Non-incendive barrier terminal

[PhilRey]

This is not specifically a PLC question, but it deals with interfacing I/O.

Does anyone know who manufactures a non-incendive barrier terminal block (not an intrinsic safety barrier) for Class I, Div. 2 hazardous locations.
The searches that I have done only show Wieland Electric. That is fine but I would like to have more options.

In the past, I have used intrinsic safety barriers for "dry-contact" inputs (i.e. Pepperl & Fuchs, Stahl, MTL, ...) but it seems like going with a non-incendive barrier may be less expensive yet still appropriate for my application.

Another issue regarding I.S. vs. non-incendive barriers is the switching current at the dry-contact input device. I.S. barriers supply a much lower voltage/current which may impair the ability of the switch to close the circuit and transfer the signal reliably through the switch. Any opinions?

Thanks.

-Phil

[rsdoran]

May be cheaper: If you can find one that is only that, intrinsic means covers it all...more or less

http://www.bently.com/articles/apnotes/an015.asp

[PhilRey]

Thanks for your reply.

I guess I should clarify exactly what I am looking for.

I am very familiar with explosion protection techniques and the application therof.

What I mean by I.S. barrier is a galvanic isolation or zener (with high-integrity ground) device that makes a NAMUR device or simple apparatus (like a dry contact) suitable for a Class I, Div. 1 hazardous location.

The non-incendive barrier terminal block (see Wieland Electric's non-incendive terminal (http://www.ecnmag.com/ecnmag/issues/2002/02012002/PACKAGING_INTERCONNECTS/ec21pi511_.asp) ) is a non-isolating current limiting device that does not drop the signal level as low as an I.S. barrier so that it may be used with more standard I/O devices. It is also less expensive.

I am looking for an alternative manufacturer of such a device other than Wieland (not that anything is wrong with them) that is agency (FM, UL, CSA, etc.) certified for a Class I, Div. 2 hazardous location.

Thanks again.:)

-Phil

[rsdoran]

Forgive my ignorance, at first I was thinking of screen barriers

Phil, check out Pepperl+Fuch's
http://www.pefu.de/pa/interptop/barriers/main_e.html
That may not be explicitly what you are looking for but they may have.

Unitec
http://www.unitec.ca/isb.html

I know what you are refering to now but never paid attention or noticed the non-incendive term used before to apply to these devices. I work with printing presses that are built/designed with explosion proofing, solvent inks use to be the thing but now we use water base.

[Ed Legenski]

Phil,

I took up an effort about 2 years ago relating to your question. Manufacturers for nonincendive barriers are Wieland, Weidmuller, and Axiomatic. The problem with these is that they all use a high resistor (470 ohms) which makes it difficult to operate transmitters, I/P's and solenoid valves. I know Wieland has a nonincendive module (16 channels) with a 250 ohm resistor that will allow more current to drive I/O devices. This same module is FM approved nonincendive and rated Class I, Div. 2, with a T4 rating.

Good Luck!