Electric forklifts have become core handling equipment widely used in modern warehouses, manufacturing workshops and logistics distribution centers, thanks to their zero-emission performance and low operating noise. Among all common safety accidents related to electric forklift operation, unplanned tip-over or rollover events account for more than 40% of total casualty cases according to public workplace safety statistics. Most of these accidents are not caused by equipment failure, but by operators’ insufficient understanding of the core stability rule of electric forklifts, that is, the stability triangle principle.

The electric forklift stability triangle is a virtual geometric area formed by three fixed supporting points of the vehicle. The three points refer to the central point of the two front load wheels, and the two end points of the rear steering axle. Connecting these three points into a closed triangle, any combined center of gravity formed by the sum of the vehicle body weight and the loaded cargo weight that falls inside this triangle can keep the forklift in a stable balanced state. Once the combined center of gravity shifts outside the boundary of this triangle, the vehicle will lose balance completely and tip over without early warning.

Many unstandardized operation behaviors will push the combined center of gravity out of the stability triangle. For example, hoisting the cargo to an extremely high position during long distance traveling will move the center of gravity upward and forward, narrowing the available stable space rapidly. Overloading the cargo beyond the rated load limit will push the center of gravity beyond the front edge of the triangle directly. Turning at a high driving speed with a high-lifted load will generate centrifugal force that pulls the center of gravity out of the side edge of the triangle. Operating the forklift on a sloped ground or turning on a ramp with loaded cargo will also create extra gravity component that breaks the balance of the stability triangle.

The stability triangle principle has very important practical meaning for operator safety, rather than being just a theoretical concept for equipment designers. When conducting pre-job safety training, enterprises can combine the triangle principle to let operators understand the internal logic of various operation rules, instead of letting them follow rigid rules blindly. Operators can develop the habit of checking the position of combined center of gravity before any special operation, avoid dangerous actions such as turning with high speed, traveling with lifted loads, and overloading. Even in unexpected working conditions, operators can adjust their operation behaviors rapidly to pull the center of gravity back to the stable area inside the triangle. Mastering this basic rule can effectively reduce the occurrence of unbalanced tip-over accidents, create a safer working environment for all on-site operators, and promote the overall safety management level of material handling work.