Flowcell Problems; Fluid Problems - GE AquaTrans AT868 User Manual

September 2004

Flowcell Problems

Fluid Problems

6-6
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
•
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.
Most fluid-related problems result from a failure to observe the
flowmeter system installation instructions, as described in
Installation. Refer to Chapter 1, Installation, 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 AT868, 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 AT868 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
AT868, will result in erratic or inaccurate flow rate readings.
Refer to Chapter 2, Programming Site Data, to make sure that the
appropriate sound speed is programmed into the meter.
Diagnostics