NIST Traceable Guided Wave Radar Calibration

Guided wave radar for level comes with its own calibration certificate straight from the factory, verifying the instrument is performing within certain parameters. All one can do is verify that the range is set correctly, which one does using a dimensioned drawing of the equipment to which it is attached.

One might expect some turbulence in the level of such a chunk of equipment, therefore the indicated level is either going to vary with the turbulence, or it is going to be some time-weighted average of the level, the slugging being selected by the Technician that last set it up on the basis of operational requirements and experience.

<...NIST...> indeed. Query the requirement.

I have no doubt as to the accuracy of the transmitter as it is triple redundant and all three transmitters show the same level. The problem is proving that they are calibrated in case of an audit. Our policy specifically states that the DA Level shall be calibrated to a NIST standard every three years, so even getting a factory calibration certificate only proves that the radar is calibrated it does not prove that the actual level detection is calibrated. We have had instances, on our high pressure heaters, of a guided wave radar giving a false level due to high pressure and the presence of steam.

I am pretty certain the only way you can effectively and accurately perform any calibration of this type of instrument is in a controlled environment test facility.

This means there will have to be a spare unit that has been calibrated to NIST standards which is installed while the other unit is shipped out for calibration and certification.

I do not see how using a portable device to verify the in-service meter can be done to the accuracy required.

If you will contact Emerson-Rosemount Technical Support they will tell you what options are available.

Verifying the DA level to prove or disprove the instrumentation reading accuracy will require a direct reading manual measurement device such as a sight gauge with a calibrated scale display. If you need/want/require remote monitoring of the direct reading gauge, a fiber-optic system can be easily mounted on the gauge that will provide a constant display in the control room.

We use Diamond Power equipment however there are several companies that provide solutions for your predicament.

A factory calibration sheet will not work in this application because it only verifies that the radar can accurately measure distance. Once installed in the process it must be calibrated to that actual tank and any deviation in the install will affect the reading. For instance if the level detector chamber is mounted higher than the tank the transmitter must be compensated to provide proper output. We do have a sight gauge that can be used to verify actual level and the transmitters output to the DCS to give the control room real time access to the tank level.

Then doing it on site at the installation in question is the only way.

Try writing a procedure, having it become a Standard Practice at the facility, and using a check sheet against the procedure to verify calibration. Over more than three years, that lot should satisfy the audit.

Of course, the plant will need to be idle and a placebo fluid will need to be in use.

<...every three years...> - the forum could have done with that information up front.

Our fleet doesn't include our dirt burners so this may not apply but here is my $.02. Someone has a similar system and already solved this, can you get a copy of their procedure as a starting point? Since there aren't many different designs in the nuclear end there is a decent flow of information between similar plants. I know fossil is a little different, but perhaps someone can get you started. We have a Metrology Lab here as part of our overall lab and that covers the NIST part. Good luck!

I am interested in the amount of dissolved oxygen control limit in (ppb )you carry (or find) with continuous monitoring and the chemical scavenging program you have(especially with the specific catalyst that is being used and it's feed location by which chemical consultant/supplier.'s recommendation)

First check its calibration, you may find that that there is nothing wrong with it.More importantly make sure you set it up correctly.

There are labs across the country that can do NIST calibration. The one we use for our in house instruments can do on site calibration. We send our instruments to them, but they advertise on site calibrations as well.

Rosemount Service is starting to provide a service for onsite certification of 5300 radars. There is a portable testing station that is used. Let me know if you are interested and I can try to get you more information.