Limited Time Offer! Free Covid-19 safety course with purchase of any Forklift or Aerial Lift Certification!
Access your free Covid-19 safety course in your members area once you have completed your purchase.

How a Forklift Hydraulic System Works

Posted by: admin on November 15, 2020

how a forklift hydraulic system works

Most people have heard of the term hydraulics for cars and other types of machinery, but few know what the hydraulic system is exactly and how it works.

Since its invention, the forklift hydraulic pressure system has helped people get difficult, heavy work done and create a force that we can’t produce on our own. If you are a heavy equipment operator, then it’s important to understand how these forces work and the different parts that go into them.

Different machines use the hydraulic system in different ways. In this post, we address the basis of this system, and more specifically, the forklift hydraulic system.

Whether your company uses forklift hydraulic pressure lifts or electric forklifts, OSHA compliant is mandatory. Without properly trained forklift drivers, your company is more susceptible to suffer accidents and injuries on the job.

The History of Hydraulics

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.

In a way, you can say that 1795 was the dawn of the hydraulic forklift era, although actual forklifts were still more than a hundred years away. However, Pascal and Bramah showed the scientific field how a forklift hydraulic system works – or would eventually work, anyway!

Forklift Hydraulic System Explained

Hydraulics work by using pressurized fluid 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.

The basics of the hydraulic system go like this: 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.

The Forklift Hydraulic System: How a Forklift Hydraulic System Works

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

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

  • 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 forklift hydraulic pressure 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 Do Hydraulics Work in a Forklift?

Using cylinders, the forklift hydraulic system works very similarly to the confined liquid example. 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 forklift hydraulic system.

Which Grade of Hydraulic Fluid 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 to Check and Fill Hydraulic Fluid in a Forklift

The hydraulic fluid reservoir is located under the hood of the lift. It has a vented cap on the top and sight cap or gauge to indicate how much hydraulic fluid is currently inside the reservoir.

Typically, a forklift’s hydraulic fluid needs to be changed after approximately 1,000 hours of equipment use. At this point, the lift should be parked on level ground, with the forks lowered to the ground, the parking brake set, and the ignition off. Next, remove the vented cap from the hydraulic fluid reservoir, insert the oil delivery pump’s discharge nozzle into the fill tube, and pump the fluid into the reservoir.

Do not overfill the tank, as doing so can impact the forklift’s steering and lifting abilities. When the tank is full, remove the delivery pump’s fill nozzle, and clean up any hydraulic fluid that may have spilled outside the tank.

Common Forklift Hydraulic System Issues

There are many problems that can affect a forklift’s hydraulic system, 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.

2. 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.

3. 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 forklift hydraulic 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 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.

Why Are Hydraulics Important to Operate a Forklift?

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.

You don’t have to be an expert on forklift hydraulics 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 forklift hydraulic 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!

Welcome to has offered online forklift certification since 1999. With Our Convenient online program. your employess can earn their certification in an hour or less.

Browse Online Certifications:

This low-cost program can be compeleted anytime, anywhere!

Click to verify BBB accreditation and to see a BBB report.

Get Started Now By Registering Your Company For Free!

  • FREE 3 Year Renewals
  • Instant Access 24/7
  • Print Your Proof of Training
  • OSHA Accepted Nationwide

*If you are an individual not currently employed by a company use your personal name in
the 'Company Name' field.