Chapter 1 – General

 The interaction of the three equal sides of the fire triangle: HEAT, FUEL AND OXYGEN, are required for the creation and maintenance of fire. When there is not enough heat generated to sustain the process, when the fuel is exhausted, removed or isolated, or when oxygen supply is limited, then a side of the triangle is broken and the fire is suppressed.

 For flammable liquids, the idea of the fire triangle is generally embodied in fire prevention by excluding the flammable mixture of oil (LFL) and (or) hot spots (Auto Ignition Point). Given 21% O₂ concentration in the atmosphere, for a flammable oil, the flammable mixture (LFL) can exist at the temperature of its flashpoint (FP) and above.

  1.2.1 Fuel control

Many kinds of flammable oils are used in ships.

When flammable oils are leaked or splashed in engine-room spaces or where potential ignition sources exist, they may cause a fire depending on the situation. To prevent leaks, splashes or spray from flammable oil service or transfer piping systems, the following measures need to be considered as described in SOLAS:

• .1 spray shields for flanged/screwed joints of pipes containing flammable oils (fuel oil, lubricating oil and hydraulic oil);

• .2 jacketed piping system for high pressure fuel pipes;

• .3 flammable oil piping location;

• .4 tank sounding pipes, air vents and level measuring devices location; and

• .5 flammable gas measurement systems.

  1.2.2 Heat control

Many hot surfaces and potential ignition sources exist in engine-rooms, cargo pump-rooms and other fire-prone spaces. To assist in preventing a fire originating as a result of flammable oil coming in direct contact with high temperature surfaces, these surfaces should be properly insulated.

Therefore, the SOLAS regulations require:

• .1 insulation of high temperature surfaces;

• .2 temperature sensing devices for cargo pumps, ballast pumps and stripping pumps installed in cargo pump-rooms and driven by shafts passing through the pump-room bulkhead;

• .3 the surface of any insulation used in spaces where penetration of oil is possible (e.g., machinery spaces) to be impervious to oil or oil vapours. This applies equally in cases where the insulation is applied to meet shipyard practice or at the owner’s request, for example to reduce heat loss or to protect the crew; and

• .4 spray protection of some electrical equipment.

  1.2.3 Oxygen control

It is not possible to exclude air from engine-rooms or pump-rooms except when actively suppressing a fire, so control of oxygen supply is not a practical means of preventing fire in these spaces. However, cargo tanks or slop tanks which are part of a cargo area could be inerted using an inert gas system.

To decrease the flammable vapours within cargo pump-rooms SOLAS requires such spaces to be mechanically ventilated. The number of air changes shall be at least 20 per hour, based upon the gross volume of the space. The ventilation shall be of the suction type using fans of the non-sparking type.

 Flammable oils have different flashpoints and auto-ignition points. The actual ignition condition may differ from the flashpoint and auto-ignition point. Table 1 shows the typical flashpoint and auto-ignition point of various flammable oils used on board ship.

  1.3.1 Flashpoint of oil fuel

• .1 Oil fuels with a flashpoint of less than 60°C (closed cup test) are not permitted, except for the following:

  • .1 ships certified for restricted service within areas having a climate ensuring that ambient temperatures of spaces where such oil fuel is stored will not rise to within 10°C below its flashpoint, but not less than 43°C;

  • .2 installations complying with IACS UR M24 regarding use of crude oil as fuel; and

  • .3 in emergency generators oil fuel with a flashpoint of not less than 43°C may be used.

• .2 Oil fuel in storage tanks should not be heated to temperatures within 10°C below the flashpoint of the oil fuel, except for the following:

  • .1 oil fuel in service tanks, settling tanks and any other tanks in the supply system may be heated above this limit, provided:

    • .1.1 the length of the vent pipes from such tanks is sufficient for cooling the vapours to at least 10°C below the flashpoint of the oil fuel;

    • .1.2 a temperature sensor is fitted in the vent pipe and adjusted to give an alarm if the temperature should exceed a limit set at 10°C below the flashpoint of the oil fuel;

    • .1.3 the vent pipes are fitted with flame screens meeting the requirements of IMO’s “Standards for devices for preventing passage of flames into cargo tanks”;

    • .1.4 there are no openings from the vapour space of the oil fuel tanks into machinery spaces, (bolted manholes are acceptable);

    • .1.5 enclosed spaces should not be located directly over such oil fuel tanks, except for well ventilated cofferdams; and

    • .1.6 electrical equipment should not be fitted in the vapour space of the oil fuel tanks, unless it is certified to be intrinsically safe.