Forklift Hydraulic Systems: What Do You Need To Know?

September 20, 2022 - Last modified: September 9, 2022 @ 11:37 am

Whether you own, rent, or simply operate a forklift, it’s important to know a little bit about how the equipment works if you’re going to be safe and efficient while using the machine. By improving your knowledge of forklift hydraulics, you’ll be able to operate the machine more effectively but also maintain the machine to avoid costly downtime. Though hydraulic systems can sound incredibly complicated, there are some basics to remember.

What Are Forklift Hydraulics?

A hydraulic system is a robust machine that can tackle jobs most simple tools can’t. It relies on incompressible liquids to generate a strong force. Because of the power that hydraulic pistons can produce, many modern-day vehicles rely on a hydraulic braking system. Even a small hydraulic system is capable of producing a strong force. If you were to hold a metal piston rod in your hand and apply pressure to it, it doesn’t come close to the strength produced by a hydraulic system. If you take the same piston rod, put it into a barrel and squeeze it against hydraulic fluid, the process turns the rod into a dangerous hammer.

The hydraulic system puts pressure on a tiny amount of liquid to generate a much more significant amount of power. The system applies pressure from one side against the contained liquid, forcing the liquid to move against a piston located on the opposite end of the container. This creates a transfer of energy which forces the piston upward. It’s only after the system releases the pressure that the piston can move in the opposite direction. With forklift hydraulics, pressure against the pistons raises and holds the forks in place until the operator releases the hydraulic pressure.

System Components

The process of generating pressure by compressing incompressible fluids is how any hydraulic system generates power. While these systems can have different sizes and capacities, the parts generally remain the same. All of the components work together for maximum efficiency with minimal heat energy. The power pack contains the control valves, the actuator, the motor and the hydraulic pump, making the power pack essential to the function of the system. A majority of forklifts contain a tank integrated into the frame of the vehicle to hold the hydraulic fluid.

Control Valve

This is the control that will stop and start the direction of the fluid. It uses spools to contain where the fluid goes. The spool is usually in a housing manufactured from steel or cast iron, and as the spool slides into different positions, the intersecting grooves and channels route the hydraulic fluid through the system. Moving a spool to one side directs the fluid to an actuator and opens a return path to the tank. Moving the spool to the other side reverses the direction of the supply and return path.

Pump

In forklift hydraulics, it’s the pump that delivers hydraulic fluid to the control valve. Many forklifts use a gear-type pump, where rotating gears push the hydraulic fluid in the opposite direction of the pump's rotation. The pump is what gives the power to move the lift up and down.

Return Line

The system has a return line, which feeds the fluid back into the tank. It’s this component that makes a complete forklift hydraulics cycle. If the return line is undersized, it can cause the system to lose too much high pressure and overheat. An oversized line can increase the cost of operating the system.

Relief Valve

Necessary for its critical safety functions to the system, a relief valve protects the system from building up too much pressure. There is a specified pressure limit for the system, and if this level is reached, the valve will respond by feeding excess flow out of the system and back into the tank.

Cylinder

The cylinder is the component that will lift the forklift forks. Hydraulic fluid moves through the control valve and a series of hoses to lift the cylinder. It's the pressure either pushing against the cylinder or releasing which causes the forks to move. The cylinders are important for determining how much a forklift can handle.

System Capacities

The overall design of the forklift hydraulics and the forklift itself determines its weight capacity. A pallet jack, often used in warehouses for lifting goods or picking orders, can tackle around 3,300 pounds. Three- and four-wheel forklifts are bigger versions of a lift and can manage much larger loads. Three-wheel forklifts are capable of lifting 4,800 pounds, while a four-wheel forklift can handle up to 8,000 pounds.

The hydraulic advantage of a specific lift depends on how much pump pressure is exerted against the cylinder. A system with 1,000 psi against a hydraulic fluid cylinder that has a surface area of 10 inches can produce a force up to 10,000 pounds. The greater the force, the higher the capabilities of a forklift hydraulic system, though the design of the machine also has an impact. Forklifts depend on a specific center of gravity to ensure safe lifting of a load.

What Are the Maintenance Requirements for Forklift Hydraulics?

Given that a hydraulic forklift is a complicated piece of machinery, it’s important to perform regular maintenance to keep it working at its best. Owners should leave some servicing tasks to the professionals, but things such as filling the forklift with the right fluid should be done regularly. The lift’s operations manual will specify what type of hydraulic oil to use, although ISO 32 hydraulic oil is a general-purpose fluid. These are important tips to remember:

• Replace the fluid every 4,000 hours
• Change the filter every 2,000 hours
• Continually check for fluid or air leaks
• Routinely inspect all seals for cracking or rotting
• Establish a maintenance program with thorough, regular inspections

Where To Purchase Equipment Using Forklift Hydraulics

It’s a lot easier to get comfortable with the systems and processes of forklift hydraulics when you own your own equipment. Find the best prices on new or used forklifts with Forklift Inventory. Get a quote today.

Find New & Used Forklifts for Sale.

Sources:

• https://www.osha.gov/etools/powered-industrial-trucks/types-fundamentals/types/classes
• https://www.forkliftinventory.com
• https://www.tmhnc.com/blog/should-i-buy-a-new-or-used-forklift
• https://www.conger.com/forklift-weight-capacity/
• https://www.certifyme.net/osha-blog/diesel-forklift-or-electric-forklift/
• https://www.forkliftinventory.com/blog/forklift-mast-types/