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Simple Apparatus AS 60079.11

Simple Apparatus AS 60079.11

Simple Apparatus AS 60079.11

I have an Zone 0 methane zone, with an RTD (PT100) connected to a ABB AI893 Barrier.  In order to ensure hazardous area safety i need to ensure this setup complies with the Entity Model or FISCO Model, however I don't know the maximum voltage and current the RTD can handle before it fries itself.
Does anyone have this information on the RTD, or know how to do this verification?


RE: Simple Apparatus AS 60079.11

If the RTD (and housing) is rated for Intrinsic Safe Zone 0 areas, and it is connected to an Intrinsic Safe barrier for Zone 0, then all is good.

RTDs produce voltage, so not sure what you mean by "fries itself"

Entity model and FISCO are for Fieldbus applications (Foundation, ProfiBus, etc).  Not for individual instrumentation...that I know of anyway.

You may get better response by posting this in the "Measurement & control instrumentation engineering" forum on this site.

This is normally the space where people post something insightful.

RE: Simple Apparatus AS 60079.11

The barrier limits the current to the RTD. The RTD does not store energy so even if the RTD could be fried into a smoldering heap the barrier will have still restricted the energy to below ignition energy.

You should not be worrying about the RTD as an ignition point after feeding it correctly with an appropriate barrier.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Simple Apparatus AS 60079.11


I agree with what you have said however, I need to show that I have connected the RTD to an appropriate barrier, by showing the RTD can withstand the maximum voltage and current that the barrier is capable of producing.  Similar to what I have done for the other instrumentaion.

RE: Simple Apparatus AS 60079.11

It's just a resistor.

Look on its data sheet for maximum allowed power dissipation.

But I am still puzzled by why? If the device doesn't store energy like batteries, capacitors, inductors, or ignitable chemicals,  you can hook it to the barrier and it can't ignite the hazard.  It could be a piece of dirt with wires stuck in it or wet hair.  The energy is greatly limited by the barriers and if the device wants to draw more, the barrier fuses go.

So since the barriers have to protect against a malfunction of the 'device' proving the device can handle the barrier power while the device is working correctly doesn't cover all cases.

Sometimes the RTD data sheet may say maximum voltage but usually not.

Keith Cress
kcress - http://www.flaminsystems.com

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