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Reference to Seal industry, there are so many types of seals to know and to use for different industries. So let us know about what O-ring seal products and its application is. In this post, we will also talk about the common types of O-Ring applications, and their impact on O-ring sizing and hardware design.

What is O ring seal?

O Ring, also known as packing or toric joint, is a kind of ring-shaped mechanical washer; it is an elastic body ring with circular cross-section, which is designed to be fixed in the groove, compress when assembling two or more parts, and form a seal at the interface. O-rings can be used in static or dynamic applications where there is relative motion between the part and the O-ring. Dynamic examples include rotating the pump shaft and the hydraulic cylinder piston. The static application of O-ring can include fluid or gas sealing application, in which: the O-ring is compressed and leads to zero clearance; the material of O-ring is sulfurized solid, which makes it impermeable to fluid or gas, and the O-ring material can resist the degradation of fluid or gas. O-rings are one of the most commonly used seals in mechanical design because they are cheap, easy to manufacture, reliable and easy to install. They have been tested to seal up to 5000 psi (35 MPa) and the maximum recommended pressure for pressure O-rings depends on seal hardness and gland clearance.

O rings are available in various metric and English standard sizes. Dimensions are specified by the inner diameter and cross-section diameter (thickness). In the United States, the most common standard inch size meets the SAE AS568c specification (e.g., AS568-214). ISO 3601-1:2012 contains the world's most commonly used standard sizes, including inches and metric. There are also standard sizes known as BS sizes in the UK, usually ranging from BS001 to BS932. Other sizes are also available.

What difference about O-ring and Gasket?

Is a product that needs to be sealed with air or liquid? You basically have two choices: washer or O-ring. However, although the two functions are similar, their performance varies depending on pressure and design specifications. This is the difference between the two.


The washer is a flat piece of material between two planes. The gasket material, whether it is neoprene, rubber, silicone or other flexible materials, prevents liquid or air (sometimes both) from leaking into or out of an area. The gasket can be cut into almost any shape. Many are circles and circles, but others may be rectangles, squares, triangles, semicircles, almost any form. As with the material used, the gasket can be layered with many different coatings. These layers contribute to end use and application. The gasket can be laminated, laminated with pressure sensitive adhesive, or a combination of several coatings.

O-ring seal

An O-ring is a circular, annular part located in a groove between two (usually cylindrical) parts. The compression of the two components forms an air tight and a liquid tight seal. O-rings can be made of many flexible materials such as rubber, neoprene or polyurethane. The shape of the ring is the main feature of the O-ring. The height and thickness of the ring can vary according to your design. Terminology note: any O-ring can be technically called a gasket because it prevents the transfer of liquid and air, but although the O-ring is a special shape of the gasket, no washer can be called an O-ring.

How many types of O-Ring applications?

Static Axial Seals

When designing grooves for static axial seals, the first consideration is whether the pressure is coming from inward or outward. When external pressure is involved, the outer diameter of the groove is the main factor, and the width of the groove is the main factor to consider the inner diameter. For internal pressure, the inner diameter is the main factor. This ensures that the O-ring needs to move a minimum distance to seal the extrusion gap.

Reciprocating Dynamic Seals

O-Rings are used in dynamic reciprocating applications, usually hydraulic or pneumatic piston or rod seals. For short stroke applications, smaller diameter O-rings perform well. Thicker cross-section O-rings are required for long stroke applications. There are many failure modes in dynamic sealing applications, and there is no problem with static O-rings. We will discuss this topic in a future blog post.

Rotary Seals

Under appropriate conditions, O-rings have been proven to be reliable rotary seals. Adequate hardness tester, hardware configuration and feet per minute must match the appropriate O-ring compound. A successful rotating O-ring usually requires a Rockwell hardness number of 55. There are some O-ring compounds designed specifically for rotary service.

How O-ring work?

The O-ring is probably the most common hydrodynamic seal. They are multi billion dollar products made by manufacturers around the world, and they prevent leakage from anything from pumps and valves to cylinders and connectors. Compact, economical components handle both static and dynamic operation in pneumatic and hydraulic applications. These simple seals consist of a ring (technically a ring) with an annular cross-section. They are usually made of elastomers such as nitrile rubber, chloroprene rubber or silicone rubber, but they are also made of plastics such as polytetrafluoroethylene, metals and other materials. Sizes range from a few inches to a few meters in diameter.

The O-ring is sealed by mechanical deformation, creating a barrier between two closely matched surfaces for a potential leak path of the fluid. The O-ring is usually installed in a groove that is machined or molded on one of the surfaces to be sealed. Their rubber like properties enable them to compensate for dimensional changes in mating parts. When the size is appropriate, the clearance between the surfaces is less than the outer diameter of the O-ring. As a result, when the two surfaces come into contact to form a gland, they compress the O-ring and deform the circular section. This radial extrusion of the seal produces a force that ensures that the surface is in contact with the inner and outer walls of the gland.