Fnico

[Dirk Diggler]

I am in the middle of installing some fieldbus segments in a cl. 1 div 2, grp. C,D area. The design isn't really complete and I don't get the idea that the designer has a complete grasp on this.

As I understand it, the power supply is a FNICO power supply (320 mA I think). If we are using Instrument Tray Cable, do we need to do anything special with the wiring or can we install it in the same way that we would in a general purpose area? When the segment is powered, can we remove devices without depowering the spurs?

Also, when they purchase field devices, what spec do they need to ask for? Do they need to be I.S., FISCO or does someone certify a transmitter that is FNICO?

:confused: :confused: :confused:

Thanks in advance for any help.

[tklatt]

Hello Dirk,
FNICO is a "standard" which isn't adopted up to now. FNICO stands for Fieldbus Non Incedive COncept. It is a simplified version of the FISCO concept and especially made for Class 2 Div 2 or Zone 2 applications.
The wiring you have to make in the same way like for IS or non-incedive applications.
The vendors of field devices start now to get devices in acordance to the FNICO concept. But if there are no (or not the required) field devices available you can also use FISCO field devices, IF the safety parameters of your field device matches the safety parameters of your power supply ("proof of intrinsic safety"). If this proof is OK then you are allowed to disconnect field devices under voltage.

I hope this helps you a little bit.

Best regards

Thomas Klatt

Manager International Sales Support/
Business Development Manager Fieldbus Systems

Pepperl+Fuchs GmbH
Koenigsberger Allee 87
D-68307 Mannheim
Tel.: ++49 (0) 621 776 2130
Fax.: ++49 (0) 621 776 1400
e-mail: tklatt@de.pepperl-fuchs.com
http://www.pepperl-fuchs.com

Signals in the world of automation

[rezabejd]

When I read this post, I'm concerned that a reader might get the impression that heroic measures must be undertaken to allow a device to be disconnected under power in a hazardous area. We have had non-IS devices in hazardous areas for decades, and we deal with it procedurally. That is, if we have to break a live circuit we get a gas test or "hot work" permit.

I think one needs to make a judgement about what measures like FNICO are worth. If you only need to break a "live" circuit once a month, is it easier / more efficient to simply use the traditional "hot work" procedure or is it worth agonizing over IS or non-incendive designs? One would hope that the need for instrument service is rare, but maybe some businesses require frequent calibration or re-certification. Seems like even this could be accomplished without breaking a circuit in a hazardous area.

[sheusel]

Dear rezabejd,

you can choose between many options if you want to select the protection method for your plant and when deciding if you want to work with "hot work" permits.

A "hot work" usually creates more hassels for the end-user:
- special measures have to be taken, when "hot work" is scheduled
- production may have to stop, which is a problem for continous reactions in the chemical industry.

Generally speaking you can save a lot of effort if you familiarize yourself with concepts like FNICO and/or FISCO once.
After all the FNICO, FISCO concepts are not that complicated -here are the basic rules:

Device data power source data
Ui/Vmax >= Uo/Voc
Ii/Imax >= Io/Isc
Pi/Pmax >= Po

-Node inductance and capacitance may not exceed: 5nF / 10 uH

-max. cable length is 1000 m (3300 ft)
-max. spur length is 30m (100 ft)

Device Type connect to FISCO source connect to FNICO source
I.S. Entity Yes Yes
Non-Incendive Entity No Yes
FISCO Yes Yes
FNICO No Yes

A little more detailed short description of all the necessary steps for the hazardous
area evalution can be read in "Fieldbus Fast Facts".
You can contact me for the pdf or if you would like a printed copy.

Best regards / mit freundlichen Grüßen

Stefan Heusel

Technical Support Manager Bus Systems
Process Automation Division

Pepperl+Fuchs GmbH
Koenigsberger Allee 87
D-68307 MANNHEIM
Phone: +49 621 776-1299
Directfax: +49 621 776-27 1299
Department Fax: +49 621 776-1429
E-Mail: sheusel@de.pepperl-fuchs.com
www.pepperl-fuchs.com

Signals for the world of automation

[spragujl]

We are using what seems to be a simple non-incendive approach to FF installation in Cl1 Div2 areas.

We use Relcom Megablocks (soon Hawke TG200 also) in the JB - and we verify our spurs meet the Ca and La limits listed on the control diagrams. So far, we haven't even come close to these limits with the transmitters/positioners and spur cables we use. And the benefit I get is live spur disconnect capability - which is nice. Plus, I get rid of some explosion proof sealing I might have had to do.

This system seems simple and straightforward to me. Is there a reason we should be considering FNICO instead?

Jim Sprague

[sheusel]

FNICO will offer you many advantages when it is acknowledged as a certified standard.
Unfortunately no field devices have been certified according to FNICO so far, but when FNICO is acknowledged, the end-user will not have to make a evaluation of Ui/Uo, Ii/Io, ... but he will be able to use any FNICO device with any FNICO power supply.
With a whole segment filled with FNICO devices/supplies, you will have live spur dis-/connect capability, plus no need for explosion proof enclosures (in Zone 2) and a very simplified documentiation (regarding the Ex-certification).
Devices like the Segment Protector are already certified according to FNICO and if you start using them today, you will be able to take advantage of FNICO when the first FNICO field devices come out tomorrow - without additional cost.

Stefan Heusel

[rhighton]

Dear Dirk

The field wiring connected to the FNICO power supply (sounds like it's an MTL 9112-NI unit) is classified as 'nonincendive field wiring' according to the device approval by Factory Mutual. This means that tray cable is OK and no special precautions are necessary. Article 501-4(b) of the National Electrical Code defines the cable types that are acceptable for nonincendive installations. These are listed as power-limited tray cable, enclosed busways/wireways and conduit. But note the special relaxation, which states, "Nonincendive field wiring shall be permitted using any of the methods suitable for wiring in ordinary locations".

As for the field devices, the FNICO specification (published in the latest draft of IEC60079-27) says that field devices in a FNICO system can be any of the following:
Nonincendive, with nonincendive field wiring parameters, or
IS (Entity approval), or
IS (FISCO approval).

They could be FNICO approved, but don't have to be. IS devices are acceptable because they exceed the requirements for a Div 2 nonincendive installation.

Therefore, there is a wide range of certified field devices available today, suitable for use in a FNICO system.

Contact me if you would like a copy of the AN9027 FNICO Application Note or the FM approval certificate for the 9112-NI FNICO power supply; this will confirm the above details, and give you a formal control drawing to refer to. Alternatively these are available by registering on the download section of our web site www.mtl-inst.com/mtlsupport.nsf (http://www.mtl-inst.com/mtlsupport.nsf)

Regards

_________________
Roger Highton
Senior Product Manager
MTL Instruments
Phone: +44 (0)1582 407200
Fax: +44 (0)1582 407467
e-mail: rhighton@mtl-inst.com

For further information on MTL, visit our web site
www.mtl-fieldbus.com (http://www.mtl-fieldbus.com)

[rezabejd]

Stefan,

I'm really troubled by this seemingly persistent idea that we (may) have to shut the plant down to service instruments. This wasn't true with 4-20 and it's not true for FF either.

[QUOTE=sheusel]
A "hot work" usually creates more hassels for the end-user:
- special measures have to be taken, when "hot work" is scheduled
- production may have to stop, which is a problem for continous reactions in the chemical industry.

Maybe different parts of the world do things differently. I have never been in a process plant where the process was shut down so some wires could be disconnected. In the process cultures with which I'm familair (North America, petroleum refining and petrochemicals) nearly everywhere is Division 2 or Zone 2, and the instances of Division 1 / Zone 1 or 0 are extremely rare, and have few if any instruments. We've been disconnecting instruments under power (with appropriate permits) for decades.

I think the methods put forth by Mr.'s Sprague and Highton are workable. There's a high likelihood I could get our code authority to "buy off" on an installation where the spurs were current limited and current limiting devices / power supplies were agency certified (UL, FM, CENELEC, etc.). Instruments certified as non-incendive have also been around for some time.

I agree I'd be happier if all my wiring was non-incendive (assuming I didn't need to make many other compromises with respect to segment loading or distance). The approach that makes spurs non-incendive seems to offer the best of both worlds. I'm never going to want to disconnect a "trunk" cable while the plant is on line anyhow.

John Rezabek
BP BDO Manufacturing

[sheusel]

John,

maybe there was a misunderstanding - I never meant to say that a plant needs to be shut down for servicing instruments. I only wanted to point out that a complete concept like FISCO, FNICO or Entity offers you the advantage of being able to service devices on the spurs without the hassles of "hot work" permits and the expensive
explosion proof enclosures.
Also the FNICO concept will simplify the segment design for the user once FNICO is
acknowledged as a standard.

Currently Pepperl+Fuchs can recommend different topologies to the user which will allow him to dis-/connect devices during plant operation. For a Zone 2 application
you can use our Segment Protectors on the trunk in a daisy chain topology, and on
the spurs FNICO, FISCO or Entity devices can be used (after Ex-parameter verification). The high MTBF value of the Segment Protectors makes this a very reliable
installation.
With the Fieldbarrier you can even create intrinsically safe spurs for Zone 1/0 applications.
The imminent benefit of one of these topologies is that you have no need for conduit and that the trunk has just to be done according to the Div 2 wiring method- this basically means that you have to use a separate cable tray for the fieldbus cable.
You can get more information about the possible topologies at http://www.fieldconnex.info

Regards,
Stefan Heusel

Pepperl+Fuchs

[Dirk Diggler]

Thanks folks. Your responses give me a much better understanding of what is up with FNICO.

[migmac]

Dirk,

You should check with a representative of the authority having local jurisiction over your installation.

Here is an excerpt that contains some answers:


From the NEC2005 Draft code:

(3) Nonincendive Field Wiring. Nonincendive field wiring
shall be permitted using any of the wiring methods
permitted for unclassified locations. Nonincendive field
wiring systems shall be installed in accordance with the
control drawing(s). Simple apparatus, not shown on the
control drawing, shall be permitted in a nonincendive field
wiring circuit, provided the simple apparatus does not interconnect
the nonincendive field wiring circuit to any other
circuit.
FPN: Simple apparatus is defined in 504.2.
Separate nonincendive field wiring circuits shall be installed
in accordance with one of the following:
(1) In separate cables
(2) In multiconductor cables where the conductors of each
circuit are within a grounded metal shield
(3) In multiconductor cables, where the conductors of each
circuit have insulation with a minimum thickness of
0.25 mm (0.01 in.)

Nonincendive field wiring containing nonincendive energy does not always require shutting down the power when a device is removed and inserted under power – check the data sheets of the devices, the control drawings and again with the proper authority. In general nonincendive energy levels will not cause ignition if for instance a spark from touching two wires occurs.

Devices used in Class 1 Div 2 must be certified for this application and installed according to the Control Drawing. Devices certified for Class 1, Div 1 must use an intrinsic safety barrier as shown in the control drawing. When these devices are used in Class 1, Division 2 and entity parameters are properly matched, some authorities may allow their uses.

Regards,

Mike McElroy
Business Development Manager, Pepperl+Fuchs, Inc.
Landline phone: 330-486-0171; Mobile: 216-214-1110
www.am.pepperl-fuchs.com