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.
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
Two useful documents have been compiled on this subject:
"The flammability hazards associated with the handling, storage and
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
(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
(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.