a set of transducers whose size does not appear on the meter list.
You may be able to use transducers on a pipe size outside of their nominal pipe OD range. During
transducer install, the flow computer recommends Spacing Indices (for spacer bars and mounting tracks)
or
Ltn, (actual distance required between transducers). Once you mount transducers and invoke the
install routine, you can determine the suitability of your transducers by checking the signal strength and
comparing the reported sonic velocity with the actual sonic velocity of the liquid to be measured.
NOTE: Transducer pairs must have matching serial numbers.
4.3.3 FLOW VELOCITY RANGE
The FUH1010 flow velocity range with clamp-on transducers is at least
±
40 ft/sec regardless of the
diameter of the pipe. Depending on application conditions, this range can extend to over 100 ft/sec. This
measurement range is greater than needed for virtually any application. For optimum accuracy at very
low flow rates and for small line sizes, consider using our 992DFT or 1011FT flow tubes.
4.3.4 OVERVIEW OF SYSTEM PERFORMANCE
Our system performance specifications are based on acceptable liquid sonic conductivity and other
pertinent application conditions. The diversity that characterizes liquid flow, makes it impossible for us to
cover all possible application conditions that have the potential to reduce performance. Performance
within specifications depends primarily on the receive signal’s signal-to-noise ratio and amplitude.