Forklift Hydraulics Systems – Understanding Vehicle Systems

Among the many engineering marvels of our modern world is the forklift. Though to most people the forklift is just a useful machine, when given a bit more thought the true impressiveness of these machines unfolds. Central to this are the forklift hydraulics systems. It is this component that enables the essential operations of any lifting, loading or material handling construction machine.

Of course, this is to assume that the importance of things such as the motor and rolling capacities of any vehicle are understood. That said, the hydraulics systems used in forklift allow machines so versatile and critical to our infrastructure that they are often taken for granted.

From telehandlers to manlifts, to skid steers, backhoes and other excavating machinery, the hydraulic is the mysterious little component responsible for all of the ‘heavy lifting.’ So to truly understand the miracle of the construction machines, it’s important to compartmentalize the hydraulic as a single entity and see how it fits into the broader machine structure.

Identifying and maintaining the hydraulics systems of a forklift are critical to the longevity of the individual unit. But before this, the operator needs to understand the principles behind the machine.

Forklift Hydraulics Systems

Basic Hydraulic Operation

First, the hydraulic system uses a liquid, typically oil, to transmit force. To achieve this force, a pump pressurizes the fluid and sends it into a cylinder with a piston. The piston, attached to a rod which transmits the force into the system, creates force through the liquid in the hydraulic line. Subsequently, the force is transmitted from the other end. It is here that the piston and rod are pressurized to extend, thus mobilizing the load.

To lower the load (or reverse the motion, depending on the hydraulic usage) the force is reduced on the initial side of the system. In turn, the pressure in the lines is reduced and the piston and rod contract. In many systems, the flow of pressure may be controlled via valves that allow regulations of the system.

Should the system have trouble, it is important to consult the correct forklift manuals for the system affected. With forklift hydraulics systems, this is more complicated as the hydraulics often serves as the link between multiple systems. Simultaneously, the hydraulics of any motorized forklift may rely on power from the engine, the electrical systems, or both.

One way to identify where to start is to determine which system is affected. Here are a few notable places hydraulics are used on a forklift.

Load Lifting Hydraulics Systems

The main and most obvious way a forklift uses a hydraulic system is to lift and lower the forks. As mentioned, the system consists of a pump, which is typically powered by the forklift’s engine, and a cylinder, which is connected to the forks. However, it should be mentioned that this differs in manual forklift systems. This is a result of the force in the hydraulic being created via a pumping motion facilitated by the operator.

As the pump pressurizes fluid and sends it to the cylinder, it pushes a piston. This, in turn, raises the forks. Inversely, lowering the forks is accomplished by releasing the pressure on the cylinder, allowing the piston to return to its original position via natural gravitational pull. The controls in the forklift cab allow the operator to adjust the pressure and control the movement of the forks.

This is very common place for a forklift to encounter mechanical failures. This is due to the high stress work and frequent use of the parts. Of course, referencing a forklift hydraulic system diagram and any other related materials when repairing the machine is imperative. Proper maintenance is one of the most critical pieces of keeping a forklift operating properly.

Forklift Hydraulics Schematic Diagram Manual
Forklift Hydraulics Schematic Diagram Manual

The original equipment manufacturer of each machine published manuals and catalogs with vital information relating to the health of the forklift. Failure to properly maintain or repair your forklift could result in costly consequences.

Hydraulic Braking Systems

The next most common use of a hydraulic in a forklift is in the braking system. In this case, the operator applies the brakes, and a brake pedal or lever activates a master cylinder. This in turn pumps brake fluid to the brakes at the wheels.

The force applied by the operator through the brake lines is transmitted to the brake calipers (or drums) at the wheels. The calipers or drums contain brake pistons that are pushed out by the brake fluid. Subsequently, the pistons move out andpress against brake pads or brake shoes, which then press against the brake rotor or brake drum. The friction between the pads or shoes and the rotor or drum slows down the wheels, allowing the forklift to safely reduce speed.

The brake system may also utilize a series of valves, which ensures that the brake fluid pressure is the same on each wheel. Subsequently, this regulates the brake force and evenly distributes braking power evenly across all the wheels.

In high-quality or newer forklift units, the brake system may designed to be self-adjusting. As the brake pads wear down, the caliper pistons will move out further. This allows the brake system to automatically maintain the correct brake pad to rotor clearance. As a result, the pads can continue to provide the same level of braking performance throughout their life. However, it is critical to frequently check the brakes for wear and replace them accordingly.

Other Hydraulics Systems Used in a Forklift

As hydraulics have become more common, the systems they are tied into have increased as well. As a result, there are often hydraulics found places you may not expect to find them on a forklift.

Hydraulic Propulsion Systems

Another place you may encounter a hydraulic in a forklift is in the propulsion system. Hydro-static systems utilize the principles of the hydraulic to advance the vehicle forward.

Steering Systems

Another system that may use hydraulics is the steering system, which uses a hydraulic cylinder or motor to steer the front wheels of the forklift

Load Articulation Hydraulics Systems

Additionally, some forklifts also use hydraulic systems to control the tilt and side shift of the forks. This movement, known as ‘articulation,’ allows the operator to adjust the angle and position of the forks while lifting. Articulating functions are common in telescoping handlers (or telehandlers) as they often work in more rugged settings. To that end, telehandlers are often required to work on uneven terrain.

Another reason for articulation is that telehandlers are occasionally used for jobs unrelated to simple lifting and loading. For example, you may see a telehandler performing functions seen by cranes or even backhoes. This adaptation allows even more flexibility in a single machine – something many small contractors and businesses consider when purchasing expensive machinery.

A Hydraulic World

It’s hard to imagine where the world would be without an invention such as the hydraulic. Much has been about our modern world, and certainly a lot of this is a result of this mechanism.

It also can’t be overstated that hydraulic systems are used to provide critical power and control to a forklift. Identifying which hydraulics systems may be malfunctioning is essential towards repairing a forklift.

It goes without saying that the humble hydraulic is an essential component of forklift operation. Proper care and daily inspections go a long way toward keeping a forklift on the job site and operating finely.