O-rings
O-rings are THE versatile and proven solution – when simplicity rhymes with performance
O-rings - Standard listed items
Imperial sizes
AS568/BS1806/BOSS
Metric sizes
ISO3601/DIN3771/BS4518/JIS B2401/METRIC
Useful information
O-rings are found in countless industrial applications. Many remember the faulty O-ring that contributed to the infamous oxygen crisis during the Apollo 13 mission, but we prefer to think that it was also thanks to their reliability in other systems that the crew was able to return safely to Earth!
Their circular shape and elasticity allow them to create a barrier between two surfaces, preventing leaks of liquids or gases, even under extreme pressures and temperatures. Made from a wide range of materials such as nitrile, silicone, Viton or EPDM, O-rings adapt to a multitude of conditions, from corrosive environments to freezing temperatures.
Got a worn or out-of-tolerance groove that seems to be causing a leak? Consider a square-shaped gasket for a larger sealing surface.
At ELASFOR, we understand that every project has unique requirements. That’s why we excel at providing custom O-rings, designed to meet our customers’ specific needs. Are you looking for an unusual size? A material resistant to a particular chemical? Or a solution for extreme conditions? Our experience in this field allows us to supply O-rings in every conceivable size and material. We guarantee reliable, durable sealing solutions that are perfectly suited to your applications.
Important criterias while choosing your O-rings
Groove dimensions
These are the basic rules for the O-ring to have enough room to function properly.
Item to Check | Key Design Rule | Why is it important |
Groove Width (b) | Must be wider than depth (h). Usually a factor of x1.35 relative to the section of the joint itself. | The elastomer seal is not compressible; it must have room to deform (creep) under pressure. |
Groove Volume | Must be at least 15% greater than the O-ring volume. | To avoid excessively crushing the seal or jamming it, which would lead to failure. |
Depth of groove () | Determines the compression ratio of the seal. An important element to meet pressure requirements and ensure good long-term compression resistance. | This is the element that guarantees initial and long-term sealing. (See below) |
Max Radial Clearance (Extrusion) | Keep clearance between parts to a minimum. | Too much clearance allows the seal to extrude (escape) under high pressure and be destroyed. Solutions exist to counter your large clearances and other groove imperfections! |
Compression Ratio (Squeeze or Deflection)
The amount of compression of the gasket by the groove. It varies depending on the movement of the parts.
Application Type | Recommended Compression Ratio | Important Note |
Static (No movement) | 15% to 25% (more or less depending on the hardness and quality of the materials) | A higher rate is not always better; above 30% it creates too much internal tension. |
Dynamic (Movement, like a piston) | 8% to 16% (max. 20% for small diameters). | A low rate reduces friction, wear and heating during movement. |
Material and hardness
The O-ring must be suitable for its environment and pressure.
Design Factor | Recommendation | Typical Use Case |
Material Hardness | Choose according to pressure and clearance. (Measured in Shore A). | High pressures/Large clearances: use harder material (e.g. 80-90 Shore A) to resist extrusion. |
Chemical Compatibility | The equipment must be compatible with all fluids in application (oil, water, gas, solvents). | Improper material selection can result in excessive swelling or rapid degradation. |
Anti-Extrusion Rings | Recommended when pressure is high (1500psi+) or clearance is critical. | These rings prevent the seal from escaping into the gap. |
Surface finish and installation
The condition of the groove surfaces is a crucial element for the life of a seal
Characteristic of the Gorge | Requirement (Surface Quality) | Assembly Tips |
Edges | All edges in contact with the seal must be rounded (radius). | Sharp corners are the main cause of gasket cuts during assembly. Unsuitable tools for stretching the gasket can cause problems. |
Surface Finish (Roughness) | The surface must be smooth, suitable for the type of material with a roughness measured in | Dynamic applications require a much smoother surface than static applications to minimize wear. |
Introduction Ramps | Provide chamfers on the parts to guide the joint. These details are available upon request. | Facilitates installation and prevents damage to the seal from abrasion or shearing. Lubricating the seal is always a good idea! |
Stretch/Compression ID | The stretch of the inner diameter (ID) of the seal should not exceed 50% in the installed position for some elastomers, and it is much less for some thermoplastics and composites. | Too much stretching or compression causes initial compression failures and accelerates the loss of initial remanence. |
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Question ?
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