Flexim FLUXUS F704**-A2 Series, User Manual

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FLUXUS F70x 19 Troubleshooting
164 UMFLUXUS_F7V4-6-2EN, 2017-10-01
19.3 Maximum Acoustic Contact
Observe the instructions in chapter 6.
19.4 Application Specific Problems
The entered sound speed of the medium is wrong
The entered sound speed is used to calculate the transducer distance and is therefore very important for the transducer
positioning. The sound speeds stored in the transmitter only serve as orientation.
The entered pipe roughness is not appropriate
Check the entered value. The state of the pipe should be taken into account.
Measurements on porous pipe materials (e.g., concrete or cast iron) are only possible under certain conditions
Contact FLEXIM.
The pipe lining may cause problems during the measurement if it is not firmly attached to the inner pipe wall or
consists of an acoustically absorbing material
Try measuring on a liner free section of the pipe.
Highly viscous media strongly attenuate the ultrasonic signal
Measurements on media with a viscosity > 1000 mm²/s are only possible under certain conditions.
A higher proportion of gas bubbles or solids in the medium scatter and absorb the ultrasonic signal and there-
fore attenuate the measuring signal
A measurement is impossible if the value is

10 %. If the proportion is high, but < 10 %, a measurement is only possible
under certain conditions.
The flow is in the transition range between laminar and turbulent flow where flow measurement is difficult
Calculate the Reynolds number of the flow at the measuring point with the program FluxFlow (free download: www.flex-
im.com). Contact FLEXIM.
19.5 Large Deviations of the Measured Values
The entered sound speed of the medium is wrong
A wrong sound speed can result in the ultrasonic signal that is reflected directly on the pipe wall being mistaken for the
measuring signal that has passed through the medium. The flow calculated on the basis of the wrong signal by the trans-
mitter is very small or fluctuates around zero.
There is gas in the pipe
If there is gas in the pipe, the measured flow will always be too high because both the gas volume and the liquid volume
are measured.
The entered 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 de-
rived from the flow velocity will also be marked as invalid. If several correct measured values are ignored, the totalizer val-
ues 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 quantities are also set to zero. The cut-off flow (default:
2.5 cm/s) has to be set to a low value in order to be able to measure at low flow velocities.
The entered pipe roughness is not appropriate
The flow velocity of the medium is outside the measuring range of the transmitter
The measuring point is not appropriate
Select another measuring point to check whether the results are better. Because pipes are never rotationally symmetric,
the flow profile is affected. Change the transducer position according to the pipe deformation.