Engine Protection:

A diesel engine is designed along with protection systems to alert the operators of abnormal conditions and to avoid the engine from destroying itself.

Overspeed device - Since a diesel is not self-speed-limiting, a failure within the governor and injection system, or unexpected loss of load could cause the diesel to overspeed. An overspeed condition is very dangerous since engine failure is commonly catastrophic and could probably cause the engine to fly apart.

An overspeed device, commonly a few categories of mechanical flyweight, that will act to cut off fuel to the engine and alarm at a certain preset rpm. This is generally accomplished through isolating the governor from its oil supply that causing it to travel to the no-fuel position, or it can override the governor and straightly trip the fuel rack to the no-fuel position.