Forklifts are essential pieces of equipment in many warehouses and manufacturing facilities. Their ability to lift and move heavy loads efficiently makes them indispensable. However, forklifts can also be dangerous if not operated properly. One of the most important factors in safe forklift operation is maintaining the center of gravity within the stability triangle.
What is the stability triangle?
The stability triangle refers to the area between the two front wheels and the centermost point of the rear axle. This forms a triangle shape on the floor that represents the forklift’s stability zone. As long as the combined center of gravity of the forklift and its load stays inside the stability triangle, the forklift is unlikely to tip over. However, if the center of gravity shifts outside the triangle, the forklift can become unstable and tip over.
Forklift manufacturers determine the size and location of the stability triangle. It varies depending on factors like:
- Weight distribution of the forklift
- Wheelbase width
- Height of the load backrest
- Counterweight size
The stability triangle establishes the forklift’s capacity for loads at different lifting heights. Exceeding the load capacity can cause the center of gravity to shift dangerously.
Why is center of gravity important?
Center of gravity is the point where all of an object’s weight is concentrated. For a forklift, it represents the balance point for both the vehicle itself and its load. This balance point shifts depending on:
- Weight distribution of the forklift
- Size and weight of the load
- Position of the load on the forks
- Height of the lifted load
If the combined center of gravity moves outside the stability triangle, it can cause the forklift to tip over. The higher a load is lifted, the more likely it is to shift the balance point too far. Exceeding the load capacity, turning too sharply, and driving over uneven surfaces can also impact the center of gravity.
How to maintain the center of gravity
Forklift operators are responsible for maintaining a safe center of gravity. Here are some ways to keep the balance point within the stability triangle:
- Do not overload the forklift beyond its capacity
- Pay attention to load capacity charts
- Drive slowly and carefully over uneven surfaces
- Avoid sudden starts, stops, and turns
- Keep loads low to the ground when moving
- Lift loads straight up without tilting forward/backward
- Spread forks as far apart as possible under the load
- Use rear wheel steering at higher lift heights
- Add a counterweight if needing to lift dense loads
- Travel with loads tilted back and forks lowered
It is also critical that loads be distributed evenly on the forklift forks. Off-center loads can shift the balance point sideways. Forklift attachments like drum clamps, rotators, and grippers should be used carefully as they also impact the center of gravity.
Dangers of an off-center load
Lifting a load that is concentrated more to one side than the other is extremely dangerous. Even if the load’s total weight is within capacity, its off-centered placement on the forks can cause the forklift to tip over. Operators should be vigilant to prevent off-centered loads by:
- Centering loads on the forks before lifting
- Securing loose or uneven loads
- Using attachments when needed to balance loads
- Avoiding uneven stacking of loads
- Looking for leaning or unbalanced loads
An uncentered load can cause sideways tipping even when driving straight on level ground. Sudden stops, turns, or bumps can spell disaster with an off-balanced load. Operators should drive slowly and use extreme caution until an uncentered load can be safely lowered and repositioned.
Effects of lift height on stability
Raising a forklift’s load has a major impact on stability. The higher a load is lifted, the more likely it is to shift the center of gravity outside the stability triangle. Load capacity decreases dramatically at higher lift heights. Most forklift manufacturers provide lift capacity charts that indicate safe load weights across different heights.
As a general rule, loads should always be kept as low as possible. Operators should also observe these precautions when lifting loads high up:
- Use rear wheel steering for better stability
- Avoid sudden movements of the mast
- Tilt the mast back slightly to shift weight backward
- Travel with loads tilted back and forks lowered
- Move slowly and avoid uneven surfaces
- Test lift new loads at low heights first
Experienced forklift operators know their equipment’s limitations and do not exceed the maximum lift height indicated on capacity plates. Excellent visibility is essential when elevating loads high up.
Maintaining stability on inclines
Driving a forklift on sloped surfaces also impacts the center of gravity. Traveling on ramps or inclines shifts weight distribution and can cause instability. Operators should observe strict precautions when on sloped or uneven ground:
- Avoid inclines exceeding 10 degrees or the forklift’s maximum rating
- Drive straight up/down slopes without turning
- Keep the load facing uphill
- Stay in low gear with no jerky movements
- Avoid stopping midway on a steep slope
- Tilt mast back and lower load when descending
- Use extra caution with empty forks downhill
The stability triangle becomes much smaller when driving along a slope. Traveling sideways across an incline is extremely dangerous, even with no load. Changes in terrain can also impact stability by shifting the balance point.
Other stability factors
Some other factors that influence a forklift’s center of gravity include:
- Tire pressure: Low pressure in one tire can skew the balance point sideways.
- Batteries: Old batteries may not be providing optimal counterbalance weight.
- Surface conditions: Slippery floors reduce traction and stability.
- Attachments: Some attachments like sideshifters alter stability.
- Modifications: Forklift alterations like lift height increase can impact the center of gravity.
Companies should perform regular maintenance and inspections to identify any issues that might compromise stability. Operators also need proper training on load charts, attachments, and workplace hazards.
Maintaining stability through operator training
Even the best safety features and mastery of load charts cannot replace proper operator training. Employers are responsible for training forklift operators on company procedures and safe driving skills. Effective training should include:
- Classroom instruction on stability triangles, center of gravity, and tip over causes
- Hands-on practice with maneuvers like turning, stopping, and backward driving
- Evaluation of operator skills and understanding
- Refresher training and evaluation every 3 years
Trainees must demonstrate proficiency on the specific forklift models they will operate. Untrained operators are unable to identify and prevent dangerous conditions that lead to tip overs. Consistent training ensures operators have the knowledge to maintain stability.
Conclusion
Keeping the combined center of gravity of the forklift and its load inside the stability triangle is essential to prevention tip overs. Forklift operators must be vigilant of their vehicle’s balance at all times. Companies should utilize load charts, strict procedures, and regular training to ensure safe stability margins are maintained in all lifting operations.