This image was created with artificial intelligence – marked under Art. 50 of the AI Act, Regulation (EU) 2024/1689. It is a placeholder until the company's photos arrive.Selecting seals for gas and pressure lines
Which gasket for gas and pressure lines? Materials, pressure ranges, standards and selection guide for safe applications.
Seals in gas and pressure lines perform a safety-critical function. Even the smallest leaks affect processes, lead to energy losses and increase the load on adjacent components. In industrial applications, this quickly results in follow-up costs, downtime or safety risks.
Selecting the right seal therefore requires a systematic consideration of all influencing factors. In addition to pressure and temperature, the medium used, the mechanical load and normative requirements play a central role. A technically sound design ensures stable processes, reduces maintenance effort and increases the service life of the entire system.
Requirements for seals in gas and pressure lines
In gas and pressure systems, several load factors act on the seal at the same time:
- high or fluctuating pressure
- temperature load
- chemical influences from gases or media
- mechanical stress from movement or vibration
A suitable seal must compensate for these factors permanently and fulfil its function reliably over a long period.
Key selection criteria
A suitable seal is always selected through the interaction of several parameters. Individual factors can be assessed in isolation, but in practice they act on the material simultaneously. The decisive factor is therefore the combination of pressure, temperature, medium and design requirements, which together determine the suitability of a seal.
Pressure
The operating pressure largely determines the material choice and design of the seal. As pressure rises, the mechanical requirements increase significantly, as the seal is permanently exposed to forces that can lead to deformation or extrusion. Pressure peaks are particularly critical, as they occur briefly and often lie above the actual operating pressure.
Materials must therefore have sufficient dimensional stability and low compressibility in order to retain their sealing effect even under load. At the same time, the installation situation plays a role, as the pressure influences the distribution of forces within the seal.
Typical classification:
| Pressure range | Requirements for the seal |
|---|---|
| Low pressure | flexible elastomers sufficient |
| Medium pressure | dimensionally stable elastomers or composite solutions |
| High pressure | PTFE or special high-performance materials |
Temperature
Temperature fluctuations directly influence the material properties of a seal. At low temperatures, embrittlement can occur, while high temperatures reduce elasticity and accelerate the ageing process. In addition, temperature changes act like a load cycle that permanently stresses the material.
Materials must therefore be selected so that they retain their function at both minimum and maximum temperatures. In addition to continuous load, short-term temperature peaks also play a role, as they occur in many applications and are often underestimated.
Medium
The medium used is one of the most important influencing factors in selection. Gases and other media react differently with sealing materials and, depending on their composition, can lead to swelling, embrittlement or chemical degradation.
In addition to pure resistance, the permeation of gases through the material is also relevant, particularly in applications with high pressures or critical gases. Precise matching between medium and material ensures that the seal fulfils its function in the long term.
Design
The design of the seal results from the design layout of the system and significantly influences the sealing effect. Different geometries lead to different force distributions and abilities to adapt to the sealing surfaces.
While O-rings are used primarily in dynamic and compact applications, flat gaskets are suitable for large-area sealing. Profile seals and customised cut pieces are used when there are special requirements for pressure distribution or the installation situation.
Choosing the right design ensures that forces are absorbed optimally and the seal works reliably in the long term.
Decision logic: Which seal fits when?
In practice, selection can be greatly simplified if typical application combinations and limit ranges are taken into account:
- over 100 bar pressure → PTFE or high-performance materials
- up to approx. 100 bar with oil-containing media → NBR
- over 150 °C → FKM or PTFE
- aggressive chemical media → FKM or PTFE
- water, steam and outdoor areas → EPDM
This classification enables a quick pre-selection. For a safe design, however, all parameters must always be assessed together.
Step by step: Selecting the right seal
Selection is ideally carried out in a clear sequence. First, the medium is defined, as it strongly restricts the material choice. Then the maximum operating pressure is considered, including possible pressure peaks, in order to ensure mechanical load capacity. This is followed by consideration of temperature, in which both continuous load and short-term peaks must be taken into account. In the next step, the design is determined based on the installation situation, before standards, approvals and tolerances are finally checked.
This structured approach significantly reduces incorrect decisions and leads to a technically sound solution.
Materials compared
Choosing the right material is the central factor for service life and safety. Further details on the individual materials can be found under:
| Material | Properties | Temperature range | Pressure suitability | Typical areas of application |
|---|---|---|---|---|
| NBR | good oil resistance, economical | -30 to +100 °C | medium | standard applications, hydraulics |
| EPDM | very good resistance to weathering and steam | -40 to +150 °C | medium | water, steam, outdoor areas |
| FKM | high temperature and chemical resistance | -20 to +200 °C | high | aggressive media, high temperatures |
| PTFE | almost universal resistance, very pressure-resistant | -200 to +260 °C | very high | high pressure, aggressive gases |
Important: The material choice must always be matched to the specific gas and the operating conditions.
Selecting seals by type of gas
Different gases place different requirements on the sealing material:
- natural gas → often NBR or special approved elastomers
- oxygen → high purity and special material approvals required
- compressed air → wide material selection, depending on pressure and temperature
- technical gases → usually FKM or PTFE for demanding applications
The exact selection always depends on the pressure level and operating conditions.
Standards and approvals
Strict requirements apply to gas and pressure lines. Relevant standards and approvals ensure the suitability of the seals:
- DVGW approval for gas applications
- DIN standards for industrial applications
- specific industry requirements depending on the area of application
Installation and assembly
In addition to the material choice, the installation situation significantly influences the sealing effect.
Important factors:
- even contact pressure
- clean and level sealing surfaces
- correct dimensioning of the seal
- avoidance of stress
Errors in assembly frequently lead to leaks, even with a suitable material.
Typical errors in selection
In practice, recurring problems occur:
- wrong material choice without consideration of the medium
- underestimation of temperature or pressure peaks
- use of unsuitable standard seals
- failure to check standards and approvals
These errors lead to premature wear or failures.
Static and dynamic sealing
In gas and pressure lines, the distinction is relevant:
- static sealing: no movement between the components
- dynamic sealing: movement or pressure changes present
Dynamic applications require significantly higher demands on material and design.
Service life and maintenance
The service life of a seal is largely determined by correct design. Material, installation situation and operating conditions interact permanently and influence ageing, deformation and sealing effect. Continuous pressure loads and short-term pressure peaks stress the structure just as much as thermal influences over the entire period of use. At the same time, chemical interactions with the medium and mechanical loads from movement or vibration lead to a gradual change in material properties.
A technically suitable seal significantly reduces these effects and ensures stable operating times. In addition, a clearly defined maintenance strategy increases operational safety by regularly checking critical sealing points, sensibly planning replacement intervals and detecting material changes at an early stage. Predictive maintenance extends the service life of the system and reduces unplanned failures.
Dimensional accuracy and tolerances
The exact manufacture of the seal directly influences its function. Deviations in thickness or geometry lead to uneven load and reduce the sealing effect. Even small tolerance deviations change the force distribution within the seal and can lead to local leaks or increased wear.
Precisely manufactured cut pieces ensure even force transmission across the entire sealing surface. At the same time, tolerances must match the respective installation situation so that the seal can adapt optimally under pressure. Material thickness also plays a central role, as it is directly related to the pressure range and mechanical load. Dimensionally accurate seals significantly increase process reliability and contribute to constant sealing performance over the entire period of use.
Typical areas of application
- industrial gas lines
- mechanical engineering
- energy supply
- chemical industry
Each area places its own requirements on the seal.
Practical examples
Typical scenarios from practice show the effects of the wrong choice:
- wrong material → seal swells and loses its function
- insufficient temperature resistance → embrittlement and leakage
- inaccurate dimensions → uneven sealing and premature wear
These examples illustrate the importance of precise design.
In conclusion
Selecting seals for gas and pressure lines requires a structured technical assessment of all influencing variables. Pressure, temperature, medium and material interact directly and together determine the performance of the seal.
A well-founded selection leads to stable processes, predictable maintenance cycles and significantly higher operational safety. At the same time, the risk of leaks, material failure and unplanned downtime is reduced.
In the industrial environment, it becomes clear that a precisely matched seal selection creates long-term economic advantages, as follow-up costs from failures, maintenance and replacement fall significantly.
Have your application checked
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FAQ
Which seal is suitable for gas lines?
The selection depends on the gas, the pressure and the temperature. FKM or PTFE are often used when requirements are high.
What role does pressure play in selection?
Pressure influences the material choice and the design. Higher pressures require dimensionally stable and resistant materials.
Why is chemical resistance important?
Gases react differently with materials. An unsuitable seal can swell or become brittle.
When is PTFE used?
PTFE is particularly suitable for high pressures and aggressive media due to its almost universal resistance.
Which errors occur frequently?
Typical errors are the wrong material choice, failure to take temperature and pressure into account, and the use of unsuitable standard solutions.
Which seal is suitable for high pressure?
For high-pressure applications, PTFE or specially reinforced materials are usually used, as these offer high dimensional stability.
Which seal is suitable for natural gas?
For natural gas, NBR-based seals with the appropriate approval are frequently used.
What is the difference between FKM and PTFE?
FKM is an elastomeric material with high flexibility, while PTFE offers very high chemical resistance and pressure resistance.
How long does a seal last?
The service life depends heavily on the operating conditions and material and ranges from a few months to several years.
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