STRIP 4M5023 - Caterpillar

An air starting motor is used to turn the engine flywheel with enough rpm in order to start the engine. Operation of the air starting motor is controlled by the engine's control system. The air starting motor will engage when the requirements for prelube have been met.The air starting motor is usually mounted on the left side on vee engines and on the right side on in-line engines. Vee engines use two starters. Air is normally contained in a storage tank. The duration for rotation of the flywheel is determined by the tank's volume, air pressure, and air restriction.Natural gas may also be used to operate the pneumatic starters. There are two basic types of starters that are used, vane and turbine. There is a low pressure and a high-pressure version of each type of starter. The maximum operating pressure is stated on the identification tag of the starter. The pressure range is from 621 kPa (90 psi) to 1551 kPa (225 psi).Note: Minimum recommended cranking speed for start-up is 100 rpm. The fuel system and the ignition system are activated at engine speeds above 50 rpm. The maximum cranking speed of the air starting motor is 150 rpm.If the engine has a heavy load which cannot be disconnected during starting, the air pressure regulator must be adjusted in order to provide enough speed for easy starting. The air consumption is directly related to speed. The air pressure is related to the effort that is necessary in order to turn the engine flywheel. The maximum pressure for use with each starter is stated on the identification tag. This will provide sufficient cranking speed for a heavily loaded engine. With the correct air pressure, the air starting motor can turn the heavily loaded engine at the same speed and for the same duration as the air starting motor can turn a lightly loaded engine. For good life of the air starting motor, ensure that the air supply is free of dirt and water. Use a lubricator with "SAE 10W" nondetergent oil for temperature above 0 °C (32 °F). Use air tool oil for temperatures below 0 °C (32 °F). A design of starter that is a turbine does not require a lubricator.