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Dynamic Seals

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About Dynamic Seals

Dynamic seals retain or separate fluids, keep out contaminants, and contain pressure. They create a barrier between moving and stationary surfaces in applications such as rotating shafts and pistons rings. Important dimensions for dynamic seals include seal inside diameter (ID), shaft outside diameter (OD), housing bore, axial cross-section, and radial cross-section. Service limits include maximum operating speed and maximum operating pressure. Sealing orientation and direction vary widely. Internal seals fit into a housing bore with the sealing lip in contact with the shaft. By contrast, external seals fit onto the shaft so that the sealing lip contacts the housing bore. Symmetric seals are suitable substitutes for both internal rod seals and external piston seals. Axial seals are used with housing or machine components. For proper sealing, the seal lip on a dynamic seal needs to point towards the medium being contained.

There are many types of dynamic seals. Oil and grease seals have a flexible lip that rubs against a shaft or housing to prevent the leakage of fluids. Some oil and grease seals include a spring to help keep the lip in contact with the shaft. Hydraulic and pneumatic seals are designed for devices that provide reciprocating motion. This category includes piston seals, rod seals, U-cups, and flange packages. Exclusion seals are dynamic seals such as wipers and scrapers that support sliding or reciprocating motion. Clearance or labyrinth seals provide positive clearance and do not rub against the shaft or housing. Many clearance seals consist of a rotor and a stator. For proper sealing, the radial gap between these members must exceed the clearance of the bearing being sealed. Clearance seals, which do not perform well at low operating speeds, include laminar products that contain a series of flat metal washer-like rings of varying diameters. Other ring seals include piston and backup rings. Metallic piston rings are used to seal cylinders and have a higher working temperature than elastomeric, fabric, or polymer materials. Backup rings are washer-like devices that are installed in the downstream side of the gland and are used to prevent a seal from extruding while under pressure. Bearing isolators, another type of dynamic seal, can feature either a labyrinth or O-ring construction.

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Products & Services Related to Dynamic Seals

Back-up Rings
Back-up rings or anti-extrusion rings are washer-like devices used to prevent seals from extruding through gaps while under pressure. Seals are installed in the downstream side of the gland.
Bearing Isolators
Bearing isolators are dynamic seals designed to protect bearings from outside contaminants.  They are comprised of a rotor (rotating) and stator (stationary) member.
Exclusion Seals
Exclusion seals are comprised of wipers, scrapers and V-ring seals.
Hydraulic Seals and Pneumatic Seals
Hydraulic seals and pneumatic seals include piston seals, rod seals, U-cups, vee, cup, and flange packings.
Oil Seals and Grease Seals
Oil seals and grease seals have a flexible lip that rubs against a shaft or housing to prevent the leakage or ingress of fluids and dirt.

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Engineering Web: Dynamic Seals

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Dynamic Seals
Dynamic Seals Sealing Products Engineering / Design Assistance
See Web Seal Inc. Information
Design and Operation of a Device for Evaluating Shaft Seals in...
Design and Operation of a Device for Evaluating Shaft Seals in Dynamic Applications
See Storming Media LLC Information
Dynamic Seals

See A.R. Wilfley & Sons, Inc. Information
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