Section 3 Electrical System

301. General

1. The requirements of this Section are to be applied in addition to the requirements of Pt.6, Ch.1

of the Rules for Steel Ships.

2. Hazardous areas on open deck and other spaces not defined in this Section are to be decided based on a recognized standard(Refer to IEC standard 60092-502, part 4.4: Tankers carrying flammable liquefied gases as applicable). The electrical equipment fitted within hazardous areas is to be ac- cording to the same standard.

3. Electrical equipment and wiring are in general not to be installed in hazardous areas of 303. unless essential for operational purposes based on a recognized standard(The type of equipment and in-

stallation 10-1).

4. Electrical

requirements should comply with IEC standard 60092-502 and IEC 60079-10-1 : Part

equipment fitted in an ESD-protected machinery space is to fulfil the following:

(1) In addition to fire and hydrocarbon detectors and fire and gas alarms, lighting and ventilation fans are to be certified safe for hazardous area zone 1.

(2) All electrical equipment in a machinery space containing gas-fuelled engines, and not certified

for zone 1 are to be automatically disconnected, if gas concentrations above 20% LEL is de- tected on two detectors in the space containing gas-fuelled engines.

5. There is to be an equalization connection between the bunker supplier and the bunkering station on the ship when a flammable gas/liquid is transferred.

6. Cable penetrations are to satisfy the requirements regulating the dispersion of gas.

302. General Area classification

1. Area classification is a method of analysing and classifying the areas where explosive gas atmos- pheres may occur. The object of the classification is to allow the of electrical apparatus able to be operated safely in these areas.

2. In order to facilitate the selection of appropriate electrical apparatus and the design of suitable elec- trical installations, hazardous areas are divided into zones 0, 1 and 2 and the area classification is to be in accordance with 303. (Refer to IEC 60079-10-1 : Part 10-1).

3. Area classification of a space may be dependent on ventilation(Refer to IEC 60092-02, table 1.)

4. A space with opening to an adjacent hazardous area on open deck, may be made into a less haz- ardous or non-hazardous space, by means of overpressure. Requirements to such pressurization are given in 110.

5. Ventilation ducts are to have the same area classification as the ventilated space.

303. Hazardous area zones

1. Zone “0”

Zone "0" includes:

(1) The interiors of gas tanks

(2) Pipes and equipment containing gas

(3) Any pipe work of pressure-relief or other venting systems for gas tanks

Instrumentation and electrical apparatus in contact with the gas or liquid gas are to be of a type suitable for zone 0. Temperature sensors installed in thermo wells, and pressure sensors without ad- ditional separating chamber are to be of intrinsically safe type Ex-ia.

2. Zone “1”

Zone "1" includes:

(1) Tank room;

(2) Gas compressor room arranged with ventilation according to 110.

4;

(3) Areas on open deck, or semi-enclosed spaces on deck, within 3 m of any gas tank outlet, gas or vapour outlet(such areas are, for example, all areas within 3 m of gas tank hatches, ullage openings or sounding pipes for gas tanks located on open deck and gas vapour outlets.), bunker manifold valve, other gas valve, gas pipe flange, gas pump-room ventilation outlets and gas tank openings for pressure release provided to permit the flow of small volumes of gas or vapour

(4) Areas on open deck or semi-enclosed spaces on deck, within 1.5 m of gas compressor and pump room entrances, gas pump and compressor room ventilation inlets and other openings into zone 1 spaces;

(5)

(6)

(7)

Areas on the open deck within spillage coamings surrounding gas bunker manifold valves and 3m beyond these, up to a height of 2.4 m above the deck;

Enclosed or semi-enclosed spaces in which pipes containing gas are located, e.g., ducts around

gas pipes, semi-enclosed bunkering stations; and

The ESD-protected machinery space is considered as non-hazardous area during normal oper- ation, but changes to zone 1 in the event of gas leakage.

3. Zone “2”

(1) Areas within 1.5 m surrounding open or semi-enclosed spaces of zone 1(Refer to IEC 60092-502 or IEC 60079-10-1 : Part 10-1)