Panametrics DigitalFlow XMT868i, Руководство по обслуживанию, Страница: 31 / 74

DigitalFlow™ XMT868i Service Manual 7
Chapter 3. Diagnostics
3.4.2 Pipe Problems
Pipe-related problems may result either from a failure to observe the installation instructions, as described in the
Startup Guide , 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 , of the Startup Guide 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, 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, Initial Setup , of the Startup Guide 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 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 C, Measuring P and L Dimensions , of the Startup
Guide 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.