DOWEL 6I3623 - Caterpillar

Shutoff and Alarm Systems
Shutoff and alarm systems are either electrically or mechanically operated. The operation of all electric shutoffs and alarms utilize components which actuate switches in a sensing unit.Shutoff switches are set at a more critical operating temperature, pressure, level or speed than the alarm components. A shutoff switch opens or closes the circuit to the fuel shutoff solenoid. Activating the circuit to the fuel shutoff solenoid moves the fuel rack to the FUEL OFF position. The particular shutoff may require resetting before the engine will start.When any sensing switch shuts the engine down, the problem causing the shutdown must be corrected before attempting to restart the engine.Familiarize yourself with the:* types and locations of the shutoff controls* conditions which cause each control to function* resetting procedure required to restart your engineAlarm switches consist of a sensor and contactor. Examples of sensors are the magnetic pickup for detecting speed, and the pressure and temperature sensors. Sensors are wired to contactors. The contactors activate alarm circuits in the Annunciator Panel.Alarm switches are set at a less critical operating temperature, pressure, level, or speed than the shutoff components. The purpose of the alarm switches is to warn the operator that an unsafe operating condition is beginning to occur.When an alarm is activated, corrective measures must be taken, before the situation becomes an emergency, to avoid possible engine damage.If corrective measures are not taken within a reasonable time, engine damage could result. Alternatively, a corresponding shutdown device (if equipped) will stop the engine.The alarm will continue until the condition is corrected or the alarm is reset by the operator. The alarm circuits merely warn the operator, they do not shut the engine down to protect it from damage.A switch may be installed in the alarm circuit for silencing the alarm while the engine is stopped for repairs. Before starting, be sure the switch is moved to the closed (ON) position and the warning lights are illuminated.If the switch is left in the open (OFF) position when the engine is started, the engine will not be protected.
Always determine the cause of the engine shutdown. Make necessary repairs before attempting restarting the engine.
Fuel Shutoff Solenoid
This solenoid is located on the governor or on the fuel injection pump. When the solenoid is activated, the solenoid moves the fuel rack (either directly or through the governor) to the FUEL OFF position.overspeed Shutoffs
A magnetic pickup mounted in the flywheel housing measures the engine speed by sensing the passage of the flywheel ring gear teeth. Should the engine speed increase above the overspeed setting of the Electronic Overspeed Switch (118 percent of rated engine speed), the magnetic pickup will sense the overspeed and send a signal to the Electronic Overspeed Switch (ESS). The ESS activates the fuel shutoff solenoid.
The Electronic Overspeed Switch (if equipped) is located inside of the engine-mounted junction box.The overspeed shutoff must be reset before the engine will restart. A reset button on the ESS must be pushed to reset the overspeed switch.The