What are the differences between socket welding and butt welding pipe fittings

There are various ways for pipes,fittings,flanges and valves to connect,socket welding and butt welding are the two popular.However,you might be confused about what are the differences between socket welding and butt welding pipe fittings,and which one would be best for your construction projects,as they all seem to have their own pros and cons.

ASTM A182 F316L Socket Weld Couplings

What is socket welding?

Socket welding(SW) is the welding method of pipeline insertion.It is welded two different sized pieces of pipe,the smaller one is inserted into the large one.The weld is completely in the periphery of the large pipe and it is fillet weld.Socket welding components contain socket weld flanges and socket weld pipe fittings(contain socket weld 45/90 degree elbows,socket weld tees,socket weld caps,socket weld cross,socket weld coupling,socket weld union,sockolet).

Socket weld drawing

Socket weld pipe fittings are defined in ASME B16.11 standard,they are high pressure pipe fittings and available in three pressure ratings:class 3000,class 6000 and class 9000.Socket weld flanges can be manufactured according to different standards such as ANSI/ASME B16.5,JIS B2220.

What is butt welding?

Butt welding is the corresponding welding of pipe fittings and pipe fittings,pipe fittings and flanges or pipe fittings and pipes whose diameters are the same.The end of butt weld pipe fittings shall be beveled.Butt welding components contain weld neck flanges and butt welding pipe fittings(contain butt welding 45/90/180 degree elbow,butt welding tee,butt welding cap,butt welding bend,butt welding cross,butt welding reducer,weldolet).

Butt weld drawing

Butt welding pipe fittings can be manufactured according to different standards such as ANSI/ASME B16.9,ANSI/ASME B16.28,DIN EN 10253,GOST 17375-17380,JIS B2311-B2313,KS B1522,KS B1541,KS B1543,MSS SP-43,MSS SP-75,GB/T 12459,GB/T 13401,SH/T 3408,HGJ528,SY/T0510.Weld neck flanges according to standards ANSI/ASME B16.5,ANSI/ASME B16.47,JIS B2220,EN 1092-1,GOST 12821-80.

Differences between socket welding and butt welding pipe fittings:

Different diameters of socket welding and butt welding pipe fittings:

Socket weld is generally used for welding pipes,which are small diameter.The commonly used specifications are diameter smaller than DN50,and the greatest diameter is DN100(or 4″).Butt weld is widely used for pipes with big and small diameters.

Different welding groove and welding seam of socket welding and butt welding pipe fittings:

Usually,there should be a beveled end from 30 to 37.5° for butt welding in order to fill the welding bead.Of course,there will be a compound beveled end for super thick walls.

Socket welding doesn’t require a bevel,and it can directly weld the part.The socket weld seams are fillet welds.

Considering the factor of the strength of the weld,the force condition and so on,the butt welding is better than the socket welding.

ASME B16.9 ASTM A403 WP304L equal tees

Different non-destructive testing of socket welding and butt welding pipe fittings:

The non-destructive testing methods for socket welding are magnetic particle testing(MT) and penetrant testing(PT).Magnetic particle testing is used for carbon steel parts and penetrant testing is used for stainless steel parts.Generally speaking,butt welding requirements are higher than socket welding requirements as well as the testing requirements.The butt welding shall be 100% tested to ensure no leakage and it is necessary to do radiographic inspection.

Butt Weld Elbow Tee Flange Steel Pipe

Different price of socket welding and butt welding pipe fittings:

Normally,the price of socket weld fittings is higher than butt weld fittings in similar size,butt welding fitting need extra more cost because it would also be more difficult to weld and fit-up properly.This would then require more time and the expertise of skilled welders.

Socket weld is easy to install.But it requires approx 1/16″of gap at the bottom of the pipe to socket into,to allow thermal expansion.This gap can lead to over stress problem that cracks the fillet weld of the fitting.Socket weld is troublesome in corrosive fluid service due to crevice corrosion.And it is easy to corrode due to the discontinuity of the smooth pipe internals.

Butt weld is the “best” in terms of strength,fatigue,corrosion resistance and temperatures compliance.However,it is more difficult to fit-up and weld properly,needing skilled welder and much time.

Socket Weld Flange Tee Elbow Union


In conclusion,both the pressure level as well as cost of the socket welding is higher than of butt welding.When the welding technology is required and fully meets the construction requirements, butt welding is an alternative choice.If the medium of the pipeline has no requirements for welding,it is recommended to use socket welding, just easy for detection.The disadvantage of a Socket Weld system is right the expansion gap and the space between the OD of the pipe and the ID of the fitting.By corrosive products, and mainly in stainless steel pipe systems, the crack between pipe and flange, fitting or Valve can give corrosion problems. In service applications, where complete weld penetration to the inside of the piping is required,socket welds are not acceptable, and generally butt welds must be made.

Haihao Group manufacture & supply & export socket weld pipe fittings,butt weld pipe fittings,threaded pipe fittings,forged flanges(such as weld neck flange,socket weld flange,blind flange,slip on flange,lap joint flange,etc) in different materials such as carbon steel,stainless steel,alloy steel.If you want to know more about our pipeline products,please email us:sales@haihaogroup.com

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