The most important use of kerosene is as aviation turbine fuel. This product has the most stringent specifications, which must be met to ensure the safety standards of the various categories of aircraft. The most important specifications are the flash and freeze points of this fuel. The initial boiling point (IBP) is adjusted to meet the minimum flash requirements of approximately 100°F. The final boiling point (FBP) is adjusted to meet the maximum freeze point requirement of the jet fuel grade, approximately —52°F. A full-range kerosene may have an ASTM boiling range between 310 and 550°F. Basic civil jet fuels are
1. Jet A, a kerosene-type fuel having a maximum freeze point of —40°C. Jet A-type fuel is used by mainly domestic airlines of various countries, where a higher freeze point imposes no operating limitations.
2. Jet A-l, a kerosene-type fuel identical with Jet A but with a maximum freeze point of —47°C. This type of fuel is used by most international airlines. Jet A and Jet A-l generally have a flash point of 38°C.
3. Jet B is a wide-cut gasoline-type fuel with a maximum freeze point of —50 to —58°C. The fuel is of a wider cut, comprising heavy naphtha and kerosene, and is meant mainly for military aircraft.
A limited number of additives are permitted in aviation turbine fuels. The type and concentration of all additives are closely controlled by appropriate fuel specifications. The following aviation turbine fuel additives are in current use:
• Antioxidants. Its use is mandatory in fuels produced by a hydrotreat-ing process, to prevent formation of hydrogen peroxide, which can cause rapid deterioration of nitrile rubber fuel system components.
• Static dissipators, also known as antistatic additives or electrical conductivity improvers. Its use is mandatory to increase the electrical conductivity of the fuel, which in turn promotes a rapid relaxation of any static charge build-up during the movement of fuel.
• Fuel system icing inhibitor (FSII). The main purpose of FSII is to prevent fuel system blockage by ice formation from water precipitated from fuels in flight. Because of the biocidal nature of this additive, it is very effective in reducing microbiological contamination problems in aircraft tanks and ground fuel handling facilities.
As most commercial aircrafts are provided with fuel filter heaters, they have no requirement for the anti-icing properties of this additive. FSII is therefore not usually permitted in civil specifications, its use is confined mainly to military fuels.
• Corrosion inhibitor/lubricity improver. Its use is optional to protect storage tanks and pipelines from corrosion and improve the lubricating properties of the fuel.
Was this article helpful?