will somebody eloborate these concepts as they are too intricately mingled to distinguish between them..... after reading a lot of literature and holding discussions with experts it seems as if both of them are same, which is actually not. a selection of one significantly effects cost of fieldbus project.....

please clear this vague concept.....

 

Here is a quotation taken directly from my book, The Consumer's Guide to
Fieldbus Network Equipment for Process Control,
http://www.spitzerandboyes.com/Product/fbus.htm

The original design of the Fieldbus standard assumed "worst case" conditions for the purposes of specifying power to the field devices, that is, that they would always demand maximum power and were installed in Division 1 (North American rating) or Zone 1 (IEC rating) hazardous locations. This is called the Entity Concept for bus power design.

FOUNDATIONT Fieldbus H1 can, but need not be intrinsically safe. The Fieldbus Intrinsically Safe Concept (FISCO) allows H1 segments to be intrinsically safe with up to 215 milliamps at a nominal 15 volts DC. An intrinsic safety barrier is required at the boundary between the hazardous area and the safe area. FISCO allows more intrinsically safe field devices to be powered from the H1 bus than
with the Entity Concept. The FISCO solution is based on experimental work that showed that the inductive effects of the Fieldbus cable could be ignored in computing the maximum current capacity for an intrinsically safe H1 segment.

The Fieldbus Non-Incendive Concept (FNICO) is based on the realization that most process areas are rated Division 2 or Zone 2, so the hazard is present only under abnormal conditions. This allows higher currents to be used, although the need for barriers is still present. As a result, more FOUNDATIONT Fieldbus H1 or
PROFIBUS-PA instruments can be connected per segment using FNICO than using the Entity Concept or FISCO.

Dick Caro
===========================================
Richard H. Caro, Certified Automation Professional, CEO, CMC Associates,
2 Beth Circle, Acton, MA 01720
Tel: +1.978.635.9449 Mobile: +.978.764.4728
Fax: +1.978.246.1270
E-mail: [email protected]
Web: http://www.CMC.us

 

FISCO equipment follows Intrinsically Safe rules and is therefore of high integrity - it maintains the explosion protection even in the event of 1 fault (Ex ib) or 2 faults (Ex ia). Ex ia can be used in any zone, while Ex ib can be used in Zone 1 or Zone 2.

FNICO equipment follows Ex nL rules. It is built to a lower level of
integrity and is not certified to be safe under fault conditions. It can be used in Zone 2 only.

 

The basic concept of the two techniques is the same, the main difference is that FNICO is limited to use in zone 2 hazardous areas whereas FISCO can cover all zones.

Please email me off-line if you would like me to email you some of our technical papers on the subject.

Steve
[email protected]

 

We are not expert on Intrinsic Safety, but we know for sure INTRINSIC SAFETY [FISCO] permits/tolerates 2 faults at a time, whereas FINICO permits only 1 fault at a time. All components used in the circuit [loop] have to be approved as per non-incendive [non-sparking], used mainly for Zone 2 application. This includes even cable glands connector. MTL do have special cable gland connectors for this.

I think entity parameter for FISCO xtrs are in the range of 300 ma, hence loop current is also less than 220 ma.

We go as per FISCO only, Non-technical reason is our [Factory] Insurance premium is much less compared to FINICO.

Regards,

Jari
iconcnl at vsnl. net

 

Yes, as the others have said, FNICO is basically for Zone 2 and FISCO is for Zone 1 and Zone 2 and sometimes Zone 0 if you get everything right.

From my own notes purloined from the Internet over the years (with apologies to the original authors):

FNICO defines "Field Bus Non-incendive Concept". FNICO provides for a Zone 2 field bus. Up to 20 devices per segment are supported (or up to 30 in a non-hazardous area). FNICO is a more relaxed version of FISCO--current limits are 180 mA and 320 mA respectively for IIC and IIB gases--typical device limits run from four devices on a 1.025 km trunk up to 16 devices on a 256 m trunk (exact limits depend on gas class, power supply configuration, etc. and must be calculated for each trunk run).

FISCO defines "Field Bus Intrinsically Safe Concept". FISCO can be deployed in a Zone 1 (or Zone 2) environment. Under strict conditions, some FISCO devices can also be operated in Zone 0. PROFIBUS-PA is an example of a field bus that can be configured in a FISCO mode. A FISCO bus is configured using an IEC 61158-2 physical level (i.e., Manchester Encoding), with one active current source on each trunk and the remainder of the devices being current sinks. For a gas IIC system, 120 mA is available and for a gas IIB system 265 mA is available--typical device limits run from four devices on a 1.025 km trunk up to 12 devices on a 340 m trunk (exact limits depend on gas class, power supply configuration, etc. and must be calculated for each trunk run).

 

FISCO is intrinsic safety Exi which can be used in zone 0, 1, and 2. FNICO is non-incendive (energy limited ExnL) which can only be used in zone 2.

FNICO provides more power than FISCO so you can connect more devices and have longer wires with FNICO.

Cheers,
Jonas

 

Yes you are right. Both different concepts are used for Intrinsic safety in Fieldbus applications. FINICO shall be used only in Zone 2 due to energy limitations. FISCO can be used for both ZONE 1 and ZONE 2 applications. No. of instruments in a segment is less comparative with FNICO.

 

> Yes you are right. Both different concepts are used for Intrinsic safety
> in Fieldbus applications. FINICO shall be used only in Zone 2 due to energy
> limitations. FISCO can be used for both ZONE 1 and ZONE 2 applications. No. of
> instruments in a segment is less comparative with FNICO.

It allows more power to an IS segment for approved FISCO devices.
Avoids the need to calculated inductances and capacitances for the proof of intrinsic safety.