Sealing technology is the technical field concerned with the controlled sealing of connection points between components. The aim of sealing technology is to prevent the escape or ingress of liquids, gases or solids, or to limit it to a technically acceptable level. Sealing technology is an indispensable part of almost all technical systems.
Seals are found in mechanical engineering, process engineering, the automotive industry, power generation, the chemical industry and electrical engineering. The seal is not a passive component. Its function always results from the interaction of material, geometry, surfaces, operating conditions and assembly.
Technical Properties and Fundamentals
Tasks of sealing technology
Sealing technology fulfils several fundamental tasks:
- Sealing against liquids, gases or dusts
- Separation of different media
- Protection of sensitive components from environmental influences
- Ensuring pressure or vacuum conditions
- Reduction of leakage to a defined level
In many applications, absolute tightness is neither required nor achievable. The technical task is to ensure a permissible leakage rate.
Basic principle of sealing action
The sealing effect arises from the overlap of surface unevenness. Technically this is achieved through:
- Elastic or plastic deformation of the sealing material
- Generation of a defined surface pressure
- Adaptation to roughness and form deviations of the sealing surfaces
Temperature changes, pressure fluctuations, relative motion and ageing directly influence the sealing effect and must be considered in the design.
Designs in Sealing Technology
Static seals
Static seals are used when no relative motion occurs between the components to be sealed. Typical applications include flange connections, housing covers and screw connections.
Examples of static seals:
- Flat gaskets
- O-rings in static grooves
- Profile seals
Static seals are relatively simple in design but react sensitively to insufficient preload, uneven sealing surfaces or incorrect material selection.
Dynamic seals
Dynamic seals seal under relative motion. This motion can be rotational or translational. Dynamic sealing technology is technically demanding because friction and wear are unavoidable.
Typical dynamic seals are:
- Shaft seals
- Piston and rod seals
- Wipers
The sealing effect strongly depends on lubrication, surface quality and motion profile.
Contactless seals
Contactless seals operate without direct contact between the sealing surfaces. Sealing takes place via defined gaps or flow guidance.
Typical designs are:
- Labyrinth seals
- Gap seals
These seals are virtually wear-free, but they permit a defined leakage and are not suitable for all media.
Materials in Sealing Technology
Elastomeric sealing materials
Elastomers are the most frequently used materials in sealing technology. Their elasticity enables good adaptation to sealing surfaces.
Typical properties:
- Good recovery properties
- Broad range of applications
- Limited temperature and media resistance
- Ageing-dependent behaviour
The specific suitability depends strongly on the chemical composition of the elastomer.
Thermoplastic sealing materials
Thermoplastics are used when higher wear resistance or chemical resistance is required.
Typical properties:
- Good dimensional accuracy
- Low friction
- High media resistance
- Low elasticity
Thermoplastics are often combined with elastic preload elements.
Fibre and composite materials
Fibre-based materials are mainly used in flange gaskets.
Typical properties:
- Good temperature resistance
- Adaptability to flange surfaces
- Limited recovery capability
The selection depends on pressure, temperature and medium.
Design of Sealing Technology
Influence of sealing geometry
The geometry of the seal determines the surface pressure and thus the sealing effect. Relevant parameters are:
- Seal cross-section
- Groove shape and groove volume
- Preload
Incorrect geometry can lead to failure even with suitable material.
Surfaces and tolerances
The surface roughness of the sealing surfaces directly affects sealing. Too rough surfaces increase leakage, too smooth surfaces can impair lubrication.
Dimensional and form tolerances are also decisive for the function of the seal.
Applications and Fields of Use
Sealing technology is relevant in almost all industrial sectors:
- Machinery and plant engineering
- Automotive and commercial vehicle technology
- Chemical and petrochemical industry
- Power generation
- Electrical engineering and electronics
- Medical technology
Requirements vary greatly depending on industry and application.
Differentiation from Related Technologies
Sealing technology differs from adhesive bonding, welding and potting. Seals enable detachable connections and maintenance access. Adhesive bonds or potting are usually not non-destructively releasable.
Limits of Sealing Technology
Sealing technology is subject to physical limits:
- Material ageing
- Wear under motion
- Temperature and pressure limits
- Media incompatibility
These limits must already be considered in the design.
GOBA Takeaway
Sealing technology is a safety- and function-relevant component of technical systems. The sealing effect results from the interaction of material, geometry, surfaces, operating conditions and assembly. There is no universal sealing solution.
Proper design of sealing technology is decisive for the reliability, service life and cost-effectiveness of machines and equipment.