6.2 Classification of hazardous areas footnote
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Statutory Documents - IMO Publications and Documents - International Codes - 1989 MODU Code – Code for the Construction and Equipment of Mobile Offshore Drilling Units, 1989 – Resolution A.649(16) - Chapter 6 – Machinery and Electrical Installations in Hazardous Areas for all Types of Units - 6.2 Classification of hazardous areas1

6.2 Classification of hazardous areas footnote

  6.2.1 For the purpose of machinery and electrical installations, hazardous areas are classified as in 6.2.2 to 6.2.4. Hazardous areas not covered in this paragraph should be classified in accordance with 6.1.

  6.2.2 Hazardous areas zone 0

The internal spaces of closed tanks and pipes for active drilling mud, as well as oil and gas products. e.g. escape gas outlet pipes, or spaces in which an oil/gas/air mixture is continuously present or present for long periods.

  6.2.3 Hazardous areas zone 1

  • .1 Enclosed spaces containing any part of the mud circulating system that has an opening into the spaces and is between the well and the final degassing discharge.

  • .2 Enclosed spaces or semi-enclosed locations that are below the drill floor and contain a possible source of release such as the top of a drilling nipple.

  • .3 Enclosed spaces that are on the drill floor and which are not separated by a solid floor from the spaces in 6.2.3.2.

  • .4 In outdoor or semi-enclosed locations, except as provided for in 6.2.3.2, the area within 1.5 m from the boundaries of any openings to equipment which is part of the mud system as specified in 6.2.3.1, any ventilation outlets of zone 1 spaces, or any access to zone 1 spaces.

  • .5 Pits, ducts or similar structures in locations which would otherwise be zone 2 but which are so arranged that dispersion of gas may not occur.

  6.2.4 Hazardous areas zone 2

  • .1 Enclosed spaces which contain open sections of the mud circulating system from the final degassing discharge to the mud pump suction connection at the mud pit.

  • .2 Outdoor locations within the boundaries of the drilling derrick up to a height of 3 m above the drill floor.

  • .3 Semi-enclosed locations below and contiguous to the drill floor and to the boundaries of the derrick or to the extent of any enclosure which is liable to trap gases.

  • .4 Outdoor locations below the drill floor and within a radius of 3 m from a possible source of release such as the top of a drilling nipple.

  • .5 The areas 1.5 m beyond the zone 1 areas specified in 6.2.3.4 and beyond the semi-enclosed locations specified in 6.2.3.2.

  • .6 Outdoor areas within 1.5 m of the boundaries of any ventilation outlet from or access to a zone 2 space.

  • .7 Semi-enclosed derricks to the extent of their enclosure above the drill floor or to a height of 3 m above the drill floor, whichever is greater.

  • .8 Air locks between a zone 1 and a non-hazardous area.

Parent topic: Chapter 6 – Machinery and Electrical Installations in Hazardous Areas for all Types of Units
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