Handling cargo oil having a flashpoint exceeding 60c without maintaining cargo oil tanks in inert condition needs extreme caution. Confirm that the use of IG is not required by regulations at the discharging port and shore facility. Refer to the special precautions as listed out in the latest edition of ISGOTT for above such operations.
Also, a formal (stage 2) Risk Assessment will need to be carried out, and the office informed, before such a decision.
Ensure that sufficient reliable evidence available that the flash point of the cargo oil is above 61 degree C and the temperature of the cargo oil does not exceed 5 degree C less than the flash point.
However, when cargoes with a flashpoint exceeding 60 degrees C are carried at a cargo temperature higher than their flashpoint less than 5 degrees C, the tank should be maintained in an inert condition.
If the previous cargo oil has a low flash point, purge the inflammable gas by IG until the level of the gas reduced down to 2% by Volume or less beforehand.
If another cargo oil having a low flash point has been loaded into other remaining tanks, prevent the mixing of such vapor by isolating vapor of such grades.
Cargo oil tanks must be inserted before washing the tanks with high-temperature water.
Take the following measures cargo discharging operations-
Ensure that flame arrestors are fitted in vent posts.
- Take preventive measures against static electricity
- Refer to relevant Chapter in the latest edition of ISGOTT.
Piping system requirement
All piping systems within cargo tanks,
saltwater ballast tanks, double-bottom
tanks, pump rooms, pipe tunnel(s) and
cofferdams, including void spaces
adjacent to cargo tanks, and pipes
that pass through the deck or connect
to the shell, are examined and tested
under working conditions. The surveyor
checks for tightness and looks to establish
if their condition is satisfactory.
In addition to annual and intermediate
survey requirements, all machinery used
for liquid cargo services is examined,
including ventilation pipes, pressure
vacuum valves and flame screens.
The inert gas systems are tested under
working conditions. The systems’ main
components are examined internally.
Based on the results of these
examinations, additional checks can
be required, which may include
dismantling, hydrostatic tests and
thickness measures, or all three.
Main articles:
Operation of inert gas system
Oil pollution control method
Gas freeing arrangement for oil tanker
Handling guideline for oil cargo
Oil pollution prevention method
Preparation for loading oil cargo
How to prevent spillage of oil cargo
General precautions for oil cargo loading in tankers
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