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Flowcell Problems
Fluid Problems
Diagnostics
If preliminary troubleshooting with the Error Code Messages and/or
the Diagnostic Menu indicates a possible flowcell problem, proceed
with this section. Flowcell problems fall into two categories:
•
liquid 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 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 and relatively clean.
Although a low level of entrained particles may have little effect
on the operation of the Model DF868, 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
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 DF868 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
Model DF868, 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.
March 2008
E1
error code message
3-5
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