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Gasket is compressible or combination of material which when clamped between two stationary members to prevents the passage of media across those members under compression. Gaskets fills in irregularities of less-than-perfect mating surfaces, also they are resilient to resist extrusion and creep under operating condition. The function of gasket is to prevent escape ingress of fluid under extreme pressure and temperature.

Properties & Material

Gaskets are made in sheets from a mixture of various fiber, rubber and filler material. Since, asbestos based gaskets are restricted to use at many places, Non asbestos gaskets are used wherever possible.

A gasket should have following characteristics

• Chemical resistance.
• Temperature resistance
• Pressure with stand capacity
• Minimum sealing stress
• Cheaper

Since it is not possible to have all properties in single gasket so gaskets are combined with other material, reinforced with wire mesh, or combination with other material or density to come up the limitations.

Factors influencing gasket performance

• Temperature of the media
• Pressure of the media
• Corrosive nature of the media
• Application details
• Flange configuration

Gaskets have to withstand high compressive loads exerted by bolt tightening in industrial application, so the vital characteristic of any gasket is to with stand high compressive loads.

Hot Compression test is one of the most accepted and accurate test to ascertain the behavior of gasket at different conditions.

Hot Compression Test

The test is carried out at both ambient temperature and elevated temperature. Gasket is compressed between two surfaces with the helpof hydraulic press, and the load is kept constant throughout the test. Over the period of 30 min. the temperature of the two surfaces is gradually raised. Any decrease in the thickness of gaskets is measured and tabulated. This test helps in selection of gasket or to ascertain behavior of gasket when subject to surface stress in hot& cold condition.

Why is Gasket Necessary!

Though the function of gasket is for sealing of joints, there are similar devises which can function better in some task. Gasket is needed for application requiring seal between external and internal elements. Eg. unit to avoid water leakage.

Shim or spacers are used to fill in gaps between components. Shims are narrow wedge used for leveling and packing purposes.

O rings are similar to gasket but are different. They are generally made of polymer based plastic or synthetic rubber and are available in ring forms only, with round and square cross section.They form barrier around area of matched components with leakage potential. They more durable, reliable, having high pressure resistance, where standard gaskets are not suitable.