O-Ring or Gasket: Which Seal Should I Use for My Application?

Selecting an o-ring vs. gasket will depend on the application. Each is a type of everyday mechanical seal frequently used in machines, motors, engines, piping, pipelines, fixtures, and the like. O-rings and gaskets join and seal parts and components found in these devices to prevent gas or fluid leakage from them.

Though size, shape, and material will certainly factor into the selection process, ultimately, the various functions a particular seal must accomplish is the prime consideration of whether an o-ring or gasket is better suited for an application, and that’s determined during the application’s design phase. To assist with the selection process, let’s take a closer look at the differences between o-rings and gaskets, their applications, pros, and cons.

What is a Gasket?

A gasket is a type of flat, mechanical seal used to mate surfaces between two components. It consists of a malleable material that can be formed to meet the design specifications of virtually any application. The insertion of a gasket between two surfaces creates an airtight seam between one or more stationary components. The compression set prevents the emission or contamination by absorption of unwanted gas or liquid, which could cause the part to fail.

Gaskets can be designed to any shape as required. Many are circular, oval, and rounded. Others are square, rectangular, oblong, triangular, even crescent-shaped and can be jacketed, double-jacketed, spiral wound, and grooved or Kammprofile. Whatever the design, gaskets prevent leakage, resist pressure, temperature fluctuations, and sometimes electrical or electromagnetic forces.

Since the functionality of a gasket relies on its compression, the material must be pliable and easily deformed for the gasket to conform to the mated surfaces. Materials for gaskets are numerous—elastomeric polymers, corks, metals, composites, rubber, and foams are common—with selection largely related to the material’s mechanical properties. For example, the silicone-based gasket material is ideal for use in extreme temperature applications. Elastomeric polymers such as nitrile, Viton, and neoprene can undergo a high degree of deformation while under pressure without loss of attributes or permanent damage to the material.

What is an O-Ring?

By definition, an o-ring is a type of gasket that serves similar functionalities as other gaskets. Yet, as the name implies, the key characteristic of an o-ring is its unique, doughnut-like shape. The looped, circular gasket with a hollow center is designed to block the passage of gases and liquids between two mating surfaces. O-rings are well-regarded for maintaining their integrity under intense vibrations and high pressure. They are widely used in the automotive and aerospace industries.

Though o-rings are available in various sizes, dimensions, and thicknesses, for both standard and non-standard sealing applications, the material generally consists of various elastomeric polymers such as nitrile rubber, silicone rubber, and fluoropolymers. The determining factor in its application is how well a particular material performs under expected environmental and operational conditions. Compression or hardness, abrasion or permeability, compatibility with oils, solvents, and gases, are all factors when considering material for o-ring applications. Normally, o-rings are fitted into a groove where two rounded surfaces come together and can be inserted for static or dynamic applications. Their circular design allows them to be fitted over or between such cylindrical-shaped components as pipes and hoses.

O-Rings vs. Gaskets

Because o-rings and gaskets essentially serve the same function, the deciding factors for the use of either relate to design and application. In other words, the shape of the seal must meet the design specifications to mate the component surfaces successfully. The operating temperature and pressure requirements of an application will also determine whether using an o-ring or other type of gasket is more appropriate. With its rounded edges and round cross-section, the unique design of o-rings makes it a better choice for high-pressure applications. In extreme temperature environments, though the material selection is vital for the seal’s effectiveness, the flat surfaces of a gasket are better suited to function.

Gaskets are commonly found in such applications as electronics, electrical motors, generators, transportation and automotive, and telecommunication devices. In contrast, o-rings are indispensable mechanical components fitted on valves, pipes, pumps, shafts, couplings, and engines to secure fuels, refrigerants, lubricants, and oils, or gases, steam, vapor, and water.

O-rings and gaskets are familiar mechanical seals used extensively to mating surfaces between varying components. Gaskets can be designed to fit virtually any shape. Though o-rings are a type of gasket, they are designed exclusively for rounded or cylindrical sealing applications. Ultimately, the shape is deciding factor between a gasket and an o-ring and, thus, determines which is more suitable for an application.

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