ELBOW AS 3574491 - Caterpillar

air/fuel ratio must be adjusted properly in order to comply with the emissions requirements of the site. The correct air/fuel ratio also helps ensure stable operation. To adjust the air/fuel ratio, perform the following procedure.
Connect a properly calibrated emissions analyzer to the exhaust stack.
Connect the Caterpillar Electronic Technician (Cat ET) to the service tool connector. Refer to Systems Operation/Testing and Adjusting, "General Information (Electronic Control System)".
Verify that the "Fuel Quality" and "Gas Specific Gravity" parameters are programmed correctly. Use the values that are obtained from the Caterpillar Software, LERW4485, "Gas Engine Rating Pro (GERP)".
Verify that the value for the "Fuel Specific Heat Ratio" parameter is correct. Enter a value of 1.4 for processed, dry pipeline natural gas.
Start the engine. Increase the engine speed to high idle rpm. Verify that the engine is stable.If the engine is unstable, perform the following procedure.
Record the values for these parameters:
"Governor Gain Factor"
"Governor Stability Factor"
"Governor Compensation Factor"
Set the values for the "Governor Gain Factor", "Governor Stability Factor", and "Governor Compensation Factor" parameters to zero.
Adjust the "Fuel Quality" parameter until the engine becomes stable and the exhaust oxygen is approximately four percent. Verify that the exhaust port temperatures are below the setpoint for a warning.
Adjust the primary governor. Refer to Systems Operation/Testing and Adjusting, "Engine Governing - Adjust".
Close the main circuit breaker for the generator in order to engage the generator.Note: When the engine load becomes greater than 25 percent, the air/fuel ratio control will operate in the feedback mode.
Slowly ramp the load up to 30 percent.Note: When the air/fuel ratio control is in the feedback mode, the Fuel Correction Factor (FCF) may no longer be 100 percent. The Electronic Control Module may adjust the FCF in order to compensate for the fuel quality and for the ambient conditions.
Set the "Desired Emission Gain Adjustment" parameter to a value of "100".
Verify that the reading on Cat ET for the generator's power output agrees with the switchgear's reading.If the readings do not agree, adjust the "Generator Output Power Sensor Scale Factor" and/or the "Generator Output Power Sensor Offset" parameters. Also, make sure that the "Engine Output Power Configuration" and the "Engine Driven Accessory Load Configuration" parameters are accurately programmed. Refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".
Slowly ramp up to 70 percent load. Verify that the engine is stable.If the engine is unstable, adjust the auxiliary governor. Refer to Systems Operation/Testing and Adjusting, "Engine Governing - Adjust".
Verify that the NOx emissions are above the desired full load setting.
Slowly ramp up to 100 percent load.
Verify that the reading on Cat ET for the generator's power output agrees with the switchgear's reading.
Adjust the "Desired Emission Gain Adjustment" parameter in order to obtain the values of emissions that are required at the site.
To lean the air/fuel mixture, decrease the gain adjustment.
To richen the air/fuel mixture, increase the gain adjustment.A small change in the "Desired Emission Gain Adjustment" causes a large change in the actual exhaust emissions. For example, an adjustment of one percent in the parameter's value