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CIVIL JET FUELS

Aviation turbine fuels are used for powering jet and turbo-prop engined aircraft and are not to be confused with Avgas. Outside former communist areas, there are currently two main grades of turbine fuel in use in civil commercial aviation : Jet A-1 and Jet A, both are kerosene type fuels. There is another grade of jet fuel, Jet B which is a wide cut kerosene (a blend of gasoline and kerosene) but it is rarely used except in very cold climates.

JET A-1

Jet A-1 is a kerosene grade of fuel suitable for most turbine engined aircraft. It is produced to a stringent internationally agreed standard, has a flash point above 38°C (100°F) and a freeze point maximum of -47°C. It is widely available outside the U.S.A. Jet A-1 meets the requirements of British specification DEF STAN 91-91 (Jet A-1), (formerly DERD 2494 (AVTUR)), ASTM specification D1655 (Jet A-1) and IATA Guidance Material (Kerosine Type), NATO Code F-35.

JET A

Jet A is a similar kerosene type of fuel, produced to an ASTM specification and normally only available in the U.S.A. It has the same flash point as Jet A-1 but a higher freeze point maximum (-40°C). It is supplied against the ASTM D1655 (Jet A) specification.

JET B

Jet B is a distillate covering the naphtha and kerosene fractions. It can be used as an alternative to Jet A-1 but because it is more difficult to handle (higher flammability), there is only significant demand in very cold climates where its better cold weather performance is important. In Canada it is supplied against the Canadian Specification CAN/CGSB 3.23

MILITARY

JP-4

JP-4 is the military equivalent of Jet B with the addition of corrosion inhibitor and anti-icing additives; it meets the requirements of the U.S. Military Specification MIL-DTL-5624U Grade JP-4. (As of Jan 5, 2004, JP-4 and 5 meet the same US Military Specification). JP-4 also meets the requirements of the British Specification DEF STAN 91-88 AVTAG/FSII (formerly DERD 2454),where FSII stands for Fuel Systems Icing Inhibitor. NATO Code F-40.

JP-5

JP-5 is a high flash point kerosene meeting the requirements of the U.S. Military Specification MIL-DTL-5624U Grade JP-5 (as of Jan 5, 2004, JP-4 and 5 meet the same US Military Specification). JP-5 also meets the requirements of the British Specification DEF STAN 91-86 AVCAT/FSII (formerly DERD 2452). NATO Code F-44.

JP-8

JP-8 is the military equivalent of Jet A-1 with the addition of corrosion inhibitor and anti-icing additives; it meets the requirements of the U.S. Military Specification MIL-DTL-83133E. JP-8 also meets the requirements of the British Specification DEF STAN 91-87 AVTUR/FSII (formerly DERD 2453). NATO Code F-34.

AVIATION FUEL ADDITIVES

Aviation fuel additives are compounds added to the fuel in very small quantities, usually measurable only in parts per million, to provide special or improved qualities. The quantity to be added and approval for its use in various grades of fuel is strictly controlled by the appropriate specifications.

A few additives in common use are as follows:

1. Anti-knock additives reduce the tendency of gasoline to detonate. Tetra-ethyl lead (TEL) is the only approved anti-knock additive for aviation use and has been used in motor and aviation gasolines since the early 1930s.

2. Anti-oxidants prevent the formation of gum deposits on fuel system components caused by oxidation of the fuel in storage and also inhibit the formation of peroxide compounds in certain jet fuels.

3. Static dissipater additives reduce the hazardous effects of static electricity generated by movement of fuel through modern high flow-rate fuel transfer systems. Static dissipater additives do not reduce the need for `bonding' to ensure electrical continuity between metal components (e.g. aircraft and fuelling equipment) nor do they influence hazards from lightning strikes.

4. Corrosion inhibitors protect ferrous metals in fuel handling systems, such as pipelines and fuel storage tanks, from corrosion. Some corrosion inhibitors also improve the lubricating properties (lubricity) of certain jet fuels.

5. Fuel System Icing Inhibitors (Anti-icing additives) reduce the freezing point of water precipitated from jet fuels due to cooling at high altitudes and prevent the formation of ice crystals which restrict the flow of fuel to the engine. This type of additive does not affect the freezing point of the fuel itself. Anti-icing additives can also provide some protection against microbiological growth in jet fuel.

6. Metal de-activators suppress the catalytic effect which some metals, particularly copper, have on fuel oxidation.

7. Biocide additives are sometimes used to combat microbiological growths in jet fuel, often by direct addition to aircraft tanks; as indicated above some anti-icing additives appear to possess biocidal properties.

8. Thermal Stability Improver additives are sometimes used in military JP-8 fuel, to produce a grade referred to as JP-8+100, to inhibit deposit formation in the high temperature areas of the aircraft fuel system.

POWER BOOSTING FLUIDS

It used to be commonplace for large piston engines to require special fluids to increase their take-off power. Similar injection systems are also incorporated in some turbo-jet and turbo-prop engines. The power increase is achieved by cooling the air consumed, to raise its density and thereby increase the weight of air available for combustion. This effect can be obtained by using water alone but it is usual to inject a mixture of methanol and water to produce a greater degree of evaporative cooling and also to provide additional fuel energy.

For piston engines, methanol/water mixtures are used and these may have 1 percent of a corrosion inhibiting oil added. The injection system may be used to compensate for the power lost when operating under high temperature and/or high altitude conditions (i.e. with low air densities) or to obtain increased take-off power under normal atmospheric conditions, by permitting higher boost pressure for a short period.

Both water alone and methanol/water mixtures are used in gas turbine engines, principally to restore the take-off power (or thrust) lost when operating under low air density conditions. Use of a corrosion inhibitor in power boost fluids supplied for these engines is not permitted.

The methanol and water used must be of very high quality to avoid formation of engine deposits. The water must be either demineralised or distilled and the only adulterant permitted in the methanol is up to 0.5 per cent of pyridine if required by local regulations as a de-naturant. In the past there were several different grades of water/methanol mixtures, e.g. 45/55/0 for turbine engines, 50/50/0 for piston engines (this was also available with 1% corrosion inhibiting oil and was designated 50/50/1) and 60/40/0, however, with decreasing demand Shell now only supplies 45/55/0. The table shows the principal characteristics of Shell demineralised water and of the commonly used methanol/water blend

Date: Wed Mar 22 13:44:15 2000

Posted By: Joseph Weeks, President, Thermal Products, Inc.

Area of science: Chemistry

ID: 952745334.Ch Message:

Free fuel sounds like a great idea, however there are several matters which

need to be considered. First, the fuel at the bottom of the tank probably

has dirt and other crud which can cause wear of the fuel injection system.

Assuming that you eliminate the dirt, then there is the question of

compatibility. I contacted Marketing Fuel Technical Service at Chevron

concerning your question. Their response is as follows:

"In regards to your inquiry about whether Jet A can be run in a diesel

engine, Chevron would never advise anyone to use a particular fuel in an

engine that was not designed for that fuel. We would advise that the

inquiry be made to the equipment (engine) manufacturer."

Remember, while there is only one basic Jet A species, there are several

kinds of diesel - diesel No. 1 and diesel No. 2 (amongst others). Jet A is

more like Diesel No. 1. Diesel No. 2 is the more common "diesel" fuel,

since it is the fuel used by vehicles "on-road".

All of the fuels are products of the refining process. One of the main

differences between them is their distillation boiling ranges. Diesel No. 2

has a higher (in temperature) boiling range and is more dense than Jet A

and/or diesel No. 1 (both of which have lower densities and lower

boiling range temperatures). A fuel which is less dense will have lower

fuel economy (less BTU's per gallon). All of this is "besides the point" as far

as the appropriateness of any of the three to perform in the engines that were

designed for their use. If the engine manufacturer indicates the use of only one

type of fuel, that is the fuel that should be used.

For further information please visit Chevron's INTERNET site at http://www.chevron.com.

There are some very informative publications at the site at http://www.chevron.com/chevr

on_root/prodserv (there is an "underscore" character after the second

"chevron" word). When you reach that site, click on the word "Fuels" and you

will then see a "Publications" option.

That said, we will break down your inquiries into a group of statements

that we have put together to answer others who have asked similar

questions:

Jet A, Diesel No. 1, and Diesel No. 2, are covered by different American

Society For Testing and Materials (ASTM) specifications. The diesel fuels are

covered by ASTM D 975, "Standard Specification for Diesel Fuel Oils". Jet A has

the designation of ASTM D 1655, "Standard Specification for Aviation Turbine

Fuels".

According to the ASTM specifications listed above, the sulfur limit for Jet

A is a maximum of 0.3 mass %. Because of an Environmental Protection Agency

1993 regulation, the specification for sulfur in "on road" Diesel No. 1 and

Diesel No. 2 is a maximum of 0.05 mass % - a large difference from the Jet A

sulfur level.

The EPA regulation would be broken if one were to use Jet A for "on-road"

Diesel. Jet A is also not taxed for "on-road" use, so would be illegal to

use in "on-road" vehicles and possibly illegal in some "off-road" uses as

well. Both the sulfur level and the tax issue need to be considered in a

legal sense when considering the uses of these fuels.

Another difference between the fuels is the viscosity. The ASTM D 1655

detailed viscosity requirement of Jet A is a maximum of 8 mm2/S (millimeter

squared/Seconds - [1mm2/S = 1 Centistoke]) at -200C. The ASTM D 975 viscosity

requirement of Diesel No. 1 is a minimum of 1.3 and a maximum of 2.4 mm2/S at

400C and of Diesel No. 2, a minimum of 1.9 and a maximum of 4.1 mm2/S at 400C.

It is hard to compare these, since the testing temperatures of the diesels do

not agree with that of the Jet A. However, the viscosities at 200 Centigrade and

in units "milliPascal/Seconds" (still another, and different unit measurement)

for the two fuels according to a national average of four semiannual surveys

taken from 1990-1992 are as follows:

Jet A & Diesel No. 1 1.33

Diesel No. 2 3.20

Jet A and Diesel No. 1 tend towards lower viscosities. Lower lubricity is

likely as the viscosity decreases. While this may not cause catastrophic instant

damage, it could cause long-term wear of pumps, etc.

Jet fuels have additional specifications that aren't required of diesel

fuels. A couple examples of these are the requirement of testing for

certain components and a volatility requirement. Some of the methods for

testing also vary from one fuel to the other. Basically, however, we have

pointed out the biggest differences. If you need more detailed comparisons,

please contact the ASTM society at their headquarters at 100 Barr Harbor Drive,

West Conshohocken, Pennsylvania 19428. They could provide you with copies of the

specifications. Their phone number is 610-832-9500.

Once again, we stress that you should contact the equipment manufacturers

and ask what fuels are proper for use in the engines you are curious about.

Also, you must make certain you are not breaking any legal regulations."

So the bottom line is that although Jet-A may not cause immediate damage to

a diesel engine and may allow the engine to run OK, its use may cause

premature wear or fouling of the fuel system, and you may be breaking EPA

regulations as well as not paying appropriate taxes. Outside the US,

differences in viscosity still mean that the use of Jet-A for Diesel No. 1

may cause early wear of the fuel system. Kind of like running 10 weight

oil in a car designed for 30 weight. So how much risk are you willing to

take, because no engine manufacturer or fuel supplier will take part of the

risk?