Section 6 System design

6.1.1 The system design, including methanol bunkering stations, fuel storage tanks, supply equipment and consumers, shall be subject to risk-based studies, see Ch 1, 3 Risk-based studies, and acceptable to LR. The system design is also to satisfy the requirements of this Section.

6.1.2 The design and construction of methanol-fuelled consumers shall permit stable and complete combustion under all expected operating conditions. The requirements are applicable to methanol-fuelled consumers, for either propulsion or auxiliary purposes, and either a single (methanol) fuel or dual-fuel type, see Ch 1, 1.3 Definitions.

6.1.3 Where power for the propulsion of the ship or other essential services is solely dependent on methanol-fuelled power generation machinery or equipment, no fewer than two independent sources of power shall be provided so that one source is retained in operation or is capable of being brought into operation in the event of unintended loss of one of the methanol-fuelled power units. Complete loss of power for propulsion and essential systems is not acceptable, see Ch 1, 1.1 Purpose and scope 1.1.1. Alternative arrangements (e.g. single engine installations) may be considered where supported by risk-based studies that demonstrate an equivalent level of dependability to a conventional fuel oilled engine.

6.1.4 A single failure within the fuel supply system shall not lead to a leakage into a non-hazardous area.

6.1.5 Mechanical and electrical equipment located within hazardous areas shall be limited to that considered necessary for operational purposes, see also Ch 1, 4.3 Components and equipment.

6.1.6 Machinery and equipment within hazardous areas shall be designed and installed to provide ease of access for inspection and maintenance.

6.1.7 At all locations where personnel may come into contact with methanol, an eyewash station and a shower shall be provided.

6.2.1 Bunkering operations shall be capable of being controlled from a safe location where tank instrumentation, including level indicators, is provided.

6.2.2 A manually operated stop valve and a remotely operated shutdown valve in series, or a combined manually operated and remote shutdown valve, shall be fitted in every bunkering line/pipe, close to the supply connection point. The remotely operated valve shall be capable of being operated locally from the bunkering control station or any other suitable safe location.

6.2.3 Bunkering lines/pipes shall not pass through accommodation, service spaces or control stations. Where bunkering lines/pipes pass through a non-hazardous area, they shall be double-walled piping or located in a ventilated gastight duct, see Ch 1, 7.2 Piping design 7.2.16.

6.2.4 If the pressure is lost in the annulus of double-walled piping or ventilation is lost in ventilated ducting, audible and visual alarms shall be provided at the bunkering control station, see Ch 1, 8 Control, alert and safety systems .

6.2.5 Connections and piping shall be positioned and arranged so that any damage to the fuel piping does not cause damage to the ship's fuel storage tanks resulting in an uncontrolled fuel discharge.

6.2.6 Arrangements shall be provided to:

1. drain any fuel from pump suctions and bunkering lines/pipes;

2. purge (i.e. make liquid and vapour free) bunkering lines/pipes;

3. confirm that bunkering lines/pipes are free of fuel upon completion of bunkering.

Liquid shall be discharged to the fuel storage tanks or other suitable location.

6.2.7 Physical arrangements shall be provided for safe management of any spilled fuel during bunkering. This shall include drip trays fitted below bunkering connections and where leakage may occur. Each drip tray shall be:

1. made of suitable material to hold spills, see Ch 1, 4 Materials, components and equipment;

2. fitted with a means to safely dispose of spills, see Ch 1, 7.3 Drainage arrangements;

3. fitted with a drain valve to enable rainwater to be drained over the ship's side;

4. of sufficient capacity to handle reasonably foreseeable spills.

6.2.8 The bunkering manifold shall be designed to withstand external loads during bunkering. The connections at the bunkering station shall be of dry-disconnect type equipped with additional safety dry break-away coupling/self-sealing quick release. The couplings shall be of an approved type.

6.2.9 The ship shall be fitted with an Emergency Shutdown (ESD) System operable from both the ship and the bunker supply facility. This shall be arranged to ensure rapid and safe shutdown of both the bunker supply and the ship’s fuel supply system without release of liquid or vapour.

6.3.1 Fuel storage tanks, including their design, materials, construction and testing shall be in accordance with the requirements of Chapters LR V, LR VI, 4, 6, 8 and 15 of the LR Rules for Carriage of Liquid Chemicals in Bulk.

6.3.2 All tank connections, fittings, flanges and tank valves shall be enclosed in a cofferdam or a space meeting the requirements of a cofferdam, see Ch 1, 6.4 Cofferdams .

6.3.3 Fuel storage tanks shall have a tank master isolation valve located as near to the tank outer shell as is practicable. This valve shall be capable of remote and local manual operation and provide full closure.

6.3.4 Arrangements shall be provided to:

1. safely drain and empty fuel from the fuel storage tanks;

2. safely purge (i.e. make liquid and vapour free) and vent the fuel storage tanks.

6.3.5 For single fuel installations (methanol only), the fuel storage shall be arranged in no fewer than two tanks so that, in the event of any one tank becoming unavailable, the remaining tank(s) will provide sufficient fuel to enable the ship to operate within its service profile, as defined in Ch 1, 2.1 Documentation required for design review 2.1.1. The tanks shall be located in separate fire-protected compartments.

6.3.6 Fuel storage tanks, supports and tank connections shall be designed to withstand loading from expected and reasonably foreseeable sloshing of tank contents.

6.3.7 Fuel storage tanks shall withstand, without leakage, the maximum static and dynamic pressures (and vacuum) expected during purging and inerting, and the maximum static and dynamic pressures that can be reasonably expected in the event of a deviation from ‘normal’ or intended purging and inerting.

6.3.8 Fuel storage tanks shall withstand, without leakage, the maximum calculated pressure increase due to fuel returning to the tank.

6.3.9 It shall be possible to isolate, drain and transfer fuel storage tank contents remotely from a safe location.

6.3.10 The maximum degree of filling of fuel tanks shall be 98 per cent. This is the maximum allowable liquid volume relative to the tank volume to which the tank may be loaded.

6.3.11 The fuel storage tank venting system shall be designed with redundancy for the relief of full flow overpressure and/or vacuum.

6.3.12 The opening pressure of the vacuum relief valves is not to be lower than 0,07 bar below atmospheric pressure.

6.3.13 The outlet from the pressure relief valves shall normally be located at least B /3 or 6 m, whichever is greater, above the weather deck and 6 m above the working area and gangways, where B is the greatest moulded breadth of the ship in metres. The outlet from pressure relief valves shall be led to the opening at least 10 m from the nearest air intake or opening to accommodation spaces, service spaces and control stations, or open decks which are accessible to personnel, or other non-hazardous spaces. It is also to be located at least 10 m from the nearest exhaust outlet from machinery installations.

6.3.14 Independent fuel storage tanks shall be designed to avoid accumulation and subsequent discharge of static electricity resulting from bunkering and fuel transfer. The following requirements shall be satisfied:

1. Fuel flow into and out of the tank shall be controlled to minimise turbulence and avoid accumulation of static electricity.

2. Tank filling arrangements shall be designed to avoid free-falling of fuel through air to prevent air entrainment, absorption of moisture, and accumulation of static electricity in the falling liquid.

3. The fuel storage tank and the bunkering and supply piping system shall be electrically grounded in accordance with the Rules.

6.3.15  Independent fuel storage tanks and their supports shall be designed to withstand all reasonably foreseeable loading.

6.3.16 Independent fuel tanks shall be provided with arrangements to ensure any leakages are contained, see Ch 1, 7.3 Drainage arrangements

6.3.17 Portable fuel tanks may be specially considered. Such tanks shall meet the requirements of this sub-Section as applicable and shall be included in the risk-based studies, see Ch 1, 3.1 Purpose.

6.4.1 Cofferdams or spaces meeting the requirements of cofferdams shall safely contain leakage from fuel tanks, tank connections, fittings, flanges and tank valves without this leakage spreading to other spaces.

6.4.2 The cofferdam shall be designed to withstand the weight of accumulated liquid from a maximum credible leakage scenario into the cofferdam, see Rules for Ships, Pt 4, Ch 1, 9.2 Watertight and deep tank bulkheads 9.2.1.

6.4.3 Cofferdams shall be protected from external heat sources.

6.4.4 Cofferdams and pump rooms shall be considered hazardous and shall be arranged with continuous liquid and vapour detection. Liquid detection may be achieved through liquid level monitoring, see also Ch 1, 7.2 Piping design 7.2.20

6.4.5 Ventilation shall be in accordance with the requirements for cofferdams in the Rules for Carriage of Liquid Chemicals in Bulk, Ch 1, 12.3 Spaces not normally entered.

6.4.6 Cofferdams shall be provided with a suitable means of removing fuel.

6.5.1 The fuel supply to each consumer shall be equipped with a manually operated isolation valve and an automatically operated master fuel valve coupled in series. The master fuel valve shall be closed and the fuel pump shall be shut down:

1. automatically in the event of:

   1. liquid detection, and/or detection on two vapour detectors within the machinery space containing the consumers;

   2. loss of the required ventilation from the pipe duct or casing;

   3. loss of pressurisation of double-walled piping;

   4. detection of a leak in the pipe duct, double-walled piping, or cofferdam;

2. using manual controls that are:

   1. located remotely from the valve;

   2. in accessible positions within the machinery space containing the methanol-fuelled consumers;

   3. at a suitable location outside the machinery space;

   4. at a location on the navigation bridge.

6.5.2 The number and location of manual controls shall be agreed with LR. Where dual-fuel engines are installed, these locations shall correspond with those required for shutting off fuel oil, see Rules for Ships, Pt 5, Ch 14, 4 Fuel oil pumps, pipes, fittings, tanks, etc..

6.5.3 Depending on the propulsion and machinery arrangement, a separate and independent fuel supply line shall be provided for each consumer.

6.5.4 The fuel line to each consumer shall be fitted with a means of purging the pipework downstream of the master fuel valve of fuel (liquid and vapour). This shall happen automatically where the master fuel valve in Ch 1, 6.5 Methanol supply system 6.5.1 is automatically closed.

6.5.5 The provisions within Ch 1, 6.5 Methanol supply system 6.5.1 and Ch 1, 6.5 Methanol supply system 6.5.4 shall be arranged for manual reset. Arrangements shall ensure that the fuel supply is not resumed until the abnormal condition that caused the shut-off of the valves has been rectified and it is safe to resume supply.

6.5.6 All fuel valves shall be arranged for both local operation and remote operation from the machinery control station.

6.5.7 For installations with a single source of propulsion power, arrangements shall be such that, in case of loss of the fuel supply, a secondary separate and independent fuel supply shall be available. Dual-fuelled consumers shall be capable of operating at their maximum continuous rating on fuel oil alone.

6.5.8 Where necessary, the fuel system shall include suitable equipment to provide fuel at constant temperature and pressure. In all cases, arrangements shall be such that the fuel storage and delivery systems are maintained at a pressure below any relief device set pressure.

6.5.9 Master fuel valves are not to be located within a machinery space.

6.5.10 All fuel supply piping within non-hazardous areas shall be enclosed in a gastight enclosure, i.e. double-walled piping or ventilated gastight ducting.

6.5.11 Prime movers for fuel supply equipment, such as engines and motors, shall be of a certified safe type suitable for the space in which they are installed or shall be located in an adjacent non-hazardous area. Prime mover shafts passing through bulkheads or decks shall be fitted with gastight seals of an approved type.

6.5.12 The arrangement and installation of the fuel piping shall provide the necessary flexibility to accommodate the movements of the machinery in order to minimise the likelihood of failure due to fatigue. The length and configuration of the branch lines are important factors in this regard.

6.5.13 All pumps in the fuel system shall be protected against running dry (i.e. protected against operation in the absence of fuel or service fluid).

6.5.14 All pumps which are capable of developing a pressure exceeding the design pressure of the system shall be provided with relief valves. Each relief valve shall be in closed circuit, i.e. arranged to discharge back to the piping upstream of the suction side of the pump and to effectively limit the pump discharge pressure to the design pressure of the system.

6.5.15 Pumps and supports shall safely accommodate expected levels of vibration.

6.5.16 Pumps within accessible spaces shall be protected from impact damage.

6.6.1 All engine components, systems and sub-systems shall be designed to prevent explosion so far as is reasonably practicable.

6.6.2 When fuel is supplied in a mixture with air through a common manifold, sufficient flame arrestors shall be installed before each cylinder head. The inlet system shall be designed to withstand explosion of a fuel-air mixture by means of:

1. explosion relief venting to prevent excessive pressure build-up; where explosion relief venting is installed, it shall discharge the combustion products to a safe location;

2. having sufficient strength to contain a worst-case explosion, in which case, documentary evidence shall be submitted.

6.6.3 The requirements in Ch 1, 6.6 Methanol-fuelled reciprocating internal combustion engines and turbines 6.6.2 may be omitted if the fuel concentration within the manifold is controlled and if combustion of an unburnt mixture within the manifolds can be eliminated. A justification to demonstrate how this can be achieved shall be submitted.

6.6.4 The exhaust system of engines shall be designed to withstand combustion of unburnt fuel-air mixture by means of:

1. explosion relief venting to prevent excessive pressure build-up; where explosion relief venting is installed, it shall discharge the combustion products to a safe location;

2. having sufficient strength to contain a worst-case explosion, in which case, documentary evidence shall be submitted; or

3. temperature-limiting arrangements to prevent the exhaust system exceeding the auto-ignition temperature of the methanol in addition to eliminating sources of ignition.

6.6.5 The requirements in Ch 1, 6.6 Methanol-fuelled reciprocating internal combustion engines and turbines 6.6.4 may be omitted if combustion of an unburnt mixture within the manifolds can be eliminated. A justification to show how this can be achieved shall be submitted.

6.6.6 Engines shall be monitored to detect misfiring. Correct operation of the ignition system shall be verified before admission of fuel to the engine. The ignition system shall be designed such that it cannot shut down without first closing off the supply of methanol to each cylinder or to the complete engine.

6.6.7 Dual-fuel engines shall be capable of immediate changeover to fuel oil at any load in the event of the methanol fuel supply being shut off and thereafter capable of continuous operation at any load up to full load on fuel oil alone. In general, fuel oil shall be used when starting the engine, when the operation of the engine is unstable, and/or during manoeuvring and port operations.

6.6.8 In the case of a normal stop or an emergency shutdown, the methanol fuel supply shall be shut off no later than the fuel oil. It shall not be possible to shut off the supply of pilot fuel without first or simultaneously closing the methanol supply to each cylinder or to the complete engine.

6.6.9 All reciprocating internal combustion engines shall be provided with crankcase explosion relief valves fitted in way of each crankthrow. The valves shall be in accordance with Pt 5, Ch 2 Reciprocating Internal Combustion Engines, of the Rules for Ships.

6.6.10 All reciprocating internal combustion engines shall be fitted with oil mist monitoring equipment that is in accordance with the requirements of Pt 5, Ch 2 Reciprocating Internal Combustion Engines, of the Rules for Ships, or engine bearing monitoring devices or equivalent devices.

6.6.11 Where trunk piston type engines are used, a means of injecting inert gas into the crankcase is to be provided and the crankcase is to be protected by the following measures:

1. The provision of breathing equipment, the outlet for which shall be led to a safe location in the open through a flame arrestor. Each engine shall have its own breather and the outlet lines of different engines are not to be connected;

2. The provision of methanol detection equipment which is suitable for hazardous areas zone 1, see Table 1.8.2 Methanol-fuelled consumers: Alarms, monitoring and safeguards.

The safety philosophy and corresponding arrangements for prevention of crankcase explosions shall be documented and submitted. If such an arrangement cannot be achieved, equivalent safety measures shall be submitted for special consideration and acceptance by LR.

6.6.12 Vapour detection equipment for the piston underside space of engines shall be provided and shall activate engine shutdown in the event of high levels of vapour concentration. Means for the injection of inert gas are also to be provided.

6.6.13 The exhaust gas manifold of engines shall be so designed as to allow the combustion of unburnt charge from an individual cylinder without detrimental effect.

6.6.14 Each cylinder is to be provided with its own fuel inlet valve, admitting fuel either to the cylinder or the air inlet port. The functioning of this valve shall be such that no fuel can pass to the exhaust during the scavenging period or to the inlet port after closure of the air inlet valve.

6.6.15 An isolating valve and flame arrestor shall be provided at the inlet to the fuel supply manifold for each engine. The isolating valve is to be arranged to close automatically in the event of low fuel pressure or cylinder misfire.

6.6.16 Arrangements shall be provided to enable purging of fuel from the exhaust system before the starting of an engine, after failure to start and following loss of ignition during operation of the engine. Interlocking devices shall be fitted to ensure that purging can be performed only when the isolating valve required by Ch 1, 6.6 Methanol-fuelled reciprocating internal combustion engines and turbines 6.6.15 is closed. The purge is to be of sufficient duration to displace at least three times the volume of the exhaust system.

6.6.17 The exhaust pipes of methanol-fuelled engines, including gas turbines, shall not be connected to the exhaust pipes of other engines or systems.

6.6.18 Indication shall be provided for identifying poor combustion from each combustion chamber, flame-out and failure-to-ignite conditions, and arrangements shall be made to ensure that the fuel supply to the combustion chambers is cut off unless satisfactory ignition has been established and maintained.

6.6.19 The exhaust system shall be designed to prevent the accumulation of uncombusted fuel. Arrangements shall be provided to purge the turbine automatically before ignition commences on starting, or recommences after failure to start, or following a loss of ignition in operation. Interlocking devices shall be fitted to ensure that purging can be carried out only when the fuel supply valves are closed. The purge shall be of sufficient duration to displace at least three times the volume of the exhaust system. Combustion shall be monitored during operation and a means of preventing poor combustion, which may lead to an accumulation of unburnt methanol in the exhaust, shall be provided.

6.6.20 Where it is possible for fuel to enter engine auxiliary systems, such as lubricating oil and cooling water systems, then a means of extracting this methanol shall be fitted at the outlet from the engine with the vapour removed being vented to a safe location.

6.6.21 Dual-fuel engines shall be fitted with an automatic fuel changeover system which can change over from oil to methanol or from methanol to oil reliably and with a minimum fluctuation in load. This shall be demonstrated during engine trials and any operational limitations on changeover loads from oil to methanol shall be recorded. The system shall be capable of changeover from methanol to oil at all loads.

6.6.22  Where turbines are fitted in gastight enclosures, the enclosure shall be provided with a minimum of two ventilation fans, each rated to provide a minimum of 30 air changes per hour and each of these fans shall be fed from a separate source of supply with no single point of failure being capable of stopping both fans. Failure of this ventilation shall result in automatic shutdown of the fuel supply. This shall be detected by means of monitoring air flow and it is not acceptable to use fan motor electrical supply monitoring for this purpose. The interior of the enclosure shall be protected in accordance with the requirements for machinery spaces containing methanol fuelled engines.

6.7.1 The arrangement of boilers and burner systems shall comply with the requirements of Pt 5, Ch 10 Steam Raising Plant and Associated Pressure Vesselsand Pt 5, Ch 14 Machinery Piping Systems of the Rules for Ships and 16.5 of the Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquefied Gases in Bulk, as applicable. The whole boiler casing shall be gastight and each boiler shall have a separate uptake.

6.7.2 Combustion chambers and furnaces of boilers shall be designed such that pockets of fuel cannot accumulate.

6.7.3 Boilers and combustion units shall be provided with forced draught arrangements. Each boiler shall have its own forced draught system.

6.7.4 Means shall be provided so that, in the event of flame failure, the fuel supply to the burners is shut-off automatically, and alarms are activated.

6.7.5 Means shall be provided for automatically purging the fuel supply piping to the burners after the burners have been extinguished. Arrangements are also to be provided to allow manual purging. Interlocking devices shall be fitted to ensure that purging can be performed only when the burner fuel supply valves are closed.

6.7.6 For dual-fuel burner units, the firing equipment shall be suitable to burn either fuel oil or methanol alone, or fuel oil and methanol simultaneously. The burner shall maintain stable firing under all firing conditions and on main/propulsion boilers shall be fitted with an automatic fuel changeover system to change from methanol to oil operation with minimum impact to the flame.

6.7.7 The fuel changeover system shall be monitored and protected from damage (e.g. from high pressure, heat, electrical overload) so as to ensure continuous availability whilst the boiler is in operation. An interlocking device shall be provided to prevent the methanol fuel supply being opened until the oil and air controls are in the firing position. It shall be possible to change from methanol to fuel oil operation without interruption of boiler firing.

6.7.8 Each burner supply pipe shall be fitted with a fuel shut-off valve and a flame arrestor, unless this is incorporated in the burner. A means shall be provided to automatically purge the fuel supply to burners using inert gas or a suitable alternative after extinguishing the burner flames.

6.7.9 In addition to the low water-level oil-fuel shut-off and alarm required by Pt 5, Ch 10, 15.7 Low water level fuel shut-off and alarm or 16.7 of the Rules for Ships for oil-fired boilers, equivalent arrangements shall be made for fuel shut-off and alarms when the boilers are operating on methanol. "

6.8.1 Provision shall be made for supply of nitrogen inert gas. This shall be either through on board generation of inert gas or through an inert gas storage system with provision for refilling from shore.

6.8.2 The inerting arrangements shall provide for:

1. inerting of all fuel piping during normal operation and emergency shutdown activation;

2. inerting of methanol-fuelled consumers;

3. atmospheric control (e.g.., double wall piping annulus and maintaining tank vapour spaces in an inert condition at all times);

4. fire protection systems.

6.8.3 The inert gas system shall be able to maintain a pressure of at least 0,007 MPa gauge within the fuel storage tank(s) at all times. The inert gas system shall not raise the fuel storage tank pressure to more than the tank’s relief-valve setting.

6.8.4 The available inert gas capacity shall be continuously monitored and replenished before it is unable to meet the functional requirements of Ch 1, 6.8 Inert gas system 6.8.2.

6.8.5 The inerting supply arrangements are to meet the applicable requirements of the Rules for Ships, Pt 5, Ch 15, 7 Inert gas systems on Tankers of 8,000 tonnes DWT and above.