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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

omohutee@yahoo.com

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?