Dangers in Bunkering Operation - Hydrogen Sulphide
Hydrogen sulphide is flammable gas which is highly toxic and corrosive. It has an odour of rotton eggs and a low odour threshold. Hydrogen sulphide is heavier compared to air, soluble in water and colourless, hence it is not detected by bare eyes, and settle down and difficult to disperse in the atmosphere. There is a chance of accumulation of the gas at the open deck where so many operations are carried out.
Sources of Hydrogen Sulphide
Un-stabilized crude oil and some refined products such as fuel oil, bitumens, bunker fuel, gasoline, even naphtha may contain benzene also other than hydrogen sulphide. Before commencing bunkering operation all the available information about the bunker fuel to be collected from the bunker supplier such as Material Safety Data Sheet (MSDS), rate of bunker supply, temperature, special requirements, presence of unusual stabilizers or inhibitors in the bunker fuel, etc.
The TLV-TWA (Threshold Limit Value - Time Weighted Average) for H2S is 5 ppm for a period of eight hours. This means any personnel can stay safely in an atmosphere containing hydrogen sulphide concentration 5 ppm (5 parts in a million parts of air) for a time period of eight hours. But, keeping safety in mind it is not advised to do so. Exposure time and limit to be reduced during working as a safe working practice.
Procedures for Handling Bunkers Containing Hydrogen Sulphide
- Concentration of H2S to be monitored before commencing, during and after bunkering operation using vapour monitoring system. Portable multi gas detectors are advised to use since they are easy to carry.
- If H2S is detected keep monitoring frequently.
- If required forced ventilation must be used to lower gas concentrations in the collected area.
- Portable gas measuring instruments to be set at a value of 5 ppm and an alram to be activated at the set value.
- Proper personal protective equipment (PPE) is to be worn.
- During bunkering gases are expelled out through tank vents and these gases normally spread around the deck. Try to avoid these areas. Periodical tank content measuring is important and in such cases emergency breathing apparatus can be used.