All vessels shall have at least two fuel oil service tanks for each fuel type used for propulsion and other operationally vital systems. Each fuel tank shall have capacity for minimum 8 hours continuous operation of the propulsion and generator plant at sea, under normal operating load. Fuel oil tanks near to boilers or other hot surfaces shall be insulated. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.2
In case the vessel is operating with heavy fuel oil, settling tanks shall be provided. Settling tanks need to be equipped with heating system, drains, emptying arrangement and temperature measuring instruments. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.2

Settling tanks and daily service tanks shall be provided with drains removing water from the bottom of the tank. The drains shall be fitted with self-closing valves or cocks, and arranged such that the waste will be collected in closed tanks. Suction lines shall be located sufficiently high above the tank bottom to avoid water and impurities entering the supply system. Suction for fuel oil separators, if fitted, shall be from the lowest point of the tank bottom. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.2 and Pt.4 Ch.6 Sec.5.4.9
All fuel oil inlet and outlet pipes from fuel tanks that can cause a leakage if damaged shall be provided with shut-off valve directly on the tank. Quick-closing valves with remote operation shall be arranged directly on fuel oil tanks in the engine room and close to the engine space bulkhead on fuel oil pipes leading to en-gine spaces. For multi-engine installations using same fuel source an additional isolation valve separately for each of the engines shall be provided. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.4 and Pt.4 Ch.6 Sec.5.4.5

Pressurized fuel oil lines in engine room and boiler room shall be routed such that the piping is well-lit and may be kept under observation. Detachable piping connections shall be kept to minimum (only necessary connections for mounting and dis-mounting is allowed) and placed on safe distance from boilers, exhaust pipes, other heated surfaces, and electrical appliances. Fuel oil lines shall not pass-through feed water, drinking water, urea, lubricating oil or thermal oil tanks. All valves on fuel oil system shall be controllable above floor plates. Flange connections, where leakage have possibility to be in contact with any potential ignition sources shall be arranged with spray shields (anti-splashing tape is accepted). //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.1 and Pt.4. Ch.6 Sec.5.4.3, MSC.1/Circ.132111 June 2009

The allowed piping thicknesses for steel pipes are defined in DNV-RU-SHIP Pt.4 Ch.6 Sec.9.1 Table 2. Fire redundance requirements and list of allowed mechanical joints can be found DNV-RU-SHIP Pt.4 Ch.6 Sec.9.5 Table 9. Fuel oil pipes with pressure under 7 bars and tem-perature below 60 ⁰C can be class III pipes. Pipes with pressure range 7 -16 bars or temperature 60 – 150 ⁰C degrees shall be documented as class II pipes. For higher pressures and temperatures class I is re-quired. Piping diagram including all fittings on settling and daily service tanks are subject for class approval. The same goes for control system functional description for pumps and valves. //DNV-RU-SHIP Pt.4 Ch.6 Sec.1, Pt.4 Ch.6 Sec.9.1 and Pt.4 Ch.6 Sec.9.5
Fuel oil supply lines for main and auxiliary machinery shall be fitted with filters, that can be cleaned without disturbing fuel supply. I.e., two filters can be arranged parallel or a duplex filter can be used. An auto-backwash filter may also be accepted. Duplex filters shall be arranged such that it is clearly visibly which chamber is in use, opening a chamber under pressure is prevented and a chamber can be vented when put back into operation. Differential pressure monitoring shall be ar-ranged when blocked filters can cause loss of propulsion. Auto back-flush filters shall be fitted with monitoring equipment for backflush intervals, and an alarm for frequent backflushing. Drip trays under filters for fuel oil shall be provided. For auxiliary and emergency generators a single filter is acceptable, as long as the emergency generator is not used as harbor generator. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.6
For heavy fuel use an additional mean for removing harmful contaminants shall be fitted. In case separators are used for that, those need to be arranged with redundancy. The same requirement goes also for pre-heaters. Purifiers and associated components should be placed in a separate room as far as practicable. In addition, an automatic viscosity controller shall be provided. The regulator needs to be equipped with temperature indicator, and each of the engines shall have local gauge for operating pressure and indicator for local operating temperature fitted directly before the engine. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.6-8, MSC.1/Circ.132111 June 2009
Fuel oil booster units shall be protected against pressure peaks by using sufficient dampers. Flexible hoses with maximum length of 1.5 m can be used when necessary to accommodate relative movement be-tween fixed piping and machinery parts, typically engine connections. Positive displacement flowmeters shall be fitted on supply lines if blockage will lead to loss of propulsion plant or auxiliary power. For vessels operating with unmanned machinery spaces an automatic by-pass shall be installed. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.9, MSC.1/Circ.132111 June 2009

Fuel oil transfer, feed and booster pumps, as well as separators shall be arranged with emergency stops. The emergency stops shall be located in easily accessible position outside the space being served. Fuel oil transfer, booster, service and fuel injection valve cooling pumps shall have product certificates. For single engine installation all active components including fuel pumps should be duplicated, i.e. there shall be a stand-by pump installed starting within 30 s in case the running pump fails. For propulsion plants where at least 40% of rated power output remains after a single failure duplication is not required. //DNV-RU-SHIP Pt.4. Ch.1 Sec.2.3 and Pt.4 Ch.8 Sec. 2.8.6
Requirements for fuel oil supply to burners and firing equipment can be found on DNV-RU-SHIP Pt.4 Ch.6 Sec.5.4.10

Last modified: Thursday, 13 April 2023, 11:48 AM