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General knowledge of ASME B16.11

General knowledge of ASME B16.11

ASME B16.11 is a standard for the forged steel fittings of pipeline, in which cover all details like pressure ratings, dimensions, tolerances, marking and material requirements for socket weld and threaded fitting only. But for special requirements of forged fittings with special dimensions, threads, or counter bores may be made by agreement between the manufacturer and user, provided they meet all other stipulations of this standard.

Note, ASME B16.11 is monitored, regulated, or may be revised by the American Society of Mechanical Engineers only, and they are owners of ASME standard. This article is only for share knowledge to beginners only. I f any body want to read full standard Kindly visit

Under this standard threaded end fittings are available in pressure ratings Class 2000, 3000, and 6000 and Socket weld end type fittings are available in pressure ratings Class 3000, 6000, and 9000.


In some places pressure  rating classes are interchangeably used as the designation 2M, 3M, 6M or 9M, where M is 1000. Generally, pressure ratings Class 2000 is not available for socket weld. The sizes for under this standard are available in sizes (NPS) from 1/8″ through 4″.  Under B16.11 socket-welding fittings are available with 90° elbow,  45° elbow, cross, tee, coupling, half coupling, boss, cap, and couplet. while threaded fittings can be furnished in product forms of 90° elbow, 45° elbow, cross, tee, street elbow, coupling, boss, cap, couplet, plug and bushing.

Note – This is general note socket weld and threaded fitting are mostly used for up to 1.5” bore size. Under this standard forged fittings may be furnished with socket-welding ends connection type, threaded ends  connection type, or a combination of both like the socket-welding end and threaded ends.

For welding the asme b16.11 fitting with pipe, both of the walls thickness should be match (same) or mismatch (difference) of walls thickness should not be more than 2mm ( this is a thumb rule for minimum losses as considered during designing) of the system. This value can be varied as per application.  

What is the welding process of ASMEB16.11 socket weld fitting?

Welding process of ASMEB16.11 socket weld fitting 

During the assembling (Welding) of pipe with ASME B16.11 socket welding fitting, first of all the pipe will insert into the fitting before welding (for this type of fitting id id slightly bigger than the pipe OD which needs to be connected). Inside the socket-weld fitting is a collar that prevents the pipe from being inserted too deeply into the fitting (the inside color raise wall thickness is equal to pipe thickness and fitting ID and pipe ID dimension ). A short amount of pipe (which is insert in to fitting) is lost when the socket-weld connections are made. Before the weld the pipe and fitting, the fitter will back the pipe off the collar approximately 1/8″ to allow for heat expansion during the welding. Pipe used for socket-weld connections will be prepared with a plain end. Plain end (PE) means the pipe is cut square, or perpendicular to the pipe OD.

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