Overview

Sulphur can be highly corrosive to steel when in contact with water. To protect ships and seafarers from potential safety incidents, specific precautions should be followed in accordance with relevant rules for the handling and carriage of bulk sulphur.

I. Example of incidents

A 2012-built bulk carrier loaded 40,000 tonnes wet sulphur which were declared as Group C cargo from a Russian port in September 2018. Hold steelwork was believed to be protected as per contract prior to loading. However, the sulphur cargo was not discharged until 65 days later when the holds are severely corroded due to port congestion. When the vessel went for dock repair in February 2019, the shipowner was demanded to replace a total of 600 tonnes of bottom plates by the classification society in accordance with the thickness measurement report. Club investigation later found out that protective product SLIP-COAT™ which works for dry cargoes was mistakenly applied instead of SLIP-COAT PLUS™ which should have been applied for the wet sulphur.

A similar case happened in October 2018 when a 2014-built bulk carrier shipped 30,000 tonnes of sulphur from the United States to Dakar. Only part of the cargo holds was limewashed prior to loading, and not in a standard way, according to the Club's investigation.

II. International Convention and Domestic Regulations

1. International Maritime Solid Bulk Cargoes (IMSBC) Code

Sulphur cargoes are divided into two categories based on their characteristics.

Group C Sulphur: a co-product recovered from sour gas processing or oil refinery operations that has been subjected to a forming process that converts sulphur from a molten state into specific solid shapes (e.g. granules, pellets, pastilles or flakes); bright yellow in colour; odourless. This cargo is non-combustible or has a low fire risk. If involved in a fire, cargo may generate harmful gases. When handled and shipped in accordance with the provisions of the schedule, this cargo poses no corrosion or dust hazards for human tissue or vessel.

Group B Sulphur: crushed lump and coarse grained, a mineral substance found free in volcanic countries. Yellow in colour, brittle, insoluble in water, but readily fusible by heat. This cargo is flammable and has a liability to dust explosion. Fine grained sulphur shall not be transported in bulk.

2. International Maritime Dangerous Goods (IMDG) Code

Sulphur (UN generic entry No.1350) is listed as Class 4.1 flammable solids, meaning readily combustible solids and solids which may cause fire through friction. According to IMDG Dangerous Goods List, sulphur evolves toxic, very irritating and suffocating gas when involved in a fire. The dust forms an explosive mixture with air which may be ignited by static electricity, and forms explosive mixtures with oxidizing substances. It is corrosive to steel, in particular in the presence of moisture. May cause dermatitis by skin contact, and rashes in worse cases.

3. Chinese National GB Standard

According to the No.1 Amendment of the Dangerous Goods List (GB12268-2005), sulphur in specific shapes (e.g. Pellets, granules, prills, pastilles or flakes) can be shipped as ordinary goods.

III. Cargo Holds Protection

Dry sulphur does not react with bare steel, but when in contact with water it becomes wet sulphur which is potentially highly corrosive. It may take in moisture in the air when being stored or handled, and sometimes water is sprayed by the crew to keep down the dust. The hold steelwork should therefore be well protected, normally by one of the three methods as listed below, for the carriage of cargoes like sulphur, salt, petroleum coke and cement.

1. LIMEWASH

It’s a universal practice, and the only practice approved by some shippers, to apply limewash which is easily available at a low price as a protection to the holds. A single layer of limewash, if applied properly, can provide good protection to the steel for about 30-40 days. First, make sure a high concentration of the limewash and apply a thicker coating at the bilge and the bottom plating of bulkhead until the original colour is fully covered. Second, spray the limewash from the front to the rear and from the top to the bottom. Sprays on the slopes can be evened with broomsticks. Third, the height at which the limewash is applied should be carefully calculated. Tank cleaning will be a headache if sprayed too high and steelwork will not be well protected if too low. Given the fact that bulk sulphur is carried on board in a lump, the limewash should be applied at a height slightly above the height of the cargo.

2. SLIP-COAT

There are two kinds of slip-coat products - SLIP-COAT™ 25 LTR, which is non-water resistant and can be used when carrying dry cargoes like coal and petroleum coke, and SLIP-COAT PLUS™ 25 LTR, which is water resistant and can be used when carrying cargoes like industrial salt, sulphur and even foodstuff. The slip-coat film will be completely dry in only 1-2 hours, ideal when difficult cargoes need to be loaded immediately after clean cargoes are discharged. The manufacturer also provides cleaning agents including Unitor™ Aquatuff™ and Unitor™ Aquatuff High Foam™.

3. HOLDBLOCK

Two solutions are included in HOLDBLOCK products - HOLDBLOCK-AP, which is applied prior to loading to protect the holds, and HOLDWASHING-HD, which is used as a cleaner for HOLDBLOCK-AP and its residues. In practice, cargo holds are well protected by the HOLDBLOCK-AP coating without showing obvious signs of corrosion and changes in painting, but HOLDWASH-HD is not as effective. The HOLDBLOCK-AP residues and sulphur stains can’t be removed easily unless washed repeatedly with water from a high-pressure fire hose and rubbed with brushes and sponges at the same time.

IV. Safety Precautions for Handling and Carrying Sulphur Cargoes

1. Prior to loading

◆ The master should confirm whether the sulphur cargo to be shipped is categorised as Group B or C in accordance with the IMSBC Code. If it is Group B Sulphur, a classification society pre-load survey should be applied with proper precautions taken to obtain a certificate of fitness for the carriage of dangerous goods;

◆ check the cargo holds for water tightness;

◆ prepare the holds for the intended cargo as per requirements and make sure they are clean and dry without any loose rust scale or paint flakes;

◆ make sure the ballast water system is in good condition and the bilge clean and drained;

◆ evaluate the vessel's condition and choose a protection method accordingly, take photos for evidence afterwards.

2. At the port of loading

◆ Officers on deck should wear personal protective equipment including respirators, gloves and goggles properly;

◆ stick to port regulations to prevent sulphur dust clouds;

◆ slope the cargo near the engine room to separate them from the aftbulkhead;

◆ wash down the sulphur scattered on the hatch track with fresh water after loading is completed;

◆ implement strict fire precautions, smoking and hot work are prohibited;

◆ cargo hold lights should be properly placed with net covers and removed in time.

3. During the voyage

◆ Ventilation is not a necessity during the voyage, and the vent should be covered with canvas to keep out sparks;

◆ avoid warming the fuel tank next to the holds as far as possible, and ask for permission from the master if it has to be done. Appoint crew members to monitor the heating and control the oil temperature below 50℃ or adjust the temperature according to specific cargo conditions;

◆ make maritime declaration available on board in case of stormy weather.

4. At the port of discharge

◆ Open the hatches in advance, weather permitting, and in a steady way to prevent sparks from crashes;

◆ let out sulphur emissions and spray fresh water on the surface of the cargo;

◆ strengthen fire prevention and strictly prohibit smoking during the discharge of sulphur; additional officers should be assigned for a 24-hour patrol;

◆ put out burning sulphur with fresh water and do not use sea water as the cargo will be damaged. Be cautious with personal safety hazards when putting out fire;

◆ extra cautions should be exercised when the cargo is about to be completely unloaded, as sulphur may be ignited by friction between the grabber and the floor.

5. Cargo hold cleaning afterwards

◆ After discharge of cargoes, it's advised to wash out the holds with fresh water before sweeping as flying dust may trigger explosion; no smoking during the cleaning;

◆ for bulkhead caked with sulphurous mud, apply 6kg high-pressure water plus 6kg high-pressure air;

◆ thoroughly wash the bilge system to prevent the residues from corroding the pipework.

For more information, please contact Managers of the Association.