IEC 60079-27:2008 pdf download – Explosive atmospheres – Part 27: Fieldbus intrinsically safe concept (FISCO)
1scope
This part of lEC 60079 contains the details of apparatus, systems and installation practice foruse with the Fieldbus Intrinsically Safe Concept (FIScO). It is based on the concepts ofManchester encoded， bus powered systems designed in accordance with IEC 61158-2 whichis the physical layer standard for Fieldbus installations.
The constructional and installation requirements of FlscO apparatus and systems aredetermined by lEC 60079-11,IEC 60079-14,and lEC 60079-25,except as modified by thisstandard.Part of a Fieldbus device may be protected by any of the methods of explosionprotection listed in IEC 60079-0,appropriate to the zone of intended use. In thesecircumstances,the requirements of this standard apply only to that part of the apparatusdirectly connected to the intrinsically safe trunk or spurs.
NOTE1 Certification to the FISCO requirements does not prevent apparatus also being certified and marked toIEC 60079-11 in the conventional manner so that they may be used in other systems.$ome apparatus certifiedbefore this standard was published but not necessarily complying with the electrical parameters of this standardmay be marked”Suitable for FISCO systems . This apparatus may be accepted in a FISCO system, if thecomparison of the electrical parameters ue’o，Po, with U,h,P, demonstrate compatibility with the remainder ofthe system, and all the other requirements of this standard are met.
NOTE 2 A typical system is illustrated in Annex A.
NOTE 3 Generally，”ic”FISco systems are intended for use in zone 2 locations. FISCO systems arepredominantly intended for use in zone 1 and 2 locations, but may enter zone 0 locations if specifically permitted todo so by the documentation.
NOTE 4 Edition 1 of this standard introduced the FNlICO concept to cover the use of Fieldbus concepts in zone 2utilizing the energy-limited [nL] concept. This standard substitutes the “ic” concept for the energy-limited concept,but permits the continued use of FNICO and nL apparatus.
2Normative references
The following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies. For undated references, the latest editionof the referenced document (including any amendments) applies.
IEC 60079-0， Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-11,Explosive atmospheres – Part 11:Equipment protection by intrinsic safety “i”
IEC 60079-14，Electrical apparatus for explosive gas atmospheres – Part 14: Electricalinstallations in hazardous areas (other than mines)
IEC 60079-15，Electrical apparatus for explosive gas atmospheres – Part 15: Construction,test and marking of type of protection “n” electrical apparatus
IEC 60079-25,Electrical apparatus for explosive gas atmospheres – Part 25: Intrinsically safesystems
IEC 61158-2,Digital data communications for measurement and control – Fieldbus for use inindustrial control systems – Part 2: Physical layer specification and service definition
3Terms, definitions and abbreviations3.1 Terms and definitions
For the purposes of this document,the terms and definitions given in IEC 60079-0,IEC 60079-11 and EC 60079-15 as well as the following apply.
NOTE Additional definitions applicable to explosive atmospheres can be found in IEv 60050-426.3.2Abbreviations
FIScoFieldbus Intrinsically Safe ConceptFNICOFieldbus Non-Incendive Concept
4Apparatus requirements
4.1General
Apparatus shall be constructed in accordance with IEC 60079-11 except as modified by thisstandard.
The apparatus documentation shall confirm that each apparatus is suitable for use in a FISCOsystem in accordance with this standard.
4.2FISco power supplies
4.2.1General
The power supply shall either be resistive limited or have a trapezoidal or rectangular outputcharacteristic.The maximum output voltage,U, shall be not greater than 17,5 V nor less than14 V under the conditions specified in lEC 60079-11 for the respective level of protection.
The maximum unprotected internal capacitance C;and inductance L; shall be not greater than5 nF and 10 uH, respectively.
The output from the power supply may be connected to earth.
No specification of the internal parameters Lj and C;or the maximum external parameters Loand Co is required on the certificate or label.
The determination of power supply output parameters shall take into account the possibleopening, shorting and earthing of field wiring connected to the field terminals of the apparatus.
4.2.2Additional requirements of “ia” and“ib”FISCo power supplies
The maximum output current lo for any “ia” or ““ib” FISCO power supply shall be determined inaccordance with IEC 60079-11 but shall not exceed 380 mA. For rectangular supplies,Table 1 may be used for assessment.IEC 60079-27 pdf download.
