Gasket and bolt used with flange

Gasket and bolt are commonly used with flange,to protect the flange in the pipeline.


Gasket is especially important for the leakproofness of flange joint.

The gasket is a compressible plate or ring used for sealing between two surfaces. Gasket materials are widely used to adapt to various extreme pressures and temperatures, including: metallic materials, semi-metallic materials and non-metallic materials.

Metallic gaskets

Metallic gaskets

The basic principle of sealing is that the gasket is pressed between two flanges, and the gasket fills the tiny gap and irregular shape of the flange sealing surface to form a seal and keep the pipeline liquid and gas. Correct installation method and gasket damage are important requirements to prevent flange joint leakage.

Common flange gasket standards include: ASME b16.20 metal and semi-metal gasket for pipe flange, and ASME b16.21 non-metal flat gasket for pipe flange.

Zinc plating of bolts and nuts

Zinc plating of bolts and nuts


The bolts connect the two flanges together. The number of bolts is the number of bolt holes on the flange. The diameter and length of the bolts are determined by the type and pressure rating of the flange.

For ASME B16.5 flange, the most commonly used bolt in petrochemical field is stud. The studs are made of threaded studs with two nuts. Other available bolts are hexagon head bolts. This website only discusses studs (because they are the most widely used).

The size and dimensional tolerance of bolts are specified by ASME B16.5 and ASME 18.2.2, and the material is specified by different ASTM standards.