COVER-FUEL 2P5197 - Caterpillar

Caterpillar Spark Ignited EnginesSUPPLEMENT: 03/30/81SERVICE MAGAZINE, JANUARY 26, 1981, PAGES 1 and 2.In the article "Ways To Prevent Damage To Spark Ignited Industrial Engines When Hydrogen Sulfide Is Present In The Fuel" make corrections that follow to the last sentence in Step 2: Infra-red analysis of the oil is needed to make sure that the level of sulfur products is below maximum acceptable limits. Sulfur products in the oil have a direct effect on the TBN of the oil. When the oil is changed, the TBN value must not be less than 2 (when D664 is used) or 50% of the original TBN of the new oil (when D2896 is used).--------------- END SUPPLEMENT ---------------Hydrogen sulfide is present in some fuels used in spark ignited industrial engines. Damage to engines can occur if the hydrogen sulfide concentration is high enough. Water vapor, which is a product of internal combustion, can mix with the hydrogen sulfide to make a stronger, liquid corrosive -- sulfuric acid (H2S04). Internal components, particularly valve guides, piston rings, and cylinder liners, become worn more quickly if sulfuric acid is present. Engine service life is shortened.
Engine oils recommended by Caterpillar have special additives in them to neutralize (make neutral) these types of acid products, but some times this is not enough. If analysis of the fuel shows the concentration of hydrogen sulfide to be greater than 0.1% of the total gas volume, then the preventive steps which follow must be taken.
1. The coolant temperature, as measured at the engine outlet, must be kept at a minimum of 88°C (190°F). This higher temperature will decrease the amount of water that condenses (becomes liquid) on the cylinder walls. A thermostatic control valve can be installed in the coolant line to maintain coolant temperatures.2. CD oil with less than 1% sulfated ash must be used instead of oils normally used in natural gas engines. CD oil has a higher TBN (Total Base Number) which gives an indication of an oil's ability to neutralize (make neutral) the acids made during combustion. Infra-red analysis of the oil is needed to make sure that the TBN does not drop below 2 and that oil change intervals are not extended beyond safe limits.3. Many sewage treatment facilities use two sources of gas for their engines -- sewer gas and municipal natural gas. Since sewer gas normally has a higher concentration of hydrogen sulfide than natural gas, it is best to start the engine with natural gas. When the coolant temperature is 88°C (190°F) sewer gas can then be used. Before the engine is shut down, natural gas must be used again for several minutes to flush the sewer gas from the fuel system.