Non-Incendive Wiring Practices - NEC - ISA

[bazak]

All -

There are many forum postings that discuss this topic. I would like to draw on everyone's practical experience as it applies to the NEC 2011 and referenced ISA standards on the subject.

Hypothetical Design:

- AB PLC 5/05 with Analog Input card rated for installation in Cl I Div 2 (no Non-Incendive rating)
- Transmitter rated FM CL I Div 2 Non-Incendive, no XP rating
- Transmitter includes control drawing including entity parameters
- Conduit installation

The analog input card, as I understand, must conform as an associated apparatus to satisfy the equations described on the control drawing. Without a NI rated associated apparatus, there are no parameters for the power source, and thus can not be considered appropriate. I believe I would need an approved Non-Incendive barrier between the PLC and transmitter to satisfy the requirements of NEC and ISA 12.12.01. Another option, would be to use Non-Incendive (also intrinsic) I/O such as the AB Flex Ex 1797.

Please comment with reasoning and feel free to supply white papers you have that discuss this specifically.

Thanks everyone in advance,
Brian, EE

 

[lacajun]

If this is still relevant, I have only used NEC for wiring practices.

Years ago, in one plant, I put the controller, I/O, and IS barriers in the non-hazardous area with the IS transmitters in the hazardous area. That eliminated the need for poured conduit seals on the factory floor. I've never seen white papers on this topic nor did I look for any. Since I was the only EE in the plant and I am registered, it was my decision.

I bet if you search A-B's website for IS barrier, you'll find information.