Panametrics DigitalFlow XGF868i, Руководство по обслуживанию

Страница: 27 / 72

DigitalFlow™ XGF868i Service Manual 19
Chapter 3. Diagnostics
3.3 Flowcell Problems
If preliminary troubleshooting with the Error Code Messages and/or the Diagnostic Parameters indicates a possible
flowcell problem, proceed with this section. Flowcell problems fall into two categories:
• Gas problems
• Pipe problems
Read the following sections carefully to determine if the problem is indeed related to the flowcell. If the instructions in
this section fail to resolve the problem, contact the factory for assistance.
3.3.1 Gas Problems
Most gas-related problems result from a failure to observe the flowmeter system installation instructions, as
described in the Startup Guide . Refer to Chapter 1, Installation , of the Startup Guide to correct any installation
problems.
If the physical installation of the system meets the recommended specifications, it is possible that the gas itself may
be preventing accurate flow rate measurements. The gas being measured must meet the following requirements:
1. The gas must be homogeneous, single-phase and relatively clean.
Although a low level of entrained particles may have little effect on the operation of the XGF868i, excessive
amounts of solid or liquid particles will absorb or disperse the ultrasound signals. This interference with the
ultrasound transmissions through the gas will cause inaccurate flow rate measurements. In addition,
temperature gradients in the gas flow may result in erratic or inaccurate flow rate readings.
2. The gas must not excessively attenuate ultrasound signals.
Some gases (i.e. high-purity carbon dioxide, hydrogen, nitrogen, etc.) readily absorb ultrasound energy. In such a
case, an E1 error code message will appear on the display screen to indicate that the ultrasonic signal strength is
insufficient for reliable measurements.
3. The gas sound speed must not vary excessively.
The XGF868i will tolerate relatively large changes in the gas sound speed, as may be caused by variations in gas
composition and/or temperature. However, such changes must occur slowly. Rapid fluctuations in the gas sound
speed, to a value that is considerably different from that programmed into the XGF868i, will result in erratic or
inaccurate flow rate readings. Refer to Chapter 2, Initial Setup , of the Startup Guide and make sure that the
appropriate sound speed is programmed into the meter.
3.3.2 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 Panametrics, 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
Vinst Displays the instantaneous velocity. N.A. N.A.
1
available only if Burst Mode = S/M
Table 3: Available Diagnostic Parameters
Option Bar Description Good Bad