Stop your forklift safely

Why your choice of lift truck braking system matters

Compared to a car, a forklift truck is usually much heavier and harder to stop. It’s also easier to tip over. These are two of the key safety challenges facing lift truck brake system designers and specifiers. Mark Nicholson summarises the essentials of forklift braking and highlights some of the choices available.

Systems and features are illustrated with reference to the Cat® Lift Trucks range of counterbalance forklifts and warehouse equipment.

Regenerative braking

Regenerative braking is common in electric counterbalance and warehouse trucks. However, as with many technologies, performance varies between different manufacturers’ products. Much depends on the qualities and advances of their electronic control.

Regenerative braking captures and recycles energy that would otherwise be wasted when a truck brakes or decelerates. In a counterbalance forklift, as you release the accelerator, the motor switches from driving the wheels to generating electricity. It converts the kinetic energy of the truck’s motion into electrical energy which charges the battery. In doing so, it also slows down the truck.

On warehouse trucks, releasing the accelerator and leaving forward/reverse direction control in neutral similarly applies a degree of ‘motor braking’. For a stronger effect, that control can be shifted to the opposite direction. The degree of such movement determines the strength of braking.

Regenerative braking technology improves energy efficiency, extends battery runtime and lifespan, and reduces wear in any mechanical brake components. (In counterbalance trucks, regenerative braking is normally combined with disc and/or drum braking. In warehouse trucks, the other brakes are electromagnetic and act directly on the electric motor.)

At the same time, good regenerative braking systems make deceleration smoother and more controlled. Operators can slow down precisely, without sudden stops or jerky movements. Fragile loads are more secure, and operation is more comfortable. Another user-friendly advantage in counterbalance trucks is that there’s no need to keep moving between accelerator and brake. Most of the time, accelerator control is enough.

To make the most of these advantages, you should drive smoothly. Anticipate the need to stop – then slow down gradually rather than braking sharply. This is always good practice anyway.

You will find advanced regenerative braking throughout the range of Cat® electric counterbalance and warehouse trucks.

Drum and disc brakes

Traditional counterbalance forklift braking systems use friction to slow down the truck. Both drum and disc brakes are friction-based systems with distinct designs and applications.

Disc brakes squeeze brake pads against the two sides of a rotating disc to generate friction. Drum brakes press brake shoes outward against the inside surface of a rotating drum to create friction. Drum and disc brakes have different performance characteristics, benefits and limitations. Based on these, manufacturers specify the most appropriate type for each truck and application. On some trucks, one axle has drums and the other has discs.

The pressure needed to apply drum and disc friction brakes in forklifts is typically supplied by a hydraulic system.

Wet disc brakes

Another category is oil-cooled disc brakes, otherwise known as wet disc brakes. In this specialised type of disc brake, there are no brake pads. What’s more, the mechanisms are totally enclosed, sealed, and cooled by circulation of oil.

They’re the ideal choice in wet, dirty, dusty or salty working conditions, as they resist damaging contamination and corrosion. Meanwhile, their cooling prevents heat damage and maximises brake system life. They’re also self-adjusting for wear and require almost no maintenance.

With these qualities, they last much longer than standard brakes and perform more consistently. They’re also superior in terms of stopping power.

Most Cat electric counterbalance forklifts are fitted with wet disc brakes. Examples include the 2.5 to 3.5 tonne and 4.0 to 5.5 tonne ranges. This specification prepares them for harsh environments, ranging from wet, saltwater fishery and fish processing plants to hot and dusty factories.

Electric brakes

Fully electric brakes are found in the Cat 1.4 to 2.0 tonne three-wheel and 1.6 to 2.0 tonne four-wheel electric counterbalance ranges. These act on the electric motor. Their benefits include fewer moving parts (less maintenance), higher energy efficiency and greater precision.

Parking brakes

As the Cat Lift Trucks 7 Deadly Sins animation reminds us, runaway forklifts are an all-too-common cause of accidents. To prevent runaways, you should always apply the parking brake when leaving a truck unattended. In addition, you should take it out of gear and lower its forks.

Choosing forklifts with automatic parking brakes reduces the risk. When the truck becomes inactive, with no driver in the seat, a parking brake is automatically applied. This feature can be found on all Cat electric counterbalance forklifts, as well as reach trucks, low-level order pickers and various others.

Automatic slow and stop

The topic of braking is closely related to that of safely controlling forklift speeds. This has been explored in a previous Eureka article. Automatic aids to maintaining safe speed include cornering control systems. Essentially, these reduce a truck’s maximum speed according to the angle of steer. They may also adjust for the operator’s speed of steering wheel movement and even for the height and weight of the load being carried. The intelligent curve control found on most Cat electric counterbalance forklifts has taken this technology to new levels.

Automatic parking brakes have already been mentioned. Another failsafe aid is automatic hill hold. This prevents a truck from rolling back when it stops on a gradient. It’s common on Cat electric counterbalance forklifts and can be found on others, including low-level order pickers.

A further group of automatic stopping aids can be described as operator presence detection systems. These work like a ‘dead man’s pedal’, preventing the truck from moving if the operator is not properly in place. On all Cat electric, diesel and LPG counterbalance trucks, these take the form of a seat switch. Unless the driver is seated, all drive and hydraulic functions are disabled. In some cases, an operator presence pedal can be fitted as an option.

On Cat reach trucks, a pedal is provided as standard for this purpose. The weight of the driver’s left foot is sufficient to register his or her presence and allow operation. On Cat order pickers, for low/second and medium/high levels, the whole operator compartment floor acts as a presence detection pedal. This gives comfort and freedom, allowing the operator to stand in any position. It also removes the need for a conventional pedal, which could be an obstacle to walk-through access.

Cat stand-in power pallet trucks and stackers use an optical presence sensor to ensure the operator remains standing safely within the truck. If he or she steps out, automatic braking is activated. The system does allow smaller foot movements, which are important for stress and fatigue relief, without activating the brakes. A similar protection device is optionally available on Cat rear entry fixed platform models in the power pallet, double pallet handler and stacker ranges.

One more emergency halting feature to mention is the belly safety button on Cat tiller-operated warehouse equipment. If an operator is in danger of being trapped by his or her reversing truck, the button is depressed. The truck then instantly moves a short distance in the fork direction. It’s part of the emPower tiller head on Cat pedestrian and platform power pallets, double pallet handlers and stackers.

Programmable deceleration and braking

Deceleration rates and stopping distances can be programmed on some lift trucks. This makes the truck’s behaviour even more predictable and helps with perfect positioning. In activities like low-level order picking, with frequent short movements, it saves vital seconds at each stop. Cat low-level order pickers, for instance, are programmable in this way. Programming can be individualised, using operator PIN code login, or applied equally for all operators. Other safety-critical parameters and modes can be programmed to limit, for example, power, speed and acceleration.

The braking behaviour of Cat man-up turret trucks and man-down VNA trucks in warehouse aisles can be controlled with appropriate options. These include automatic slowdown and/or precise stopping at the end of an aisle. Such controls can be varied between zones.