EEx ia vs EEx [ia] vs [EEx ia]

I

Intrinsic Safety

Mr Rajesh,

You can go with Pepperl& Fuchs make Zener barriers and Isolators. WWW.pepperl-fuchs.com.

You will get all range of intrinsic safety isolators and barriers,
upto SIL3 safety level.

Jayasimha A M
 
B
Hi Neetika,

Ex ib is intrinsically safe and remains safe even with a single internal fault, so is good for Zone 1 or Zone 2 use. The basic principle is that the current and voltage, along with electrical parameters in the protected circuit, are limited so that there is insufficient energy present to ignite a release of flammable material if one should occur.

Ex nA is "non-sparking" - which inherently limits it to Zone 2, so it cannot be used in Zone 1. The principle used is that the device is constructed to minimise the likelihood of an ignition source occurring during normal operation - so it is essentially a low-integrity version of Ex e.

So, if you are checking if they are compatible, the simple answer is no. And you can't connect Ex n apparatus into an Ex i circuit.

Cheers,
Bruce.
 
Hi Bruce,

So are you saying I can't put Ex 'n' equipment into an Ex 'e' enclosure. Can you tell me where to look for supporting documentation? Much appreciated.

Cheers,
Bolter
 
B
Hi Bolter,

An Ex e enclosure doesn't change the risk of ignition in any way - the atmosphere can still penetrate the enclosure and there is no allowance made for suppressing the effects of any internal ignition. So any equipment installed an Ex e enclosure in Zone 1 must be suitable for Zone 1 as well - it could be Ex d or Ex i for instance. Ex n is acceptable only in Zone 2 so cannot be fitted to an Ex e enclosure in Zone 1.

The main restriction on an enclosure is that it must provide environmental protection to keep dust and moisture from affecting internal creepage and clearance distances.

The basis of Ex e protection is that extra precautions are taken to greatly reduce the probability of an electrical source of ignition developing (such as a hot-spot or an arc). The equipment must remain safe even with unusual faults present. Similar requirements apply with Ex n equipment, but to a lesser degree: ignition is avoided only in normal operating conditions and some common faults. For instance, fuses are not allowed in Ex e apparatus but some types are allowed in Ex n.

Hope this helps,
Bruce.
 
Hi Bruce,

Thanks for the great info above. I have a few questions I hope you can help me with.

Firstly I would like to find a good book that answers a lot of Ex questions about installation, inspections and the minimum acceptable pass rate. Also information on Exde and Exed products.

Secondly do you know anything about aluminum gland plates on motors. Are these acceptable indoors / outdoors.

Finally is it possible to drill holes in Ex boxes that are NOT Exd rated if the IP rating is maintained.

Any help with these questions are greatly appreciated.

Thanks
Oliver
 
Dear Bruce I would like small clarification:

> If it is protected in some other way, this will be indicated eg the
> example I gave of Ex d [ia] which is applicable to an item with
> flameproof protection and containing equipment suitable to supply
> Ex i apparatus in Zone 0. As you say the format Ex [ia] should not
> be found in isolation but should carry another method of
> protection as well.

when instrument is certified Ex d [ia], it means that instrument shall not be installed in Zone 0 but when installed in other Zone (i.e 1 or 2) is it the instrument "double certified"? So I can choose if installed following the IS philosophy or not. Is it correct ?

Thank you in advance
Kind Regard
 
Hi Bolter,

An Ex e enclosure doesn't change the risk of ignition in any way - the atmosphere can still penetrate the enclosure and there is no allowance made for suppressing the effects of any internal ignition. So any equipment installed an Ex e enclosure in Zone 1 must be suitable for Zone 1 as well - it could be Ex d or Ex i for instance. Ex n is acceptable only in Zone 2 so cannot be fitted to an Ex e enclosure in Zone 1.

The main restriction on an enclosure is that it must provide environmental protection to keep dust and moisture from affecting internal creepage and clearance distances.

The basis of Ex e protection is that extra precautions are taken to greatly reduce the probability of an electrical source of ignition developing (such as a hot-spot or an arc). The equipment must remain safe even with unusual faults present. Similar requirements apply with Ex n equipment, but to a lesser degree: ignition is avoided only in normal operating conditions and some common faults. For instance, fuses are not allowed in Ex e apparatus but some types are allowed in Ex n.

Hope this helps,
Bruce.
Hello Bruce
I have read a few of your explanations regarding the difference between EExia and EEx[ia] & [EExia]
Very Interesting and informative.
Would you mind if I ask you a very simple doubt.
I was going through a Certificate and following was mentioned in it:

  • What does the T500 represent?
  • Sometimes why do they mention two temperatures?
  • Sometimes they have 500 mentioned in Subscript (like below T500 150°C) what is this in the subscript and Why do they mention in subscript?
  • Sometime they have 400°C T500 80°C, any idea why?
 
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