Cat Gas Engine Lubricant, Fuel, and Coolant Recommendations Caterpillar

• Some wellhead gases

• Landfill gas

• Digester gas

Sweet gas pertains to fuels that have less than 0.43 mg of H₂S/MJ (.450 µg of H₂S/Btu). Typically, propane and processed dry natural gas are in this category.

Without precautions, maintenance costs are greatly increased by the introduction of hydrogen sulfide into the engine's fuel. For sour gas, Caterpillar recommends engine arrangements for landfill gas.

The use of gases that have hydrogen sulfide can damage the engine. Products of combustion (water vapor and sulfur oxides) form sulfurous acid and sulfuric acid. Sulfur reacts easily with bright metals such as copper. Therefore, oil coolers are usually the first components that are affected by the acids. Other engine parts that are attacked by the acids include the following components:

• Valves

• Valve guides

• Piston pin bushings

• Piston rings

• Cylinder liners

• Exhaust manifolds

• Aftercoolers

Analyze the gas before use. If the gas has more than 0.43 mg of H₂S/MJ (.450 µg of H₂S/Btu), treat the gas in order to reduce the content of hydrogen sulfide.

Various devices can reduce the content of hydrogen sulfide. Examples are chemically active filters, reactive beds, and solutions. The performance of the devices deteriorates as the reactive chemicals are depleted. The devices must be serviced or replaced in order to maintain effectiveness.

Take the following precautions even if the gas is treated in order to reduce the level of hydrogen sulfide. This will help to protect the engine against intervals when the devices for treating the fuel deteriorate. Even brief intervals of operation with high sulfur fuels can damage the engine, unless precautions are taken.

• Maintain the temperature of the coolant outlet to a minimum of 110 °C (230 °F). Do not allow the rise in temperature across the engine to exceed 8.3 °C (15 °F). A rise in temperature of 5.6 °C (10 °F) is preferable.

Lower jacket water coolant temperatures permit water vapor and hydrogen sulfide to condense on the cylinder liners. Higher temperatures will reduce this condensation.

• Establish an oil analysis program in order to ensure that the oil change intervals are not extended beyond the condemning limits of the oil. The oil analysis will also be able to detect other problems that may occur.