Typical Fuel quality requirements for a Gas Turbine:

A separate starting fuel is required for applications with single oil conventional burner if the fuel viscosity is above 4.1 mm²/s at 40°C.

The viscosity of the fuel at the injectors must not exceed 6.0 mm²/s (2nd gen. DLE burner) or 7.0 mm²/s (conventional burner) for good atomisation. A fuel with a higher viscosity than 6.0 respectively 7.0 mm2 /s, at the lowest temperature the fuel system may experience, requires preheating and trace heating of fuel piping in order to achieve correct viscosity at the fuel injectors.

Fuels with viscosity less than 2.0 mm2/s at highest fuel operating temperature, such as naphtha or kerosene, require dosage of anti-wear additives in order to prevent pump failures. 

The supply temperature of minimum 5°C prevents eventual free water from freezing in pipes and valves. The supply temperature shall also always be higher than the cloud point.

Fuels that are handled at temperatures close to or above the flash point require explosion proof equipment and a separate starting fuel. Special safety regulations will apply which vary from country to country.

The fuel must be kept at least 10°C above the cloud point.

In the specification polyaromatic compounds are defined as tricyclic compounds and higher, i.e. no di-aromatics included.

For fuels with higher water and/or sediment content separators should be installed.

Generally less than 0.5 ppm(w) heavy metals is required in order to conform to the condition for the ash sticking point. Somewhat higher contents can often be handled by employing corrosion inhibition additives. The quantity of the additive shall be enough to keep the ash sticking temperature above 950°C. However, a high content of additives requires additional cleaning of the turbine. Siemens will advise on equipment, additive type and dosage.

Generally less than 0.5 ppm(w) sodium + potassium is required in order to conform to the condition for the ash sticking point. Somewhat higher concentrations of sodium, potassium and calcium can be reduced to acceptable limits by fuel washing and/or separation. However, the washability of the fuel has to be checked. Siemens will advise on equipment.

The use of a fuel having an ash sticking point temperature below 950 °C introduces a great risk of high temperature corrosion for the gas turbine and must not be permitted even for a short period of time. The sticking point temperature can be raised by additive treatment of the fuel. Any such additive must be approved by Siemens