Resolution MSC.285(86)

INTERIM GUIDELINES ON SAFETY FOR NATURAL GAS-FUELLED ENGINE INSTALLATIONS IN SHIPS

(adopted on 1 June 2009)

 

 

THE MARITIME SAFETY COMMITTEE,

 

RECALLING Article 28(b) of the Convention on the International Organization concerning the functions of the Committee,

 

NOTING that the International Convention for the Safety of Life at Sea, 1974 currently does not have any provisions for use of gas as fuel on ships other than gas carriers,

 

RECOGNIZING a need for the development of a code for gas-fuelled ships,

 

ACKNOWLEDGING that, in the interim, there is an urgent need to provide guidance to the Administrations on the gas-fuelled engine installations in ships,

 

HAVING CONSIDERED the Interim Guidelines prepared by the Sub-Committee on Bulk Liquids and Gases at its thirteenth session,

 

1. ADOPTS the Interim Guidelines on safety for natural gas-fuelled engine installations in ships, the text of which is set out in the Annex to the present resolution;

 

2. INVITES Governments to apply the Interim Guidelines to gas-fuelled ships other than those covered by the IGC Code;

 

3. URGES Member Governments and the industry to submit information, observations, comments and recommendations based on the practical experience gained through the application of these Interim Guidelines and submit relevant safety analysis on gas-fuelled installations;

 

4. AGREES to continue the work on the development of the International Code of Safety for Gas-fuelled Ships (IGF Code).

 

Annex.

INTERIM GUIDELINES ON SAFETY FOR NATURAL GAS-FUELLED ENGINE INSTALLATIONS IN SHIPS

 

PREAMBLE

 

1. These Interim Guidelines have been developed to provide an international standard for ships, other than vessels covered by the IGC Code, with natural gas-fuelled engine installations.

 

2. The goal of these Interim Guidelines is to provide criteria for the arrangement and installation of machinery for propulsion and auxiliary purposes, using natural gas as fuel, which will have an equivalent level of integrity in terms of safety, reliability and dependability as that which can be achieved with a new and comparable conventional oil-fuelled main and auxiliary machinery.

 

3. To achieve this goal, the functional requirements described below are embodied in the relevant parts of these Interim Guidelines:

 

.1 Minimize hazardous areas as far as is practicable to reduce the potential risks that might affect the safety of the ship, personnel and equipment.

 

.2 Minimize equipment installed in hazardous areas to that required for operational purposes. Equipment installed in hazardous areas should be suitable and appropriately certified.

 

.3 Arrange hazardous areas to ensure pockets of gas cannot accumulate under normal and foreseeable failure conditions.

 

.4 Arrange propulsion and electrical power generating installation to be capable of sustained or restored operation in the event that a gas-fuelled essential service becomes inoperative.

 

.5 Provide ventilation to protect personnel from an oxygen deficient atmosphere in the event of a gas leakage.

 

.6 Minimize the number of ignition sources in hazardous spaces by design, arrangements and selection of suitable equipment.

 

.7 Arrange safe and suitable gas fuel storage and bunkering arrangements capable of taking on board and containing the gas fuel in the required state without leakage and overpressure.

 

.8 Provide gas piping systems, containment and overpressure relief arrangements that are of suitable design, construction and installation for their intended application.

 

.9 Design, construct, install, operate and protect gas-fuelled machinery, gas system and components to achieve safe and reliable operation consistent with that of oil-fuelled machinery.

 

.10 Arrange and locate gas storage tank rooms and machinery spaces such that a fire or explosion in either will not render the machinery/equipment in other compartments inoperable.

 

.11 Provide safe and reliable gas-fuel control engineering arrangements consistent with those of oil-fuelled machinery.

 

.12 Provide appropriate selection of certified equipment and materials that are suitable for use within gas systems.

 

.13 Provide gas detection systems suitable for the space concerned together with monitoring, alarm and shutdown arrangements.

 

.14 Provide protection against the potential effects of a gas-fuel explosion.

 

.15 Prevent explosion and hazardous consequences.

 

.16 Provide fire detection, protection and extinction measures appropriate to the hazards concerned.

 

.17 Provide a level of confidence in a gas-fuelled unit that is equivalent to that for an oil-fuelled unit.

 

.18 Ensure that commissioning, trials and maintenance of gas utilization machinery satisfy the goal in terms of reliability, availability and safety.

 

.19 Provide provision for procedures detailing the guidelines for safe routine and unscheduled inspection and maintenance.

 

.20 Provide operational safety through appropriate training and certification of crew.

 

.21 Provide for submission of technical documentation in order to permit an assessment of the compliance of the system and its components with the applicable rules and guidelines.

 

4. The Interim Guidelines address the safety of ships utilizing natural gas as fuel.

 

5. Natural gas (dry) is defined as gas without condensation at common operating pressures and temperatures where the predominant component is methane with some ethane and small amounts of heavier hydrocarbons (mainly propane and butane).

 

6. The gas composition can vary depending on the source of natural gas and the processing of the gas. Typical composition in volume (%):

 

Methane        (C₁) 94.0%

 

Ethane         (C₂) 4.7%

 

Propane        (C₃) 0.8%

 

Butane         (C₄+) 0.2%

 

Nitrogen                 0.3%

 

Density gas     0.73 kg/sm³

 

Density liquid  0.45 kg/dm³

 

Calorific value (low) 49.5 MJ/kg

 

Methane number  83

 

The gas may be stored and distributed as compressed natural gas (CNG) or liquefied natural gas (LNG).

 

CHAPTER 1.
GENERAL

 

1.1 Application

 

1.1.1 These Interim Guidelines apply to internal combustion engine installations in ships using natural gas as fuel. The engines may use either a single fuel (gas) or dual fuel (gas and oil fuel), and the gas may be stored in gaseous or liquid state.

 

1.1.2 These Interim Guidelines should be applied in addition to the relevant provisions of the International Convention for the Safety of Life at Sea (SOLAS), 1974 and the Protocol of 1988 relating thereto, as amended.

 

1.1.3 The Interim Guidelines are applicable to new ships. Application to existing ships should be decided by the Administration to the extent it deems necessary.

 

1.2 Hazards

 

These Guidelines address the hazards related to the arrangements for the storage, distribution and use of natural gas as a fuel.

 

1.3 Definitions

 

For the purpose of these Guidelines, unless otherwise stated below, definitions are as defined in SOLAS chapter II-2.

 

1.3.1 Accidents mean uncontrolled events that may entail the loss of human life, personal injuries, environmental damage or the loss of assets and financial interests.

 

1.3.2 Certified safe type means electrical equipment that is certified safe by a recognized body based on a recognized standard¹. The certification of electrical equipment is to correspond to the category and group for methane gas.

 

1.3.3 CNG means compressed natural gas.

 

1.3.4 Control stations mean those spaces defined in SOLAS chapter II-2 and additionally for these Guidelines, the engine control room.

 

1.3.5 Double block and bleed valve means a set of three automatic valves located at the fuel supply to each of the gas engines.

 

1.3.6 Dual fuel engines mean engines that can burn natural gas and fuel oil oil fuel simultaneously or operate on oil fuel or gas only.

 

1.3.7 Enclosed space means any space within which, in the absence of artificial ventilation, the ventilation will be limited and any explosive atmosphere will not be dispersed naturally².

________________

¹ Refer to IEC 60079 series, Explosive atmospheres and IEC 60092-502:1999 Electrical Installations in Ships – Tankers – Special Features.

² See also definition in IEC 60092-502:1999.

 

1.3.8 ESD means emergency shutdown.

 

1.3.9 Explosion means a deflagration event of uncontrolled combustion.

 

1.3.10 Explosion pressure relief means measures provided to prevent the explosion pressure in a container or an enclosed space exceeding the maximum overpressure the container or space is designed for, by releasing the overpressure through designated openings.

 

1.3.11 Gas means a fluid having a vapour pressure exceeding 2.8 bar absolute at a temperature of 37.8°C.

 

1.3.12 Hazardous area means an area in which an explosive gas atmosphere or a flammable gas (flashpoint below 60°C) is or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of electrical apparatus.

 

Hazardous areas are divided into zones 0, 1 and 2 as defined below³:

______________

³ Refer also to the area classification specified in Sec. 2.5 of IEC 60079-10-1:2008 Explosive atmospheres – Part 10-1: Classification of areas – Explosive gas atmospheres.

 

.1 Zone 0 is an area in which an explosive gas atmosphere or a flammable gas with a flashpoint below 60°C is present continuously or is present for long periods.

 

.2 Zone 1 is an area in which an explosive gas atmosphere or a flammable gas with a flashpoint below 60°C is likely to occur in normal operation.

 

.3 Zone 2 is an area in which an explosive gas atmosphere or a flammable gas with a flashpoint below 60°C is not likely to occur in normal operation and, if it does occur, is likely to do so only infrequently and will exist for a short period only.

 

1.3.13 Non-hazardous area means an area which is not considered to be hazardous, i.e. gas safe, provided certain conditions are being met.

 

1.3.14 High-pressure piping means gas fuel piping with maximum working pressure greater than 10 bar.

 

1.3.15 IEC means the International Electrotechnical Commission.

 

1.3.16 IGC Code means the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, as amended.

 

1.3.17 LEL means the lower explosive limit.

 

1.3.18 LNG means liquefied natural gas (refer to 1.3.22).

 

1.3.19 Main tank valve means a remote operated valve on the gas outlet from a gas storage tank, located as close to the tank outlet point as possible.

 

1.3.20 MARVS means the maximum allowable relief valve setting of a gas tank.

 

1.3.21 Master gas fuel valve means an automatic valve in the gas supply line to each engine located outside the machinery space for gas-fuelled engines and as close to the gas heater (if fitted) as possible.

 

1.3.22 Natural gas means a gas without condensation at common operating pressures and temperatures where the predominant component is methane with some ethane and small amounts of heavier hydrocarbons (mainly propane and butane).

 

1.3.23 Open deck means a deck that is open on both ends, or is open on one end and equipped with adequate natural ventilation that is effective over the entire length of the deck through permanent openings distributed in the side panels or in the deck above.

 

1.3.24 Organization means the International Maritime Organization (IMO).

 

1.3.25 Risk means the expression of the danger that an undesired event represents to persons, to the environment or to material property. The risk is expressed by the probability and consequences of an accident.

 

1.3.26 Recognized standards means applicable international or national standards acceptable to the Administration or standards laid down and maintained by an organization which complies with the standards adopted by the Organization and which is recognized by the Administration.

 

1.3.27 Safety management system means the international safety management system as described in the ISM Code.

 

1.3.28 Second barrier means a technical measure which prevents the occurrence of a hazard if the first barrier fails, e.g., second housing of a tank protecting the surroundings from the effect of tank leaks.

 

1.3.29 Semi-enclosed space means a space limited by decks and or bulkheads in such manner that the natural conditions of ventilation are notably different from those obtained on open deck⁴.

 

1.3.30 Single gas fuel engine means a power generating engine capable of operating on gas-only, and not able to switch over to oil fuel operation.

 

1.3.31 SOLAS Convention means the International Convention for the Safety of Life at Sea, 1974, as amended.

 

1.3.32 Source of release means any valve, detachable pipe joint, pipe packing, compressor or pump seal in the gas fuel system.

 

1.3.33 Tank room means the gastight space surrounding the bunker tank, containing all tank connections and all tank valves.

 

1.4 Survey requirements

 

1.4.1 Surveys should be performed and certificates issued in accordance with the provisions of SOLAS 1974, as modified by its 1988 Protocol and as amended, chapter 1, part B, regulation 6 or 7, as applicable⁵.

 

⁴. Refer also to IEC 60092-502:1999 Electrical Installations in Ships – Tankers – Special Features.

 

⁵. Refer to the Revised survey guidelines under the harmonized system of survey and certification (resolution A.997(25)).

 

CHAPTER 2.
SHIP ARRANGEMENTS AND SYSTEM DESIGN

 

2.1 General

 

2.1.1 For any new or altered concept or configuration a risk analysis should be conducted in order to ensure that any risks arising from the use of gas-fuelled engines affecting the structural strength and the integrity of the ship are addressed. Consideration should be given to the hazards associated with installation, operation, and maintenance, following any reasonably foreseeable failure.

 

2.1.2 The risks should be analysed using acceptable and recognized risk analysis techniques and loss of function, component damage, fire, explosion and electric shock should as a minimum be considered. The analysis should ensure that risks are eliminated wherever possible. Risks which cannot be eliminated should be mitigated as necessary. Details of risks, and the means by which they are mitigated, should be included in the operating manual.

 

2.1.3 An explosion in any space containing open gas sources should not:

 

.1 cause damage to any space other than that in which the incident occurs;

 

.2 disrupt the proper functioning of other zones;

 

.3 damage the ship in such a way that flooding of water below the main deck or any progressive flooding occur;

 

.4 damage work areas or accommodation in such a way that people who stay in such areas under normal operating conditions are injured;

 

.5 disrupt the proper functioning of control stations and switchboard rooms for necessary power distribution;

 

.6 damage life-saving equipment or associated launching arrangements;

 

.7 disrupt the proper functioning of fire-fighting equipment located outside the explosion-damaged space; or

 

.8 affect other areas in the vessel in such a way that chain reactions involving, inter alia, cargo, gas and bunker oil may arise.

 

2.2 Material requirements

 

2.2.1 Materials used in gas tanks, gas piping, process pressure vessels and other components in contact with gas should be in accordance with IGC Code, chapter 6, Materials of construction. For CNG tanks, the use of materials not covered by the IGC Code may be specially considered by the Administration.

 

2.2.2 Materials for piping system for liquefied gases should comply with the requirements of the IGC Code, section 6.2. Some relaxation may, however, be permitted in the quality of the material of open-ended vent piping, provided the temperature of the gas at atmospheric pressure is -55°C or higher, and provided no liquid discharge to the vent piping can occur. Materials should in general be in accordance with recognized standards.

 

2.2.3 Materials having a melting point below 925°C should not be used for piping outside the gas tanks except for short lengths of pipes attached to the gas tanks, in which case the low melting point materials should be wrapped in class A-60 insulation.

 

2.3 Location and separation of spaces

 

2.3.1 The arrangement and location of spaces

 

The arrangement and location of spaces for gas fuel storage, distribution and use should be such that the number and extent of hazardous areas is kept to a minimum.

 

2.3.2 Gas compressor room

 

2.3.2.1 Compressor rooms, if arranged, should be located above freeboard deck, unless those rooms are arranged and fitted in accordance with the requirements of these Guidelines for tank rooms.

 

2.3.2.2 If compressors are driven by shafting passing through a bulkhead or deck, the bulkhead penetration should be of gastight type.

 

2.3.3 Machinery spaces containing gas-fuelled engines

 

2.3.3.1 When more than one machinery space is required for gas-fuelled engines and these spaces are separated by a single bulkhead, the arrangements should be such that the effects of a gas explosion in either space can be contained or vented without affecting the integrity of the adjacent space and equipment within that space.

 

2.3.3.2 ESD-protected machinery spaces for gas-fuelled engines should have as simple a geometrical shape as possible.

 

2.3.4 Tank rooms

 

2.3.4.1 Tank room boundaries including access doors should be gastight.

 

2.3.4.2 The tank room should not be located adjacent to machinery spaces of category A. If the separation is by means of a cofferdam the separation should be at least 900 mm and insulation to class A-60 should be fitted on the engine-room side.

 

2.4 Arrangement of entrances and other openings