Ex'd' Certified Transmitter in Ex'i' loop

S

Thread Starter

sachinrk

If Ex'd' Certified transmitter connected to Intrinsically Safe (I.S.) loop/Barrier of PLC/DCS will it be work? and what should be the loop Electrical certification (Ex'd' Or Ex'i')?
 
Simple - Ex'i'

And if I were the end user/client I'd want evidence that the Ex'd' Certified transmitter was also Intrinsically Safe. Even though there is a barrier wired in doesn't necessarily mean the loop is safe.
 
With an Ex i circuit, every component in the circuit after the energy limiter (barrier or isolator) must be certified as Ex i (even if it's actually installed in a safe area). So if you connect an Ex d transmitter (which does not have Ex i certification) into the loop, it is no longer Ex i and will not comply with the standards.

You can install the transmitter provided you (a) meet all the requirements for an Ex d installation and (b) remove all signs, labels, and other indications that the circuit is IS. In particular, live maintenance is no longer an option.
 
The Tx will work but the loop will be unsafe.

In the other hand, in a safe Area, you can install all types of certified Tx (Ex d, Ex ia, etc) without any accessories.
 
S
Dear Sachin,

it works perfectly with Ex"d but which zone are you going to use? nonetheless it is allowed to use in Zone 1 & 2 but not for Zone 0 as per the ISA-12.06.
 
I repeat - if a circuit is protected using Intrinsic Safety,
<b>**ALL COMPONENTS IN THE CIRCUIT AFTER THE BARRIER OR ISOLATOR MUST BE CERTIFIED AS INTRINSICALLY SAFE!**</b>

A device rated as Ex d may have sufficient internal capacitance or inductance to create an incendive spark if the circuit is interrupted or shorted. Ex i is a method of protection that requires the whole circuit to be considered, rather than a single element such as a transmitter. This applies even to components within the protected circuit but installed outside the zoned area - so an indicator connected on a local panel in a safe area but in series with the transmitter must also be rated as Ex i.
 
Check the certification of the transmitter. Most recent transmitters have dual certification as IS and explosion proof. But; YES it has to be certified as IS to be in an IS loop.

> If Ex'd' Certified transmitter connected to Intrinsically
> Safe (I.S.) loop/Barrier of PLC/DCS will it be work? and
> what should be the loop Electrical certification (Ex'd' Or Ex'i')?
 
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