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What Are O-Rings and How Do They Work? An Overview + Maintenance Tips

What Are O-Rings and How Do They Work? An Overview + Maintenance Tips

What Are O-Rings and How Do They Work? An Overview + Maintenance Tips

Reading time: 5.5 min

When it comes to heavy equipment, even the smallest components can play a huge role in keeping your equipment up and running. Sometimes called toric joints or packings, O-rings are one such component found in heavy equipment machines and hydraulic systems.

Though tiny, O-rings perform a crucial function in heavy equipment machines. Essentially rubber rings, these flexible gaskets are used to create powerful seals between interfacing components, thereby preventing fluid leaks.

O-rings are vital to maintaining the efficiency and longevity of heavy equipment. Therefore, it’s essential for fleet operators to understand what O-rings are, the functions they perform and how to properly maintain them. 

Uses of O-rings In Heavy Equipment

O-rings are essential components in nearly all heavy equipment. They provide a reliable, inexpensive and simple way to seal interfacing parts, thereby preventing gas and liquid leaks.

These small, donut-shaped rings are commonly made from pliable materials such as rubber, silicone or elastomer. They can be found throughout a machine’s hydraulic systems and engine. For example, O-rings may be used to seal connections between fuel lines and injectors in your machine’s fuel system, ensuring proper fuel flow and preventing leaks.

How do O-rings Work?

The way O-rings work is incredibly straightforward, yet reliable and effective. O-rings are typically fitted into grooves, known as glands, located at the point where two components come together, or interface. 

As the components are fastened together, the additional squeeze on the O-ring causes it to expand in the gland, resulting in a more powerful seal between the interfacing components. The seal created by an O-ring keeps fluid, such as oil or hydraulic fluid, from leaking as it passes through the interfacing components.

O-rings vs Gaskets and Seals

O-rings are similar in function to other components, such as gaskets and seals. However, O-rings are typically used in high-pressure applications, whereas gaskets and seals are used in lower-pressure applications. In addition, gaskets are usually larger and flatter than O-rings and are used to seal larger surface areas.

Types of O-rings Used In Heavy Equipment

When it comes to O-rings used in heavy equipment, an O-ring can either be classified as dynamic or static. Understanding the difference between these two types is essential for selecting the right O-ring for a particular application.

Static O-rings are used when there is no relative motion between the two interfacing components. In other words, the two components sealed together by a static O-ring are not articulating or rotating around one another – they are stationary.

Dynamic O-rings, on the other hand, are used in applications where there is relative motion between the sealing surfaces. Dynamic O-rings are commonly used in hydraulic cylinders, pumps and other components where there is a moving piston or rotation between components.

O-ring Maintenance for Heavy Equipment

Proper maintenance of your machine’s O-rings is crucial for maintaining your machine’s efficiency and reducing down time. When O-rings degrade or break, fluid leaks can occur, potentially leading to even bigger mechanical failures.

Some of the symptoms of a failing or broken O-ring include:

  • Fluid Leaks: O-rings are specifically designed to prevent fluid leaks, so one of the biggest indicators of a failing O-ring is a noticeable leak of fuel, oil, grease or hydraulic fluid.
  • Reduced Performance: If you notice your machine has reduced power output or feels sluggish, it could be due to a failing O-ring in the machine’s engine or hydraulic system.
  • High Temperatures: Overheating in a hydraulic system can be caused by a failing O-ring.

O-rings should be inspected regularly as part of your ongoing preventative maintenance plan

To determine the location of O-rings on your machine, consult its service manual. Your machine’s service manual should provide a list of maintenance checks for your machine, along with any details about maintaining and replacing its O-rings.

Replacing an O-ring on Heavy Equipment

While the exact steps for replacing an O-ring will depend on the type of machine, the location of the O-ring and the type of O-ring, here are some general steps you should follow:

  1. Identify the location of the O-ring and carefully pry it out using a small tool, such as a flathead screwdriver.
  2. Clean the gland where the O-ring was inserted using warm water or a suitable cleaning solution.
  3. Carefully insert the new O-ring into the gland, or groove, ensuring it is lying flat in the groove and not twisted.
  4. If indicated by the service manual, apply a light coat of lubricant to the O-ring to create a better seal between components.
  5. Reassemble the components and test the equipment for proper operation.

When installing a new O-ring, be careful not to damage it. Since they are made of flexible, rubber-like material, they can easily become damaged during installation if you do not handle them gently. If you accidentally scratch, chip or otherwise damage the O-ring during installation, do not use it. Discard the damaged O-ring and install a fresh, undamaged one.

Additionally, it’s crucial you only use O-rings that match the specifications laid out in your machine’s service manual. Using the incorrect size or type of O-ring could cause damage to your machine.

Generally speaking, O-rings will need to be replaced every 3-5 years, or sooner if you notice damage or wear.

While the cost of replacing an O-ring will depend on the machine and type of O-ring, they are generally very affordable to replace. A replacement O-ring should cost in the range of $1-$10.

Twelve different O-rings lined up in rows

Choosing an O-ring

O-rings come in a vast array of types, sizes and materials, so it isn’t always easy knowing which O-ring is best for your application.

Importantly, different O-rings are made to withstand different pressures and temperatures. If you select an O-ring made from the wrong material, it may degrade quickly once installed or lead to inefficient performance.

Whenever possible, avoid these pitfalls by only using the type of O-ring listed in your machine’s service manual. If you are still unsure after consulting your machine’s service manual, work with an experienced parts dealer to decide on the best O-ring for your particular machine and application. 


O-rings play a vital role in ensuring the proper function of heavy equipment machines. These small components are the key to creating powerful seals between interfacing components and preventing fluid leaks.

There are many types and sizes of O-rings to choose from, and it isn’t always easy to find the one you need for your machine. The EquipmentShare Shop features a wide variety of O-rings for machines from popular manufacturers like Takeuchi, Wacker Neuson, Sany, Terex and more. Still can’t find the one you need? Get in touch with one of our parts experts for personalized assistance.

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