Analysis and emergency treatment method of excavator diesel engine runaway

The excavator uses diesel engine, and the runaway issue of diesel engine is often encountered. Diesel engine runaway refers to the failure that the speed of diesel engine is out of control and the speed is higher and higher. Runaway will cause serious accidents, such as cylinder clubbing and shaft breaking. Generally, the diesel engine runaway happens when it starts up or when the load suddenly disappears or lightens, but this will not happen if it works under load,
  
The causes of runaway can be summarized as follows:
1、Too much lubrication in the governor shell causes the speed regulation to be too fast to be thrown off, which affects the speed regulation function; the friction clutch of the governor slips; the high-speed limit screw and safety gear of the governor are loose; the high-speed limit screw and safety gear of the governor are loose; the speed regulating spring is broken, and the thrust bearing or governor bearing is damaged, which causes the governor to malfunction and cause the runaway. 
2、The sliding sleeve of governor of unit injection pump of single cylinder diesel engine is stuck, which causes speed regulation failure and runaway issue.   
3、The plunger coupling parts of fuel injection pump can rotate due to installation skewness or oil pollution, which makes the speed regulating rack lose it. Especially for multi cylinder oil pump, the load will be reduced and the fuel supply can not be changed, resulting in runaway  
4、The fuel quantity regulating gear of the fuel injection pump is stuck at the maximum oil position or the rack is detached from the governor rod, resulting in runaway. 
5、The inlet and return holes on the plunger sleeve of some fuel injection pumps are in the same position. If the position screw of plunger sleeve is too long to block the oil return hole, the oil return is not smooth, resulting in a huge increase in fuel supply, which will also cause runaway.  
6、Too much oil in the air filter is sucked into the cylinder for combustion, which is equivalent to increasing the oil supply and speeding up the speed of the engine, resulting in runaway.  

In case of runaway of diesel engine, serious consequences will be caused if the engine is not shut down immediately. Therefore, in case of runaway, something must be taken to stop the diesel engine immediately. There are four emergency ways to avoid this happens:  
1、Put the throttle handle to the position of none oil supply, open the pressure reducing device, so that the cylinder has no compression force, and the engine can be stopped   
2、Loosen the nut of high pressure oil pipe joint with spanner to stop the diesel engine can not be able to supply oil, it also can shut down the diesel engine. 
3、If the intake pipe is blocked, the diesel engine will shut down if it can not absorb air. 
4、High-grade & heavy load can be used during the driving, then to use brake to reduce the engine speed and then turn off the engine.   
Well known the above four emergency methods, I believe that such runaway failures can be avoided.