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| Illustration 1 | g00334020 |
Air starting system (left hand shown) (1) Lubricator. (2) Relay valve. (3) Line. (4) Tee. (5) Starter control valve. (6) Hose. (7) Starting motor. (8) Deflector. (9) Line. (10) Drive housing. (11) Line. | |
The air starting motor can be mounted on either side of the engine. Air is normally contained in a storage tank. The volume of the tank will determine the length of time that the engine flywheel can be turned. A full storage tank must hold the volume of air at 1720 kPa (250 psi).
For starting the engines which do not have heavy loads, the regulator setting is approximately 690 kPa (100 psi). This setting gives a good relationship between the cranking speeds that are fast enough for easy starting and the length of time that the air starting motor can turn the engine flywheel before the air supply is gone.
If the engine has a heavy load which cannot be disconnected during starting, the setting of the air pressure regulating valve needs to be higher in order to get high 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 setting of the air pressure regulator can be up to 1030 kPa (150 psi). This will get the correct cranking speed for a heavily loaded engine. With the correct setting, the air starting motor can turn the heavily loaded engine as fast and as long as the air starting motor can turn a lightly loaded engine.
Other air supplies can be used if the air supplies have the correct pressure and the correct volume. For good life of the air starting motor, the air supply should be free of dirt and water. Use a lubricator with "SAE 10" nondetergent oil for temperature above 0°C (32°F). Use air tool oil for temperatures below 0°C (32°F). The maximum pressure for use in the air starting motor is 1030 kPa (150 psi). Higher pressures can cause problems.
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| Illustration 2 | g00543377 |
(12) Vanes. (13) Rotor. (14) Pinion. (15) Gears. (16) Piston. (17) Spring. | |
A separate air compressor system supplies the air that is used by the starting motor. The air is sent through a pressure regulator. From the pressure regulator, the air goes through hose (6) to tee (4). The flow of air is then stopped by relay valve (2) until the starter control valve (5) is activated. The starter control valve (5) is connected to the air supply line before relay valve (2) by line (3). When the starter control valve (5) is activated, the air is sent from the starter control valve through line (11) to the drive housing (10). The air flows to piston (16) for pinion (14). The air pressure on piston (16) compresses spring (17). The compression of spring (17) allows pinion (14) to engage the flywheel gear. When the pinion is in engagement, the air flows from the drive housing (10) through line (9) to relay valve (2). This air activates relay valve (2). This allows the main air supply from tee (4) to go through lubricator (1) and into starting motor (7) .
The air that contains lubrication oil goes to the air motor. The air pressure pushes the vanes (12) in the rotor (13). This turns the rotor which is connected by gears (15) to the starter pinion (14). The starter pinion (14) turns the engine flywheel. The air flows out of the starting motor through the deflector (8) or an air silencer.
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| Illustration 3 | g00334027 |
The flow of air through the starting motor as seen from the pinion end of the motor (typical example) | |
Once the engine starts running, the flywheel will start to turn faster than the starter pinion (14). The pinion (14) retracts under this condition. this prevents damage to the motor, the pinion (14) or the flywheel gear.
When the starter control valve (5) is released, the air pressure and the flow to the piston (16) behind starter pinion (14) is stopped. The piston spring (17) retracts the pinion (14). The relay valve (2) stops the flow of air to the air starting motor.