Pipe Problems - GE AquaTrans AT868 User Manual

Pipe Problems

Diagnostics
Pipe-related problems may result either from a failure to observe the
installation instructions, as described in Chapter 1, Installation or
from improper programming of the meter. By far, the most common
pipe problems are the following:
1. The collection of material at the transducer location(s).
Accumulated debris at the transducer location(s) will interfere
with transmission of the ultrasound signals. As a result, accurate
flow rate measurements are not possible. Realignment of the
flowcell or transducers often cures such problems, and in some
cases, transducers that protrude into the flow stream may be used.
Refer to Chapter 1, Installation, for more details on proper
installation practices.
2. Inaccurate pipe measurements.
The accuracy of the flow rate measurements is no better than the
accuracy of the programmed pipe dimensions. For a flowcell
supplied by GE Infrastructure Sensing, the correct data will be
included in the documentation. For other flowcells, measure the
pipe wall thickness and diameter with the same accuracy desired
in the flow rate readings. Also, check the pipe for dents,
eccentricity, weld deformity, straightness and other factors that
may cause inaccurate readings. Refer to Chapter 2, Programming
Site Data, for instructions on programming the pipe data.
In addition to the actual pipe dimensions, the path length (P) and
the axial dimension (L), based on the actual transducer mounting
locations, must be accurately programmed into the flowmeter. For
a GE Infrastructure Sensing flowcell, this data will be included
with the documentation for the system. If the transducers are
mounted onto an existing pipe, these dimensions must be precisely
measured. See Appendix D, Measuring P and L Dimensions, for a
thorough discussion of this topic.
3. The inside of the pipe or flowcell must be relatively clean.
Excessive build up of scale, rust or debris will interfere with flow
measurement. Generally, a thin coating or a solid well-adhered
build up on the pipe wall will not cause problems. Loose scale and
thick coatings (such as tar or oil) will interfere with ultrasound
transmission and may result in incorrect or unreliable
measurements.
September 2004
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