What’s the difference between butt welding and flat welding in stainless steel flanges?

The difference between the flat welding and the butt welding of the stainless steel flange refers to the two welding methods when the flange is connected with the stainless steel pipe. The flat welding flange welds only one side, without welding the inner mouth of the welded stainless steel pipe and flange. The welding and installation of the welding flange requires double side welding of the flange.

Large caliber flat flanges used for wind power industry

Large caliber flat flanges used for wind power industry

Therefore, flat welding stainless steel flanges are usually used in low and medium pressure pipes, and the welding flanges are mostly used in middle and high pressure pipes. The welding flanges are usually at least PN2.5MPa. The use of butt welding is to reduce the stress concentration, and the common butt flange is mostly with the neck flange. Therefore, the installation cost, labor cost and auxiliary material cost of welding flange are higher, because there is more than one working procedure.

Welding flanges are not all inside and outside welding, no special requirements are usually only outside welding, welding flanges welding is easier, because the stainless steel pipe and flange good vertical, pipe will not tilt.

Stainless steel SS316 weld neck flanges and slip on flanges

Stainless steel SS316 weld neck flanges and slip on flanges

But flat welding flange and socket welding flange are different, socket welding flange is suitable for small diameter, high pressure and high temperature pipeline connection mode.

The flat welding flange has a step sealing surface to compress the sealing gasket, and then the stainless steel tube is inserted to weld inside. Socket welding is no boss, directly on the flange body to open a groove, similar to the blind flange opened a hole, then open a groove.
The welding performance of flat welding is better than that of socket welding. Usually flat welding stainless steel flanges are used in many places, basically all can be used.

It is best to use butt welding flanges for pressure above 4.0MPa and inflammable and explosive toxic media. Plain welding flange is used in common occasions. Socket welding flanges are usually not suitable for high pressure applications because they are not available. If you do penetrant flaw detection, you can’t do it.

Butt welding flanges and flat welding flanges are the two most commonly used flanges, butt welding flanges are necked, while flat welding flanges are not. If it is best to use the butt welding from the safety point of view, if it is the ordinary medium, its pressure is not high, and the leakage will not lead to the use of flanges when it is not dangerous.