Rubber O rings are a form of gasket or seal that features a round cross-section. They are commonly used to prevent leaks of either fluids or gases from occurring in products, systems, or machinery and find use across a variety of industries. Because of their low cost, simple production process, ease of installation, and pressure resistance, they have found application in a lot of common products, such as automobiles and engines. The aerospace industry useso-ringsin many types of rockets and aircraft applications.
This article will review information on the types of o-rings and material options available, along with their suitability for different applications.
The fact that o-rings can function in so many applications is largely attributable to the fact that there is a wide range of materials available from which they may be fabricated.This range of selection allows the designer to consider the properties of the material and select a suitable option based on how well that material performs against the expected operating conditions of the application. The factors that are usually considered when selecting a material for an o-ring include:
The material’s compressibility or hardness (durometer)
The performance against environmental and operational conditions, including:
The abrasion performance of the material
The permeability of the material (permeation)
The cost of the material
O-rings are usually produced from some form of elastic polymer or elastomer. These polymers are cured, often through vulcanization, resulting in improved strength, durability, and elasticity. Different materials have different properties, though, with some exhibiting greater elasticity and others possessing more tear-resistance.
Temperature range:Between -100 degrees Fahrenheit and 500 degrees Fahrenheit.
Suited for:PurePTFE O ringsare very rigid and hard to apply, butPTFEencapsulated o-rings handle surface wear well, in addition to exhibiting corrosion and abrasion resistance, non-permeability, chemical inertness, and low absorption.
Avoid:Like silicone,PTFEis rigid and is better suited to static applications.
Applications:Examples of PTFE o-ring uses include automotive steering devices and paint guns.
Solid O-ring is solid-rubber seals that are shaped like a doughnut. When pressed between two mating surfaces, O-rings block the passage of liquids or gases.
Types of Seals
O-rings can form a static or dynamic seals. A static seal is where the O-ring does not move and is used simply for containing pressure or maintaining a vacuum.Dynamic sealscan be reciprocating (like a piston and cylinder), or rotating (shaft rotating in a housing). Straight threads used with O-rings provide a better seal than tapered threads used alone.
A boss seal is also an O-ring, however it does not fit the standard sizes for an O-ring. A boss is a cylindrical projection on a casting or forging. The end of that projection is machined to provide a flat, smooth surface for sealing.
Axial squeeze and radial squeeze are two methods for applying an O-ring. An axial squeeze is when the ring is compressed parallel to a line drawn through the center or axis of the ring. In a radial squeeze the ring is compressed between the internal diameter (ID) and overall diameter (OD).
Imporant specifications for hollow O-ring include size, material, hardness rating and features.