IS Smoke Detector without IS Barrier

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Thread Starter

Etherhat

An offshore platform has smoke detectors installed in the accommodation module. The smoke detectors are intrinsically safe (IS) & wired back to the F&G system without an IS barrier installed in the loop. Note - the smoke detectors are installed in a non hazardous area. Has anyone come across a similar type of installation & why would an IS smoke detector be installed in a non hazardous area? Would an IS smoke detector installed in a non hazardous area without an IS barrier be considered an acceptable & compliant with industry standards?
 
An IS smoke detector could be installed in a non-hazardous area if the same installation also uses IS detectors in hazardous areas - having a one-size-fits-all approach ensures there is no chance that a non-certified device could be accidentally installed in a location requiring certification.

Since the application is non-hazardous, there are no specific requirements for how the device should be installed and circuits without barriers are acceptable. Note however that they must be part of a certified system, even if both ends are in safe areas.
 
Thanks. The smoke detectors are certified Exia & both ends of the loop (ie: smoke detector & F&G system I/O Module) are in a safe area. How would you demonstrate the smoke detector is part of a certified system? Are IS cable calcs still required? Is cable scren still earthed at an IS earth or is a clean earth satisfactory?

> An IS smoke detector could be installed in a non-hazardous area if the same installation also uses IS detectors in
> hazardous areas - having a one-size-fits-all approach ensures there is no chance that a non-certified device could
> be accidentally installed in a location requiring certification.
 
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Bob Peterson

I suspect the certification the other poster was referring was not IS related but rather for the FA system.

There are no special cable requirements other than that it has to be a type of cable that is suitable for use with those kind of detectors.

Since it would not be an IS circuit, whatever earthing is done would not be done at the IS earth.

--
Bob
http://ilbob.blogspot.com/
 
An Ex ia smoke detector can be used on its own as a non-IS device without any special requirements for earthing, cable calculations etc. Then of course the installation is not an IS one.

The only danger with this is that if the zoning changes for some reason so that IS is required, someone could take the attitude that "the existing detector is certified so there is no need to do anything." So don't label the box as IS, use blue cable, or do any of the other things normally done for an IS system, and DO label the related drawings to make it quite clear that the existing installation is non-IS compliant.

Also - make sure that the cabling associated with the non-compliant sensors does not use the same JBs as any true IS wiring (unless the requirements for segregation are met).
 
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