Guide to O-rings: Types and Applications
Even though they're small and simple in shape, O-rings prevent leaks, block contamination, and enable more stable operations. Because they are compact, affordable, and easy to install, they’re commonly found in hydraulic systems, pneumatic equipment, automotive parts, and semiconductor applications.
However, material, size, and compression can influence sealing performance and service life. When those factors are matched correctly to the application, a small sealing ring can do a very big job.
What Is an O-Ring?
An O-ring, one of the most widely used sealing elements, is a ring-shaped mechanical gasket made from an elastomer. Its cross-section is usually circular, which helps it create a reliable seal between connected parts.
O-rings are typically installed in a groove and compressed between two or more mating parts during assembly. This compression creates a sealing interface that helps prevent leakage while also blocking outside air, dust, and other contaminants from entering the system.
Benefits of O-Rings
O-rings are a popular sealing solution because they offer a practical balance of performance, simplicity, and cost.
Cost-effective and versatile sealing performance
Many manufacturers choose O-rings because they’re an economical sealing solution. They provide reliable sealing performance without a hefty price tag.
O-rings can be used in systems exposed to oil, water, chemicals, pressure, or temperature changes. Their simple design and broad material options make them suitable for a wide range of applications and operating conditions.
Simple installation and compact design
Easy to install, O-rings simplify assembly and maintenance in many kinds of equipment. Because they have a simple shape and fit directly into a groove, they make installation and routine maintenance easier in limited spaces.
Their compact structure is especially useful in tight spaces where other sealing solutions may not fit, such as valves, pumps, and small automotive components.
Common O-Ring Materials
O-rings are available in various material options to match different sealing needs and working environments. Here are some of the most common options used in industrial sealing:
1. NBR
NBR, or nitrile rubber, is one of the most common O-ring materials. It offers good oil resistance, and is used in applications involving oils, fuels, and other petroleum-based fluids.
Because of this, it’s popular in automotive systems, hydraulic equipment, and general industrial machinery.
2. SIL
Silicone rubber is often chosen for its flexibility and temperature-related performance. It’s able to maintain sealing performance in both high or low temperatures.
This makes it a great option for applications where temperature stability is a priority, such as medical equipment, kitchen appliances, and electrical insulation components.
3. EPDM
For applications involving water, steam, or weathering, EPDM is a widely used material option. Its resistance to water and ozone helps it perform reliably in moisture-heavy and outdoor applications.
You can often find it in steam valves, water treatment equipment, HVAC systems, boilers, and other outdoor equipment exposed to the elements.
4. FKM
FKM is applied in more demanding operating conditions, such as chemical processing equipment, automotive engine systems, and hydraulic systems.
It offers strong chemical resistance and high-temperature performance, making it suitable for environments where standard O-ring materials may wear out faster.
5. PTFE
Known for its strong chemical resistance, PTFE is a practical choice for applications exposed to aggressive chemicals and demanding media.
Because PTFE can resist a wider range of chemicals and process media than many standard elastomer materials, it’s ideal in systems that need broad chemical compatibility, like chemical processing equipment, pumps, and valves.
Main Types of O-Ring Seal Standards
These are some of the main types of O-ring seals used across different markets and applications:
AS568
One of the main O-ring size standards used in the U.S. It’s mainly used for inch-based O-rings and helps support more consistent sizing and part selection.
DIN 3771A
A German standard that defines O-ring dimensions and specifications. It’s commonly referenced for metric sizing in industrial applications.
JIS B 2401
A Japanese industrial standard for O-rings. It’s used for metric sizing in Japanese equipment and includes different series for different application needs.
ISO 3601
An international standard for O-ring dimensions, tolerances, and designation codes. It supports consistent global sizing and better interchangeability across markets and systems.
Common O-Ring Applications
What are O-rings used for? They're used in many types of equipment where compact, effective sealing is needed:
Hydraulic and pneumatic sealing systems
In hydraulic and pneumatic systems, O-rings are used to seal fluid or air pathways between components. This helps reduce leakage and supports more consistent pressure control during operation.
Automation and industrial machinery
Automation equipment and industrial machinery rely on O-rings for reliable sealing in moving and stationary components. They can be used in both moving and fixed parts, helping machines like robotic arms and conveyor systems run more smoothly and consistently.
Automotive parts and engine systems
O-rings are used in many automotive applications to help contain oil, fuel, coolant, and other fluids. They're commonly found in fuel and lubrication systems, where reliable sealing is important for preventing leaks and maintaining system performance.
Medical and food-grade equipment
Medical equipment and food-grade processing machinery also use O-rings for sealing in connected components and fluid-handling systems. Because these applications involve stricter standards, choosing the right material is important for reliable sealing and hygiene and safety compliance.
Semiconductor and vacuum applications
In semiconductor and vacuum applications, O-rings seal systems where process stability and cleanliness cannot be overlooked. Even small sealing problems can affect system performance and contamination control. So material selection must be matched to the application's operating environment and sealing demands.
FAQs About O-Rings
Q1. Why does an O-ring leak or get damaged right after installation?
O-rings can leak or get damaged right after installation if they are scratched, stretched too much, or cut by sharp groove edges during assembly.
To reduce this risk, use lubricant during installation, avoid sharp edges, and design grooves with rounded corners. In addition, choose a proper hardness, such as 70–90 Shore A, confirm accurate sizing for a compression rate of around 15–30%, and keep the installation area clean.
Q2. Why does an O-ring deform or lose elasticity over time?
Compression set is one of the main reasons O-rings deform or lose elasticity over time. Excessive compression, heat, or unsuitable material selection can prevent the seal from returning to its original shape.
Prevent this by optimizing groove design and using low-compression-set materials in demanding environments. FKM may be a better choice for high-temperature or chemical-heavy conditions.
Regular inspection, avoiding rapid temperature changes, and keeping replacement O-rings in stock can also help reduce downtime.
Q3. How do you choose the right O-ring material to prevent chemical corrosion or aging?
If media, temperature, or pressure are overlooked, the O-ring may swell, crack, harden, or fail earlier than expected. Manufacturers need to look closely at the actual working environment. Material choice depends on the application. NBR is commonly used for oil resistance, EPDM for water and ozone resistance, and FKM for high-temperature and chemical-heavy conditions.
Standard references such as AS568 and JIS can support sizing, while compatibility testing and on-site evaluation can help confirm the best material.
Reliable O-Ring Solutions From FYC (H2)
Though small and simple, O-rings are critical sealing components in many types of equipment. The right choice in material, sizing standard, and application fit makes a big difference in sealing performance and service life.
FYC offers O-rings in a wide range of material options for different operating conditions. As a specialist in premium oil seal production, FYC helps you find sealing solutions that better match your performance and application needs.
Explore FYC's complete O-ring portfolio and other sealing solutions — Get in touch now.