5-2
1010PVNFM-3A
Section 5
5.3 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. Nevertheless, all are usually acceptable. Unsuitable pipes in-
clude 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.
5.3.1 PIPE DIMENSIONS
Controlotron manufactures transducer assemblies to service pipes from 0.25" to 360" in outer
diameter. During the transducer install procedure, the flow computer will recommend trans-
ducer 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).
5.3.2 PICKING THE APPROPRIATE TRANSDUCER
To ensure that you select the appropriate transducers for your application, consider the pipe
outer diameter, 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 configu-
ration for greater accuracy and flow profile aberration immunity.
Initial transducer size recommendations are based on your pipe outer diameter, wall thick-
ness and pipe material entries. However, you can override the meter recommendations to
accommodate specific situations. 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 trans-
ducers). 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.
5.3.3 FLOW VELOCITY RANGE
System 1010’s 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.
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