The term bunker dates back to the days when ships were powered by coal and it is still used today. Because it referred to the depots where coal was stored, today ship fuel is called bunker and refueling is known as bunkering.
Diesel is the main product obtained during the petroleum distillation process with a boiling point between 200-300 Celsius and is used in diesel motors.
Fuel oil is also a bunker obtained from the petroleum distillation process.
Distillation of crude oil take place in a steel cylinder in refineries known as a distillation tower. In order for distillation to take place, crude oil is heated and sent to the tower, where hydrocarbons are separated according to their type. Hydrocarbons with different structures are removed from the distillation tower at different points. At the very bottom of the distillation tower is the heavy residue which does not boil at temperatures less than 380 Celsius. New products with different viscosities known as heavy fuel or fuel oil are obtained by blending this residue in different ways.
Because a large portion of vessel operating expenses consist of bunker expenditures, it is necessary that bunker comply with the standards that have been set to ensure proper performance of the ship’s equipment and prevent the huge expenses that can result from problems. Another important issue related to this is the recommendations of the equipment manufacturers.
HISTORICAL DEVELOPMENT OF BUNKER STANDARDS
Though viscosity is an important characteristics, it tells us nothing about the other characteristics of fuel oils. The petroleum crisis of 1973 raised the price of a barrel of crude oil to 40 American dollars and forced operators and shipping companies to search for cheaper fuels to replace distilled fuels. Subsequently, they began to use fuel oils whose sulfur content and viscosity were higher but which were extremely cheap instead of expensive diesel fuels. As a result of the use of poor grades of these fuels, equipment on ships was significantly affected. For these reasons, a number of standards emerged and were developed regarding diesel bunker for ships.
The impact of low-grade bunker on equipment became doubly important for the technical departments of shipping companies and they became more selective in their choice of bunker for their ships. Gradually the shipping sector came to realize that when ordering bunker, viscosity is not a sufficient criteria and that other characteristics of bunker must be taken into consideration.
In 2005, the last revision of ISO 8217 was published and today many bunker buyers place their orders in accordance with the ISO 8217 2005 standards.
NAMES AND ABBREVIATIONS THAT CONFORM TO THE STANDARDS
Heavy Fuel Oil/ Bunker Fuel Oil/ Marine Fuel Oil
Many manufacturers refer to residual fuels as Bunker C, as well as ‘Heavy Fuel Oil’, ‘Bunker Fuel Oil’ and ‘Marine Fuel Oil’. These bunkers have high viscosity and are sold around the world at cheaper prices.
Medium Fuel Oil
Sometimes bunkers with lower viscosity than the cheap bunker is available. These are referred to as ‘Intermediate Fuel’ or ‘Medium Fuel Oil’.
Light Fuel Oil
Manufacturers also call these bunkers ‘Light Fuel Oil’. Light fuel oils are characterized by a maximum viscosity of 50 degrees Celsius. For example, IFO 180 is a bunker with a maximum viscosity of 50 degrees and a cSt of 180.
R for ‘Residue’
RM is a bunker term specified in the ISO standards and indicates the bunker grade. The ‘R’ stands for ‘Residue’. For example, RMC10 indicates a residual bunker with a viscosity of 100°C and cSt of 10. This is true of the other standards as well.
D for ‘Distillation’
Similarly, the ‘D’ in ISO and other standards refers to ‘Distillation’. For example DMX,DMA,DMB and DMC
DMX: This bunker is a highly volatile distilled product and is used in high-speed or super high-speed diesel engines running at 1200 rpm or higher. These bunkers are generally used in emergency engines on the ship.
DMA: A distilled product that has medium volatility and is bright and clean. This bunker is generally known as ‘Marine Gas Oil’.
DMB: A distilled product with low volatility. It is similar to DMA but because it contains some residual fuel, it has a black appearance.
DMC: DMB is a bunker that contains a higher percentage of residual fuel. Compared to the others, it has higher levels of aluminum + silicone, vanadium, carbon emission and residues.