Rod Seal
Due to their importance in a hydraulic cylinder, rod seals should be mentioned first. A leak at this important point would lead to serious influences on the operating system and would cause damage to the environment. The rod seal must have a tight fit and make a perfect seal when in motion and motionless. For this reason, some types of seals include pre-loading elements (usually made out of NBR) to ensure a tight fit and seal even in a motionless or depressurized state. At higher operating pressures, additional support rings are used on the rod seal in order to avoid losing the seal.
Materials: Rod seals are mostly made out of PU, NBR or FPM, but a combination of elastomers and plastomers is also possible. The same applies here, PU rod seals are usually much more wear and tear resistant than those made from rubber materials. Depending on operating conditions, for example, at temperatures above 100°C (212°F), FPM seals are used. In pneumatic applications NBR is the preferred material for seals.
Wiper
Sealing elements intended for prevention of solid particles from entering a hydraulic or lubrication system are referred to as wipers or dirt scrapers. There are also scrapers used for preventing liquids from penetrating and sometimes both tasks have to be fulfilled simultaneously. There is usually no hydraulic pressure applied to a scraper. It is imperative to have the scraper in a stable position in the groove, which can be improved by additional axial or radial support.
Materials: Scrapers are mostly made out of NBR or PU. PU scrapers are extremely resistant to wear and tear compared to NBR scrapers, so PU scrapers are increasingly used nowadays. Scrapers can also be equipped with a stiffening ring (for example, out of metal) and then pressed into the axial bore holes, instead of the snap-on versions.
Piston seals
A single-acting piston seal operates in the same way like a rod seal, but with the difference that the dynamic sealing lip of a piston seal is located on the outside. Double acting piston seals are designed symmetrically as they are pressurized from both sides. Even piston seals are sometimes equipped with pre-loading elements in order to create an even tighter seal. At higher operating pressures, additional support rings are used in order to avoid seal extrusion.
Materials:
Piston seals are mostly made out of PU or NBR or FPM, but a combination of elastomers and plastomers is also possible. It is important to consider the installation conditions when selecting the material for a symmetrical piston seal.
Symmetrical seals
Symmetrical seals can be used both as a piston and rod seal due to their geometry. They are, so to speak, a universal solution without a specific design of the sealing lip.
Materials: Symmetric seals are mostly made out of PU or NBR or FPM, but when they are used in combination with a pressure or support ring, PU and POM materials are usually used.
Flange seals
Flange seals are used as an alternative to O-rings, mostly used for the static sealing of housing covers.
Materials: Flange seals made out of NBR or PU are preferable.
Rotary seals
Rotary seals are generally classified for applications under pressure, and for pressure-less applications.
Materials: Due to different requirements, rotary seals are made of elastomers, plastomers and are partially manufactured with metallic housings.
Guide rings
Guide rings are used to guide pistons and piston rods. This is necessary to avoid contact of metallic surfaces that are moving close to each other. Guide rings are usually cut at an angle in order to deliver sufficient hydraulic oil between both metal surfaces.
Materials: Guide rings are made of filled PTFE, POM or hard fabric.
Back Up Rings
Depending on the application, back up rings prevent the gap extrusion of the seals or O-rings.
Materials: Back up rings are made out of PU, PTFE or POM.
O-rings
O-rings are mainly used as static seals, but can get used for dynamic applications as well. Due to their geometry, they may be used as double-acting.
Materials: We offer O-rings made out of standard materials such as NBR70, NBR90, FPM80 as well as special materials, like PTFE, PU, FFPM and AFLAS. In addition to standard dimensions, we can manufacture almost any special dimension with our materials NBR85, NBR95, FPM85, as well as PTFE, PU and AFLAS.
Mining seals
Mining seals usually are multi-part seals with additional back-up rings and preloading elements in order to meet the increased requirements. Pertaining to their geometry these seal types resemble the usual piston- and rod seals, but they got adapted to the comparatively high hydraulic pressure of mining applications.
Materials: PU dominates as a seal material, NBR is mostly used for preloading elements. For back-up rings normally POM gets used as an additional material.
