Clasification Society Rulefinder 2016 - Version 9.25
Clasification Society Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, January 2016 - Part 7 SAFETY SYSTEMS, HAZARDOUS AREAS AND FIRE - Chapter 2 Hazardous Areas and Ventilation - Section 8 Electrical equipment for use in explosive gas atmospheres

Section 8 Electrical equipment for use in explosive gas atmospheres

Parent topic: Chapter 2 Hazardous Areas and Ventilation

8.1 General

8.1.1 The requirements for electrical equipment for use in explosive gas atmospheres are given in Pt 6, Ch 2, 14.1 General, Pt 6, Ch 2, 14.2 Selection of equipment for use in explosive gas atmospheres and Pt 6, Ch 2, 14.9 Cable and cable installation of the Rules and Regulations for the Classification of Ships (hereinafter referred to as the Rules for Ships), which are to be complied with where applicable.

8.1.2 Additional or amended requirements are given in Pt 7, Ch 2, 8.1 General 8.1.3 to Pt 7, Ch 2, 8.1 General 8.1.14.

8.1.3 In locations classified as Zone 0, and in various enclosed spaces identified in Section 9, only intrinsically safe equipment of category ‘ia’, or simple apparatus as defined in Pt 6, Ch 2, 14.2 Selection of equipment for use in explosive gas atmospheres 14.2.4 of the Rules for Ships and complying in full with the relevant requirements of IEC 60079 for intrinsic safety, category ‘ia’, is permitted.

8.1.4 In locations classified as Zone 1 and in spaces and locations identified in Pt 7, Ch 2, 9 Additional requirements for electrical equipment on oil storage units for the storage of oil in bulk having a flash point not exceeding 60°C (closed-cup test) as permitting the installation of safe type equipment, other than locations described in Pt 7, Ch 2, 8.1 General 8.1.5, only the following equipment may be installed:

8.1.5 In locations classified as Zone 2, and on open deck in well ventilated positions not within 3 m of any flammable gas or vapour outlet, equipment having the types of protection listed underPt 6, Ch 2, 14.2 Selection of equipment for use in explosive gas atmospheres 14.2.5 of the Rules for Ships, or as described under Pt 6, Ch 2, 14.2 Selection of equipment for use in explosive gas atmospheres 14.2.6 to Pt 6, Ch 2, 14.2 Selection of equipment for use in explosive gas atmospheres 14.2.6of the Rules for Ships may be installed.

8.1.6 Any electrical equipment which has to remain operational during a Major Accident Event (e.g. rupture of a process vessel or pipe), whether or not installed in a hazardous zone or location, is to be suitable for use in an explosive gas atmosphere. Such equipment is to be of a type permitted within Zone 1 locations, unless it is demonstrated that the equipment is appropriately protected against potentially coming into contact with a flammable atmosphere by being located in an enclosed safe area with appropriate mitigating measures (i.e. enclosed safe area is equipped with gastight barriers, gastight doors, rated gas dampers, suitable gas detection within the enclosure and its ventilation air intakes, etc.).

8.1.7 Flame-proof enclosures and intrinsically safe electrical apparatus, and apparatus incorporating flame-proof or intrinsically safe components or otherwise tested or certified for particular groups, with reference to the group(s) of gas(es) that may be present, is to be selected with reference to IEC/TR 60079-20: Electrical apparatus for explosive gas atmospheres – Part 20: Data for flammable gases and vapours, relating to the use of electrical apparatus.

8.1.8 The electrical apparatus shall be so selected that its maximum surface temperature as indicated by its temperature class, or otherwise documented, will not reach the auto-ignition temperature of any gas or vapour, or mixture of gases or vapour, which can be present. The ambient temperature range for which the apparatus is certified is to be taken to be minus 20°C to 40°C, unless otherwise stated, and account is to be taken of this when assessing the suitability of the equipment for the auto-ignition temperature of the gases encountered.

8.1.9 Cables are not permitted to pass through locations classified as Zone 0, and are permitted to enter such locations only where required for the operation of any electrical equipment located therein.

8.1.10 Cables are to be either:
  1. Mineral insulated with copper sheath; or
  2. Armoured or braided, except where:
    1. The cable is associated with an intrinsically safe circuit; or
    2. The cable does not pass into or through any location classified as Zone 1, and is routed or protected so as to present only a low risk of mechanical damage; or
    3. A cable of flexible construction is demanded by operational requirements, and its construction, routing and means of support are such as to present only a low risk of mechanical damage; or
    4. The cable is installed within a conduit system meeting the relevant requirements of IEC60079-14.

8.1.11 Metal coverings of cables installed in hazardous zones or spaces are to be effectively earthed at both ends, at least, except where otherwise permitted by IEC 60079-14.

8.1.12 Cables associated with intrinsically safe circuits are to be used only for such circuits. They are to be physically separated from cables associated with non-intrinsically safe circuits, e.g. neither installed in the same protective casing nor secured by the same fixing clip, except where alternative arrangements are permitted by IEC 60079-14.

8.1.13 No more than one intrinsically safe circuit should be run in any multicore cable unless:
  1. No circuit is required to be of category ‘ia’, and either:
    1. The cable is run or protected so as to present little risk of its suffering mechanical damage; or
    2. Each intrinsically safe circuit is contained within an earthed metallic screen; or
  2. It can be shown that no combination of faults between the intrinsically safe circuits within the cable can lead to an unsafe condition.

8.1.14 Cabling, wiring, and connections within enclosures containing more than one intrinsically safe circuit, or containing both intrinsically safe and other circuits, are to be arranged in accordance with the relevant requirements of IEC60079-11 and IEC60079-14 so as to minimise the risk of inadvertent interconnections between different circuits.

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