China’s current national standard GB/T 17411-2015 for marine fuel
was made based on ISO 8217. It is a mandatory standard covering
such major technical indicators as kinematic viscosity, sulfur content,
hydrogen sulfide, flash point, moisture, acid value, and total sediment.
Kinematic viscosity. This is the most important performance indicator
for fuel oil and also the main criterion by which fuel oil is graded.
Kinematic viscosity measures a fluid’s resistance to flow and its value
indicates how easily fuel oil can flow, be pumped and atomized. The
unit of kinematic viscosity is mm2
/s.
Sulfur content. The sulfur content in residual fuel depends on that of
the blending components and is classified by concentration into levels
I, II, and III. Starting from January 1, 2020, IMO requires all ships
traversing international waters to use fuel oils with a maximum sulfur
content of 0.50% m/m. It is the responsibility of the buyer to determine
the maximum permissible sulfur content in fuel oil based on the design
of the marine engine, emission regulations, and the local regulations of
the region where the fuel oil and related equipment will be used.
Density. This refers to the mass of fuel per unit volume. The quantity
of fuel can be accurately determined after measuring its density and
volume, making density a key number in fuel trading. As the density of
fuel is related to chemical composition, it can be used to determine the
class and quality of the fuel.
Calculated carbon aromaticity index (CCAI). This is an indicator of the
ignition performance of residual fuel, computed from the fuel’s density
and viscosity. The inclusion of CCAI into the national standard is
intended to prevent prolonged ignition delay potentially caused by fuel
oil with an abnormal density-viscosity relation.
Flash point. This is an effective indicator for the risk of fire from fuel oil.
Hydrogen sulfide. H2S is a highly toxic gas. Exposure to high
concentrations of H2S is hazardous or even fatal. H2S can be formed
during the refining process or build up from fuel oil in storage tanks,
barges, and customer (consumption) tanks.
Acid value. Highly acidic fuels arising from acidic compounds can often
accelerate the damage to marine diesel engines, most often starting
from the fuel injection parts.
Total sediments. Sediments in fuel will exacerbate equipment wearand-tear and clog fuel injectors. Sediments may accumulate in storage
tanks, filter screens, or equipment, leading to blockage between the oil
tank and burner.
Carbon residue. This refers to the percentage by mass of the carbon
residues formed after evaporation and thermal cracking of fuel at a
specific high temperature.
Pour point. This refers to the lowest temperature at which a fuel
specimen can flow under specified laboratory conditions. Buyers should
ensure the pour point of fuel oil meets the requirements of on-board
equipment, especially when the vessel is sailing in a cold environment.
Moisture. Water content reduces the calorific value of fuel oil and the
performance of combustion machinery. Because water may lead to
furnace flameout, shutdown, or other incidents, its concentration in fuel
must be strictly controlled.
Ash content. All residual fuels contain some forms of metals. Some
are from the fuel itself, such as vanadium, calcium, and nickel, while
others – sodium, aluminum, silicon, and iron, for example – are from
foreign sources. When fuel oil is burned, metals are turned into oxides,
sulfides, or more complex compound particulates and then coalesce
into ash content. The melting point of ash content varies widely based
on its composition. The ash content from fuel oil may deposit on pipe
walls, boiler heating surface, or other equipment, thus lowering the
efficiency of heat transfer.
Vanadium. It is commonly found in crude oil. Because its organic
forms are soluble in crude oil, it is also present in residual fuel. Burning
vanadium with sodium produces low-melting point compounds which
cause serious furnace erosion and high-temperature corrosion.
Sodium. As salt is corrosive, this metric is used to determine whether
salt concentration is increased by seawater introduced during
transport. When residual fuel is combusted to generate power, sodium
compounds with low melting points are one of the reasons why scale
would form on, and thereby corrode, the valves and nozzles of marine
diesel engines and the blades of turbo blowers.
Aluminum + silicon. Generally coming from the catalyst powder left
over in residues, silicon and aluminum form hard oxides which can
easily abrade combustion equipment
Net calorific value. The amount of heat released from complete
combustion of a unit weight of fuel minus the heat of formation and
dissolution of acid is called the total calorific value, which less the heat
of vaporization of water yields the net heat value.
Used lubricating oil (calcium + zinc or calcium + phosphorus). The
acidic materials formed from oxidation of ULO are corrosive; the metal
additives in lubricating oil increase ash content; and the abrasive
particles present in ULO cause accelerated wear. For these reasons,
fuel oil should not contain ULO.
Compatibility (level). A standard-conforming fuel may work flawlessly
when used alone but flocculate when mixed with a different type of
naphtha or heavy fuel oil. This phenomenon is also very common
during blending, reflecting the incompatible nature of the types of fuels
used in the blending.
Cleanness. Cleanness measures the number of suspended particles in
fuel and indicates the product’s stability.
Styrene and phenol have significant adverse effects on the quality of
low sulfur marine fuel, including coking, corrosion, and stratification,
and thus affecting its normal use
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