Panametrics DigitalFlow XMT868i, Руководство по обслуживанию

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Chapter 3. Diagnostics
6 DigitalFlow™ XMT868i Service Manual
3.4 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: fluid problems or 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 GE for assistance.
3.4.1 Fluid Problems
Most fluid-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 fluid itself may
be preventing accurate flow rate measurements. The fluid being measured must meet the following requirements:
1. The fluid must be homogeneous, single-phase, relatively clean and flowing steadily. Although a low level of
entrained particles may have little effect on the operation of the Model XMT868i, excessive amounts of solid or
gas particles will absorb or disperse the ultrasound signals. This interference with the ultrasound transmissions
through the fluid will cause inaccurate flow rate measurements. In addition, temperature gradients in the fluid
flow may result in erratic or inaccurate flow rate readings.
2. The fluid must not cavitate near the flowcell. Fluids with a high vapor pressure may cavitate near or in the
flowcell. This causes problems resulting from gas bubbles in the fluid. Cavitation can usually be controlled
through proper installation design.
3. The fluid must not excessively attenuate ultrasound signals.
Some fluids, particularly those that are very viscous, 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.
4. The fluid sound speed must not vary excessively.
The Model XMT868i will tolerate relatively large changes in the fluid sound speed, as may be caused by variations
in fluid composition and/or temperature. However, such changes must occur slowly. Rapid fluctuations in the
fluid sound speed, to a value that is considerably different from that programmed into the XMT868i, 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.