Cat Gas Engine Lubricant, Fuel, and Coolant Recommendations Caterpillar

• Landfills

• Facilities that produce digester gas

Although these gases are both the result of organic decomposition, the compositions are different.

Landfill Gas

The decomposition of organic material produces landfill gas. The composition of landfill gas depends on the materials that are in the landfill. The gas is collected through a grid of pipes that are laid out within the landfill.

Landfill gas may contain contaminants that can cause harmful effects on engines:

• Chlorine

• Fluorine

• Siloxanes

• Sulfur

• Water vapor

Fuel analysis is required in order to provide guidelines for treatment of the fuel.

The sulfur compounds in landfill gas cause the same engine problems as sulfur in sour gas. When landfill gas is used, follow the precautions that are recommended for sour gas.

Landfills can also contain chlorine and fluorine compounds in the form of volatile organic compounds and chlorofluorocarbons. When these substances are burned in engines, corrosive hydrochloric acid and hydrofluoric acid can be produced.

Landfill gas can corrode both the equipment that handles the gas and the engine. Vapor is produced by combustion. If that vapor condenses in the crankcase, a solution that is potentially corrosive to the engine can form.

Landfill gas and digester gas can contain siloxanes. Siloxanes are formed when silica ions attach to the methane hydrocarbon chain. These gaseous compounds enter the combustion chamber with the fuel. This creates deposits in the cylinders.

In addition, calcium from engine oils contributes to deposits. Hence, deposits in the combustion chamber are generally a combination of these materials: silicon, calcium and some traces of other elements.

Siloxane particles can be abrasive to exhaust valve faces and to valve seats. This causes the valves to become pitted and indented. The particles can also build up on the valve seat. The buildup can cause guttering of the valves.

Deposits also form on the pistons and on the bottom deck of the cylinder heads. These deposits can increase the compression ratio, which can lead to detonation and/or preignition. Detonation and/or preignition can loosen the deposits. The deposits that are loosened can be trapped between the valve and the valve seat. The valve will be held open. Guttering of the valve will result.

The formation of deposits depends on the following factors:

• Composition of the fuel

• Operating conditions

• Type of lubrication oil

Most landfill applications will generate some deposits in the combustion chamber and in the turbocharger. Siloxanes are a major contributor to these deposits. The fuel requires treatment in order to remove the siloxanes. For information on equipment for processing landfill gas, refer to the most current revision level of Special Publication, LEBW4977, "Gaseous Fuels - Application and Installation Guide".

Note: The amount of silicon in the fuel can be measured with a test that was developed by Caterpillar and by Bio-Engineering Services. The test kit enables a sample of the fuel to be analyzed. The fuel can also be analyzed for other harmful contaminants such as chlorines, fluorines, sulfur, and halides. The Portable Silicon Evaluation Unit (#SI 110V) is used to process fuel samples on site, and the Silicon Sample Sets (#SI 20) are the fluid sets that are processed by the Portable Silicon Evaluation Unit. The processed fluid sets are then sent to the laboratory for analysis. Details can be obtained from the following address:

Note: Caterpillar is not responsible for the performance or quality of aftermarket products.

During normal combustion, some exhaust gas is forced past the piston rings and into the crankcase. The contaminants in this blowby are vented away from the crankcase by positive crankcase ventilation. The contaminants are diluted and purged.

The formation of water in the crankcase and in the valve mechanisms can result in an acid solution which allows corrosion to occur. A high jacket water coolant temperature helps to prevent the condensation of water in the crankcase. Engines that are used for landfill gas have a high temperature jacket water cooling system as standard equipment.

In order to protect the service life of the engine, it is necessary to follow the guidelines for operation and maintenance that are recommended by Caterpillar. Engines operating on Landfill gas need to a have positive crankcase ventilation system to help decrease acid formations. Landfill gas also requires regular, careful maintenance of the spark plugs. Misfire causes the engine to run rough and the cylinder temperatures are reduced. Cooler cylinders allow deposits to build up faster in the combustion chamber, in the exhaust manifold, and in the turbocharger. Exhaust port temperatures can indicate the performance of the spark plugs. An exhaust port temperature that decreases more than 66 °C (150 °F) below the average operating temperature may indicate the misfire of a spark plug. Inspect the spark plug in accordance with the engine Operation and Maintenance Manual, "Ignition System Spark Plug - Inspect/Adjust/Replace" article.

Note: For more information on bio-gas, refer to the most current revision level of Special Publication, LEBW4977, "Gaseous Fuels - Application and Installation Guide".

Digester Gas

A variety of materials can produce digester gas:

• Sewage

Digester gas has properties that are similar to the properties of landfill gas. Digester gas usually has some sulfur and siloxanes. However, the chlorofluorocarbons that are commonly found in landfill gas are not usually found in digester gas. The same precautions for treatment of the fuel and protecting the engine are required. Until experience proves otherwise, the same maintenance recommendations are used.

• Ag Biogas

Ag Biogas is a methane based fuel created from an anaerobic digestion process of animal waste or a combination of animal waste and agricultural products. It does not include landfill, gasifier (syngas) or wastewater treatment plant type gas producing applications. Ag biogas usually has some variable amounts of sulfur, which can reduce maintenance intervals. Regular maintenance of the product will depend on quality of the fuel. Oil sampling and data trending will determine optimum oil change interval. Spark plugs may have reduced life as well based on the quality of the fuel.