Enclosures and I/O in hazardous zones.

[skorp]

Been looking over regulations for a while now, and still new at trying to figure out what is needed. What I have is equipment that moved around the world to differnet oil/gas rigs for a few weeks/months at a time. Sometimes the equipments falls under Class 1 Div 2 zoning or sometimes needs to be ATEX.

I want to assemble an I/O enclosure that can be mounted on a piece of equiment that may need to be in those zones. Everything in there will be 24V. Right now just using terminal blocks and multiconductor cables to connect to a PLC panel in a safer zone area. I want to reduce the cabling between units and add I/O capability.

What I would be running would be some solenoids controlling hydraulic flow, and 4-20ma current loops for feedback.

I would just like to add in some type of I/O base or multiplexer that way I can use a single, armored cable between equipment. I prefer to use ethernet/ip for communication, but have the issue that I need power for the modules. Thought about Power-over-ethernet, but I do not think that will provide enough internal power for possible expansion, so I may run an additional single pair cable for 24V power source.

So thats a run down of the background of what i got.

Can I use a enclosure like Hawke S-Series that has certifications for zone 1, Atex that I can drill holes in for many glands, or do I need a explosion proof box that is a pain to work with and have many bolts to remove in order to work on?

In the end, I want to equipment to be easy to install and remove, and have reduced wiring between modules for easier troubleshooting in field.

Any thought or suggestions?

 

[djs]

How about purging? Peperrel-Fuchs has an assortment of purging systems for various clasifications. Most need an air supply. In general to enclosure non certified equipment in a classified area you will need an explosion proof enclosure. In addition all fittings will also need to be certified. A real PITA.

 

[itsmoked]

And the PITA here - can't be understated. Purge is a great idea.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[skorp]

Thanks for the response, but I have looked at purging, but that was shot down. The air on rigs tend to be very dirty and using it for instrumentation tends to be very messy, even with filters. Plus if air supply goes down, we will have to shut down, which is a big no-no.

My biggest confusion with enclosures is I have been told that if the enclosure is rated for a particular zone, it doesn't matter what is inside, as long as the wiring glands, cable coming out of the box, and panel controls are rated for the same zone. Then I hear that everything inside the enclosure must be certified for that zone.

Are there good sources that can explain zoning, classification in simpler terms. I may be an electronic engineer and can read and design circuits with little problem, but when it comes to regulations and legal talk, it gives me one hell of a headache.

Heck, I wouldn't even be ashamed if there was a for dummies guide on this
Still starting out so will take a few more years till I get used to it.

 

[djs]

The area inside an explosion-proof enclosure is un- classified. You are allowed to place anything you want there.

The idea behind an explosion proof enclosure is that if the atmosphere inside the enclosure ignites, it not ignite the atmosphere outside it.

 

[simonsk]

This is a useful source of reference:

http://www.rotork.com/public/backen...umentversion/item/primary/204/file1/G007E.pdf

 

[skorp]

Thanks, looks like it will be a good read.