5 Ship Design and Arrangement

5.1 Goal

The goal of this chapter is to provide for safe location, space arrangements and mechanical protection of power generation equipment, fuel storage systems, fuel supply equipment and refuelling systems.

5.2 Functional requirements

5.3 Regulations – General

5.3.1 Fuel storage tanks shall be protected against mechanical damage.

5.3.2 Fuel storage tanks and or equipment located on open deck shall be located to ensure sufficient natural ventilation, so as to prevent accumulation of escaped gas.

5.3.3 The fuel tank(s) shall be protected from external damage caused by collision or grounding in the following way:

• .1 The fuel tanks shall be located at a minimum distance of B/5 or 11.5 m, whichever is less, measured inboard from the ship side at right angles to the centreline at the level of the summer load line draught;

  where:

  • B is the greatest moulded breadth of the ship at or below the deepest draught (summer load line draught) (refer to SOLAS regulation II-1/2.8).

• .2 The boundaries of each fuel tank shall be taken as the extreme outer longitudinal, transverse and vertical limits of the tank structure including its tank valves.

• .3 For independent tanks the protective distance shall be measured to the tank shell (the primary barrier of the tank containment system). For membrane tanks the distance shall be measured to the bulkheads surrounding the tank insulation.

• .4 In no case shall the boundary of the fuel tank be located closer to the shell plating or aft terminal of the ship than as follows:

  • .1 For passenger ships: B/10 but in no case less than 0.8 m. However, this distance need not be greater than B/15 or 2 m whichever is less where the shell plating is located inboard of B/5 or 11.5 m, whichever is less, as required by 5.3.3.1.

  • .2 For cargo ships:

    • .1 for V_c below or equal 1,000 m³, 0.8 m;

    • .2 for 1,000 m³ < V_c < 5,000 m³, 0.75 + V_c x 0.2/4,000 m;

    • .3 for 5,000 m³ ≤ Vc < 30,000 m³, 0.8 + V_c/25,000 m; and

    • .4 for V_c ≥ 30,000 m³, 2 m,

    • where:

      • V_c corresponds to 100% of the gross design volume of the individual fuel tank at 20°C, including domes and appendages.

• .5 The lowermost boundary of the fuel tank(s) shall be located above the minimum distance of B/15 or 2.0 m, whichever is less, measured from the moulded line of the bottom shell plating at the centreline.
• .6 For multihull ships the value of B may be specially considered.
• .7 The fuel tank(s) shall be abaft a transverse plane at 0.08L measured from the forward perpendicular in accordance with SOLAS regulation II-1/8.1 for passenger ships, and abaft the collision bulkhead for cargo ships.
  • where:
    • L is the length as defined in the International Convention on Load Lines (refer to SOLAS regulation II-1/2.5).
• .8 For ships with a hull structure providing higher collision and/or grounding resistance, fuel tank location regulations may be specially considered in accordance with section 2.3.

LR 5.3-01 The Tank Master Isolation Valve (TMIV) and pipework from the TMIV to the fuel tank shall be located at the minimum distance required for the fuel tank as determined by 5.3.3.

LR 5.3-02 Subject to agreement by the National Administration, physical protection of fuel tanks from collisions and groundings may be provided where the protection is equivalent to the intent of 5.3.3 and the boundary of the fuel tank is not closer to the shell plating or aft terminal than determined by 5.3.4.

5.3.4 As an alternative to 5.3.3.1 above, the following calculation method may be used to determine the acceptable location of the fuel tanks:

• .1 The value f_CN calculated as described in the following shall be less than 0.02 for passenger ships and 0.04 for cargo ships.^footnote

• .2 The f_CN is calculated by the following formulation:

  • f_CN = f_l X f_t X f_v

  • where:

    • f_l is calculated by use of the formulations for factor p contained in SOLAS regulation II-1/7-1.1.1.1. The value of x1 shall correspond to the distance from the aft terminal to the aftmost boundary of the fuel tank and the value of x 2 shall correspond to the distance from the aft terminal to the foremost boundary of the fuel tank.

    • f_t is calculated by use of the formulations for factor r contained in SOLAS regulation II-1/7-1.1.2, and reflects the probability that the damage penetrates beyond the outer boundary of the fuel tank. The formulation is:

      • f_t = 1 - r(x1, x2, b) ^footnote

    • f_v is calculated by use of the formulations for factor v contained in SOLAS regulation II-1/7-2.6.1.1 and reflects the probability that the damage is not extending vertically above the lowermost boundary of the fuel tank. The formulations to be used are:

      • f_v = 1.0 - 0.8 · ((H - d) /7.8), if (H - d) is less than or equal to 7.8 m. f_v shall not be taken greater than 1.

      • f_v = 0.2 - (0.2 · ((H - d) - 7.8)/4.7), in all other cases f_v shall not be taken less than 0.

    • where:

      • H is the distance from baseline, in metres, to the lowermost boundary of the fuel tank; and

      • d is the deepest draught (summer load line draught).

• .3 The boundaries of each fuel tank shall be taken as the extreme outer longitudinal, transverse and vertical limits of the tank structure including its tank valves.

• .4 For independent tanks the protective distance shall be measured to the tank shell (the primary barrier of the tank containment system). For membrane tanks the distance shall be measured to the bulkheads surrounding the tank insulation.

• .5 In no case shall the boundary of the fuel tank be located closer to the shell plating or aft terminal of the ship than as follows:

  • .1 For passenger ships: B/10 but in no case less than 0.8 m. However, this distance need not be greater than B/15 or 2 m whichever is less where the shell plating is located inboard of B/5 or 11.5 m, whichever is less, as required by 5.3.3.1.

  • .2 For cargo ships:

    • .1 for V_c below or equal 1,000 m³, 0.8 m;

    • .2 for 1,000 m³ < V_c < 5,000 m³, 0.75+ V_c x 0.2/4,000 m;

    • .3 for 5,000 m³ ≤ V_c < 30,000 m³, 0.8 + V_c/25,000 m; and

    • .4 for V_c ≥ 30,000 m³, 2 m,

    • where:

      • V_c corresponds to 100% of the gross design volume of the individual fuel tank at 20°C, including domes and appendages.

• .6 In case of more than one non-overlapping fuel tank located in the longitudinal direction, f_CN shall be calculated in accordance with paragraph 5.3.4.2 for each fuel tank separately. The value used for the complete fuel tank arrangement is the sum of all values for f_CN obtained for each separate tank.

• .7 In case the fuel tank arrangement is unsymmetrical about the centreline of the ship, the calculations of f_CN shall be calculated on both starboard and port side and the average value shall be used for the assessment. The minimum distance as set forth in paragraph 5.3.4.5 shall be met on both sides.

• .8 For ships with a hull structure providing higher collision and/or grounding resistance, fuel tank location regulations may be specially considered in accordance with section 2.3.

5.3.5 When fuel is carried in a fuel containment system requiring a complete or partial secondary barrier:

• .1 fuel storage hold spaces shall be segregated from the sea by a double bottom; and
• .2 the ship shall also have a longitudinal bulkhead forming side tanks.

5.4 Machinery space concepts

5.4.1 In order to minimize the probability of a gas explosion in a machinery space with gas-fuelled machinery one of these two alternative concepts may be applied:

• .1 Gas safe machinery spaces: Arrangements in machinery spaces are such that the spaces are considered gas safe under all conditions, normal as well as abnormal conditions, i.e. inherently gas safe.

  In a gas safe machinery space a single failure cannot lead to release of fuel gas into the machinery space.

• .2 ESD-protected machinery spaces: Arrangements in machinery spaces are such that the spaces are considered non-hazardous under normal conditions, but under certain abnormal conditions may have the potential to become hazardous. In the event of abnormal conditions involving gas hazards, emergency shutdown (ESD) of non-safe equipment (ignition sources) and machinery shall be automatically executed while equipment or machinery in use or active during these conditions shall be of a certified safe type.

  In an ESD protected machinery space a single failure may result in a gas release into the space. Venting is designed to accommodate a probable maximum leakage scenario due to technical failures.

  Failures leading to dangerous gas concentrations, e.g. gas pipe ruptures or blow out of gaskets are covered by explosion pressure relief devices and ESD arrangements.

LR 5.4-01 With respect to 5.4.1.2, electrical equipment not of a certified safe type shall be automatically disconnected in the event of abnormal conditions involving gas hazards, see 2.2.4.

LR 5.4-02 Premixed engines using fuel gas mixed with air before the turbocharger shall be ESD protected.

LR 5.4-03 Regulations for gas turbines are located in 10.5.

5.5 Regulations for gas safe machinery space

5.5.1 A single failure within the fuel system shall not lead to a gas release into the machinery space.

5.5.2 All fuel piping within machinery space boundaries shall be enclosed in a gas tight enclosure in accordance with 9.6.

5.6 Regulations for ESD-protected machinery spaces

5.6.1 ESD protection shall be limited to machinery spaces that are certified for periodically unattended operation.

5.6.2 Measures shall be applied to protect against explosion, damage of areas outside of the machinery space and ensure redundancy of power supply. The following arrangement shall be provided but may not be limited to:

• .1 gas detector;
• .2 shutoff valve;
• .3 redundancy; and
• .4 efficient ventilation.

LR 5.6-01 A description of the ESD philosophy is to be submitted demonstrating how the probability of a gas explosion will be minimised and is to include the following as a minimum:

(a) a hazardous area classification study in accordance with 60079-10-1, see 12.3;

(b) the risk assessment described in 4.2;

(c) the systems and equipment which will be isolated;

(d) the systems and equipment which will remain operational;

(e) ventilation rates during ESD procedure;

(f) performance of gas detection systems when high ventilation rates are present and;

(g) equipment classification for the certified safe type which is to remain operational.

5.6.3 Gas supply piping within machinery spaces may be accepted without a gastight external enclosure on the following conditions:

• .1 Engines for generating propulsion power and electric power shall be located in two or more machinery spaces not having any common boundaries unless it can be documented that a single casualty will not affect both spaces.
• .2 The gas machinery space shall contain only a minimum of such necessary equipment, components and systems as are required to ensure that the gas machinery maintains its function.
• .3 A fixed gas detection system arranged to automatically shutdown the gas supply, and disconnect all electrical equipment or installations not of a certified safe type, shall be fitted.

5.6.4 Distribution of engines between the different machinery spaces shall be such that shutdown of fuel supply to any one machinery space does not lead to an unacceptable loss of power.

LR 5.6-02 Where gas leakage in an ESD-protected machinery space would result in the shutdown of the engine(s) in that space, sufficient propulsion and manoeuvring capability including essential and safety systems is to be maintained. The minimum power to be maintained shall be assessed from the operational characteristics of the ship, subject to consideration by LR. The safety concept of the engine shall clearly indicate application of the ‘double wall’ or ‘single wall’ arrangement. It shall be noted that the ‘safety concept’ is a document describing the safety philosophy with regard to gas as fuel. It describes how risks associated with this type of fuel are controlled under reasonably foreseeable abnormal conditions as well as possible failure scenarios and their control measures. A detailed evaluation regarding the hazard potential of injury from a possible explosion is to be carried out and reflected in the safety concept of the engine.

5.6.5 ESD protected machinery spaces separated by a single bulkhead shall have sufficient strength to withstand the effects of a local gas explosion in either space, without affecting the integrity of the adjacent space and equipment within that space.

5.6.6 ESD protected machinery spaces shall be designed to provide a geometrical shape that will minimize the accumulation of gases or formation of gas pockets.

5.6.7 The ventilation system of ESD-protected machinery spaces shall be arranged in accordance with 13.5.

5.7 Regulations for location and protection of fuel piping

5.7.1 Fuel pipes shall not be located less than 800 mm from the ship's side.

5.7.2 Fuel piping shall not be led directly through accommodation spaces, service spaces, electrical equipment rooms or control stations as defined in the SOLAS Convention.

5.7.3 Fuel pipes led through ro-ro spaces, special category spaces and on open decks shall be protected against mechanical damage.

5.7.4 Gas fuel piping in ESD protected machinery spaces shall be located as far as practicable from the electrical installations and tanks containing flammable liquids.

5.7.5 Gas fuel piping in ESD protected machinery spaces shall be protected against mechanical damage.

5.8 Regulations for fuel preparation room design

Fuel preparation rooms shall be located on an open deck, unless those rooms are arranged and fitted in accordance with the regulations of this Code for tank connection spaces.

LR 5.8-01 Fuel preparation rooms, regardless of location, shall be arranged to safely contain any cryogenic leakages.

LR 5.8-02 The material of the boundaries of the fuel preparation room shall have a design temperature corresponding to the lowest temperature it can be subjected to in a probable maximum leakage scenario unless the boundaries of the space, i.e. bulkheads and decks, are provided with suitable thermal protection.

LR 5.8-03 The fuel preparation room shall be arranged to prevent surrounding hull structure from being exposed to unacceptable cooling, in case of leakage of cryogenic liquids.

LR 5.8-04 The fuel preparation room shall be designed to withstand the maximum pressure build up during such a leakage. The pressure relief venting via the vent mast shall be in accordance with the applicable requirements indicated in 6.7.2.

5.9 Regulations for bilge systems

5.9.1 Bilge systems installed in areas where fuel covered by this Code can be present shall be segregated from the bilge system of spaces where fuel cannot be present.

5.9.2 Where fuel is carried in a fuel containment system requiring a secondary barrier, suitable drainage arrangements for dealing with any leakage into the hold or insulation spaces through the adjacent ship structure shall be provided. The bilge system shall not lead to pumps in safe spaces. Means of detecting such leakage shall be provided.

5.9.3 The hold or interbarrier spaces of type A independent tanks for liquid gas shall be provided with a drainage system suitable for handling liquid fuel in the event of fuel tank leakage or rupture.

5.10 Regulations for drip trays

5.10.1 Drip trays shall be fitted where leakage may occur which can cause damage to the ship structure or where limitation of the area which is effected from a spill is necessary.

5.10.2 Drip trays shall be made of suitable material.

LR 5.10-01 Suitable material is to ensure any leakage cannot come into contact with other equipment/structures and is safely collected. In this regard the integrity of the drip tray is to be maintained if subjected to cryogenic temperatures associated with LNG leakages.

5.10.3 The drip tray shall be thermally insulated from the ship's structure so that the surrounding hull or deck structures are not exposed to unacceptable cooling, in case of leakage of liquid fuel.

5.10.4 Each tray shall be fitted with a drain valve to enable rain water to be drained over the ship's side.

5.10.5 Each tray shall have a sufficient capacity to ensure that the maximum amount of spill according to the risk assessment can be handled.

5.11 Regulations for arrangement of entrances and other openings in enclosed spaces

5.11.1 Direct access shall not be permitted from a non-hazardous area to a hazardous area. Where such openings are necessary for operational reasons, an airlock which complies with 5.12 shall be provided.

5.11.2 If the fuel preparation room is approved located below deck, the room shall, as far as practicable, have an independent access direct from the open deck. Where a separate access from deck is not practicable, an airlock which complies with 5.12 shall be provided.

5.11.3 Unless access to the tank connection space is independent and direct from open deck it shall be arranged as a bolted hatch. The space containing the bolted hatch will be a hazardous space.

LR 5.11-01 Subject to agreement by the National Administration, consideration will be given to direct access from a non-hazardous area to a zone 2 hazardous area where the zone 2 area has a bolted hatch that provides direct access into, for example a tank connection space. Refer to LR 12.5-03.

5.11.4 If the access to an ESD-protected machinery space is from another enclosed space in the ship, the entrances shall be arranged with an airlock which complies with 5.12.

5.11.5 For inerted spaces access arrangements shall be such that unintended entry by personnel shall be prevented. If access to such spaces is not from an open deck, sealing arrangements shall ensure that leakages of inert gas to adjacent spaces are prevented.

5.12 Regulations for airlocks

5.12.1 An airlock is a space enclosed by gastight bulkheads with two substantially gastight doors spaced at least 1.5 m and not more than 2.5 m apart. Unless subject to the requirements of the International Convention on Load Lines, the door sill shall not be less than 300 mm in height. The doors shall be self-closing without any holding back arrangements.

5.12.2 Airlocks shall be mechanically ventilated at an overpressure relative to the adjacent hazardous area or space.

5.12.3 The airlock shall be designed in a way that no gas can be released to safe spaces in case of the most critical event in the gas dangerous space separated by the airlock. The events shall be evaluated in the risk analysis according to 4.2.

5.12.4 Airlocks shall have a simple geometrical form. They shall provide free and easy passage, and shall have a deck area not less than 1.5 m². Airlocks shall not be used for other purposes, for instance as store rooms.

5.12.5 An audible and visual alarm system to give a warning on both sides of the airlock shall be provided to indicate if more than one door is moved from the closed position.

5.12.6 For non-hazardous spaces with access from hazardous spaces below deck where the access is protected by an airlock, upon loss of underpressure in the hazardous space access to the space is to be restricted until the ventilation has been reinstated. Audible and visual alarms shall be given at a manned location to indicate both loss of pressure and opening of the airlock doors when pressure is lost.

5.12.7 Essential equipment required for safety shall not be de-energized and shall be of a certified safe type. This may include lighting, fire detection, public address, general alarms systems.