Section 2 Fuel oil - General requirements

2.1.1 The flash point (closed-cup test) of fuel oil for use in naval ships classed for unrestricted service is, in general, to be not less than 60ºC.

2.1.2 The use of fuel having a lower flash point than specified in Vol 2, Pt 7, Ch 3, 2.1 Flash point 2.1.1 may be permitted provided that such fuel is not stored in any machinery space and the arrangements for the complete installation are specially approved.

2.1.3 Fuel oil in storage tanks is not to be heated to a temperature exceeding 10ºC below its flash point. Higher temperatures will be considered for fuel oil stored in settling and service tanks where:

1. The tanks are vented to a safe position outside the engine room and, as in the case of all fuel oil tanks, the ends of the ventilation pipes are fitted with gauze diaphragms.

2. Openings in the drainage systems of tanks containing heated fuel oil are located in spaces where no accumulation of oil vapours at temperatures close to the flash point can occur.

3. The length of vent pipes from such tanks and/or a cooling device is sufficient for cooling oil vapours to below 60°C, or the outlet of the vent pipes is located at least 3 m from sources of ignition.

4. There is no source of ignition in the vicinity of openings in the drainage systems.

5. There are no openings from the vapour space of the fuel tanks into machinery spaces other than bolted sealed manhole covers.

6. Enclosed spaces are not located directly over such fuel tanks, except for vented cofferdams.

7. Electrical equipment is not fitted in the vapour space of tanks unless it meets the requirements of Vol 2, Pt 9, Ch 5, 4.1 General 4.1.1 for electrical equipment in zone 0 explosive atmospheres.

2.1.4 The temperature of any heating medium is not to exceed 220ºC.

2.2.1 When it is desired to carry a quantity of fuel having a flash point below 60ºC for special services, e.g. aviation spirit for use in helicopters or vehicles, full particulars of the proposed arrangements are to be submitted for consideration, see Vol 2, Pt 7, Ch 4 Aircraft/Helicopter/Vehicle Fuel Piping and Arrangements.

2.3.1 Sampling points are to be provided within the fuel oil system. The design and location of sampling points is to that enable samples of fuel oil to be taken easily and in a safe manner.

2.3.2 The position of a sampling point is to be such that the sample of the fuel oil is representative of the fuel oil quality at that its location within the system, e.g. by ensuring steady state flow past the sampling point.

2.3.3 Sampling points are to be located so as to reduce the possibility of fuel oil coming into contact with any heated surface or electrical equipment under reasonably foreseeable operating conditions and therefore shall be positioned as far away as possible from such surfaces or equipment. Where contact is still likely, positions are to be shielded from any heated surface or electrical equipment. The shielding shall be sturdy enough to endure leaks, splashes or spray under design pressure of the fuel oil supply line.

2.3.4 A sampling point or points shall be provided:

1. Taking into account different fuel oil grades being used for the fuel oil combustion machinery item;
2. Downstream of the in-use fuel oil service tank; and
3. As close to the fuel oil combustion machinery as safely feasible taking into account the type of fuel oil, flow-rate, temperature, and pressure behind the selected sampling point.

2.3.5 The sampling arrangements within the machinery space are to be capable of safely providing samples when the machinery is running and are to be provided with isolating valves and cocks of the self-closing type.

2.4.1 The spaces in which the fuel oil burning appliances and the fuel oil settling and service tanks are fitted are to be well ventilated and easy of access.

2.5.1 The boilers are to be suitably lagged. The clearance spaces between the boilers and tops of the double bottom tanks, and between the boilers and the sides of the storage tanks in which fuel oil and refuelling oil is carried, are to be adequate for the free circulation of the air necessary to keep the temperature of the stored oil sufficiently below its flash point.

2.5.2 Where water tube boilers are installed, there is to be a space of at least 760 mm between the tank top and the underside of the pans forming the bottom of the combustion spaces.

2.5.3 Smoke-box doors are to be shielded and well fitting, and the uptake joints made gastight. Where the surface temperature of the uptakes may exceed 220ºC, they are to be efficiently lagged to minimise the risk of fire and to prevent damage by heat. Where lagging covering the uptakes, including flanges, is oil-absorbing or may permit penetration of oil, the lagging is to be encased in sheet metal or equivalent. In locations where the Surveyor is satisfied that oil impingement could not occur, the lagging need not be encased.

2.6.1 Dampers which are capable of completely closing the gas passages are not to be fitted to inner funnels of ships equipped for burning fuel oil only.

2.7.1 Where steam is used for heating fuel oil or lubricating oil, in bunkers, tanks, heaters or separators, the exhaust drains are to discharge the condensate into an observation tank in a well lighted and accessible position where it can be readily seen whether or not it is free from oil.

2.7.2 Where hot water is used for heating, means are to be provided for detecting the presence of oil in the return lines from the heating coils.

2.7.3 Where it is proposed to use any heating medium other than steam or hot water, full particulars of the proposed arrangements are to be submitted for special consideration.

2.7.4 The heating pipes in contact with oil are to be of iron, steel, approved aluminium alloy or approved copper alloy, and, after being fitted on board, are to be tested by hydraulic pressure in accordance with the requirements of Vol 2, Pt 7, Ch 1, 16.1 Hydraulic tests before installation on board.

2.7.5 Where electric heating elements are fitted, means are to be provided to ensure that all elements are submerged at all times when electric current is flowing and that their surface temperature cannot exceed 220ºC, see Vol 2, Pt 7, Ch 3, 9.5 Miscellaneous machnery.

2.8.1 Tanks and heaters in which oil is heated are to be provided with suitable means for ascertaining the temperature of the oil. Where thermometers or temperature sensing devices are not fitted in blind pockets, a warning notice, in raised letters, is to be affixed adjacent to the fittings stating ‘Do not remove unless tank/heater is drained’.

2.8.2 Controls are to be fitted to limit oil temperatures in oil storage and service tanks in accordance with Vol 2, Pt 7, Ch 3, 2.1 Flash point 2.1.4 and in oil heaters to the maximum approved operating temperature, see Vol 2, Pt 7, Ch 3, 9.5 Miscellaneous machnery.

2.9.1 As far as practicable, fuel oil tanks are to be part of the ship's structure and are to be located outside machinery spaces of Category A. Where fuel oil tanks, other than double bottom tanks, are necessarily located adjacent to or within machinery spaces of Category A, at least one of their vertical sides is to be joined to the machinery space boundaries. Such tanks are also preferably to have a common boundary with the double bottom tanks, and the area of a tank boundary common with the machinery spaces is to be kept to a minimum. Where such tanks are situated within the boundaries of machinery spaces of Category A they are not to contain fuel oil having a flash point of less than 60°C.

2.9.2 In general, the use of free-standing fuel oil tanks is to be avoided. Such tanks are prohibited in Category A machinery spaces on ships carrying more than 50 embarked personnel. Where free-standing tanks are permitted, they are to be placed in an oil-tight spill tray of ample size having a suitable drain pipe leading to a suitably sized drain tank.

2.9.3 Tanks containing flammable liquids are not to be situated above or within one metre of engines, boilers, exhausts/uptakes or other highly heated surfaces.

2.9.4 Fuel oil pipes are not to be installed above or near high temperature equipment. Fuel oil pipes should also be installed and screened or otherwise suitably protected to avoid oil spray or oil leakages onto hot surfaces, into machinery air intakes, or other sources of ignition such as electrical equipment. Pipe joints are to be kept to a minimum, and where provided are to be of a type acceptable to Clasifications Register (hereinafter referred to as 'LR'). Pipes are to be led in well lit and readily visible positions, see also Vol 2, Pt 7, Ch 2, 2.8 Miscellaneous requirements 2.8.2.

2.9.5 Pumps, heaters, filters and strainers and heaters are to be located to avoid oil spray or oil leakages onto hot surfaces or other sources of ignition, or onto rotating machinery parts. Where necessary, shielding is to be provided and the arrangements are to allow easy access for routine maintenance. The design of filters and strainers is to be such as to avoid the possibility of them being opened inadvertently when under pressure. This may be achieved by either mechanically preventing the pressurised filter from being opened or by providing pressure gauges which clearly indicate which filter is under pressure. In either case, suitable means for pressure release are to be provided, with drain pipes led to a safe location.

2.9.6 The arrangement and location of short sounding pipes to oil tanks are to be in accordance with Vol 2, Pt 7, Ch 2, 10.12 Short sounding pipes. For alternative sounding arrangements, see Vol 2, Pt 7, Ch 2, 10.10 Sounding arrangements.

2.9.7 Water service pipes and hoses are to be fitted in order that the floor plates and tank top or shell plating in way of boilers, fuel oil apparatus or deep storage tanks in the engine and boiler spaces can at any time be flushed with sea-water.

2.9.8 So far as is practicable, the use of wood is to be avoided in the engine rooms, boiler rooms and tunnels of ships burning fuel oil.

2.9.9 Drip trays are to be fitted at the furnace mouths to intercept oil escaping from the burners, and under all other fuel oil appliances such as fuel oil filters, which are required to be opened up frequently for cleaning or adjustment. Alternative arrangements may be acceptable and full details should be submitted for consideration.

2.9.10 Oil-tight drip trays of ample size having suitable drainage arrangements are to be provided at pipes, pumps, valves and other fittings where there is a possibility of leakage. Valves should be located in well lighted and readily visible positions. Drip trays will not be required where pumps, valves and other fittings are placed in special compartments either inside or outside the machinery space with approved overall drainage arrangements or for valves which are so positioned that any leakage will drain directly into the bilges, see Vol 2, Pt 7, Ch 3, 2.9 Precautions against fire 2.9.4.

2.9.11 Where drainage arrangements are provided from collected leakages, they are to be led to a suitable drain tank not forming part of the overflow system.

2.9.12 Separate fuel oil tanks are to be placed in an oil tight spill tray of ample size having drainage arrangements leading to a drain tank of suitable size.

2.9.13 Where level switches are used below the tank top, they are to be contained in a steel enclosure or other enclosures which provide an equivalent protection against fire.

2.10.1 The materials and/or their surface treatment used for the storage and distribution of fuel oil are to be selected such that they do not introduce contamination or modify the properties of the fuel. The use of copper or zinc compounds in fuel oil piping systems where they may come into contact with the fuel is not permitted except for small diameter pipes in low pressure systems, see Vol 2, Pt 7, Ch 3, 4.6 Low pressure pipes 4.6.1.

2.10.2 Corrosion resistant materials are to be used for fuel oil pipes between the treatment system required by Vol 2, Pt 7, Ch 3, 3.9 Fuel oil treatment for supply to engines and gas turbines 3.9.3 and the combustion system.

2.10.3 For prevention of ingress of water into fuel oil tanks via air pipes, see Vol 2, Pt 7, Ch 2, 10.4 Termination of air pipes 10.4.4.

2.10.4 The piping arrangements for fuel oil are to be separate and distinct from those intended for lubricating oil systems to prevent contamination of fuel oil by lubricating oil.

2.10.5 The piping arrangements for gas oil, distillate and diesel grades are to be separate and distinct from those intended for residual grades, up to the service tanks required by Vol 2, Pt 7, Ch 3, 4.18 Fuel oil service tanks, to prevent cross-contamination. Cross-connection is permitted between separate arrangements in the event of failure of a designated item of equipment.

2.11.1 Tanks containing fuel oil are to be separated from vehicle spaces, crew, embarked personnel, passenger and baggage compartments by a gastight and watertight boundary or a cofferdam which is suitably ventilated and drained.