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Gasket

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A gasket is a mechanical seal used to join two or more mating surfaces together.

gaskets
gaskets

Its primary purpose is to prevent leakage from or into the objects being joined. This is critical in mechanical assemblies where fluids or gases must be contained. Gaskets are made from deformable materials, meaning they can change shape under pressure. This ability allows them to fill irregularities or "less-than-perfect" surfaces on machine parts. By filling these tiny gaps, the gasket creates a reliable, static seal.

Compressed fiber jointing
Compressed fiber jointing

The mechanism of a gasket relies heavily on compression. When parts are joined, bolts typically exert a force that squeezes the gasket material. This compressive load forces the material to yield and flow into the spaces between the surfaces. In many industrial applications, this load can reach 14 MPa (2000 psi) or even higher. A common rule in engineering is that a higher compressive load often helps a gasket last longer. To ensure quality, manufacturers often use a "hot compression test" to measure how well a material withstands these loads.

PTFEseet
PTFEseet

Gaskets are categorized by their design and the materials used to build them. Sheet gaskets are common and fast to produce by punching shapes out of flat materials. These can be made from rubber, silicone, cork, or even matted graphite. Some sheet gaskets are used to handle corrosive chemicals, acids, or steam. Solid material gaskets are another type, often made of metal. These are used when much higher temperatures and pressures are required. However, the metal used must be softer than the flange it seals to prevent warping the machine parts.

Used copper flange gaskets for ultrahigh vacuum systems
Used copper flange gaskets for ultrahigh vacuum systems

More complex designs combine different materials to achieve specific goals. Spiral-wound gaskets, invented by Flexitallic in 1912, use a mix of metal and filler.

Asbesthaltige Flachdichtungen
Asbesthaltige Flachdichtungen

In these, a metal strip and a filler like flexible graphite are wound in alternating layers. The metal provides structural support, while the filler acts as the sealing element. Another advanced design is the constant seating stress gasket. This uses a solid carrier ring to ensure the sealing stress remains uniform across the entire area. This design helps prevent failure caused by vibration or thermal cycles.

Other specialized designs include double-jacketed and Kammprofile gaskets. Double-jacketed gaskets consist of a metal shell with a filler material pumped inside. Kammprofile gaskets, which resemble the profile of a camshaft, feature a solid grooved core with a soft covering. These allow for very high compression without damaging the gasket itself. More recently, fishbone gaskets have been developed using CNC machining. These are designed to replace older spiral-wound or Kammprofile styles. They include a "Stop Step" to prevent the gasket from being over-compressed during installation.

Material selection is a vital part of gasket engineering due to safety and cost. In the past, gaskets for high-pressure steam often contained asbestos. Because asbestos exposure poses significant health hazards, modern engineers use non-asbestos materials whenever practical. Today, a wide variety of synthetic materials are used, such as EPDM, Nitrile, and Neoprene. Some gaskets also use PTFE, which is a plastic commonly known as Teflon. Choosing the wrong material can lead to process contamination, oxidation, or dangerous leaks.

In large-scale piping, engineers often use flange gaskets. These are designed to fit between two sections of pipe that have been flared. Flange gaskets are divided into categories like ring gaskets, also known as RTJ (Ring Type Joints). These are frequently used in offshore oil and gas pipelines because they handle extreme pressure. They are shaped as solid metal rings in forms like oval or octagonal cross-sections. Whether they are simple rubber sheets or complex metal rings, gaskets are essential for maintaining the integrity of mechanical systems.

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File:gaskets.jpg
gaskets.jpg
File:PTFEseet.JPG
PTFEseet.JPG
File:Compressed fiber jointing.JPG
Compressed fiber jointing.JPG
File:Asbesthaltige Flachdichtungen.jpg
Asbesthaltige Flachdichtungen.jpg
File:Used copper flange gaskets for ultrahigh vacuum systems.jpg
Used copper flange gaskets for ultrahigh...
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