Nonincendive Circuit

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jusme123

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NY
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JW
Nonincendive Circuit. A circuit, other than field wiring, in which any arc or thermal effect produced under intended operating conditions of the equipment is not capable, under specified test conditions , of igniting the flammable gas?air, vapor?air, or dust?air mixture.


Would a fire alarm pull stations circuit qualify as a Nonincendive Circuit in C1D1 location and in a C1D2 location?
 

rbalex

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Mission Viejo, CA
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Nonincendive is not a recognized Class I, Division 1 technique. [See Section 500.7] That said, for Division 2, the pull stations would be considered Nonincendive Field Wiring Apparatus. [See the definition in Sec 500.2] See also 501.10 (B)(3).
 

jusme123

Senior Member
Location
NY
Occupation
JW
...thanks Bob, that's a tough enough section to navigate through without the added problem of nonincendive circuit in the mix.
 

G._S._Ohm

Senior Member
Location
DC area
Nonincendive Circuit. A circuit, other than field wiring, in which any arc or thermal effect produced under intended operating conditions of the equipment is not capable, under specified test conditions , of igniting the flammable gas?air, vapor?air, or dust?air mixture.


Would a fire alarm pull stations circuit qualify as a Nonincendive Circuit in C1D1 location and in a C1D2 location?

"The minimum energy density thresholds for incendive and non-incendive sparks were found to be 10 J/m2 and 0.25 J/m2, respectively."
And here I thought any spark could ignite an explosive mixture. :blink:
So now what does Joules per square meter mean? :?
 

cadpoint

Senior Member
Location
Durham, NC
So now what does Joules per square meter mean? :?

From you this is a trick question, Right!

I'll go out on a limb and say Power per SQ. for those playing along.... (frankly even "E" now
that I think about it)...
 

G._S._Ohm

Senior Member
Location
DC area
From you this is a trick question, Right!

I'll go out on a limb and say Power per SQ. for those playing along.... (frankly even "E" now
that I think about it)...
The thing is, the more questions asked and answered, the more are raised. :huh::thumbsdown:

On second thought, arc-flash energy is measured in J/cm^2 and since these sparks are much smaller I guess it's only natural to use J/m^2; it's 10,000x smaller.
But what the rules say and what the science says are not always equivalent. :(

BTW,
Nonincendive Circuit.
A circuit,
other than field wiring,
in which any arc or thermal effect produced under intended operating conditions of the equipment
is not capable under specified test conditions of igniting the flammable gas–air, vapor–air, or dust–air mixture.


may reduce to


Nonincendive Circuit.
not field wiring,
in which normal arcing or heating
is not capable of igniting the flammable gas–air. . .mixture, etc.
 
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cadpoint

Senior Member
Location
Durham, NC
Most of us work to some completion where no potential is desired. Fine that's my understanding of it. The Service/Circuit is addressed-with understanding, sized and terminated.

If your making fun of the two different numbers both being Squared, let me stand down.
 

sgunsel

Senior Member
At a former employer we made electrostatic spray equipment that was designed to safely operate in a Class I, Division 1 environment.The electrostatic spray guns operated at up to 120,000 volts DC. All of our spray equipment was listed by FM for use in a Class I, Division 1 area and had to pass rigorous tests demonstrating that ignition would not occur under any operating conditions or likely failure conditions. The maximum allowable energy criteria was 0.25 mJ. This was proven in a chamber filled with 4% (as I remember) methane. Some tests required hydrogen, even more easily ignited). After successful equipment testing, the gas mixture was exposed to a 0.25 mJ spark to verify that it was at its most easily ignitible concentration. No BANG, start all over. I can assure you that a 0.25 mJ spark is pretty small, barely noticeable under favorable conditions. Also, more than a few microamps at 100k volts is definitely incendive.
 

G._S._Ohm

Senior Member
Location
DC area
At a former employer we made electrostatic spray equipment that was designed to safely operate in a Class I, Division 1 environment.The electrostatic spray guns operated at up to 120,000 volts DC. All of our spray equipment was listed by FM for use in a Class I, Division 1 area and had to pass rigorous tests demonstrating that ignition would not occur under any operating conditions or likely failure conditions. The maximum allowable energy criteria was 0.25 mJ. This was proven in a chamber filled with 4% (as I remember) methane. Some tests required hydrogen, even more easily ignited). After successful equipment testing, the gas mixture was exposed to a 0.25 mJ spark to verify that it was at its most easily ignitible concentration. No BANG, start all over. I can assure you that a 0.25 mJ spark is pretty small, barely noticeable under favorable conditions. Also, more than a few microamps at 100k volts is definitely incendive.
So, materials and fumes require a minimum energy to ignite.
This is definitely out of my field but I guess it makes sense.
An electric arc can ignite paper but probably a static discharge can't, but a static discharge can ignite Gasoline fumes but there are some discharges that are so weak they can't.

This also may have some overlap with the so-called dry circuit switching. And the square meter or square cm I guess refer to the surface of an expanding bubble of energy.
 
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BPoindexter

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Location
MT Vernon, WA
Nonincendive is not a recognized Class I, Division 1 technique. [See Section 500.7] That said, for Division 2, the pull stations would be considered Nonincendive Field Wiring Apparatus. [See the definition in Sec 500.2] See also 501.10 (B)(3).

Doesn't a non-incendive device have to be listed as such? All of the devices and equipment that I have seen are always marked.

From ISA 12.12.01-2000 Section 9.1.2 (Marking):

For associated nonincendive field wiring apparatus, a statement that the equipment provides nonincendive field wiring outputs and the hazardous location suitability of the output: Class, Division, and Group(s). In lieu of Group(s), a specific gas, vapor, dust, fiber, or flying
 
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rbalex

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Location
Mission Viejo, CA
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Doesn't a non-incendive device have to be listed as such? All of the devices and equipment that I have seen are always marked.

From ISA 12.12.01-2000 Section 9.1.2 (Marking):

For associated nonincendive field wiring apparatus, a statement that the equipment provides nonincendive field wiring outputs and the hazardous location suitability of the output: Class, Division, and Group(s). In lieu of Group(s), a specific gas, vapor, dust, fiber, or flying
This is one of the purposes of the control drawing (See the definition in Section 500.2) and general marking references in 500.8(C)(6)(c) and (d). The control drawing is a mandatory installation document.

Of course, the entire reason for Nonincendive/Intrinsically Safe wiring is to permit "...using any of the wiring methods permitted for unclassified locations". You will also note that nothing in the text you quoted from in ISA 12.12.01-2000 Section 9.1.2 mentions specific listing requirements. Section 501.10(B)(3) cites the control drawing requirements.
 
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