Section 3 Hazardous Areas and Electrical Installations

301. General

Electrical installations onboard single point moorings are to comply with the requirements of Ch 10 of "Rules for Mobile Offshore Units" and the additional or modified requirements contained in this Section. Alternatively, consideration will be given to installations that complying with the require- ments contained in this Section and applicable standards deemed by the Society, provided that they are not less effective.

302. Hazardous areas

1. Definitions

(1) Hazardous areas are all those areas where a flammable atmosphere may be expected to exist continuously or intermittently.

(2) Hazardous areas are subdivided into Zones 0, 1 and 2 defined as follows:

Zone 0: A zone in which an explosive gas-air mixture is continuously present or present for long periods.

Zone 1:

A zone in which an explosive gas-air mixture is likely to occur in normal operating

conditions.

Zone 2: A zone in which an explosive gas-air mixture is it will exist only for a short time.

(3) Enclosed space is considered to be a space bounded by may not have doors, windows, or other similar openings.

2. Classification of areas

(1) The area within 3 meters of a cargo or product swivel is non-enclosed area.

not likely to occur, and if it occurs,

decks and bulkheads which may or

considered a Zone 2 area when in a

(2) When a cargo or product swivel is installed within an enclosed space, the space is considered a Zone 1 area.

(3) The inside of tanks, swivels or pipes containing hydrocarbons are considered Zone 0 areas.

(4) In addition to the hazardous areas defined in (1) to (3) above, the principles of API RP 500 Section B "Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities" are to be considered in delineating hazardous areas associated with compo- nents of the SPM.

303. Cables and types of electrical equipment permitted in hazardous areas

1. Electrical equipment

The following equipment and cables are acceptable for installation in hazardous locations:

(1) Zone 0 areas

Only certified intrinsically-safe circuits or equipment and associated wiring

(2) Zone 1 areas

(A) Certified

intrinsically-safe circuits or equipment and associated wiring

(B) Certified flameproof (explosion proof) equipment

(C) Certified

given to

increased safety equipment; for increased safety motors due consideration is to be the protection against overcurrent

Ch 4

(D) Pressurized enclosure type equipment(pressurization systems are to comply with applicable industry standards)

(E) Permanently installed cables with metallic armor, a metallic sheath, or installed in metallic

conduit with explosion proof gastight fittings. However, flexible cables, where necessary, may be installed provided they are of heavy duty type.

(3) Equipment and cables permitted in Zone 2 areas are all equipment approved for Zone 1 areas and the following equipment provided the operating temperature does not exceed 315좧 and

provided any brushes, switching mechanisms, or similar arc-producing devices are approved for Zone 1 areas:

(A) Enclosed squirrel-cage induction motors

(B) Fixed Lighting fixtures protected from mechanical damage

(C) Transformers, solenoids, or impedance coils in general purpose enclosures

(D) Cables with moisture-resistant jacket (impervious sheathed) and protected from mechanical damage.

2. Cable installation

Electrical conductors are to be run with a view to avoiding as far as practical, spaces where gas may normally be expected to accumulate. No cable splices are allowed in hazardous areas except in intrinsically-safe circuits.

Where it is necessary to join cables in a hazardous area (e.g. flexible cable connections to non- flexible cables), the joints are to be made in approved junction boxes.

304. Electrical swivels

If installed in a hazardous area, the electrical swivel is to be certified by an independent testing laboratory as suitable for installation within such an area as per 302. above.

The amperage ratings of electrical swivels (slip rings) are to be adequate to carry the full load cur-

rent of the equipment supplied.