BUNKER FUEL

About Bunker

Fuel Oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. The term “Bunker Fuel” refers to any type of fuel oil used aboard ships. Presently, fuel cost remains as one of the largest item in the overall operating cost of a merchant ship. The great increases in the price of the oil fuel have caused ship owners to increase their efforts to obtain improved and better quality of bunker.

Beside related to efficient operational cost, cargo carrying capacity of a vessel also could be optimized by strategic bunkering arrangements.

Bunker Type

In the maritime field another type of classification is used for fuel oils:

·MGO (Marine Gas Oil): roughly equivalent to No.2 fuel oil, made from distillate only

·MDO (Marine Diesel Oil): a blend of heavy gasoil that may contain very small amounts of black refinery feed stocks, but has a low viscosity up to 12 cSt so it need not be heated for use in internal combustion engines

·IFO (Intermediate Fuel Oil): a blend of gasoil and heavy fuel oil, with less gasoil than marine diesel oil

·HFO (Heavy Fuel Oil): pure or nearly pure residual oil, roughly equivalent to No.6 fuel oil

·MFO (Marine Fuel Oil): same as HFO (just another “naming”)

Marine dieasel oil contains some heavy fuel oil, unlike regular diesels. Also, marine fuel oils sometimes contain waste products such as used motor oil. Marine fuels were traditionally classified after their kinematic viscosity. This is a mostly valid criteria for the quality of the oil as long as the oil is made only from atmospheric distillation. The unit of viscosity used is the Centistokes.

The fuels most frequently quoted are listed below in order of cost, the least expensive first:

·IFO 380: Intermediate fuel oil with a maximum viscosity of 380 CST

·IFO 180: Intermediate fuel oil with a maximum viscosity of 180 CST

·LS 380: Low-sulphur (<1.5%) intermediate fuel oil with a max viscosity of 380 CST

·LS 180: Low-sulphur (<1.5%) intermediate fuel oil with a max viscosity of 180 CST

·MDO: Marine Diesel Oil

·MGO: Marine Gas Oil

Bunker Characteristics

The bunker quality information which must be considered is calorific value, metallic constituents, density, pour point, flash point, and specific gravity, etc. In this section we will focus on density, viscosity, and contaminants.

Information concerning the density of specific gravity of fuel is important for three reasons. For the operation of centrifuges, to calculate the volume of space required for stowing the bunker, and for expressing quantities of oil purchased or used in simple terms.

To both ship owner and ship’s crew information about the viscosity serve as an important guide to its pumpability, determination of the point of injection into engine’s operating cycle, and for the control of separating and heating requirements.

The main contaminant which are found in bunker fuels are sulfur, sometime appear as free sulfur, but usually found in combination with other substances or chemical compound. The presence of sulfur in the fuel leads to the formation of sulfuric and sulfurous acids which may cause corrosion of the cylinder liner, exhaust system and exhaust gas boilers.

Likely the most wearisome ash component in fuel oil is vanadium which is present in varying proportions in oil soluble form. It’s usually found where there are large proportions of sodium in the fuel. As the vanadium is not water soluble it cannot be removed by the centrifuging method. The most serious operating problems occur when vanadium combines with sodium and form ashes, melted sodium vanadium ash will directly corrode steel.

Application

Now that bunkers may often represent nearly 50 percent of a vessel’s operating expenses  owners are paying closer attention to the choice of bunkering ports, quality and price issue.

One of the most important step that has been taken to protect owner from fuel quality issue is the development of Marine Fuel Standard which approved by the International Standards Organization (ISO). The first British standard for fuel oil came in 1982. The latest standard is ISO 8217:2005.

In conjunction with the BIMCO, the international Chamber of Shipping (ISC) drafted a new charter party clause “Bunker Fuel Quality Clause” which sets out the conditions to be met in the provision of suitable fuels for the main and auxiliary engine of the vessel. In accordance with this clause, the ISC has drafted a Bunker Delivery Note and this was published in September 1980. The BDN gave details of the fuel such as viscosity, relative density, flash point, water content, pour point, sediment, vanadium, sulfur, etc.

Operators must ensure and remind ship’s engine staff that BDN filled in correct manner. Samples of fuel from each bunkering are properly collected, labeled, and retained on board so as to provide important evidence in the event of a dispute involving fuel quality. Min 4 samples taken, 1 sample will serve as MARPOL sample and can’t be used for other purposes.

Also, Bunkering or the pumping over of fuel into partially filled tanks containing a fuel received on a previous bunkering also not recommended, in order to avoid stability and compatibility issue.

In today’s climate, operator must be aware that precise data is essential if the efficiency of an engine is not to be reduced and the overall operating cost of a ship increased.