Can anyone tell me what difference between EEx ia and EEx [ia] and [EEx ia]? Thanks in advance.

 

Ex ia means protection is guaranteed with a combination of two faults while Ex ib means protection is guaranteed with only one fault.

And EXi means a circuit designed to develop very low energy below ignition levels during normal and abnormal conditions

[email protected]

 

Ex ia, without the brackets, is standard Intrinsically Safe apparatus and can be installed in the hazardous area - since it is ia, it is good for Zone 0 and can be installed in any Zone. Ex ia equipment will also carry ratings for equipment group (IIA, IIB, or IIC) and a temperature rating.

Ex [ia] or [Ex ia] with the brackets is "Associated apparatus" - it usually indicates a barrier or isolator. This equipment is not suitable for installation in the hazardous area but must be either in the safe area or inside an enclosure using some other method of protection. Ex [ia] or Ex [ib] equipment will carry an Equipment Group rating IIA, IIB, IIC but no temperature rating (since it is not exposed to the flammable material).

(The additional E in EEX simply indicates equipment certified to EN standards.)

Cheers,
Bruce

 

Is the above explanation applicable to Ex ib too???

Could you please explain what is the difference in barriers for the Ex [ia] and [Ex ia].

One more thing is Ex d applicable for zone 0?

Thanks & Regards
Seetharam

 

Seetharam,
The meanings of Ex ib and [Ex ib] are the same - the difference between them
is that Ex ia equipment is designed to be safe with 2 independent faults and
can be used in Zone 0 while Ex ib has a lower level of integrity and cannot.
An [Ex ib] barrier will usually contain fewer zener diodes for example.

There is no difference between Ex [ia] or Ex [ib] and [Ex ia] or [Ex ib].
The first will be used where there is another method of protection such as
Ex de [ia] which could apply to for example a servo-operated level
transmitter which is basically flameproof with increased safety terminal box
and generates an IS signal for transmission - so contains barrier elements
internally.

Ex d equipment cannot be used in Zone 0 - it is good for Zones 1 or 2 only.

Bruce.

 

Fantastic Bruce. Right on! I agree on all counts. Are you in the petrochemical or marine industry by any chance?

Any ideas on Ex(s) - special type protection systems?

 

Fantastic answer,Bruce. Thank you very much. it was one of the questions which I could not find answer.

 

May I ask the meaning of "Ex nA[nL]"?

This instrument has two connection, one for power and one for signal. Supplier is saing that the signal is said to be Eex-ia. I've already told to the supplier that this should be reported in the Eex mark, but I don't know which part of the label is wrong, if nA or [nL]

 

No, Ex d isn't aplicable for zone 0, only Ex ia is a normalized device to instal in this kind of zone (zone 0). Maybe is possible to find some equipment Ex s (special construction) to install in zone 0.

Weber Carvalho
Instrumentation Engineering
Tecap - Tecnologia, Comércio e Aplicações Ltda.
São José dos Campos
São Paulo
Brasil

 

Dear Bruce

Your answer was so perfect but it may drop someone in mistake where you've wrote:
Ex [ia] and [Ex ia] are the same.

I should say We never see Ex [ia] because [] shows that application need another protection method like d so we see Ex d [ia] which means that we can use apparatus which is IS in an Ex enclosure.

But it is possible to see [Ex ia] which means the apparatus is not acceptable for Zone 0.

If you think I am wrong please discuss

best regards
Soheili

 

The square brackets [ ] indicate only that the equipment is "associated apparatus". They do not give any indication as to where it may be installed. The same applied to Ex [nL].

If there are no other explosion protection methods given, the associated apparatus has no inherent explosion protection and cannot be installed in an explosive atmosphere. 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.

 

Dear Mr.Bruce,

First of all i would like to thank you for your support to all engineers who needs help about Area Classification and IP rating.

Is it possible for us to USE EEx ib certified instruments in place of EEx ia ?

Please explain in detail about area classification if you find time.

Thanks & Regards,
S.K.S

 

What is the zone you will be working in?

If the equipment is to be installed in Zone 0, then you cannot use Ex ib - but it is suitable for use in Zone 1 or 2. You should also check that the equipment rating is suitable (IIA, IIB, or IIC). IS equipment rated for Group IIC is ok for use in IIB and IIA.

Cheers,
Bruce.

 

Bruce

Do you publish or recommend a book on this subject I'm impressed by your knowledge and would like to have something on the bookshelf

actuators [at] bigpond.com

 

Allan,

Contact me off-list at bruce ^dot^ durdle ^at^ xtra ^dot^ co ^dot^ nz.

Bruce

 

Hi Bruce,

I have to install in Zone 0 a device (I/P transducer) with the label EExia. Do I have to use a related Zener barrier?

Thanks a lot
Gianluca

 

HI Gianluca,

Yes. Since the field equipment is going into Zone 0 the whole of the IS circuit has to have high integrity and provide protection eve with 2 internal faults - it will be rated as Ex [ia]. The brackets indicate it is not installed in the hazardous area itself.

Cheers,
Bruce.

 

Hi there,

In Zone 0 the minimum protection is IS so you need to install the Zener barrier in order to make the loop IS. The Zener barrier needs to be installed in the safe are like a RTU.

 

Hi Bruce,

Can you suggest good make of Zener Barrier

Regard & Thanks

Rajesh Patel
India

 

Hi Rajesh,

There are a number of reputable manufacturers and what is suitable for you will depend on your local applicable regulations and standards and requirements for compliance. A Google search with country filter should bring up specific equipment available where you are.

However, I have dealt with some manufacturers who seem to have a good range of barriers and isolators, and cover most regulatory bases. Try
MTL (www.mtl-inst.com);
Pepperl & Fuchs (www.pepperl-fuchs.com);
Turck (www.turck.com);
Phoenix Contact (www.phoenixcontact.com)