Fuel System Safety
The fuel system has two safety devices on the fuel tank:
- Overfill level switch
- Fuel leak detection switch
The overfill level switch is used to prevent too much fuel from being pumped into the tank. The fuel leak detection switch is used to determine if the inner wall of the tank has been breeched.
The fuel level sensor is a resistive type sender. The fuel level sensor monitors fuel level in "percent units" for display on the EMCP3 screen. The fuel level is also displayed SCADA systems via the modbus data link. The fuel level information allows the EMCP3 to show alarms for the following:
| Message | Default Setting |
| Fuel Level Low Warning | 25% |
| Fuel Level Low Shutdown | 10% |
| Fuel Level High Warning | 90% |
| Fuel Level High Shutdown | off |
Note: All four of the set points in Table 1 are programmable.
Fuel Transfer Controls
There are two operator switches that provide the option to load or unload the fuel automatically or manually to the onboard fuel tank.
The fuel control switch (20) is a 2 position switch. The load and unload positions are referred to as "maintained" positions.
The fuel mode switch (21) is a 3 position switch. The auto position is a "maintained" position. The off (center) position is a "maintained" position. The manual position is a "spring return, momentary" position.
 | |
| Illustration 1 | g02154014 |
(15) E-Stop push button (16) Speed potentiometer (17) Voltage adjustment switch (18) CB3L DC breaker trip lamp (19) Fuel level gauge (20) Fuel control switch (21) Fuel mode switch (22) Fuel overfill lamp | |
Fuel Transfer Sequence of Operations
The fuel transfer system requires that customer fuel lines be connected from an external fuel tank to the power module.
Auto Load
While the control switches are in the Auto and Load positions, the fuel level will be maintained between 50% and 85% automatically. For example, when the fuel level drops to 50% or below, an EMCP3 relay output will turn on the "load" relay. The load relay will power the fuel pump motor in the forward rotation. The forward rotation results in pumping fuel from the external supply into the fuel tank. Once the fuel level reaches 85% or higher, the pump motor will turn off automatically.
Auto Unload
The following criteria must exist for the EMCP3 to turn on the output for the "unload" relay:
- Control in "Auto"
- Control set for "Unload"
- Fuel level above 10%
The relay output will power the fuel pump motor in the reverse rotation. The reverse rotation results in pumping fuel from the fuel tank into an external tank. Once the fuel level drops to 10% or lower, the pump motor will turn off automatically. To continue unloading fuel until the tank is empty, refer to the "Manual Unload" section that is below.
Manual Load
With the toggle switch in the Load position, the operator must turn and hold the selector switch in the Man position. The operator has complete control of what level the fuel will be loaded to. The only thing that limits this operation is activation of the overfill switch.
Manual Unload
With the toggle switch in the "Unload" position, the operator must turn and hold the selector switch in the "Man" position. The operator has complete control of what level the fuel will be unloaded to. There is no device that limits this operation so that the fuel tank can be emptied.
Note: Do not drain the fuel pump completely. Damage to the pump can occur if the fuel pump drained completely.
Note: The fuel load or fuel unload function can be used independent of engine state.
Note: The auto mode set points are hard-coded into the EMCP3.3 flash file. The auto mode set points cannot be changed.
Fuel Transfer Circuitry
 | |
| Illustration 2 | g02153843 |