Section 5 Electrical equipment
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 7 Other Ship Types and Systems - Chapter 5 Ships Equipped for Oil Recovery Operations - Section 5 Electrical equipment

Section 5 Electrical equipment

Parent topic: Chapter 5 Ships Equipped for Oil Recovery Operations

5.1 General

5.1.1 The electrical installation is to comply with the relevant requirements of Pt 6, Ch 2 Electrical Engineering, with the specific exceptions of Pt 6, Ch 2, 14.1 General, Pt 6, Ch 2, 14.3 Selection of equipment for use in explosive gas atmospheres, Pt 6, Ch 2, 14.7 Ventilation, Pt 6, Ch 2, 14.8 Pressurisation and Pt 6, Ch 2, 14.10 Requirements for tankers intended for the carriage in bulk, which are replaced by Pt 7, Ch 5, 5.3 Hazardous areas to Pt 7, Ch 5, 5.6 Selection of electrical equipment for installation in hazardous areas of this Chapter.

5.1.2 The requirements of Pt 7, Ch 5, 5 Electrical equipment are not applicable for assignment of the notation Oil Recovery (F.P. >60°C).

5.1.3 The electrical installations on board ships to be assigned the notation Oil Recovery (F.P. >60°C) are to satisfy the relevant requirements of Pt 6, Ch 2 Electrical Engineering.

5.2 Systems of supply and distribution

5.2.1 Only the systems of generation and distribution, listed under Pt 6, Ch 2, 5.1 Systems of supply and distribution 5.1.2, are acceptable.

5.3 Hazardous areas

5.3.1 Hazardous areas associated with oil recovery operations are classified into zones based upon the frequency of the occurrence and duration of an explosive gas atmosphere, as follows:
  • zone 0: an area in which an explosive atmosphere is present continuously or for long periods or frequently
  • zone 1: an area in which an explosive atmosphere is likely to occur periodically or occasionally in normal operation
  • zone 2: an area in which an explosive atmosphere is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

See IEC 60079-10-1: Explosive atmospheres – Part 10-1: Classification of areas – Explosive gas atmospheres.

5.3.2 The following areas are regarded as hazardous, zone 0:
  1. The interiors of tanks intended for the storage of recovered oil.
  2. The interiors of piping systems intended for the handling of recovered oil.
  3. The interiors of equipment containing or contaminated with recovered oil.
  4. Unventilated spaces housing piping systems or other equipment containing or contaminated with recovered oil and having flanged joints or glands or other openings from which leakage of fluid may occur under normal operating conditions.
5.3.3 The following areas are regarded as hazardous, zone 1:
  1. Unventilated spaces:
    1. separated by a single bulkhead, deck or other tank boundary from the interior of a tank intended for recovered oil, or
    2. having a bulkhead immediately above or below and in line with a bulkhead of a tank intended for recovered oil, unless protected by a diagonal plate in accordance with Pt 4, Ch 9, 1.2 Application and ship arrangement 1.2.9 or the arrangements comply with the requirements of Pt 7, Ch 5, 3.1 Structural arrangement 3.1.7.
  2. Ventilated spaces housing piping systems or other equipment containing or contaminated with recovered oil and having flanged joints or glands or other openings from which leakage of fluid may occur under normal operating conditions.
  3. Areas on open deck within a 3 m radius of:
    1. ventilation outlets of tanks intended for recovered oil; or
    2. inspection hatches permitted to be opened under normal operating conditions of tanks intended for recovered oil; or
    3. any sampling or sounding points of tanks intended for recovered oil; or
    4. any flanged joints, glands or other parts of any equipment containing or contaminated with recovered oil from which leakage may occur under normal operating conditions; or
    5. ventilation outlets from spaces described by Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3.(a) or Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3.(b).

    Where the hazard results from flammable gas or vapour having a density relative to that of air of more than 0,75, the hazardous zone is considered to extend vertically downward to solid deck, or for a distance of 9 m, whichever is the lesser.

  4. Areas on open deck within the confines of, and extending 3 m beyond, any bund or barrier intended to contain a spillage of recovered oil, up to a height of 2,4 m.
  5. Areas on open deck within a 1,5 m radius of any opening into a space described by Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3.(a) or Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3.(b).
  6. Enclosed or semi-enclosed spaces with direct opening into a zone 1 hazardous area.
5.3.4 The following areas are regarded as hazardous, zone 2:
  1. Ventilated spaces as defined by Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3.(a).
  2. Areas on open deck extending 1,5 m beyond those defined by Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3.(c) to Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3.(f).
  3. Areas on open deck with unrestricted natural ventilation over all tanks intended for recovered oil, where the tops of the tanks are exposed to the weather, to the full width of the ship plus 3 m fore and aft of the forward-most and aft-most tank bulkhead, up to a height of 0,45 m above the deck or to the height of any bulwarks.
  4. Enclosed or semi-enclosed spaces with direct opening into a zone 2 hazardous area.

5.3.5 Vertical and horizontal extent of hazardous areas defined by Pt 7, Ch 5, 5.3 Hazardous areas 5.3.3 and Pt 7, Ch 5, 5.3 Hazardous areas 5.3.4 is to be additionally considered with reference to density relative to air of flammable gas or vapour encountered. See IEC 60079-10-1: Explosive atmospheres – Part 10-1: Classification of areas – Explosive gas atmospheres.

5.3.6 Consideration may also be given to hazardous areas and sources of hazard defined in accordance with IEC 60079: 10-1: Explosive atmospheres – Part 10-1: Classification of areas – Explosive gas atmospheres and the following are to be submitted.
  1. Design statement that defines the service profile of the oil recovery ship;
  2. A concept of operation (ConOps) document, which is to include:
    1. a functional description of how the ship is intended to be operated; and
    2. details of the ship’s intended service, including the overall purpose(s), and the maximum duration of oil recovery operations per year;
  3. Hazardous area classification data sheets, as required by IEC 60079-10-1: Explosive atmospheres – Part 10-1: Classification of areas – Explosive gas atmospheres;
  4. Hazardous area plans, indicating the location of hazardous areas, and their openings, access and ventilation arrangements;
  5. the hazardous areas classification study is to consider the operation of the oil recovery equipment in reasonably foreseeable normal and abnormal operations; and
  6. Schedule of electrical and mechanical equipment to be located in hazardous areas.

5.4 Ventilation

5.4.1 The extent of any hazardous within an enclosed or semi-enclosed space may be limited to that defined for an equivalent situation on open deck, provided that the ventilation arrangements fulfill all the following conditions:

  1. Mechanical ventilation is provided, with the air intake and outlet located outside any hazardous area defined by Pt 7, Ch 5, 5.3 Hazardous areas 5.3.1, ensuring at least 12 air changes per hour, and leaving no region of stagnant air.

  2. Ventilation air flow is continuously monitored and so arranged that, in the event of failure of ventilation, an alarm is given at an attended station.

5.4.2 An enclosed or semi-enclosed space having a ventilation outlet situated in a hazardous area, as defined under Pt 7, Ch 5, 5.3 Hazardous areas or Pt 7, Ch 5, 5.3 Hazardous areas 5.3.4.(c), may be regarded as non-hazardous if fulfilling all the following conditions:

  1. The space has mechanical ventilation with the air intake from a non-hazardous area.

  2. The ventilation outlet is equipped with a self-closing flap or other suitable means of closure operating automatically on loss of ventilation airflow.

  3. The space contains no equipment of a type described in Pt 7, Ch 5, 5.3 Hazardous areas 5.3.2, or vent from or opening into any hazardous space or zone defined by Pt 7, Ch 5, 5.3 Hazardous areas 5.3.1, other than the ventilation outlet under consideration.

  4. The space is separated by at least two gastight bulkheads from the interior of any tank intended for recovered oil.

5.5 Pressurisation

5.5.1 A space having access to a hazardous area defined as zone 1 may be regarded as non-hazardous if all following requirements are met:
  1. access is by means of an air-lock, having gastight steel doors, the inner of which, as a minimum, is self-closing without any hold-back arrangement;
  2. it is maintained at an overpressure (minimum 0,25 mbar) relative to the external hazardous area by ventilation from a non- hazardous area;
  3. the relative air pressure within the space is continuously monitored and so arranged that:
    1. in the event of loss of overpressure, an alarm is given;
    2. the electrical supply to all equipment not of a type suitable for zone 1 is automatically disconnected;
    3. where the disconnection of equipment could introduce a hazard, an alarm may be given, in lieu of automatic disconnection, upon loss of overpressure; and
    4. a means of manual disconnection of electrical equipment not of a type suitable for zone 1, capable of being controlled from an attended station, is to be provided in conjunction with an agreed operational procedure; and
    5. where the means of disconnection, capable of being controlled from an attended station, is located within the space then it is to be of a type suitable for zone 1;
  4. any electrical equipment required to operate upon loss of overpressure, lighting fittings and equipment within the air-lock, is to be of a type suitable for zone 1;
  5. means are to be provided to prevent electrical equipment, other than of a type suitable for zone 1, being energised until the atmosphere within the space is made safe, by air changes of at least 10 times the capacity of the space; and
  6. it is separated by at least two gastight bulkheads from the interior of any tank intended for recovered oil
5.5.2  A space having access to a hazardous area defined as zone 2 may be regarded as non-hazardous if all following requirements are met:
  1. access is by means of a self-closing gastight steel door without any hold-back arrangement;
  2. it is maintained at an overpressure (minimum 0,25 mbar) relative to the external hazardous area by ventilation from a non- hazardous area;
  3. the relative air pressure within the space is continuously monitored and so arranged that:
    1. in the event of loss of overpressure, an alarm is given; and
    2. a means of manual disconnection of electrical equipment not of a type suitable for zone 2, capable of being controlled from an attended station, is to be provided; where the means of disconnection, capable of being controlled from an attended station, is located within the space then it is to be of a type suitable for zone 2;
  4. any electrical equipment required to operate upon loss of overpressure (e.g. lighting fittings), is to be of a type suitable for zone 2;
  5. means are to be provided to prevent electrical equipment, other than of a type suitable for zone 2, being energised until the atmosphere within the space is made safe, by air changes of at least 10 times the capacity of the space; and
  6. it is separated by at least two gastight bulkheads from the interior of any tank intended for recovered oil.
5.5.3 A space having access to a hazardous area defined as zone 1 may be regarded as zone 2 if all following requirements are met:
  1. access is by means of a self-closing gastight steel door without any hold-back arrangement;
  2. it is maintained at an overpressure relative to the external hazardous area by ventilation from a non-hazardous area;
  3. the relative air pressure within the space is continuously monitored and so arranged that:
    1. in the event of loss of overpressure, an alarm is given; and;
    2. a means of manual disconnection of electrical equipment not of a type suitable for zone 1, capable of being operated from an attended station, is to be provided; where the means of disconnection, capable of being operated from an attended station, is located within the space then it is to be of a type suitable for zone 1;
  4. any electrical equipment required to operate upon loss of overpressure (e.g. lighting fittings), is to be of a type suitable for zone 1; and
  5. means are to be provided to prevent electrical equipment, other than of a type suitable for zone 1, being energised until the atmosphere within the space is made safe, by air changes of at least 10 times the capacity of the space.

5.6 Selection of electrical equipment for installation in hazardous areas

5.6.1 The installation of electrical equipment in hazardous areas is to be minimised.

5.6.2 When electrical equipment is to be installed in hazardous areas,it is to be of a type appropriate for Group IIA, temperature class T3 and compliant with the relevant Parts of IEC 60079: Explosive atmospheres, or an acceptable and relevant National Standard, unless permitted otherwise by Pt 7, Ch 5, 5.6 Selection of electrical equipment for installation in hazardous areas 5.6.4Pt 7, Ch 5, 5.6 Selection of electrical equipment for installation in hazardous areas 5.6.5, or Pt 7, Ch 5, 5.6 Selection of electrical equipment for installation in hazardous areas 5.6.6.

5.6.3 Equipment for zone 0 or zone 1, with the exception of simple apparatus as defined in Pt 7, Ch 5, 5.6 Selection of electrical equipment for installation in hazardous areas 5.6.4 or Pt 7, Ch 5, 5.6 Selection of electrical equipment for installation in hazardous areas 5.6.5, is to be certified or approved by a National or other appropriate authority. Equipment without independent certification or approval may be considered for installation in zone 2.

5.6.4 In zone 0, the following may be considered:

  1. intrinsically safe, category‘a’ (Ex‘ia’);
  2. simple electrical apparatus and components (for example thermocouples, photocells, strain gauges, junction boxes, switching devices), included in intrinsically safe circuits of category ‘ia’,compliant with IEC 60079-14: Explosive atmospheres — Part 14: Electrical installations design, selection and erection; and
  3. submersible pumps, having at least two independent methods of shutting down automatically in the event of low liquid level.
    Note Oil recovery equipment deployed over an oil spill pool is to be appropriate for zone 0.

5.6.5 In zone 1, the following may be considered:

  1. apparatus permitted within zone 0;
  2. intrinsically safe, category‘b’ (Ex‘ib’);
  3. simple apparatus as defined above, included in intrinsically safe circuits of category ‘ib’;
  4. increased safety (Ex ‘e’);
  5. flameproof (Ex ‘d’);
  6. pressurised enclosure (Ex ‘p’);
  7. powder filled (Ex ‘q’); or
  8. encapsulated (Ex ‘m’).

5.6.6 In zone 2, the following may be considered:

  1. apparatus permitted within zone 1;
  2. type of protection ‘n’ or ‘N’;
  3. equipment such as control panels, protected by purging and pressurisation and capable of being verified by inspection as meeting the requirements of IEC60079-2: Explosive atmospheres – Part 2: Equipment protection by pressurized enclosures "p"; or
  4. radio aerials having robust construction, meeting the relevant requirements of IEC 60079-15: Explosiveatmospheres– Part 15: Equipment protection by type of protection "n". Additionally, in the case of transmitter aerials, it is to be shown, by detailed study or measurement, or by limiting the peak radiated power and field strength to 1 W and 30 V/m respectively, that they present negligible risk of inducing incendive sparking in adjacent structures or equipment.

5.6.7 Consideration may also be given to other types of protection, selected in accordance with the requirements of IEC 60079-14: Explosive atmospheres – Part 14: Electrical installations design, selection and erection.

5.6.8 Electrical equipment not essential for the safety or operation of the ship and which is not of a type providing protection against ignition of the recovered oil gases is to be completely disconnected and protected against unauthorised re-connection. Disconnection is to be made outside the hazardous areas and be effected with isolating links or lockable switches.

5.6.9 Electrical installations in machinery spaces adjacent to recovered oil tanks, where permitted by Pt 7, Ch 5, 3.1 Structural arrangement 3.1.7, are to be of a type described in Pt 7, Ch 5, 5.6 Selection of electrical equipment for installation in hazardous areas 5.6.6 within 0,45 m of the tank bulkhead or the bottom of the space.

Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.