Hydraulic Seals and Pneumatic Seals Information
Hydraulic seals and pneumatic seals are designed for the reciprocating motion that is common in hydraulic and pneumatic applications, such as cylinders.
Types of Hydraulic Seals and Pneumatic Seals
Hydraulic seals and pneumatic seals include:
- Piston seals
- Rod seals
- U-cups
- Vee
- Cup
- W
- Piston
- Flange packings
Applications
Hydraulic seals are designed for high-pressure dynamic applications such as hydraulic cylinders. Pneumatic seals are used in pneumatic cylinders and valves and generally are designed for lower operating pressures than hydraulic seals. Pneumatic applications also typically demand higher operating speeds and lower friction seals than hydraulic applications. These seals may be used for rotary and reciprocating motion.
Materials
Some hydraulic seals and pneumatic seals are composite. Composite seals are two-or multi-part seals manufactured as an integral unit. A typical composite seal consists of an integral PTFE ring and elastomer ring, providing the properties of an elastomeric ring with a rigid, low friction (PTFE) working face. These seals can have a variety of different cross sections. Some forms of composite seals are also referred to as polyseals, wedge-action seals, crown seals and tri-seals (3 part seals).
Seal Configurations
Common sealing orientation and directions for hydraulic seals and pneumatic seals include internal or rod seal, external or piston seal, symmetric seal, and axial seal.
- Rod seals are radial seals. The seal is press-fit into a housing bore with the sealing lip contacting the shaft. Also referred to as a shaft seal.
- Piston seals are radial seals. The seal is fit onto a shaft with the sealing lip contacting the housing bore. V-rings are considered external lip seals.
- Symmetric seals are symmetrical and works equally well as a rod or a piston seal.
- An axial seal seals axially against a housing or machine component.
Sealing direction pertains primarily to hydraulic and pneumatic seals that are used in applications with axial motion, such as cylinders and pistons. The action can be single or double. Single acting, or unidirectional seals, offer an effective seal in one axial direction only. In order to seal in both directions for a reciprocating motion, more than one seal must be used. Double acting, or bi-directional seals, are effective when sealing in both directions.
Specifications
Important spefications for hydraulic and pneumatic seals include dimensions, operating parameters and materials.
Dimensions
- Shaft outer diameter or seal inner diameter
- Housing bore diameter or seal outer diameter
- Axial cross section or thickness
- Radial cross section
Parameters
- Maximum operating speed
- Maximum operating pressure
- Vacuum rating
- Operating temperature
Material
Rubber sealing element or lip material choices for hydraulic and pneumatic seals include:
- ethylene acrylic
- EDPM
- fluoroelastomer
- fluorosilicone
- nitrile
- nylon or polyamide
- polychloroprene
- polyetheretherkeytone
- polyoxymethylene
- polytetrafluoroethylene
- polyurethane or urethane
- natural rubber
Seal material choices include:
- Sintered bronze
- Cast iron
- Stainless steel
- Felt
- Leather
Many seal manufacturers use their own proprietary material. Consult with manufacturer for proprietary material specifications.
Features
Common features for hydraulic seals and pneumatic seals include spring loaded, integral wiper, and split seal.
Standards
BS 6241 - Specification for dimensions of housing for hydraluic seals incorporating bearing rings for reciprocating applications
GOST 14896- Rubber u-packing seals for hydraulic devices
ISO 7632 - Road vehicles - elastomeric seals
Image credits:
Hi-Tech Seals, Inc. | Hallite Seals International | SKF/North America
- Composite Seals
- Cup Packing
- Double Acting
- EPDM
- Ethylene Acrylic (AEM - Vamac®, etc.)
- External / Piston Seal
- Flourosilicone (FVMQ, FMQ, FPM, FSI)
- Fluoroelastomer (FKM - Viton®, Fluorel®, etc.)
- Internal / Rod Seal
- Nitrile (NBR - Buna-N)
- Nitrile - Highly Saturated (HNBR)
- Nylon / Polyamide
- Piston Ring
- Polychloroprene (CR - Neoprene)
- Polytetrafluoroethylene (PTFE- Teflon®, etc.)
- Polyurethane / Urethane
- Rubber - Natural (NR)
- Seal is Spring-energized
- Single Acting
- Split Seal
- Symmetric Seal
- U-ring / Block Vee Ring
- Vacuum Rated
- Vee Packing
- dual shaft mixer
- dual shaft motor
- w seal
- double acting piston pump
- flange mount lip seal
- hydraulic hand pump seals
- intertek seal
- oil pump seals
- water pump seals
- air compressor piston seals
- automotive water pump seals
- cast iron piston seals
- ceramic water pump seals
- diesel fuel pump seals
- hand water pump piston seals
- high pressure hydraulic pump seals
- high temperature pump seals
- hydraulic jack pump seals
- hydraulic wear rings
- hydrodynamic pump seals
- mechanical metric pump seals
- mechanical water pump seals
- metal bellows pump seals
- piston pump seals
- pneumatic piston seals
- pressure washer pump seals
- PTFE piston seals
- water pump piston seals