Radar Level Instrument Showing Hardware Fault on SCADA?

It appears that the radar signal jumps from 75% level to 116% level (failsafe full scale up scale) when the compressor starts and air is pumped into the surge vessel. Is that correct?

Does the condition correct itself when the compressor turns off?

Yet you said it works fine for 20 hours. Does the compressor not come on for 20 hours at a time? Or does the compressor cycle and the levels read correctly for a period of 20 hours, but then for 4 hours the radar indicates failsafe 116%?

You have two radar units. Are they identical?

Do both radars go into failsafe (full scale, upscale) at the same time? Do both radars go back into normal operation at the same time?

Do both radars have the same problem?

What size and rating power supply is being used? How many field devices on this power supply?

Are you measuring distance or level? dimension? 3m? 15m?

Does the level/distance track correctly during the 20 hour 'working well' period?

Are these HART or Profibus radars?

Do you have PDM software and a HART modem?

How big are the horns? (diameter of open end)

What is the surge tank shaped like? horizontal cylinder? vertical cylinder? no roof? flat roof? domed roof?

What are the surge vessle dimension, roughly (like 3m diameter x 17m length)

If surge vessel is a horizontal cylinder, does the LR200 threaded process connection screw into the top of the tank, or is there a stand-off/nozzle/raised above the tank into which the radar is mounted? (illustration of nozzle below)

Where is the radar unit installed in relationship to the top, sides, edge?

How close to the bottom edge of the horn is the liquid supposed to come ? No more than 75% of tank height? and the tank height is?

Is there any possibility that due to changing temperature that the horn is cooler than the dewpoint of the air in the vessel, causing condensation on the horn? Like just before dawn, when the night air is the coolest and the top of the tank tends to follow the ambient temperature changes because it does not touch liquid, ony air.

What did you reprogram ?

What difference did the change make?

The set air mass for compresor is 630cu.meter. If the air mass in the surge vessel goes below set point then compressor starts. But the level doesnt shoots when the compressor starts/stops.. Its very random that the level gets overanged at irregular time.

Compressor starts automatically if the level goes overanged say above 100 and actual air mass figure also shows reading below 630cu.meter(wrong reading) and after few minutes compressor starts and trips at field as there is already enough air in the vessel. Compressor starts due to actual air mass fomula which is taking the level of the vessel in the calculation.

Yes the two flanged horn type radar units are identical.

Their behavior is very random with each other. They never go into failsafe at the same time.

Initially only one of them was having the problem so we had temporarily modified the program and selected the signal from the other which. is ok. Then now we are having common problem with both.

Nominal 24vdc with max 550 ohm loop resistance. For this area we are having 6 intruments.

we are measuring the level and for reference on the field we have Level guage and the total diameter of the horizontal vessel is 2.718m. whenever there is discrepancy in level reading then we are measuring the actual level from the level guage.

These are HART radars.

I can modify the built in parameters via a graphical local user interface or via SIMATIC PDM remotely. Usually we use SIMATIC PDM

horn diameter is 6.0" (152.4mm)

Surge vessel are in horizontal cylinderical shape. (2.718m(DIA) x 17m length)

instrument in mounted left top of the surge tank

we were suspecting the abnormality was due to humidity as our Plant is near the sea and the normal recorded temperature is 47deg to max 55deg

I have changed the confidence value in the program. Changes was like the instrument got resetted.

Thanks for you support!