Usage:
Emergency shutoff devices are either electrically, mechanically or hydraulically operated. Familiarize yourself with the types and locations of the shutoff devices, the conditions which cause each control to function, and the resetting procedure required to start your engine.
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Always determine the cause of the shutdown, and have the necessary repairs made before restarting the engine. Emergency shutoff controls are for emergency use only. Do not use an emergency shutoff device for a normal stopping procedure. |
Electric Shutoff Controls
The operation of all electric shutoff controls is similar: A critical operating condition actuates a switch in the sensing unit. The switch closes the circuit to the shutoff solenoid which moves linkage to bypass the fuel to the cylinders; thus stopping the engine. The shutoff control may require resetting before the engine can start.
High Water Temperature Shutoff:
The shutoff switch is located in the water temperature regulator housing. Excessive water temperature closes the switch. No resetting procedure is required: As the coolant cools, the switch opens.
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The sensing element must be submerged in the coolant to operate. A low coolant level cannot actuate the shutoff. |
Low Oil Pressure Shutoff Switch:
This device is usually mounted on the side of the engine with oil lines connected to the switch. Low oil pressure closes the switch.
Manually operated systems require resetting of this switch before starting. Automatic start-stop systems use a pressure switch which resets itself.
To reset the switch, push the button until it latches. After the engine starts and develops oil pressure, the oil pressure will push the button to the extended running position.
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The engine will not be protected if the engine is operated with the button latched in the START position. |
If the button remains in the reset position, the engine oil pump is not developing normal oil pressure and a check should be made.
Overspeed Shutoff Switch (Electro-Mechanical):
This switch is mounted either on the tachometer drive or on the governor. Excessive engine speed closes a switch by centrifugal force.
TWO INSTALLATIONS OF OVERSPEED SWITCH
To reset the switch, push the button marked RESET. The knob will remain down until the engine overspeeds.
Overspeed Shutoff Switch (Electronic):
This switch is a magnetic pick-up which is mounted on the flywheel housing and senses engine speed. The control box is mounted on the engine block. Excessive engine speed closes a circuit breaker. To reset the switch, push arm of breaker to the run position.
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This switch will not provide overspeed protection if there is no power to the control box. |
Fuel/Oil Pressure Switch:
This switch is mounted in the fuel manifold between the clean side of the fuel filter and the fuel injection pump housing. Low fuel pressure (below 3 psi) opens the switch and the electrical circuit to either the shut off solenoid or the circuit between the alternator and the alternator regulator. Opening of these circuits prevents the battery from becoming discharged while the engine is stopped.
This switch can also be used with an electric governor. In this application, oil pressure closes the switch to allow the electric governor to control engine speed.
This switch does not require resetting.
Mechanical Safety Shutoff Control
The mechanical safety shutoff is both a low oil pressure and an overspeed shutoff device. A high water temperature shutoff can be installed which uses the low oil pressure shutoff device to stop the engine.
On 6 cylinder engines, the mechanical shutoff is mounted on the side of the engine. On vee engines, the shutoff is mounted in the vee of the engine between the two banks of cylinders.
The high water temperature shutoff is installed in the temperature regulator housing of all engines.
If an overspeed, low oil pressure, or high water condition occurs, a spring loaded rod is mechanically tripped internally, which moves and holds the rack in the shutoff position.
Difficult starting with long periods of cranking can trip the low oil pressure shutoff. The reset lever must be moved and latched in the run position before starting can be accomplished. Normal stopping of the engine will not trip the shutoff device.
The basic cause for the shutdown can be determined by the manner in which the shutoff must be reset:
- 1. Push the reset lever (or handle).
If the rod latches, an overspeed condition stopped the engine. Investigate the cause for overspeed condition.
If the rod does not latch, the engine was stopped because of a low oil supply to the shutoff control. This could be caused by either low engine oil pressure, or by the high water temperature shutoff bypassing the oil to the mechanical shutoff. Therefore, perform checks for both low oil supply and high water temperature. Reset the control by the following steps:
- 1. Push the reset button firmly.
- 2. Push the reset lever (or handle) until the rod latches.
If the reset lever does not move freely, check the reset cable for kinks, binds, or lack of lubrication. Make needed repairs or adjustments.
Air Safety Shutoff Control
The air shutoff control is an attachment to the mechanical safety shutoff device installed on large bore vee type engines. When an emergency condition occurs, the mechanical shutoff pushes the rack into the shutoff position and pulls a butterfly valve, located in each inlet manifold, to the closed position. The air safety shutoff control must be reset before starting.
If an overspeed condition shut the engine down:
- 1. Pull the air shutoff reset lever on the air inlet manifold to the RESET position.
- 2. Release the lever. The lever should move slightly and then latch in the RUN position.
- 3. Push the mechanical shutoff reset lever until the rod latches.
If a low oil pressure or high water temperature condition shut the engine down:
- 1. Firmly push the reset button in the vee of the engine.
- 2. Pull the air shutoff reset handle on the air inlet manifold to the RESET position.
- 3. Release the lever. The lever should move slightly and latch in the RUN position.
- 4. Push the mechanical shutoff reset lever until the rod latches.
Hydraulic Shutoff Controls
The hydraulic shutoff control is mounted on (or near) the governor. When oil pressure drops below 8 PSI, the fuel injection pumps bypass the fuel to the cylinders.
To start the engine, move and hold the reset lever against the stop while cranking the engine. After the engine starts, the lever will stay in the running position. Manually reset the control each time the engine is stopped.
A high water temperature shutoff can be used with this shutoff control. Excessive coolant temperature causes the temperature sensor to open a dump valve which empties the pressure oil from the low oil pressure shut off device. The low oil pressure shutoff control shuts down the engine.
Reset the oil pressure control as instructed above. Allow the water sensor to cool: No resetting of the water temperature shutoff switch is required.
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The water temperature sensor must be submerged in the coolant to operate. A low coolant level, or a failed water pump cannot actuate the shutoff. |
Alarm Switches
Alarm switches are set at a less critical temperature, pressure, or level limit than the comparable shutoff control. The purpose of the alarm switch is to warn the operator an unsafe operating condition is starting to occur, and that corrective measures should be taken to avoid possible damage to the engine and/or a possible shutdown of the engine.
LOW OIL PRESSURE ALARM SWITCH
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It could be hazardous to have the engine stop unexpectantly when engine power is needed. However, if the engine overspeeds, the engine should be stopped immediately. |
When the preset temperature, pressure or fluid level occurs, the sensor of the alarm switch will move and close an electrical circuit. Either a light or an audible alarm will be energized. The light or alarm will continue to operate until the condition is corrected. When the condition is corrected the alarm will automatically reset and the light will turn off.
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The cause of the shutdown must be investigated and corrected before starting and operating the engine. |
Alarm Shutoff Switch:
A switch may be installed in the alarm circuit for silencing the alarm while the engine is stopped for repairs. Be sure the switch is moved to the closed (ON) position and the warning lights are lit before starting.
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If the switch is left in the open (OFF) position when the engine is started, the engine will not be protected. |
Testing Indicator Lights:
Most control panels are equipped with a test switch. By turning the switch ON, all of the indicator lights can be checked for proper operation. Test the indicator lights periodically, replace burned out light bulbs immediately.
