Rosemount Transmitter water intrusion

[Calgrl]

Hello I have a Rosemount transmitter used for flow (0-250" H2O). It is getting water inside of the 4-20mA module side only. It gets about a teaspoon/tablespoon of water in it. Eventually it shorts/corrodes the module and I have to replace it. I have tried absolutely everything! I have replaced the transmitter, sealed it completely with and without the conduit/flex sealed. Placed a housing over the top. Covered it with insulating fabric and duct tape... We have redundant units only one transmitter does this. Any suggestions would be great! Thanks in advance!

 

[MikeHalloran]

Inches of water is not a unit of flow.
What stream are you measuring?
What quantity are you measuring?
What is the range, and units?
What model transmitter?
Is there a water source outside the measured stream?





Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

The transmitter is probably measuring a pressure drop across an orofice. From the pressure drop expressed in inches of H₂O a square root extractor will be able to infer the flow.
Try drilling a hole to let the water out.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Calgrl]

Mike - The Control Room reads it as Kpph. It is approx 52 Kpph during normal operation. The range is 0-105 Kpph. The transmitter is a Rosemount 3051, 0-1000" H20. It is used for fuel gas feedwater flow. It is not enclosed so it is exposed to the outdoor environment.

Bill - My next step was to drill a seep hole, BUT my inquiring mind wants to know a cause for the water intrusion. Condensation is the only thing I can think of and that still doesn't seem to make sense because it is a lot of condensation in a little area.

Thanks for the info.

 

[waross]

Temperature cycling in a damp environment may cause a build-up of condensation. The water vapour is carried in on each temperature cycle and when it condenses it can't get out and so accumulates.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MikeHalloran]

I could swear that the electrical side of that transmitter is closed and sealed and maybe explosionproof, assuming that they've actually plugged and sealed the spare conduit openings.



Mike Halloran
Pembroke Pines, FL, USA

 

[Calgrl]

waross - Okay I understand that, but why is the other transmitter which is in an identical situation not accumulating water? That is what doesn't make sense to me. I was told the accumulation of water wasn't always an issue which makes it more strange!

Mike - I am with you and it is indeed sealed. This one is a true stumper!

Thanks for the feedback.

 

[MikeHalloran]

I don't know if this violates your plant rules/ codes/ whatever, but I'd replace the last few feet of the wires connecting the transmitter with solid conductor wire, at least as a test.

My operating hypothesis here is that some stranded wire includes anti-wicking treatment, and some does not, and you got some that wicks, and it has a water source somewhere.



Mike Halloran
Pembroke Pines, FL, USA

 

[Thealanator]

Does the conduit enter the transmitter from the top? Does the transmitter sit at a low point in the conduit run? You might try installing a junction box with a drain fitting (can be had in explosion-proof versions) below the transmitter and running the flex conduit from the box up to the transmitter.

 

[Calgrl]

Mike - I will check into that, thanks.

Thealanator - No and no. The conduit comes up, I have even went as far as disconnecting and pointing the flex down to eliminate theory of the underground conduit filling with water.

 

[ScottyUK]

Over here we used armoured cables and glands with our Rosemount transmitters. I've never seen the problem you describe, and we have thousands of the things. My gut feeling is that the problem lies with the way it installed, and not with the transmitter unless it has been damaged in some way. Does your conduit have a compound barrier adjacent to the transmitter (typical for a flameproof application), or is it plain conduit? If the latter look for water entering further back in the conduit, maybe a pulling elbow or something similar. Once in vapour state the water will permeate through the smallest orifice given enough time, and the the seals of a Rosemount transmitter serve equally well to keep water in as well as out.


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