Table of Contents
Advertisement
Section 5
1020NFM-1D
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 include concrete or other non-homoge-
neous 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
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 com-
puter 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 indepen-
dent 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 spe-
cific 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 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.
5.3.3 FLOW VELOCITY RANGE
±
System 1020'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. For optimum accuracy at
very low flow rates and for small line sizes, consider using our 992DFT or 1011FT flow tubes.
5.3.4 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
5-2
Advertisement
Table of Contents
