Guide to Different Types of O-ring Applications

Nov 28, 2017 Rod Seals | FDA O-Rings

The O-ring is one of the important and simplest types of seals used in various dynamic, as well as static applications. It basically comprises of a cross-section, which is designed into a groove. This cross section provides an initial compression. The force needed to compress the seal is produced by the cross-section diameter, and the durometer. The sealing compression is affected by the stretch. This compression also affects the sealing potential of this seal. An O-ring is described as a static or a dynamic seal, depending on the direction of the squeeze applied to its cross section. This post discusses static and dynamic types in detail.

An Introduction to Static Seals

Static seals are categorized on the basis of squeeze, which is applied on the cross section of the O-ring.

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Know about Different Types of Static Seals

Static seals are mainly classified as:

Static Axial Seals: This seal acts similar to the gasket, which is squeezed on both ends – top and bottom of an O-ring cross section. These seals are used in flange or face type applications. Internal or external pressure must be taken into consideration when it is used as a face seal. It is important to position the seal in a low-pressure side of the groove. This helps cut down the movement of the seal, as well as wear in the groove. It is easier to design these seals. Also, one can control tolerances easily.
Static Radial Seals: The seal of this type is well-suited for plug and cap type applications. Typically, static radial seals are squeezed between the outer and inner surface.
Static Crush Seals: These seals are pressure deformed and confined within a triangular gland. The gland is created by machining the male cover in a 45 degree angle. In various crush seal applications, the seal is usually squeezed at an angle to the axis of the O-ring.
Static Seals with Dovetail Glands: Many times, O-rings are used in slow moving or static applications, which may involve various dovetail glands. Controlling tolerances of these glands isn’t easy, due to the angles. These glands help holding the seal in place during maintenance, or while machine is moving. The seal is squeezed in axial direction, thus use of lubricant is recommended, while placing it in the dovetail gland. This seal application should only be used, whenever required.

Basic Information on Dynamic Seals

The seals used in rotating, reciprocating, or oscillating motion are known as dynamic seals. Performance of these seals is affected by various variables. These variables may include pressure of the system, surface finish of metal parts, O-ring stretch, and squeeze, etc. As, many of these variables are related to each other, thus they are considered important in dynamic sealing conditions.

Know About Dynamic Seals and Their Applications

The following are different types of dynamic seals:

Reciprocating Seals: These seals are used in conditions involving a rod and a moving piston.
Oscillating Seals: In an O-ring application, the shaft always creates an arc while moving. Also, the shaft comes in touch with ID of the seal. The shaft has a tendency to twist, while in rotation. Thus, durable seals are used in such applications.

The O-rings act as rotary seals under appropriate conditions. Appropriate hardware configuration, durometer, and feet-per-minute values are important for a proper sealing. To ensure a proper working of these seals, it is important that you source them from a reliable manufacturer. SSP Manufacturing, Inc. is a manufacturer of several static and dynamic O-ring seals. The company provides them in various specifications.