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Hydraulic Seals and Oil Seals and Their Use

Modificar: Mar. 22, 2022

oil seal

Hydraulic seals are typically made from elastomers, natural and synthetic polymers that have weak molecular attraction and high elastic properties. The two primary sources of hydraulic seals are rubber and plastics (including PTFE, such as Teflon and polyurethane). Other elastomeric materials used to make seals include butadiene, nitrile, butyl and silicone resins.

Seals can also be made from non-elastomeric materials, such as felt and leather. Some specific types of hydraulic seals, such as bonded seals, are made from metallic materials including brass, bronze, aluminum, carbon steel and stainless steel. The bond between the rubber material of the bonded seal and the metal is created by chemical bonding.

Main types

Hydraulic seals are most commonly found in hydraulic cylinders, mechanical actuators that convert hydraulic pressure (from oil, water or other pressurized fluids) into unidirectional force for use in agricultural and forestry vehicles, construction equipment and similar mechanisms.

Typically, hydraulic seals are located in cylinder heads, connecting rod shafts or pistons. In these locations, the seals prevent fluid from leaking through the interface between the rod and the cylinder head, leaking to the outside of the cylinder, and flowing through the piston.

Static and Dynamic

Static seals are typically located in recesses and other confined spaces and are used as gaskets. In this document, the term "gasket" refers to a mechanical seal that fills the space between two or more mating surfaces without any movement between them and is held in place by tightening the pressure exerted by the bolt.

Dynamic seals, also called shaft seals, seal the gap between two surfaces that share relative motion. The types of motion between them include reciprocating, oscillating and rotating.

Reciprocating dynamic seals are located within a gland that maintains relative motion. Here, they move along an axis between the inner and outer surfaces. In most cases, they are used to power linear actuators, hydraulic cylinders and pistons in internal combustion engines.

oil seal


O-rings are unique in this list because they are identified primarily by their shape rather than by their location or specific function. As their name implies, O-rings are ring-shaped and come in many different materials (e.g., rubber, silicone, fluorocarbon) and sizes (e.g., less than an inch to several meters wide). When these types of seals are mechanically deformed by pressure, they create a very effective sealing barrier. Due to their low cost and relative simplicity, O-rings are the most common type of hydraulic seal on the market today.

oil seal


Because hydraulic seals are critical to the efficiency of hydraulic systems, they are used in a wide range of industries. Industries served by hydraulic seals include aerospace manufacturing, agriculture, automotive manufacturing, chemical processing, defense contracting, food processing, seafood manufacturing, medical and pharmaceutical product development, nuclear power, pulp and paper, and waste processing.

The specific applications for hydraulic seals are as diverse as the industries in which they are used. Hydraulic seals can be found in construction equipment, agricultural machinery, braking devices, clean rooms, conveyors, mixers, presses, valves and test equipment.

oil seal


Those considering which hydraulic sealing solution is right for them must consider a number of things. While hydraulic seals are primarily designed to prevent fluid leakage, it is important to remember that hydraulic seals also provide other important functions and should only be properly maintained under the right conditions.

One of the most important factors to keep in mind is the working space of the hydraulic seal. This will affect the diameter of the inner and outer seals as well as the size of the housing bore and outer shaft.

In addition, purchasers of hydraulic seals should be aware of vacuum ratings, operating temperatures, chemical compatibility (between the seal and the hydraulic fluid), maximum and minimum operating speeds, and minimum and maximum pressures.

With the proper products in mind, operators in all industries can expect reliable and efficient seals. An experienced and trusted hydraulic expert and supplier is worthy of assistance in the seal selection process. Contact HONGLEI for more information!

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