safety of bulk carriers and IMO

IMO and the safety of bulk carriers

Bulk cargo carriers are often described as the "workhorses" of the world merchant fleet. There are about 4,600 of them operating in the world today, forming about 30% of the world fleet in tonnage terms. They include some of the world's biggest ships (only some crude oil carriers are bigger) and without them world trade and industry would be paralysed. Yet, for all their importance to modern life, bulk carriers are among the most anonymous of ships. They usually operate between terminals situated well away from cities and traditional port areas and are rarely noticed by the general public. When they are seen they are often mistaken for oil tankers, with which they share some similarities in appearance. And when they sink - which they have done all too often in recent years - they usually do so unnoticed by the world at large, far away from the television cameras and leaving little unsightly pollution to worry the environmentalists. This paper examines the development of bulk carriers, their contribution to the world economy, the safety problems they face - and what IMO has done to make them safer.

The development of bulk carriers

The bulk carrier was first developed to carry dry cargoes which are shipped in large quantities and do not need to be carried in packaged form. The principle bulk cargo consists of grains (like wheat), coal, iron ore, bauxite, phosphate and nitrate. The advantage of carrying such cargo in bulk is, that packaging costs can be greatly reduced, while loading and unloading operations can be speeded up. Before the Second World War, however, there was no real demand for special bulk carriers. Sea borne trade of all mineral ores amounted to only 25 million tons in 1937 and this could be carried in conventional tramp ships. By the 1950s, however, movements of bulk cargo was increasing. Very often ores and other commodities were found far away from where they were needed and the most convenient and cheapest way of shifting them was by sea. Companies in the United States, Europe and increasingly in Japan, began to build ships designed exclusively for the carriage of cargo in bulk. As demand increased and shipbuilding technology advanced so these ships tended to become bigger in size and carrying capacity. This afforded the same economies of scale that were to make the Very Large Crude Carrier (VLCC) so attractive to oil tanker operators in the 1970s. Doubling the amount of steel used in constructing a ship enabled the amount of carrying capacity to be cubed, yet the size of the crew required did not increase greatly and other costs, such as fuel, also rose relatively slowly, especially since speed was not vital to bulk transport. The modern bulk carrier has evolved gradually but since the 1960s the standard design has been a single hull ship with a double bottom, large cargo holds with hopper tanks and topside tanks covered by hatches. As with crude oil tankers the engine room, navigating bridge and accommodation areas are nearly always located at the stern of the ship. By the 1970s bulk carriers of more than 200,00 dwt were operating and rivaled VLCCs as the largest ships afloat. There are several other similarities between bulk carriers and tankers, which help to explain the frequency with which they are mistaken for each other. The simplest way of telling a bulk carrier from an oil tanker is that the holds of the bulk carrier are covered by hatches raised above the deck level, while the deck of the tanker is covered by fuel pipes. A bulk carrier of 36,000 dwt may have five cargo holds while one of 250,000 dwt may have as many as nine.

By the 1970s ships were being built which could carry oil, ore or other types of dry bulk cargoes. This was done to increase operational flexibility. One of the problems with the bulk trades (as with oil transportation) is that ships normally carry cargo one way but return in ballast because there is nothing to take back. However, oil/bulk/ore (OBO) ships have never become as popular as dedicated bulk or oil carriers, partly because their complexity increases building and operating costs. Today bulk carriers transport a high percentage of world trade - and in most cases they do so safely. According to the International Association of Dry Cargo Shipowners (Intercargo), in 1990-1994 99.90% of dry bulk cargoes were delivered safely. In the case of iron ore the figure was 99.71% and for both grain and coal reliability was 99.97%. The amount of cargo carried was enormous. In 1993, according to Intercargo, 993 million tonnes of iron ore, coal, grain, bauxite and phosphates were carried by sea. Their total value was US$77 billion, representing approximately 4% of the gross national product of the 24 developed countries within the Organisation for Economic and Cultural Development (OECD). A further 177 million tonnes of products such as steel, cement, non-ferrous ores and petroleum coke were also carried by bulk carriers.

The work of IMO

Because shipping is such an international industry, it is generally accepted that safety and other issues have to be dealt with at an international level. This is true of bulk carriers as well as other ship types and since it came into existence in 1959 the organization chiefly responsible for their safety has been the International Maritime Organization, the United Nations specialized agency concerned with shipping safety and the prevention of pollution from ships. IMO is the only United Nations agency to be exclusively concerned with shipping and the sea. It is a highly technical organization whose main tasks are often summed up in the phrase "safer shipping and cleaner oceans." It carries out this mandate primarily by developing conventions, codes and recommendations which are intended to be applied universally. The most important of these instruments have certainly achieved this target: several of the most important have been ratified by well over 120 countries and apply to more than 98% of the world fleet of merchant shipping. In practice, it is impossible to operate a ship on an international voyage which is not built and equipped to IMO requirements (although the way they are implemented can vary enormously). As far as safety is concerned, IMO has developed treaties dealing with the safety of life at sea, the prevention of collisions, the improvement of radio communications at sea, the training and certification of seafarers, the creation of an international system for search and rescue and other matters. The most important of all the Conventions adopted by IMO is the International Convention for the Safety of Life at Sea (SOLAS). The first SOLAS Convention was adopted in 1914 (as a direct result of the Titanic disaster) and revised versions were adopted in 1929 and 1948. One of IMO's first tasks was to update the treaty again and the new version was adopted in 1960. Although bulk carriers as such were then still in the early stages of their development, the carriage of cargoes in bulk had been going on for many decades and one of IMO's many responsibilities was to improve the way it was done. It concentrated on two main areas - the safety of the cargo and of the structure of the ship itself.

Improving cargo safety

As we have seen, many different products are carried on ships in bulk and grains, such as wheat, maize, millet and rye have been transported by sea for centuries - the wheat trade between north Africa and Italy was a major economic feature of the Roman Empire, for example. Since the last century, the grain trade has grown in importance and much of it is carried by sea. In 1993-1994 the biggest producers were the United States (32 million tons), the European Union (18 million tons), Canada (17.7 million tons), and Australia (12.2 million tons). The biggest importers were Far East Asia (including Japan, China and the Republic of Korea) and Africa. Originally grain was transported in sacks, but by the middle of the present century the normal procedure was to carry it in bulk. It could be stored, loaded and unloaded easily and the time taken to deliver it from producer to customer was greatly reduced, as were the costs involved. However, there were problems.

Grain has a tendency to settle during the course of a voyage, as air is forced out when the individual grains sink. This leads to a gap developing between the top of the cargo and the hatch cover. This in turn enables the cargo to move from side to side as the rolls and pitches. This movement can cause the ship to list and, although initially the ship's movement will tend to right this, eventually the list can become more severe. In the worst cases, the ship can capsize. This problem was well known and the 1960 SOLAS Convention devoted an entire chapter (Chapter 6) to measures designed to prevent it from occurring. These regulations were more advantageous from an economic point of view than those adopted in SOLAS 1948 (which required a more extensive use of increasingly expensive temporary fittings and/or bagged grain) and many countries quickly put them into effect, even though the Convention itself did not enter into force until 1965. Experience soon showed, however, that the new regulations still had some deficiencies as far as safety was concerned, and during a period of four years six ships loaded under those rules were lost at sea. IMO began studying this problem early in 1963 and in order to gain the necessary data initiated a study to which masters of ships of many nationalities contributed. Further studies and tests showed that some of the principles on which the 1960 regulations were based were invalid. In particular, it was shown that the 1960 Convention had underestimated the amount of "sinkage" which occurs in grain cargoes loaded in bulk. The fact that the Convention had underestimated this sinkage made the basic requirements of the Convention unattainable. As a result, new grain regulations were prepared and adopted by the IMO Assembly in 1969 (resolution A.184). These regulations became generally known as the 1969 Equivalent Grain Regulations. Governments were invited to use the new regulations instead of the requirements concerning grain contained in SOLAS 1960. This was done because it was recognized that an amendment to the Convention would take a very long time to enter into force. A recommended Code would, if implemented quickly by Governments, be much more immediate in its impact. Voyage experience over a three-year period showed that the 1969 Grain Equivalents were not only safer but were also more practical and economical than the 1960 regulations and, with slight amendments, based upon operational experience, they were used as the basis of new international requirements which were subsequently incorporated into chapter VI of the 1974 SOLAS Convention. Although grain was the only bulk cargo to be given a special chapter in the 1960 SOLAS Convention, the 1960 conference recommended that IMO draw up an international Code of Safe Practice for Solid Bulk Cargoes (BC Code), which was adopted in 1965. The Code has been updated at regular intervals since then and is kept under continuous review by the Sub-Committee on Dangerous Goods, Solid Cargoes and Containers. The practices contained in the Code are intended as recommendations to Governments, ship operators and shipmasters. Its aim is to bring to the attention of those concerned an internationally-accepted method of dealing with the hazards to safety which may be encountered when carrying cargo in bulk. The BC Code was amended on several occasions, but in 1991 IMO decided to amend Chapter VI of SOLAS and in the process completely re-write it. The main change made in the amendments, which entered into force on 1 January 1994, was to extend the chapter to cover other cargoes, including bulk cargoes. The new Chapter VI was re-titled Carriage of Cargoes. It is a great deal shorter than the existing text, but its provisions are backed by a number of codes. The advantage of including requirements in a code rather than the convention itself is that codes can be amended much more easily. The codes that are most relevant to the safety of bulk carriers are the revised BC Code and a new International Code for the Safe Carriage of Grain in Bulk (International Grain Code). The latter is the only code referred to in the chapter which is mandatory. Like the original grain rules, the Code is designed to prevent the particular qualities of grain threatening the stability of ships when it is carried in bulk. It applies to all ships - including existing ships and those of less than 500 tgt - which carry grain in bulk. Part A contains special requirements and gives guidance on the stowage of grain and the use of grain fittings. Part B deals with the calculation of heeling moments and general assumptions. The revised BC Code deals with three basic types of cargo: those which may liquefy; materials which possess chemical hazards; and materials which fall into neither of these categories but may nevertheless pose other dangers. The Code highlights the dangers associated with the shipment of certain types of bulk cargoes; gives guidance on various procedures which should be adopted; lists typical products which are shipped in bulk; gives advice on their properties and how they should be handled; and describes various test procedures which should be employed to determine the characteristic cargo properties. The Code contains a number of general precautions and says it is of fundamental importance that bulk cargoes be properly distributed throughout the ship so that the structure is not overstressed and the ship has an adequate standard of stability. Loaded conditions vary according to the density of the cargo carried. The ratio of cubic capacity to deadweight capacity of a normal ship is around 1.4 to 1.7 cubic metres per tonne and the ratio of volume of cargo to its mass is known as the stowage factor. When high density bulk cargoes with a stowage factor of about 0.56 cubic metres per ton or lower are carried, it is particularly important to pay attention to the distribution of weight in order to avoid excessive stresses on the structure of the ship. All bulk cargoes when loaded tend to form a cone. The angle formed between the slope of the cone and the bottom of the hold will vary according to the cargo and is known as the angle of repose. Some dense cargoes, such as iron ore, form a steep cone while others - such as grain - have a much shallower angle. Cargoes with a low angle of repose are much more prone to shift during the voyage and special precautions have to be taken to ensure that cargo movement does not affect the ship's stability. On the other hand, the sheer weight of dense cargoes can affect the structure of the ship. After dealing with general precautions, the Code then goes on to deal with cargoes having an angle of repose of 35 degrees or less and then with those who angle of repose is greater than 35 degrees. Cargoes with a low angle of repose are particularly liable to dry-surface movement aboard ship. To overcome this problem, the Code states that such cargoes should be trimmed reasonably level and spaces in which they are loaded should be filled as fully as is practicable, without resulting in excessive weight on the supporting structure. Special provisions should be made for stowing dry cargoes which flow very freely, by means of securing arrangements, such as shifting boards or bins. The Code says that the importance of trimming as a means of reducing the possibility of a shift of cargo can never be over-stressed. This is particularly true for smaller ships of less than 100 metres in length. Trimming also helps to cut oxidation by reducing the surface area exposed to the atmosphere. It also helps to eliminate the "funnel" effect which in certain cargoes, such as direct reduced iron (DRI) and concentrates, can cause spontaneous combustion. This occurs when voids in the cargo enable hot gases to move upwards, at the same time sucking in fresh air. After listing various regulations adopted by the International Labour Organisation (ILO), which should be taken into account during cargo handling operations, the Code gives details of other dangers which may exist. Some cargoes, for example, are liable to oxidation which may result in the reduction of the oxygen supply, the emission of toxic fumes and self-heating. Others may emit toxic fumes without oxidation or when wet. The shipper should inform the master of chemical hazards which may exist and the Code gives details of precautions which should be taken. The Code gives details of the various sampling procedures and tests which should be used before transporting concentrates and similar materials and also contains a recommended test procedure to be used by laboratories. There are six appendices to the Code, giving information about particular cargoes. A list of cargoes which may liquefy is contained in appendix A to the Code, for example while appendix B gives an extensive list of materials possessing chemical hazards. Some of the classified materials listed also appear in the International Maritime Dangerous Goods (IMDG) Code when carried in packaged form, but others become hazardous only when they are carried in bulk - for example, because they might reduce the oxygen content of a cargo space or are prone to self-heating. Examples are wood chips, coal and direct reduced iron (DRI). Appendix C deals with bulk cargoes which are neither liable to liquefy nor possess chemical hazards. More detailed information concerning test procedures, associated apparatus and standards which are referred to in the Code are contained in appendix D. Emergency Schedules for those materials listed in appendix B are contained in appendix E. Recommendations for entering cargo spaces, tanks, pump rooms, fuel tanks and similar enclosed compartments are shown in appendix F. In 1990 the MSC issued a circular (MSC/Circ.531) which warned against the risks of shifting cargo and requested Member Governments to implement revised recommendations for trimming cargoes which were included in the 1989 edition of the Code and are intended to minimize sliding failures. It was agreed that a study into the use of voyage data recorders should be carried out.