Hi,

I would like to know whether a transmitter certified as ex-proof can be used in a intrinsically safe loop?

Just to briefly describe my understanding,

For ex-proof: The transmitter enclosure is designed based on ex-proof concept(enclosure thickness to withstand the explosion & cable entry for flame path)& electronic circuits components may be different from Intrinsically safe instruments(I am not sure).

For Intrinsic safe: This is achieved by limiting the current to the hazardous area using barrier.

With the above info. I feel that a trasmitter certified as ex-proof can be used in instrinsically safe loop provided the ELECTRONICS ARE SAME.Please correct me, if i am wrong.

Also, as per the Rosemount 3051 model there are 3 different certifications:
The code: E5--ex-proof certification; I5--for instrinsic safe certification;I5-for both ex-proof & instrinsic safe;

When we select either one of 3 options whether Rosemount will supply the same transmitters with different certifications for documentation purpose or the electronics are different?

Thanks in advance.

Regards,
GB

 

GB,
Any component connected on the protected side of a barrier or isolator in an Intrinsically Safe circuit must itself be certified as Intrinsically
Safe. (There are exceptions for low-power or low-voltage devices such as switches or thermocouples, which are identified as "simple apparatus".) The complete circuit, including wiring and connections, must be incapable of
causing igniton if a short should occur, and extra capacitance (for instance) in a transmitter may put sufficient energy into a spark in a
different part of the circuit to cause a bang.

Yes, the electronics of your Rosemount Explosion-proof pressure transmitter are probably identical to the electronics of the IS version of the same
device - but you don't know for sure. So No - you can't use an explosion proof transmitter on an IS loop.

Bruce.

 

Bruce is correct- Explosion Proof refers to the capacity of the equipment to contain the energy released from combustion within the device in an explosive atmosphere. Intrinsic Safety is the use of electrical isolation the reduce the potential of a circuit below the Lower Explosive Limit (LEL) of a potentially explosive environment. Typically Explosion proof devices often contain non-intrinsically safe circuits, while the protected side of an intrisincally safe circuit does not generally require an explosion proof housing.

 

Hi,
You are right about the concepts of ex-proof and IS.

- An ex-proof device is mechanically designed to withstand an explosion in
its interior without letting the flame originated by the explosion reach the
external environment (provided that the transmitter cover is tightly closed,
and the other installation components (conduit, cable entry connector,
etc..) are also ex-proof rated.
- An IS device has its circuitry designed to limit the amount of energy
released by faulty components. An IS installation requires also approved
associated apparatus, such as the safety barriers, to be used in conjunction
with the IS field devices.

In case of 3051C with FM certifications, although each certification has a
different ordering code, both the electronics and housing are always the
same. The only difference is the plate in the housing showing the specific
type of certification ordered, which is a requirement from FM and also for
traceability purposes.

Regards,

Paul Garrone
Rosemount Inc.

 

I have a Question: what should we do to reuse a ex-proof transmitter and wire it into a new intrinsically safe loop? Can we send the Rosemount certified ex-proof transmitter to rosemount facilities and get a intrinsically safe certification for the same transmitter? or Rosemount have some upgrade retrofit to do that?

 

I am not sure of the exact answer, but many of the Rosemount XP xmtrs I have used were also certified for use in IS circuits.

I think the answer is to call them and just ask.

--
Bob