Flexim FLUXUS F704**-A2 Series, User Manual

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19 Troubleshooting FLUXUS F70x
UMFLUXUS_F7V4-6-2EN, 2017-10-01 163
19.1 Problems with the Measurement
A measurement is impossible because no signal is received. A question mark is displayed in the lower line on the
right
• Check if the entered parameters are correct, especially the outer pipe diameter, the pipe wall thickness and the sound
speed of the medium. (Typical errors: The circumference or the radius was entered instead of the diameter. The inner
pipe diameter was entered instead of the outer pipe diameter.)
• Make sure that the recommended transducer distance was adjusted when mounting the transducers.
• Make sure that an appropriate measuring point has been selected (see section 19.2).
• Try to establish better acoustic contact between the pipe and the transducers (see section 19.3).
• Enter a lower value for the number of sound paths. The signal attenuation might be too high due to a high medium vis-
cosity or deposits on the inner pipe wall (see section 19.4).
The measuring signal is received but no measured values can be obtained
• An exclamation mark "
!
" in the lower line on the right indicates that the defined upper limit of the flow velocity is exceed-
ed and, therefore, the measured values are marked as invalid. The limit has to be adapted to the measuring conditions or
checking has to be deactivated (see section 11.4).
• If no exclamation mark "
!
" is displayed, a measurement at the selected measuring point is not possible.
Loss of signal during the measurement
• If the pipe had run empty: Was there no measuring signal afterwards? Contact FLEXIM.
• Wait briefly until acoustic contact is reestablished. The measurement can be interrupted by a temporarily higher propor-
tion of gas bubbles and solids in the medium.
The measured values substantially differ from the expected values
• Wrong measured values are often caused by wrong parameters. Make sure that the entered parameters are correct for
the measuring point.
• If the parameters are correct, see section 19.5 for the description of typical situations in which wrong measured values
are obtained.
19.2 Selection of the Measuring Point
• Make sure that the recommended min. distance to any disturbance source is observed (see chapter 5, Tab. 5.2).
• Avoid measuring points with deposit formation in the pipe.
• Avoid measuring points in the vicinity of deformations and defects on the pipe and in the vicinity of welds.
• Measure the temperature at the measuring point and make sure that the transducers are suitable for this temperature.
• Make sure that the outer pipe diameter is within the measuring range of the transducers.
• When measuring on a horizontal pipe, the transducers have to be mounted on the side of the pipes.
• A vertical pipe always has to be filled at the measuring point and the medium should flow upward.
• No gas bubbles should form (even bubble-free media can form gas bubbles when the medium expands, e.g., upstream
of pumps and downstream of great cross-section enlargements).