Flash Point

 The flash point of a fuel is the temperature at which vapour given off will ignite when an external flame is applied under specified test conditions. A flash point is defined to minimize fire risk during normal storage and handling.

 The minimum flash point for fuel in the machinery space of a merchant ship is governed by international legislation. According to the ISO Standard requirements the flash point for all distillate and residual grades except DMX shall be a minimum of 60'C . Ship classification society rules specifically stipulate that fuels with the flash point of less than 60'C are not permitted but with some exception. Solas 1974 has similar provisions.

 Flash point is considered as a useful indicator of the fire hazard with regard to the storage of marine residual fuels.  Flammable vapors may still develop in the tank headspace even if fuels are stored at temperatures below the determined flash point. Two useful documents have been compiled on this subject:

    "The flammability hazards associated with the handling, storage and carriage 
    of residual fuel oil"; published by the Oil Companies International Marine Forum 
    (OCIMF) dated December 1989.
    "International safety guide for oil tankers and terminals" published by the International 
    Chamber of Shipping.
    Some basic precautions from the above important papers are given below:
    (1) Flame screens on tank vents shall be maintained in good order and condition.
    (2)
    Temperatures in the fuel system shall conform to recognized codes of practice.
    (3)
    All electrical fittings in tank headspaces must be designed for hazardous conditions and meet appropriate safety standards.
    (4) Any sources of ignition in the vicinity of the vents shall not exist.
    (5) In case that levels of fuel in storage tanks is low, heating coils should be shut down.
    (6) Gas detectors shall be calibrated correctly before they are used to check the flammability of headspace gas.
    (7)
    Headspace flammability readings shall be considered hazardous if they exceed 50% lower flammable limit (LFL). Low pressure air purging of the headspace will assist to reduce the hazard.
    (8) The risks of electrical charges should be taken into account when using metallic sounding or sampling devices. Such devices should be earthed or bonded to the tank structure.