Rosemount Transmitters and seal requirements

[TIGERTECH]

We have been following Manufactors suggested requirements and not installing a seal where the transmitter states on it's tag that it is "Factory Sealed" and the manual states that a seal is not required. Now the NEC has come up with a section on secondary seal protection. This really creates a problem in industry due to installations already cramped for space. In my 40 years of being in the field, I have never heard or witnessed a transmitter failing and process fluids pouring from conduit. They say it is to prevent process fluids from entering a control room, but most of our wiring goes to an open cable tray via short runs of conduit or into a box which does not contain any arching devices. It seems to me that we are putting more and more seals where they are not really necessary. I would like to hear your thoughts. Thanks

• 
  

 

[don_resqcapt19]

This does not apply to all instruments. It applies to instruments or other devices that have direct contact with the process and only a single barrier between the process and the instrument. Many instruments have more than one barrier, for example a temperature element installed in a thermo well.
I am not exactly sure what types of devices have only a single barrier.

 

[petersonra]

This does not apply to all instruments. It applies to instruments or other devices that have direct contact with the process and only a single barrier between the process and the instrument. Many instruments have more than one barrier, for example a temperature element installed in a thermo well.
I am not exactly sure what types of devices have only a single barrier.

what he said. normally XP devices already have this built into the xmtr itself.

 

[rbalex]

Section 501.17 [2011 NEC] is not new but only a rewrite of 501.15(F)(3) [2008 NEC and earlier] with a few specific, but not exclusive, means to address the issue of process equipment (NOT electrical seal) failures that could permit process materials to enter electrical raceways or cables. Although the text of 501.15(F)(3) and its predecessors has been tweaked a few times, addressing the process leakage issue itself has been a requirement for much more than 40 years.

 

[Mavtech]

Rosemount Transmitters, Seal Requirements and other Questions

Rosemount Transmitters, Seal Requirements and other Questions

This is my first time to the forum and I may be in the wrong area, but I noticed Tigertech's post and perhaps someone can help answer some related questions. I recently finished a project where the client has a contracted inspector come in for a final approval. There where some questions in regards to the transmitter rack (Rosemounts) and some other minor repairs, however, the biggest problem was the epoxy sealed Hawke connectors. We had to strip close to 48" of the cable to do terminations within the enclosure which resulted in lengthy shield drain wires that had to be clear cover heat shrink, usually 1/16". The inspector said that I could not run heat shrink through a sealed or potted connector because their is no verification that the heat shrink tubing has completely surrounded the drain wire, thereby forming a "conduit" or "passage" for any volatile gases to pass through the sealed connector. It made sense to me, but after removing the heat shrink we now had the problem of isolated instrument grounds shorted to protected earth grounds. This problem arose out of very carefully trying to place and pack epoxy within the connector void and trying not to push bare drain wires against the outer shell of the connector. It was a very long and labor intensive change, but we managed to be successful. I was curious if anyone has any solutions or has been confronted by this particular problem before. The real bust on this was yet another inspector, who had come in on a final inspection on another unit told me it wasn't necessary.

 

[rbalex]

The second inspector was correct.

Look at Section 501.15 Informational Note No.1 [2011 NEC] or FPN No.1 [2008 NEC and earlier]. The first sentence notes seals are intended to "minimize", NOT eliminate, the passages of gasses and vapors. The second sentence indicates a seal is NOT "...intended to prevent the passage of liquids, gases, or vapors at a continuous pressure differential across the seal."

The fact is, there is nothing that guarantees that regular insulation meets the criteria the first inspector imposed; it certainly isn't tested for it.

Section 501.15 (E)(2) indicates actual seal test pressures. Why it isn't in Section 501.15(C), I don't know. BTW, NO cable is tested to meet 501.15(E)(2). Many are declared to have a "gas/vaportight continuous sheath" suitable for applying 501.15(E)(3).

While it doesn't directly apply, you may also want to review 501.15(D)(1) Exception, where it recognizes isolating shields is important. Again, the seal is only to minimize.