O-Ring Technology

O-Ring Technology

Date: December 05, 2019Category: technical announcements

The O-Ring is a circular section ring, usually made of elastomeric material (Example: Rubber), O-Rings are mainly used as seals for static or dynamic applications. It is considered, almost by definition, "the most economical, simple and effective way to seal between two surfaces".

Thanks to their versatility, O-Rings are always used on static applications, but can also be applied in dynamic applications on pistons and alternating movements. Usually for the most demanding applications they are used in combination with specific anti-extrusion rings.

The circular section of the O-Ring is designed to be deformed and compressed inside specific housings.

The compressive force inside of the groove is added to the pressure force of the fluid or gas to be retained, causing the deformation and expansion elastomeric material of the O-Ring  that and interpose itself between the metal surfaces, creating the seal. (Dis.1)


O-Ring - Sealing Technology - ATS


Normally O-Rings are made of elastomeric materials, and are obtained by hot injection molding or compression molding in dedicated molds which allow the desired mixture to be crosslinked.

Through the subsequent cutting, tumbling and finishing processes, accompanied by the required checks and inspections, the O-ring's compliance is inspection checked according to the international standard reference Norms.


Standardization of O-Rings:

The dimensions and tolerances for the O-Rings are defined according to the DIN ISO 3601 and DIN 3771 Standards.

These Regulations determine scrupulous dimensional standards, regulated according to the internal diameter and the diameter of the cross section and performance, to define a complete range of Standard O-Rings, designed to fulfill the most disparate application need.


O-Ring materials:

The O-Rings, according to the needs, can be made of different elastomeric materials suitable to withstand the needs for temperature (generally from -60 ° C to + 320 ° C), chemical compatibility, and pressure.

These materials can be classified according to the performances in service into three distinct groups, within which there is a response to almost all fields of application.

Elastomers for general uses, such as NR and SBR, which deteriorate in aggressive environments such as hot air, mineral oils, fuels, oxidants, ozone. The advantage of these materials is their low price as well as the good performance at low temperatures. These O-Rings are almost never applied in hydraulic or pneumatic applications.

High performance elastomers, such as CR, NBR and EPDM, provide good performance even in aggressive environments at the expense of a slight price increase compared to the products described above. The most commonly used in Hydraulics and Pneumatics are those in NBR.

Special elastomers, such as FFKM, FPM, FMQ and VMQ, provide high performance that meets specific needs of the designer. The O-Rings of this group most commonly used in Hydraulics and Pneumatics are those in FKM (Viton).


Choice and use of O-Rings:

Choosing O-rings that have suitable dimensions and material for the specific application requirement is essential for the seal to be effective.

The dimensions of an O-ring are defined by: inner diameter and cross-section.

The internal diameter Ød of the O-ring is twice the distance between the center and the inner surface. (Dis.2)

The cross section C, commonly called "cord" is half the difference between the internal and external diameters. (Dis.2)




All dimensions are usually indicated in millimeters (mm) for O-rings in units of the metric system, and in inches (in) for O-rings measured with the imperial system.

ATS catalogue shows all the Standard dimensions for the O-Rings and the correct sizing of the grooves, to obtain the best application results based on the type of application (static-dynamic) and the characteristics of pressure / speed / temperature.

For applications in specific sectors, O-Rings can be supplied in compliance with the relative certifications issued by the approval institutes.


Preservation of O-Rings:


O-Rings do not require any special storage conditions, however we recommend stocking the seals inside their original bags, in a box that protects them from external factors such as high temperatures, sunlight, fluids contamination or gas (Example: ozone). A simple layer of lubricating oil on the surface of the O-Ring is useful for preserving from premature aging. Specific guidelines for the preservation of O-Rings can be found in the ATS Catalogue.