Flat seal
Flat gaskets usually belong to the static gaskets and are mainly installed in apparatus or pipeline construction as a sealing element between two flanges .
Working principle
The flat gasket is an auxiliary material in the flange connection. This is pressed into the connection after installation. A locally higher pressure must be generated in the sealing connection than the pressure of the fluid in the system. Pressing the seal serves the purpose of reducing the leakage to the specified technical tightness required for the application. The pressure is applied to the seal via the flange surfaces . The force that is required to generate the required surface pressure is usually achieved with screw connections; at low pressures to be sealed, clamp connections are also used.
Influences on the sealing connection
The flat gasket is usually the weakest component in the gasket connection. Because it is often made of softer, easier to deform materials than the flanges, which are made of steel or GRP. In order for the flat seal to fulfill its function, it and the influences acting on it can only be viewed in isolation from one another to a limited extent. The main factors affecting the flat gasket are pressure, the media to be sealed and the resulting chemical stresses, the temperature, but factors such as sudden temperature and pressure drops / increases that can lead to failure of the sealing connection due to the inertia of the flat gasket. The influences of the flange and screw connections, on the other hand, are the nature of the flanges (roughness, waviness), the geometry of the connection (round, oval, special shape, e.g. the surface of the gear housing), the material properties of the screws or the degree of wear.
Norms
- Series of standards DIN EN 1514 - Seals (dimensions) for flange connections according to DIN / EN
- Series of standards DIN EN 12560 seals (dimensions) for flange connections according to ANSI / ASME B16.5
Types of flat gaskets and materials
- Paper or cardboard flat seals
- Flat gaskets based on plastics
- Silicone gasket
- Flat rubber seals ( ethylene propylene diene rubber , acrylonitrile butadiene rubber , fluororubber )
- Polytetrafluoroethylene flat seals
- High temperature plastics (PEEK, PAI, PEI)
- Fiber seal (matrix: carbon fiber , mineral fiber, aramid fiber, filler elastomer )
- Graphite flat seals
- High temperature seals ( mica group )
- Corrugated ring seals (body: metal, pads: graphite or other soft material)
- Comb profile seals (body: metal, pads: graphite or other soft material)
- Spiral seals (base body: winding made of metal and soft materials such as graphite or PTFE, chambers: metal rings)
- flat metal sealing rings
- Asbestos. In the case of older flat gaskets, it is expected that they consist of weakly bound asbestos, which is why such gaskets fall within the scope of the Hazardous Substances Ordinance , TRGS 519 and the Asbestos Directive and may only be dismantled by experts. Remounting of undamaged asbestos-containing flat gaskets is prohibited.
Fiber gaskets and PTFE flat gaskets are sometimes reinforced by means of metal inserts in the case of high mechanical loads. The materials listed are only an extract from the possible range of base materials.
Covered flat seals
Sheathed flat gaskets consist of a core (any flat gasket material, usually fiber gasket), which is covered by a PTFE or metal shell (steel or corrosion-resistant nickel alloys). The shell can completely or only partially enclose the flat seal. The sheathing protects the core against chemical attack from the medium to be sealed. The core itself has a supporting function that gives way due to the contact pressure. The required contact pressure must be selected higher than with a simple flat gasket without a cover, stable flanges are a prerequisite for achieving this. A particular example of a (partially) encased flat gasket is the cylinder head gasket in automotive engineering .
Web links
- Overview of static seals in the points: Flange seals: Basics - fachwissen-dichtungstechnik.de and [fachwissen-dichtungstechnik.de designs - fachwissen-dichtungstechnik.de] and static seals special designs - fachwissen-dichtungstechnik.de .
- Summary and comparison of the individual flange calculation methods - flangevalid.com
- Guide to the assembly of flange connections in process engineering systems - vci.de Practical recommendations for the professional assembly and storage of flat gaskets
- Approvals in sealing technology - industrietechnik-schneider.de approvals represent the requirements of individual industrial sectors for a flat seal when installed
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Database gasket parameters according to EN 13555 for flat gaskets - gasketdata.org Detailed definition of the parameters and
- Basic course in sealing technology - ima.uni-stuttgart.de from the IMA of the University of Stuttgart , p. 5 Table 2.1 illustrates the relationship between individual parameters of different standards
Individual evidence
- ↑ a b Alexander Riedl: Handbuch Dichtungspraxis . 4th edition. Vulkan Verlag, Essen 2018, ISBN 978-3-8027-2214-1 , p. 520 and X .
- ^ Industrietechnik Frank Schneider GmbH: Static seals. P. 2 , accessed on November 19, 2019 (factors influencing sealing connection Fig. 3).
- ↑ a b Heinz K. Müller and Bernard S. Nau: Flange seals: types of construction - calculation. P. 7 and 8 , accessed on November 19, 2019 (information on metal inserts on p. 7, information on encased flat gaskets on p. 8).