How to Choose A Sealing Element?

Seal elements control the behavior of the fluid between two pressure zones in a system; they are used to prevent the flow of fluid from one zone to the other. With the help of a pump or compressor, a force is generated when a pressurized fluid acts on a zone.

Consider, for example, a hydraulic or pneumatic cylinder, where the work is done by the entry and exit of the rod. Very high power can be obtained by using the principle of incompressibility of the hydraulic fluid. Compared to hydraulic systems, pneumatic systems are less powerful. Depending on the purpose of use, sealing elements can be divided into two main headings: static and dynamic.

How To Choose A Sealing Element?

System pressure, sliding speed, temperature, media, surface roughness and system tolerances are important parameters when selecting the type of sealing element.

Pressure

The first important characteristic of the system that should be looked at is the pressure, as the system working force is obtained from the cylinder bore and the system pressure. When calculating the system pressure, we recommend considering a shock pressure which is usually higher than the normal working pressure. Today, the demand for higher forces has led to an increase in system pressure in hydraulic systems. This is why there are new profiles and new engineering materials.

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CDType Sealing Components

Temperature

The medium and the working temperature are the two most important factors in the selection of materials for sealing elements. The ideal operating temperature for sealing elements and systems is 50°C, but application temperatures are often up to 100°C.

In dynamic applications, the sealing elements do come into direct contact with sliding surfaces, which is why they are subject to the heat generated by friction. The system temperature should be lower than the operating temperature.

For special applications requiring high temperatures, we recommend using sealing elements made of FKM and/or PTFE. For low temperatures, it is thought that the sealing element will become harder (glass transition) and will not do the required work, but in reality, depending on the medium, the sealing element can function at temperatures up to -40°C.

D Type Sealing Components

Speed

Depending on the material, design and application of the sealing element, the speed of the cylinder can be up to 15 m/sec. Speed is one of the important characteristics that defines oil film generation and friction.

Media

The minimum and maximum operating temperature of the sealing element varies depending on the medium used. Sealing elements can be used with mineral oils (DIN 51524), non-flammable hydraulic fluids (VDMA 24317 or DIN 24320), atmosphere, water, and different types of media (see chapter; Chemical resistance of rubber materials).

The viscosity of the medium is one of the reasons for the wear of the sealing elements. Pressure and temperature change the viscosity of the medium. The viscosity of the medium increases with pressure. An increase in temperature reduces the viscosity of the medium (this change depends on the type of medium). When selecting the type of medium, the effect of operating pressure and temperature on viscosity should be studied.

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