Intrinsically safe barrier

I was just reading another thread about trying to lock a door in a hazzard area, and it got me wondering. http://www.plctalk.net/qanda/showthread.php?t=58094

In my plant, we have hazzard areas and use Pepperl+Fuchs barriers. These were installed long before I came in here, and all I have ever done is add or replace them when the bosses say I should according to the wiring diagrams. I have no idea how they really work, what they actually do, or when they can be used.

Could one of these be used to control his door locks, and make them I.S. for the hazzard area?

See link below for what they are.

http://www.omega.com/techref/intrinsic.html

They limit the amount of power available, so the spark is not capable of igniting anything. In my case, if the wires to our prox switches were sheared and shorted, we would avoid "spontanious relocation of personel and/or equipment." (My boss is fond of that one when talking about burners, but I think it applies here).

So the size of the load (I.S. side) is determined by the Imax? If (in the other thread) a system was available with a current draw within the Imax, he could have sent his signal thru a barrier and been ok?

Turck has a very good tutorial on IS.
Here's a link:
http://www.turck-usa.com/Literature...D=Lit{32}Selection&MenuID=Intrinsic{32}Safety

It's brochure # B1020

Depending on the load of the locks it is possible. We use I.S. Barriers to fire solenoids all over our vessels.
So I agree it is a possible.

Kleinstick said:

Could one of these be used to control his door locks, and make them I.S. for the hazzard area?

Click to expand...

Most likely not. Just putting a barrier in the circuit does not satisfy the requirements. The actual device must be identified as I.S. by the manufacture, unless it is a 'simple' device. Simple devices include RTD's LED lights, potentiometers, etc. They do not produce heat, sparks, arcs, nor store energy.

mjaye65: Your solenoids would have to be I.S. rated if they are in a Class I Division 1 Area. I have used hundreds of that type.

theDave2 said:

Most likely not. Just putting a barrier in the circuit does not satisfy the requirements. The actual device must be identified as I.S. by the manufacture, unless it is a 'simple' device. Simple devices include RTD's LED lights, potentiometers, etc. They do not produce heat, sparks, arcs, nor store energy.

mjaye65: Your solenoids would have to be I.S. rated if they are in a Class I Division 1 Area. I have used hundreds of that type.

Click to expand...

So, I can only use an IS barrier on a device that is already certified to be IS, and does not need a barrier? I know I am the newbie here but my "you made that up" detector is pinging.

There's no need for any disagreement on this issue.
Simply read Article 504 in NFPA 70.

If I were trying to 'lock a door' in a haz. area, I'd remove all the electrical stuff, and use a non-electrical system, like a captive key exchange lock, or something similar.

Kleinstick said:

So, I can only use an IS barrier on a device that is already certified to be IS, and does not need a barrier? I know I am the newbie here but my "you made that up" detector is pinging.

Click to expand...

Another thread on another forum on the same subject.

http://forums.mrplc.com/index.php?showtopic=20476

Kleinstick said:

So, I can only use an IS barrier on a device that is already certified to be IS, and does not need a barrier? I know I am the newbie here but my "you made that up" detector is pinging.

Click to expand...

I didn't say that. And I'm not trying to argue. But rather be very explicit. A device that is I.S. rated will need an I.S. circuit. You could use a Barrier, Isolator or other means of protection. If fact, I don't think the Code actually mentions Barriers or Isolators.

I didn't say Certified, but rather Identified. A Barrier is one type of protection technique. The device itself is documented by its manufacture how to be used in an I.S. circuit.

Now all this talk is about "Hazardous Areas", but yet the actual classification type of the area has not been specified. For each type there are different protection type minimums that are required.

If you would like to view the NEC code book online for free, register at nfpa.org and see page http://www.nfpa.org/onlinepreview/online_preview_document.asp?id=7008SB

You may also with to read the messages at http://forums.mikeholt.com/forumdisplay.php?f=73 about Hazardous Areas

Properly installing an I.S. circuit is not easy, there are many details that must be met and maintained per NEC Article 504. The benefit, though, is a large savings in electrical circuit installations in Div 1 locations.

Generally, for a Class 1, Div 1 hazardous area you will see electrical systems installed using explosionproof wiring methods or I.S. wiring methods, or both.

Barriers are necessary for a properly installed I.S. circuit, but are also sometimes used as supplemental protection for explosionproof installations (many times because the intention was to have I.S. circuits, but the installations fell short of meeting all requirements during construction so the can't be true I.S. circuits..)

Also relating to barriers, there are different barriers used depending on the circuit - a discrete output, a discrete input, an analog input, and a 3-wire RTD for example would use different barriers with different diode configurations inside of them and with different specs.

I keep wondering what is wrong with a hasp and padlock. Make them out of brass or beryllium if it is such an explosive atmosphere.

Dan Bentler

leitmotif said:

I keep wondering what is wrong with a hasp and padlock. Make them out of brass or beryllium if it is such an explosive atmosphere.

Dan Bentler

Click to expand...

Cause then you have to keep up with the keys. Electronic locks are so much cooler.