What Are O-Rings Made of?

An O-ring is a ring-shaped seal with a circular cross-section, resembling a donut. They are basically rubber rings used as seals.

Also known as a toric joint — in reference to its torus shape — an O-ring is a gasket with a circular-looped design that’s used to seal two working surfaces. The valve stems in automotive engines, for example, often use O-rings to prevent oil from entering the combustion chamber. The O-ring creates a air- and liquid-tight mating surface between the valve stem and the valve guide. Without this small and otherwise simple component, oil may leak into the valve guide where it’s burned inside the combustion chamber.

O-rings are one of the most widely used seals in machinery and equipment because they are cheap, easy to produce, reliable and easy to install. o-rings are made primarily of an elastomer. For this reason, O-rings are also known as rubber O-rings or rubber rings. o-rings can also be manufactured from LSR, other thermoplastic materials, FKM (fluoroelastomer O-rings) and metal, both solid and hollow. This article tells you what you need to know about O-rings.

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Operation of O-Rings

O-rings are used as seals in recesses that are milled or turned in the structure. When the (rubber) O-ring is subjected to pressure, it deforms. In this way, the O-ring seals the two parts of the part surface against each other. If a normal O-ring is not sufficient, a flat rubber ring can also be used. In most cases, the connection is static, but it can also be dynamic. Because the O-ring is flexible, it can easily be adapted to the tolerances in the structure to be sealed.

In construction, rubber O-rings are one of the most important elements. Often, they are invisible, but must perform their task. They are available in various metric and imperial sizes, of which imperial sizes are the most common and are also widely used in Europe. As mentioned before, it is also possible to obtain flat rubber O-rings.

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Materials Used to Make O-Rings

O-rings are available in many different materials, each with different properties. Some of the most common materials used to make O-rings include the following.

Fluoroelastomer: Typically used in applications where heat is an issue, fluoroelastomer O-rings are heat resistant, durable and long lasting.

Silicone rubber: Silicone rubber O-rings have a soft, spongy design and are used in the food service industry because they are safe and non-toxic.

Ethylene-propylene diolefin monomer: Although not suitable for use with lubricants or fuels, ethylene-propylene-monomer O-rings are highly resistant to moisture, steam, silicone and grease.

Thermoplastic polyurethane: Providing high levels of tensile strength, thermoplastic polyurethane O-rings are resistant to degradation.

Sealing Pressure

When selecting an O-ring, it is important to consider the maximum pressure at which the O-ring can seal. O-rings are designed to compress naturally when installed between two working surfaces, which prevents air or liquid leakage. However, if too much pressure is applied to the O-ring, it may fail. According to Wikipedia, some O-rings are capable of sealing to 5,000 pounds per square inch (PSI). Of course, most manufacturers do not need to seal surfaces at such high pressures, but this is still a testament to the sealing ability of O-rings.

For advice on O-ring uses and materials, contact our team of experts about our product range.