Sealing systems have become indispensable in modern everyday life. Wherever equipment, machines, engines, and piping systems are in operation, and wherever gases, liquids, or solids need to be transported, sealing elements designed for the specific application are used.
Seals compensate for manufacturing tolerances in the functional assembly of paired components, making the cost-effective production of housings, containers, shafts, pipes, and many other components possible in the first place.
Across the wide range of possible applications, a wide variety of temperature and pressure ranges must be taken into account. Throughout the entire specified product lifespan, resistance to a large number of substances – some of which are highly aggressive – that come into direct contact with the sealing material must be ensured.
Our application engineering team is happy to assist you in selecting the combination of materials and sealing elements best suited to your requirements. If no suitable standard sealing element is available, custom molded parts can be developed quickly and in close coordination with our R&D department.
O-rings are ring-shaped sealing elements with a circular cross-section that are widely used in sealing technology. They are used to seal static and dynamic joints against liquids and gases. Their function is based on the elastic deformation of the material, which reliably closes the gap between two components.
Fietz offers O-rings made of PTFE (FiKumer®-F), polyurethane (FiPur®), and elastomer (FiLomer®). Depending on the customer’s application and the media involved, Fietz can select the right material from its extensive portfolio.
PTFE is a thermoplastic with excellent chemical and thermal resistance
• Properties: virtually universal chemical resistance, very low coefficient of friction, high temperature resistance (−200 °C to +260 °C)
• Advantages: ideal for aggressive chemicals, high temperatures and dry media; no aging
• Disadvantages: no elasticity – PTFE O-rings often need to be pre-stressed or designed as composite seals (e.g., PTFE with an elastomer core)
• Applications: low-pressure hydraulics, chemical industry, food processing, vacuum technology
Polyurethane combines high mechanical strength with good elasticity
• Properties: high abrasion resistance, good elasticity, good resistance to oils and greases. FiPur® materials are highly resistant to hydrolysis
• Advantages: particularly durable in dynamic applications, resistant to extrusion and wear
• Disadvantages: limited chemical resistance, sensitive to hot water and steam
• Applications: hydraulic cylinders, mobile hydraulics, applications subject to high pressure or movement
Elastomers (NBR, EPDM, FKM, FFKM) are the most commonly used materials for O-rings
• Properties: high elasticity, good resilience, wide range of temperature and media resistance
• Advantages: good sealing performance due to elastic behavior, cost-effective, easy to install
• Disadvantages: limited chemical resistance, not suitable for extreme temperatures or aggressive media
• Applications: hydraulics, pneumatics, automotive fluid systems, general mechanical engineering applications
Jacket gaskets are specialized sealing elements that are frequently used in combination with O-rings or other elastomer seals. Their primary function is to protect the O-ring or the actual seal from mechanical damage, extrusion, or chemical attack. They thus act as protective or supporting elements within a sealing system.
Fietz jacket gaskets are available as internally sealing, double-acting rod sleeve rings and as externally sealing, double-acting piston sleeve rings for every rod and piston diameter, as well as scrapers.
Depending on the material selection, operating pressures of up to 800 bar (80 MPa) – and even higher under static loads – speeds of up to 15 m/min, and temperatures between -54°C and +200°C can be achieved.
Use in applications involving rotary or helical motion is only possible to a limited extent. Fietz jacket gaskets are available in various material combinations, each optimized for specific application areas.
• Properties: excellent chemical resistance, wide operating temperature range (−200 °C to +260 °C), very low friction
• Advantages: ideal for aggressive media and high temperatures, no sticking or adhesion
• Disadvantages: low elasticity – usually used in combination with an elastomer inner part (e.g., PTFE jacket gasket with FKM core)
• Applications: chemical industry, vacuum technology, food processing
• Properties: good elasticity, resistance depending on the medium
• Advantages: good adaptability, easy installation
• Disadvantages: limited temperature and pressure resistance compared to PTFE or PU
• Application: standard jacket gaskets for general hydraulic and pneumatic applications
• Properties: highly abrasion-resistant, good mechanical strength, high extrusion resistance
• Advantages: ideal for dynamic sealing systems with high pressures and movements
• Disadvantages: limited chemical resistance to hot water, acids and bases
• Applications: mobile hydraulics, cylinder seals, high-pressure applications
Step rings are specialized sealing elements used as support or retaining rings in combination with O-rings or other sealing systems. Their main function is to protect the sealing material – usually an elastomer O-ring – from extrusion (bulging into the gap between sealing surfaces) at high pressures. This significantly increases the operational reliability and service life of sealing systems.
They are used in particular in hydraulic and pneumatic applications involving high pressures or large gaps.
The stepped ring has a characteristic asymmetrical shape with a step (hence the name). This geometry ensures that the ring mechanically supports the O-ring on the side away from the pressure, while the sealing effect remains unchanged on the pressurized side.
Typically, the stepped ring is used in pairs (one ring per side of the O-ring) when the pressure direction changes, or on one side when the pressure is constant.
• Properties: high chemical resistance, very low coefficient of friction, wide operating temperature range (−200 °C to +260 °C)
• Advantages: virtually no aging, very good sliding properties, ideal for aggressive media
• Disadvantages: low elasticity, therefore only usable as a support element, not as a primary seal
• Applications: Chemical industry, hydraulic systems with high temperatures or aggressive media
• Properties: high mechanical strength, excellent abrasion and extrusion resistance
• Advantages: highly resistant to fluctuating pressure loads, ideal for dynamic applications
• Disadvantages: limited chemical resistance to hot water and certain chemicals
• Applications: mobile hydraulics, construction machinery, cylinders with high pressure spikes
• Properties: high dimensional stability, good wear resistance, easy to process
• Advantages: cost-effective, mechanically robust
• Disadvantages: lower chemical resistance than PTFE
• Application: Standard support rings in hydraulics and pneumatics
Ball valve seals are key components in the sealing technology of ball valves, which are used as shut-off valves in piping systems. Their primary function is to ensure a tight seal between the ball (closing element) and the valve body, thereby guaranteeing leak-free shut-off of liquids or gases.
A ball valve operates by rotating the ball, which has a bore that opens or closes the flow path. To ensure that the seal remains effective under varying pressures, temperatures, and media, high-quality and suitable sealing materials are required.
• Properties: excellent chemical resistance, low coefficient of friction, wide operating temperature range (−200 °C to +260 °C)
• Advantages: universally applicable, very good sliding and sealing properties, non-aging
• Disadvantages: limited pressure and wear resistance
• Reinforced variants: PTFE filled with glass, carbon, or graphite improves wear and pressure resistance
• Applications: chemical industry, food processing, pharmaceutical industry, water and gas valves
• Properties: high pressure and temperature resistance, excellent chemical stability
• Advantages: suitable for extreme conditions, long service life
• Applications: high-pressure ball valves, offshore, chemical, and high-temperature plants
Scrapers (also known as wipers) are sealing elements primarily used in hydraulic and pneumatic systems. Their main function is to remove dirt, dust, moisture, or other contaminants from the piston rod or shaft before they enter the interior of a cylinder or housing.
They are therefore protective seals that prevent the ingress of foreign substances, thereby extending the service life of primary seals, guides, and the entire system.
Various designs are available, depending on requirements and the operating environment:
• Simple wipers: wiper lip only – for protection against dirt and dust
• Double-acting wipers: with an additional sealing lip – also prevent oil film leakage
• Metal-encased scrapers: with a metal housing for secure mounting in the cylinder head
• Combination seals: a combination of a primary seal and a scraper in a single component
• Properties: good elasticity and resilience, adaptable to surfaces
• Advantages: cost-effective, universally applicable, good sealing performance
• Disadvantages: limited wear and weather resistance, sensitive to ozone and UV radiation
• Applications: standard hydraulic cylinders, pneumatics, general mechanical engineering applications
• Properties: high abrasion resistance, good mechanical strength and dimensional stability
• Advantages: very long service life, resistant to dirt, pressure, and wear
• Disadvantages: limited chemical resistance to hot water and certain media
• Applications: mobile hydraulics, construction and agricultural machinery, applications with high levels of contamination
• Properties: very low friction, high chemical resistance, wide operating temperature range
• Advantages: excellent sliding properties, no dirt adhesion, temperature-resistant
• Disadvantages: no inherent elasticity – often combined with elastomer preload
• Applications: high-quality hydraulic systems, chemical and process industries
Rod seals are key components in hydraulic and pneumatic sealing technology. They seal the moving piston rod of a cylinder against the outside environment and prevent the working fluid (e.g., hydraulic oil or compressed air) from escaping the system. At the same time, they must prevent the ingress of dirt, dust, and moisture from the outside.
Their function is crucial for the leak-free operation, efficiency, and service life of a hydraulic or pneumatic system.
There are different designs, depending on the application and load:
• Single-acting rod seals: Seal in one direction (inward to outward)
• Double-acting rod seals: Seal in both directions – under alternating pressure loads
• Combination seals: Combination of primary and secondary seals to optimize sealing performance
• Profile and groove seals: With special lip profiles to adapt to operating pressure and medium
• Properties: good elasticity, adapts to surfaces, reliable recovery forces
• Advantages: easy installation, good sealing performance, cost-effective
• Disadvantages: limited temperature and media resistance
• Applications: standard hydraulics, pneumatics, mechanical engineering
• Properties: high mechanical strength, abrasion and extrusion resistance, good resilience
• Advantages: very durable, resistant to high pressures and dynamic loads
• Disadvantages: limited chemical resistance to hot water and acids
• Applications: mobile hydraulics, construction machinery, agricultural machinery
• Properties: very low coefficient of friction, high chemical and thermal resistance
• Advantages: ideal for high speeds and temperatures, low wear
• Disadvantages: no inherent elasticity – usually combined with elastomer preload elements (e.g., O-ring)
• Applications: high-performance hydraulics, chemical plants, precision systems
Piston seals are key components in hydraulic and pneumatic sealing technology. Their purpose is to reliably seal off the pressure chamber on the piston rod side from the pressure chamber on the bottom side of a cylinder. In doing so, they enable the conversion of fluid pressure into linear motion – the actual function of a hydraulic or pneumatic cylinder.
Their main task is to prevent pressure losses, ensure operational safety, and increase the system’s service life.
There are various designs of piston seals, which are selected based on the application and load:
• Single-acting seals: Seal in one direction, usually in combination with a support ring
• Double-acting seals: Seal in both directions – for cylinders with alternating pressure loads
• Combination seals: Multi-part systems consisting of sealing and support components for high pressures
• Lip seals: With one or two sealing lips for good adaptation and low friction
• Properties: good elasticity, reliable springback, adaptable
• Advantages: cost-effective, proven standard solution, easy installation
• Disadvantages: limited temperature and media resistance
• Application: pneumatics, hydraulics with moderate pressures and temperatures
• Properties: very high mechanical strength and abrasion resistance
• Advantages: ideal for high pressures, dynamic loads and long service life
• Disadvantages: limited chemical resistance to hot water and acids
• Applications: mobile hydraulics, construction machinery, high-pressure cylinders
• Properties: extremely low coefficient of friction, excellent chemical and thermal resistance
• Advantages: low wear, temperature-resistant, suitable for high speeds
• Disadvantages: no inherent elasticity – usually combined with an elastomer preload element (e.g., O-ring)
• Applications: high-performance hydraulics, chemical industry, precision systems
Valve seals are key components in valve and fluid technology. They ensure a leak-free seal and the safe control of fluid flow in valves. Their main function is to either allow the controlled flow of liquids or gases or to completely prevent it by creating a tight seal between the valve body and moving components (e.g., valve cone, disc, or ball).
They are found in virtually all industrial sectors – from hydraulic and pneumatic systems to process and chemical engineering, and on to the food and energy industries.
• Properties: virtually universal chemical resistance, very low coefficient of friction, wide operating temperature range (−200 °C to +260 °C)
• Advantages: ideal for aggressive media, high temperatures, low friction
• Disadvantages: no elasticity – often used as a seat ring or in combination with elastomer support elements
• Applications: Chemical and process engineering, food industry, ball and globe valves
• Properties: high elasticity, good resilience, resistance dependent on the medium
• Advantages: good sealing performance even at low contact pressures, versatile application
• Disadvantages: limited temperature and pressure resistance, dependent on the medium
• Applications: Pneumatic valves, water and gas systems, sanitary engineering
• Properties: High abrasion and extrusion resistance, good elasticity
• Advantages: Robust, durable, resistant to mechanical stress
• Disadvantages: Limited chemical resistance to hot water and acids
• Applications: Hydraulic valves, high-pressure systems, mobile machinery
• Properties: High mechanical strength, dimensional stability, and thermal resistance
• Advantages: Suitable for extreme operating conditions, long service life
• Applications: High-pressure, high-temperature, and offshore valves, chemical plants
Custom seals are individually designed sealing solutions that are specifically tailored to the requirements and operating conditions of a particular system or product.
While standard seals are sufficient for many applications, complex or heavily stressed systems often require custom-made seals to ensure optimal performance, service life, and cost-effectiveness.
Such custom seals are used, for example, in the hydraulic, pneumatic, chemical, food, energy, and automotive industries – anywhere standard components reach their limits.
• Optimal adaptation to geometry, pressure, temperature, and medium
• Improved performance compared to standard solutions
• Longer service life and reduced maintenance requirements
• Reduction of friction, wear, and leakage
• Integration of additional functions, e.g., guidance, damping, or electrical insulation
• Cost efficiency through longer service life and reduced downtime
The development of custom seals takes place in close collaboration between the manufacturer and the user and comprises several phases:
1. Analysis of operating conditions: Determination of pressure, temperature, medium, motion, installation space, and service life requirements
2. Material selection: Selection of the optimal material or composite material based on chemical, thermal, and mechanical requirements
3. Design and simulation: Development of the seal geometry, taking into account friction, extrusion, compression, and installation behavior
4. Prototyping and testing: Production of initial samples, functional and service life tests
5. Series production and quality assurance: Production with defined tolerances, documented traceability, and, where applicable, industry-specific certification (e.g., FDA, ISO, DIN)
The Fietz Group develops high-performance materials – including FiPur® polyurethanes, as well as PTFE and PTFE compounds – and tailors them precisely to the requirements of your application. The Fietz Group offers a standardized range of seals for O-rings and hydraulic cylinders. For custom solutions, you benefit from our many years of experience and the expertise of our application engineering team.
The Fietz Group relies on end-to-end local manufacturing – from consultation and development through production to final inspection. This ensures short delivery times, strict quality control, and greater environmental efficiency.
Fietz seals are characterized by:
• Extremely high abrasion resistance
• Very low wear rates
• Excellent pressure resistance – up to approx. 400 bar
• Minimal permanent deformation
• Easy installation
Fietz seals are successfully used in the hydraulics, fluid technology, machinery, and food industries. They offer pressure resistance, chemical resistance, hygienic standards, and precision – all “Made in Germany.”
Our team of application engineering and materials experts looks forward to hearing from you and assisting you with:
