Common Specifications of Flange Bolts

Flange bolts are core fasteners for pipeline flange connections.Their specifications are formulated according to national standards,pressure ratings,flange sizes and working conditions.A variety of standard sizes are widely used in industrial piping,chemical engineering,water treatment and high-temperature&high-pressure systems.

First,in terms of common thread standards,metric flange bolts are the most popular,including M10,M12,M14,M16,M20,M24,M27 and M30.Among them,M16,M20 and M24 are the most mainstream sizes for conventional pipe flanges.For large-diameter flanges and high-pressure vessels,larger specifications such as M33,M36 and M42 are commonly adopted to ensure connection strength.

Second,regarding length selection,flange bolt lengths are customized based on flange thickness,gasket thickness,nut and washer size.Conventional common lengths range from 40mm to 150mm.Short bolts are used for thin standard flanges,while longer bolts are applied to thickened flanges,high-temperature insulation structures and heavy-duty equipment connections.

In terms of strength grades,matching grades are selected for different working conditions.Ordinary low-pressure flanges usually use 4.8 and 8.8 grade carbon steel bolts.For high-pressure,high-temperature and corrosive pipeline flanges,10.9 grade high-strength bolts and stainless steel bolts are the mainstream choices to improve tensile resistance and sealing stability.

Besides,flange bolts follow international common standards,including GB,ANSI,DIN and ISO.American standard flange bolts mostly adopt inch sizes,while metric sizes are dominant in domestic and most Asian engineering projects.Different pressure levels such as PN10,PN16,PN25 and PN40 correspond to matched bolt quantities and specification requirements.

In conclusion,M16,M20,M24 are the daily conventional specifications for flange bolts.Reasonable matching of thread diameter,length,strength grade and standard is essential to ensure safe,tight and leak-free flange connection.