Rosemount Radar Level Transmitters

[msolorzano 0]

I have a level measurement system by fmcw radar (Rosemount tankradar), for a filling-emptying process, of very large water chambers.

Very sporadically, the radar is momentarily lost and measures 4 to 7 feet below the actual level, only when filling the water chamber.  Sometimes the measurement freeze in the middle of the filling process. 

Due to the criticality of the process, this behavior is dangerous, as it can cause flooding inside the plant

This behavior is very sporadically so we are baffled about the root cause of this problem.

[DanW 41]

Water has a high dielectric so it should be a no-brainer application for radar, but non-contact radar is complex so the fault could be any of a dozens of reasons.   

Diagnosis, remediation and root cause analysis require data.   Data for top mount, non-contact radar level includes stuff like
- as complete a description of the fault/failure that can be compiled
- accurate dimensional sketch or drawing or annotated photos of the installation with respect to geometry (slopes and angles) of the tank ceiling, nozzle, walls, interior structures and its fill/empty ports, radar mounting (angular aimers, flange/screw thread), antenna purge
- written narrative on the process: temperature, pressure, atmosphere, mixing/agitation, -when, where and how it fills and empties, condition of the interior of the tank (steam?  dust?  rats?)
- written record of the device model number, technology, beam angle, blanking zone distance for that device, range and accuracy
- device's spec sheet and operating manual
- written record of the existing setup (parameters, as found)
- written report of device diagnostic log
- screen shots of the echo profile at various levels
- maintenance history
- written notes on periodic inspections of the process side of the instrument - condition of the antenna for water, dust or material deposits
- recorded trend charts of the level at a fairly high sample rate so that you can analyze the frequency, duration and time of the faults, to analyze whether the faults are event-related.

A skilled (factory) technician with field experience for that manufacturer might be able to identify some probably causes and provide some remediation.

 

[NevergoldMel 38]

Does it foam up ever?

[DanW 41]

> only when filling the water chamber.

Is the radar positioned so it shoots through partially through the fill stream?

Does the fill splash onto the antenna?

Does the fill create turbulence like waves or agitation ?  Is the algorithm one designed for turbulence (which does not reflect the beam energy straight back up) ?

[dFx 0]

Had once a similar problem.

Installing PVC pipes around the measurement column did the job (almost up to the sensor head). Make sure you let a suffisient under spacing for the water to flow.

Edited 5 Feb 2019 by dFx
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