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How a Hydraulic Forklift Works

Posted by: admin on January 27, 2022

how a forklift hydraulic system works

Since their invention, hydraulic forklifts have helped people get difficult, heavy work done. If you are a heavy equipment operator, it’s important to understand how these forces work and the different parts that go into them.

How a Forklift Hydraulic System Works

Understanding how a forklift hydraulic system works is simpler than you might expect. It all depends on special pressurized fluid used to power the engine of a car or machine. Hydraulic presses put pressure on a small amount of liquid to create a large amount of power.

Confined liquid has pressure on it from one side. That pressure forces the liquid against a piston on the other side of the container. That transfers energy into the piston, forcing it upward. The piston cannot move in the opposite direction unless the pressure is released. In terms of the forklift hydraulic system, the pistons raise the forks and keep them lifted until the hydraulic pressure is released by the operator.

In most forklifts, the tank is integrated into the frame of the vehicle. That’s what holds the forklift hydraulic fluid.

Besides the tank, the components of the forklift hydraulic system include:

The Pump 

Produces a constant flow of hydraulic fluid to supply the control valve. Most forklifts use a gear-type pump. The pump consists of a pair of rotating gears that push the fluid in the opposite direction of the rotation.

Control Valve

Starts and stops the direction of fluid and controls where the fluid moves using spools. Without a control valve, forklift hydraulic pressure would be useless.

Relief Valve

Protects the hydraulic system from too much pressure. This part is considered a critical safety component of hydraulic forklift hydraulic pressure.

Return Line

Returns the fluid to the tank. The return line completes the forklift hydraulics cycle.

The types of fluids used in hydraulic forklifts include water-based fluids, petroleum-based fluids, and synthetic fluids. Water-based fluids are fire-resistant but do not provide as much lubrication as the other types. Petroleum-based fluids are customized to the hydraulic system with additives and are the most popular. Synthetic fluids are useful for high temperature and high-pressure systems.

how does a hydraulic forklift work infographic

Hydraulic Forklift FAQs

With the basics of the forklift hydraulic system explained, let’s dive into some of the most frequently asked questions about this technology:

How Do Hydraulics Work in a Forklift?

If you’ve ever put your finger over a hose while it’s running at full blast, you’ve experienced the power of hydraulic pressure. The same principle is at work in forklift hydraulics. While air can be compressed, liquids cannot, so when you exert pressure in a confined space, you create hydraulic pressure. 

Giant pistons on the front of forklifts are responsible for hydraulic pressure. They’re fed by fluid hoses with a high pressure pump at the end. They supply the pressure necessary to move hydraulic fluid through the system and move pistons up and down. 

hydraulic forklift The cylinders are sealed tubes with an inserted rod. As the hydraulic lines put pressurized fluid into the tube, the rod is pushed out as the fluid looks for the path of least resistance. Resistance is introduced to run the fluid through the hoses and connections on the different components that are powered via hydraulic pressure.

Tubing pumps the hydraulic fluid into a reservoir. The pump creates the pressure that moves the fluid through the hydraulic forklift system.

What happens when there is a very heavy load for the forklift to lift? That’s when the Flow Divider comes into play. It can split one line of fluid into two, three, or more.  By splitting or recombining the hydraulic line, the force can be increased or decreased. The hydraulic pump exerts a finite amount of pressure, but each load requires a different amount of pressure, so the flow divider can reduce the pressure by diverting fluid back into the reservoir, or increase it by sending all the fluid through to the cylinders. 

Another crucial part of the system is the Return Filter, which is exactly what it sounds like.  It cleans the forklift hydraulic fluid of any contaminants before it goes back into the reservoir.  

Why Are Hydraulic Forklifts Used?

Forklift hydraulics raise the load-bearing prongs off the ground. A hydraulic forklift lifts and holds the load in the air while the forklift moves. A forklift hydraulic system is the heart of the machine because it is responsible for moving pallets. And the heart of your company’s safety program is proper hydraulic forklift training and certification! The levers control the hydraulic system in a forklift. The operator needs to be very careful with them. It’s important that only trained and certified operators use forklifts. They need to properly calculate the load and how much lift power is needed to move it. The hydraulics of a forklift have a lot of power, and only a small amount of effort can create enough force to move a large, heavy load.

The proper usage and maintenance of a forklift will keep the forklift hydraulic pressure system in good working condition, without needing constant repair work.

When Were Hydraulics Invented?

French scientist Blaise Pascal discovered the principle behind the hydraulic system over 300 years ago. Pascal learned that liquid cannot be compressed. When pressure is put on a confined liquid, the liquid transmits pressure in all directions. Those are the basic principles behind the forklift hydraulic pressure system. For example, if a container holding liquid has an opening, the liquid will try to escape at a pressure that’s equal to the pressure put into the container.

In the late 1700s, British mechanic and engineer, Joseph Bramah, used Pascal’s principles to experiment on practical applications. In 1795, Bramah patented the first hydraulic press which became the basis for the modern-day hydraulic system.

Which Kind of Hydraulic Oil Does a Forklift Use?

To determine which grade of hydraulic fluid a forklift uses, consult the lift’s operations manual. Here, you can find full details about the proper type of hydraulic fluid for a forklift, how often the fluid should be changed, and other pertinent information. If you cannot find the lift’s operations manual, use a general purpose fluid like ISO 32 hydraulic oil.

When it comes to hydraulic fluid for a forklift, stick to the recommendation included in the lift’s operations manual. Using the proper hydraulic fluid limits the risk of wear and tear on your lift.

How Do You Fill a Forklift’s Hydraulic Fluid?

Forklift hydraulic fluid must be regularly topped up for maximum effectiveness. Locate the hydraulic reservoir on your lift. It should have a vented fill cap with a fill gauge or sight glass on the side to indicate fluid level. Remove the cap and then pour in the oil and begin pumping the liquid into the reservoir. Keep an eye on the levels; once the oil reaches the maximum fill line, you can stop pumping. Remove the fill nozzle and replace the cap. 

How Much Hydraulic Pressure Does a Forklift Have?

To fully comprehend the power of hydraulic forklifts, it helps to understand Pascal’s Law. It explains how force changes pressure. To calculate the hydraulic advantage of your particular lift, understand that the force exerted is equal to the pump pressure multiplied by the surface area of the hydraulic fluid cylinder. For instance, a system with 1000psi pushing against a cylinder with a surface area of 10 inches provides forces of up to 10,000 pounds. 

What are the Most Common Hydraulic Forklift System Issues?

There are many problems that can affect a hydraulic forklift, such as:

  1. Mast Drift

Mast drift occurs when a lift’s mast changes position when elevated under load. The problem may seem minor at first. However, when left unaddressed, the issue can escalate quickly and cause a lift to tip over.

  1. Hose Leak

Hydraulic system hoses are used to transfer fluid pressure. But, a hose deteriorates over time, and it can crack and leak. Other factors that can cause a hose to crack or leak include the use of an improperly fitted hose fitting or use of an incompatible type of hydraulic fluid.

  1. Clogged Suction Filter

A suction filter can become clogged if it goes unchanged for an extended period of time. In this instance, the filter can no longer catch and remove contaminants from the hydraulic fluid. It can also stop the flow of hydraulic fluid.

How Are Hydraulic Problems Diagnosed?

There are several warning signs that hydraulic forklift problems may be present, including:

  • Strange noises from the lift
  • Hydraulic fluid temperature above 180°F (82°C)
  • Slow operation

At the first sign of any hydraulic forklift problems, it is beneficial to diagnose and address these issues. This ensures that a forklift can be fixed or replaced before it can potentially put the health and wellbeing of lift operators in danger.

On-Demand Forklift Operator Training 

You don’t have to be an expert on hydraulic forklifts to know that well-trained drivers are essential for workplace safety. Whether your warehouse runs electric lifts or hydraulic forklifts, is your #1 source for OSHA compliant training and certification.

Even if you don’t know how a hydraulic forklift system works, that’s OK – we’ll explain all the critical safety concepts so your employees can avoid accidents. Gain the peace of mind that comes with complete OSHA certification and sign up for our hydraulic forklift training programs today!

Operator training will keep all workers safe in the vicinity of the forklift, and ensure that operators have the proper understanding of how the hydraulic system works and how it is used most effectively.

Check out the online forklift training from for the most convenient and comprehensive forklift training available. Operators learn how to run a forklift, perform equipment inspections and operate the forklift hydraulic pressure system correctly. Sign up today for same-day certifications! Have questions about our certification opportunities or want to speak with our team? Reach out online or dial 1-888-699-4800 today.

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