Increase Fail-Safe Timer Value; Install A Transducer With A Narrower Beam; Fixed Reading; Obstructions In The Sound Beam - Siemens SITRANS LUT400 Series Operating Instructions Manual

Increase Fail-safe Timer Value

2.4.2. LOE Timer
Increase the
larger value.
Try this only if LOE exists for short periods of time.

Install a Transducer with a Narrower Beam

A consistent, incorrect level reading may result due to interference echoes from the sides
of a vessel. If this occurs, try installing a longer range (narrower beam) transducer, enter
2. 1 .6. Transducer
the new
Always contact Siemens service personnel before selecting a transducer to solve this
type of problem.

Fixed Reading

If the Reading is a fixed value, regardless of the transducer to material surface distance,
ensure the:
1. Transducer acoustic beam is free from obstruction.
2. Transducer is properly aimed
3. Transducer is not in contact with any metal object.
4. Material mixer (if used) is operating while the SITRANS LUT400 is operating. If it is
stopped, ensure that the mixer blade is not stopped under the transducer.

Obstructions in the Sound Beam

Check for (and remove if present) any acoustic beam obstruction, or relocate the
transducer.
If an obstruction cannot be removed or avoided, adjust the Time Varying Threshold (TVT)
curve to reduce the Echo Confidence derived from the sound reflected by the obstruction.
Use SIMATIC PDM to adjust the TVT curve. (See
LUT400 Communications manual

Nozzle Mountings

If the transducer is mounted on or in a nozzle, grind smooth any burrs or welds on the
inside or open end (the end that opens into the vessel). If the problem persists, install a
larger diameter or shorter length nozzle, bevel the inside of the bottom end, or cut the
open end of the nozzle at a 45° angle.
See the transducer manual for complete mounting instructions.
If the mounting hardware is over tightened, loosen it. Over tightening changes the
resonance characteristics of the transducer and can cause problems.
1.
Communications for SITRANS LUT400 (HART) Manual (7ML19985NE01)
A5E33329501 SITRANS LUT400 (HART) – OPERATING INSTRUCTIONS
value, if fail-safe operation will not be compromised by the
model, and (if necessary) optimize aiming and frequency again.
1
.
)
TVT Shaper Echo Profile Utilities
under in
Page 245