Dear Friends,

Could anyone please help me how to identify IS Barrier Circuit in a exixting system.

In a system there are RTDs and Temp Transmitter installed in Hazardous area and Instrument JB, Power supply for Instrument JB, and Control Room are located in Safe Area.

I would like to understand how IS verification is carried out?

What are the important Entity Parameters to do IS calculation?

What factors are very very sensitive that should not be neglected?

Thank you.

With Kind Regards
Biky

 

Intrinsic Safety is one approach to dealing with electrical apparatus in hazardous areas. Principles are covered in the vendors' engineering guides.

Omega's Intrinsic Safety Circuit Design
http://www.omega.com/temperature/z/pdf/z131-148.pdf

MTL Cooper Crouse Hinds

Principles of Explosion Protection
http://www.coopercrouse-hinds.eu/download/1/Principles_of_Explosion_Protection_2012.pdf

Users Guide to Intrinsic Safety
http://www.mtl-inst.com/images/uploads/datasheets/App_Notes/AN9003.pdf

Be sure to take out any space character in the URL that the forum inserts

 

Dear David,

Thank you for your email & helpful materials.

Could you please explain this for me?

There is a servo level gauge (01143) located at the top of tank (Haz. Area). And a level indicator is at the tank base ( Safe Area).

I did IS verification between gauge and indicator and result came OK. But I am not sure about my calculation. Do I have to check the form Instrument JB (Safe Area) to Servo Gauge too?

According to my knowledge, there should be a barrier circuit. But JB has simple TB connection diagram. So is it possible that barrier circuit is in-built in Servo gauge?

Hope to have positive response soon.

With Kind Regards,
Biky

 

The Whessoe 01146 spec sheet says
ATEX approval:
- Category: Ex II 2(1)G
- Marking: EEx d[ia]IIB T6

I read that as a flameproof design, EX d, with some element that is intrinsically safe [ia].

On a servo gauge, the I/S element is likely to be an I/S 4-20mA output.

But apparently Wartsila does not publish the 01146 servo manual on the web, so details, specifically the control drawing, are not readily available to the public.

If such is the case, the 4-20mA output is like a transmitter's output, which would require an appropriate I/S barrier in the safe area.

You really need the instrument's control drawing to determine what's what.