19928100 Force SCREW (.312-18 x 1.00)

Overspeed
In general, an overspeed condition is the result of a fuel system that fails to operate correctly. This in turn allows the combustion system to get more fuel than the engine load needs. The excess fuel can accelerate the engine to a point that engine failure can be the result.The rate of engine acceleration is controlled by several factors. Friction horsepower, attached inertial loads and operating loads make up the main affects on acceleration. In most all cases, the protective system must have a response time of less than one second. Response time is the time interval between the overspeed and the actuation of the protective system. The protective system must provide this response under different conditions such as engine start up at extreme ambient temperatures and under full load operation.For an overspeed condition the fuel control linkage is moved to the "SHUTOFF" position and the engine combustion air supply is stopped.Low Engine Oil Pressure
As engine speed increases, the required oil pressure for main bearing protection increases. The engine oil pump is a positive displacement type pump, therefore, engine oil pressure varies in direct proportion to speed until the pump goes on controlled bypass. From Figure 1, it can be seen that if only the low range oil pressure protection level was used for the full speed range, the engine could operate at rated speed with oil pressure below the required level. Also, if only the high range oil pressure protection level was used for the full speed range, the system would shutdown the engine at low idle, since the engine oil pump develops lower pressure at that speed. Therefore, the protective system must operate between the required oil pressure curve and the engine oil pressure curve. This is done with a step action of pressure versus speed.The hydramechanical protective system operates within the two ranges of engine oil pressure. As engine speed increases, the minimum oil pressure needed at the main bearings also increases. At low engine speed, an alarm or fuel shutoff actuator will activate when oil pressure is reduced to within 140 35 kPa (20 5 psi). At high engine speeds, an alarm or fuel shutoff actuator will activate when oil pressure is reduced to within 205 35 kPa (30 5 psi).For a low oil pressure condition, the protective system activates an alarm or moves the fuel control linkage, through the governor, to the "SHUTOFF" position. The combustion air supply is not shutoff for this condition.High Coolant Temperature
If the coolant temperature of an engine goes above a set limit, the protective system activates an alarm or moves the fuel control linkage to the "SHUTOFF" position to shutdown the engine. The combustion air supply is not stopped under this condition.System Components
The system consists of an emergency manual shutoff, a shutoff control group, a diverter valve, a thermostatic pilot valve, an air inlet shutoff and a fuel shutoff actuator for the governor.The air and fuel shutoff systems are separate from each other to give complete engine shutdown for an overspeed condition. If the engine fuel is held in the "ON" position, the air inlet shutoff must work to shutdown the engine.Emergency Manual Shutoff
This shutoff is used under emergency conditions to shutdown the engine manually. When operated, this shutoff simulates an engine overspeed condition in the protective system. Thus, the air and fuel to the combustion chambers is stopped. The shutoff is also used to check the protective system for correct operation at regular engine maintenance periods.The emergency manual shutoff can be operated at the engine or from a remote location. For remote operation, either air or electric power can be used.Shutoff Control Group
SHUTOFF CONTROL GROUP
1. Spring for overspeed adjustment. 2. Emergency manual shutoff valve. 3. Valve spool (not used). 4. Selector valve. 5. Speed sensing valve spool. 6. Speeder spring. 7. Flyweights. 8. Low speed oil protection valve. 9. High speed oil protection valve. 10. Oil pump. 11. Oil pressure relief valve. 12. Pressure control valve group which consists of: the fuel and air inlet sequence valves, the two-way pilot operated valve and emergency manual shutoff valve (2).A flyweight controlled, speed sensing valve spool is used to feel engine speed. The speed sensing valve spool is moved by flyweights which are turned by a drive shaft. The drive shaft is driven by the engine camshaft through an accessory drive group that has an oil reservoir for the shutoff system. When engine speed increases, the flyweights move out and push the speed sensing valve spool out to open and close passages to put oil pressure into the correct system circuits. This gives correct protective system operation under the two engine oil pressure ranges.Diverter Valve
If there is a low oil pressure, high coolant temperature or engine overspeed condition, the diverter valve moves to put system oil pressure in the fuel shutoff circuit. This moves the governor and fuel control linkage to the "SHUTOFF" position to shutdown the engine.Thermostatic Pilot Valve
This valve is used to feel engine coolant temperature. If the coolant temperature goes above the limit of the thermostatic pilot valve, the valve opens and causes engine shutdown through the fuel shutoff circuit of the protective system.Water Temperature Contactor
The contactor switch for water temperature is installed in the water manifold housing (below the regulator housing). This is normally where the thermostatic pilot valve is installed. No adjustment to the temperature range of the contactor can be made. The element feels the temperature of the coolant and then operates a micro switch (in the contactor) when the coolant temperature is too high. The element must be in contact with the coolant to operate correctly. If the cuase for the engine being too hot is because of low coolant level or no coolant, the contactor switch will not operate.The switch is connected to an alarm system and activates an alarm under high coolant temperature conditions. When the temperature of the coolant lowers to the operating range, the contactor switch opens automatically.
WATER TEMPERATURE CONTACTOR SWITCHAir Inlet Shutoff
The air