168 UMG70XV3-4EN 12.01.2009
19 Troubleshooting
19.3 Maximum Acoustic Contact
Observe the points in section 10.7.
19.4 Application Specific Problems
The entered sound velocity of the medium is wrong
The entered sound velocity will be used to calculate the transducer distance and, thus, is
very important for the transducer positioning. The sound velocities programmed in the
flowmeter only serve as orientation values.
The entered pipe roughness is not appropriate
Check the entered value, taking into account the state of the pipe.
Measurements on porous pipe materials (e.g. concrete or cast iron) are only possi-
ble under certain conditions
Contact FLEXIM.
The pipe liner may cause problems during measurement if it is not attached tightly
to the inner pipe wall or consists of acoustically absorbing material
Try measuring on a liner free section of the pipe.
Higher proportions of droplets or solids in the medium scatter and absorb the ul-
trasound and therefore attenuate the measuring signal
A measurements is impossible if the value is 10 %. If the proportion is high, but < 10 %,
a measurement might be possible under certain conditions.
19.5 High Measuring Deviations
The entered sound velocity of the medium is wrong
A wrong sound velocity can result in the ultrasonic signal reflected on the pipe wall being
mistaken for the measuring signal passing the medium. The flow calculated from the
wrong signal by the flowmeter is very small or fluctuates around zero.
The defined upper limit of the flow velocity is too low
All measured flow velocities that are greater than the upper limit will be ignored and
marked as invalid. All quantities derived from the flow velocity are marked as invalid, too.
If several correct measured values are ignored, the totalizer values will be too low.
The entered cut-off flow is too high
All flow velocities below the cut-off flow are set to zero. All derived values are set to zero
as well. The cut-off flow (default 2.5 cm/s) has to be set to a low value to be able to mea-
sure at low flow velocities.
The entered pipe roughness is inappropriate
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