Siemens SITRANS LUT400 Operating Instructions Manual page 276

Symptom
Reading is fixed, but
material level changes
or reading does not
follow material level
Accuracy Varies
274
Possible Cause
Weak echo
Foam on surface of mate-
rial
Rapid temperature
changes
Faulty temperature sensor Verify operation;
Vapours
Incorrect speed of re-
sponse
Loss of Echo condition
(LOE)
Agitator blade stopped in
front of transducer (false
echo)
Foam on surface of mate-
rial
Incorrect Algorithm used
Transducer mounting:
wrong location or incor-
rectly mounted
Incorrect transducer used
for the application
Unavoidable false echoes
from obstructions
Faulty temperature sensor Verify operation; Replace if required, or use
Vapours present in vary-
ing concentrations
Thermal gradients
Action
Determine cause; Check noise, confidence,
FOM, and echo strength. See Echo Quality
(3.2.9.) (Page 244).
Eliminate source of foaming; Use stilling well.
Use an external temperature sensor. See
Temperature Source (2.12.1.3.) (Page 218).
Replace if required, or use fixed temperature.
See Temperature Source (2.12.1.3.)
(Page 218).
If fluctuation is unacceptable, consider an
alternative technology. Contact your Siemens
representative.
Verify response speed setting is adequate for
process. See Quick Start (Page 59) (set in the
Quick Start Wizard).
Check Noise, Echo Strength, Confidence.
See Echo Quality (3.2.9.) (Page 244).
Check LOE Timer is not set too short. See
LOE Timer (2.4.2.) (Page 175).
Ensure agitator is running.
Eliminate source of foaming. Use stilling well
Set algorithm to default. If no improvement,
try a different algorithm. See Algorithm
(2.12.2.1.) (Page 220).
Ensure beam has a clear path to material
surface;
Verify transducer is not too tight;
Use an isolation coupling.
Use correct transducer. Contact your Sie-
mens representative.
Relocate transducer to ensure beam has a
clear path to material surface;
Use manual TVT shaping or Auto False Echo
Suppression. See TVT Shaper (2.12.4.)
(Page 223) or Auto False Echo Suppression
(2.12.3.1.) (Page 222).
fixed temperature. See Temperature Source
(2.12.1.3.) (Page 218).
Eliminate vapours or consider a different
technology. Contact your Siemens repre-
sentative.
Insulate vessel;
Consider external temperature sensor.
Operating Instructions, 07/2019, A5E33329501-AC
SITRANS LUT400