RTD's intrinsically safe
RTD's intrinsically safe
(OP)
Can RTDs be used as intrinsically safe items without the need for a barrier?
We have an RTD in an EExd enclosure and we wish to reuse the rtd with a tank gauge. My question is would the tank gauge need to have barriers fitted to allow the circuit to be intrinsically safe?
Thanks
We have an RTD in an EExd enclosure and we wish to reuse the rtd with a tank gauge. My question is would the tank gauge need to have barriers fitted to allow the circuit to be intrinsically safe?
Thanks





RE: RTD's intrinsically safe
If the RTDs are rated for the location they are probably OK.
Are you using transmitters to transition from the resistance measurement to a 4-20 mA loop? Are the transmitters field mounted or remote mounted? Are the transmitters intrinsically safe?
Bill
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"Why not the best?"
Jimmy Carter
RE: RTD's intrinsically safe
RE: RTD's intrinsically safe
If the power comes into the hazardous area from outside it it must come thru barrier protection unless it's powered thru an I.S. approved device, which is essentially providing its own barrier protection.
Keith Cress
kcress - http://www.flaminsystems.com
RE: RTD's intrinsically safe
The same is true of a thermocouple.
RE: RTD's intrinsically safe
Bill
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"Why not the best?"
Jimmy Carter
RE: RTD's intrinsically safe
Keith Cress
kcress - http://www.flaminsystems.com
RE: RTD's intrinsically safe
I'm saying that the RTD is certified using the Ex'd' protection concept: our 'flameproof' is broadly equivalent to your 'explosion proof'. As such it already has all the protection it needs for use in a hazardous area, without use of a barrier. If some hypothetical fault caused the RTD to reach a temperature where it ignited flammable gas inside the enclosure then the flameproof enclosure would contain the explosion and vent it through a controlled flamepath at a temperature where it couldn't cause an external ignition. Flameproof protection isn't especially common for instruments because it makes them bulky and expensive, but it's certainly possible.
I'm not saying that an intrinsically safe solution isn't possible for an RTD, but having spent a considerable sum on a flameproof RTD why would you want all the additional requirements of using it in an IS application when there's no need to do so?
RE: RTD's intrinsically safe
Yes, yes, I'm with you now! Your flameproof~>ExP cleared that up handily. I totally agree with you.
Never seen an ExP RTD before. Seems likely to lag the poor thing horridly.
I could see them wanting to change out ExP for two reasons. One would be having to run the requisite thick-wall conduit and bulkhead plugging hassles and the other would be maybe needing a more responsive sensor.
Keith Cress
kcress - http://www.flaminsystems.com
RE: RTD's intrinsically safe
Explosion proof is what Scotty described.
Another option is intrinsically safe.
In
mostall of the Petro-chemical plants that I see, heavy wall conduit has been replaced by hazardous location rated cable.Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: RTD's intrinsically safe
RE: RTD's intrinsically safe
Bill
--------------------
"Why not the best?"
Jimmy Carter