Intrinsic safety "i" EN50020

[Pedersen]

Does anyone have experience with faults in the European EN50020 Intrinsic safety "i" standard ?

I'm questioning the Minimum igniting voltages curve in figure A.3. Group II capacitive circuits, while I have found curves in UL1604 and BS5501 part 7 (which are applicable for Group IIC - hydrogen and acetylene), which are NOT identical to figure A.3. in EN50020 ?

This is not the case, while the specific curve in EN50020 is more restrictive - why ?

In my opinion the Minimum igniting voltages curves (applicable to group IIC - 22 percent hydrogen) should be the same if the circumstances are identical (mixture, spark test apparatus etc.) !

It would be nice with others opinion, but accepts the limited chance of a "hit".

 

[don01]

pederson
I believe the readson for hydrogen and acetelyne to have tighter curves is due to the higher level of flamability.
What I mean by that is it takes a very small amount of energy to ignite a combustible mix cotaining these gases rather than say petrol vapours.

This is also reflected in th "T" ratings given to ex "d" & "i" devices cases

hope this helps
Don