O-Rings

The O-Ring is one of the most widely used sealing elements in industry. Its geometry is simple, but correct selection requires several parameters to be considered:

• inside diameter;
• cord diameter;
• material;
• hardness;
• fluid;
• temperature;
• pressure;
• type of movement;
• groove geometry;
• risk of extrusion or explosive decompression.

European Sealing Technology combines stock of common sizes with an extensive manufacturer network and the capacity to produce selected large diameters by hot vulcanisation.

Common materials include:

• NBR;
• FKM;
• EPDM;
• MVQ / silicone.

Other elastomers or specific formulations can be supplied on request.

International dimensional standards such as ISO 3601 or AS568 provide a basis where the application uses a standard size.

European Sealing Technology can manufacture custom O-Rings by hot-vulcanising cord in several elastomers, including:

• NBR;
• EPDM;
• MVQ / silicone;
• NR;
• CR.

This technique provides a prompt solution for many non-standard requirements, particularly where the dimensions are too large or specific for a standard moulded O-Ring.

An encapsulated O-Ring combines:

• an elastomer core providing elasticity;
• a continuous FEP or PFA jacket providing high chemical resistance and a low-friction surface.

Cores are generally FKM or silicone, depending on the temperature range and required performance.

FFKM perfluoroelastomers are intended for applications combining aggressive chemicals and/or severe temperatures.

Because performance varies significantly between compounds, selection must be validated against the fluid, temperature, pressure and application requirements.

In pressurised gas service, some elastomers can be damaged by rapid decompression. Special AED compounds are developed to limit this phenomenon.

Selection must be based on:

• the gas;
• pressure;
• the compression/decompression cycle;
• temperature;
• required approvals.

In addition to O-Rings, EST also supplies X-Rings/Quad-Rings, including NBR and FKM subject to availability.

The four-lip profile can be advantageous in certain dynamic applications or where the risk of the seal twisting in its groove needs to be reduced.

Different formulations of the same polymer can have different performance characteristics.

Information required for a technical enquiry:

• dimensions or standard reference;
• fluid;
• temperature;
• pressure;
• static or dynamic movement;
• quantity;
• any required approvals.