I know this should be a simple question, but I already have 3 different answers to it, so what could a few more hurt, right?

I have an above-ground water storage tank open to the atmosphere with the overflow at 82.5'. I have a HART-equipped Rosemount 3051 in a pit at the bottom of the tank 2.6' below ground level. I have the 3051 hooked to a 4-20 mA input card. The 3051 is almost new, and factory-calibrated

QUESTION: If I want 0' (ground level) of water in the tank to give a 4 mA signal, and 82.5' (overflow) to give a 20 mA signal, what do I set my LRV and URV on the 3051 to?

Are there any other settings I need to adjust?

Thanks in advance!

 

What is it about the three answers you have that compels you to obtain others? You should be asking yourself (and those you obtained the answers from) why they are different.

Your lower range value should be:
2.6 ft-wc = 4 mA (With an empty tank and a filled pressure line the transmitter you will want the transmitter to read 4 mA.)

Your upper range value should be:
85.1 ft-wc (2.6 ft-wc + 82.5 ft-wc) = 20 mA

Which ever way you choose to go you will also be providing scaling in the PLC.

 

I am obtaining other answers because I did what you (and Rosemount) recommended and the tank overflowed at 80.9 feet, an amount lower than the design overflow of the tank by exactly the amount of the offset. I thought it was probably more than a coincidence.

I am going out today to force 4mA and 20mA to make sure there isn't a scaling problem in the PLC or HMI programs.

Thanks for the advice.

 

If your forcing test points to a transmitter error, make sure the "zero trim" was performed with an empty transmitter, open to atmosphere, in it's final mounting position. If the transmitter was calibrated, (zero trim, LRV and URV) with the 2.6 ft-wc applied (unusual, but possible)it would give the error you mention. Not likely by the factory, but possibly done this way in the field.

Also verify LRV= 31.2"H2O (2.6 ft-wc), URV= 1021.2"H2O (85.1 ft-wc).

 

Hey My friend,

You should be to put this range LRV= 31.2"H2O (2.6 ft-wc) and URV= 1021.2 "H2O (82.5 ft-wc), then if you wanna put both side high and low to the atmosphere and you should see (0) ZERO "H2O and low mA (below 4mA) in your hart comunicator, if not make a zero trim. Next step fill the high side tubing with water for seal and with the tank empty you will see aproximately 31.2"H2O and 4mA in your Hart Comunicator, when the tank get fill up and reach 82.5 ft-wc you will see 20mA and 1021.2"H2O in your Hart Comunicator.

Check the transmitter´s unit with your Hart Comunicator and put it in Inch of water and change the range for this values LRV = 31.2"H2O and URV= 1021.2"H2O, also check your transmitter capsule range number, I mean CD1 or CD2 or CD3, Which one you have? I recommend CD4, also I wanna make a question, Do you have a tee in your high side tubing for fill with water for seal or your let in the water inside the tubing by itself. One more thing very important put your low side to the atmosphere ever.

Please let me know if this make a sense for you.

Best Regards
Juan Pinzon
Maintenance Technician

 

Thanks for all of your replies. It turned out that the settings in the HART-enabled Rosemount were just fine. There turned out to be a Phoenix Contact input isolator inline between the device and the controller, and it had screwdriver trim pots that a technician had used to put in the offset instead of using the HART communicator. Thus, when I put in the proper offset on the HART, it made the tank overflow "early" by exactly the amount of the offset. I took the offset out of the isolator and all is well.

It pays to go out to the field and look, sometimes!