ASME B16.11 is the standard covering ratings, dimensions, tolerances, marking and material requirements for forged fittings, both socket-welding and threaded. Custom-design forged fittings with special dimensions, threads, or counterbores may be made by agreement between the manufacturer and purchaser, provided they meet all other stipulations of this standard. Threaded fittings are available in pressure ratings Class 2000, 3000, and 6000; Socket welding fittings are available in pressure ratings Class 3000, 6000, and 9000. Generally, both fittings are available in sizes (NPS) from 1/8″ through 4″. ASME B16.11 socket-welding fittings can be furnished in product forms of 90° elbow, 45° elbow, cross, tee, coupling, half coupling, boss, cap, and couplet; while ASME B16.11 threaded fittings can be furnished in product forms of 90° elbow, 45° elbow, cross, tee, street elbow, coupling, boss, cap, couplet, plug and bushing.
The schedule of the pipe corresponding to each Class designation of ASME B16.11 fitting is shown in Table-1. The maximum and minimum design temperature and other service conditions shall be limited as provided by the applicable ASME Boiler and Pressure Vessel Code or ASME Code for the material of construction of the fitting. The fitting is suitable for the application if the wall thickness of the joining pipe equals or less than the ASME B36.10M schedule number or pipe wall designation correlated with the fitting in Table-1.
|Type of |
|SCH No.||Wall Designation|
ASME B16.11 forged fittings may be furnished with socket-welding ends, threaded ends, or a combination of the socket-welding end and threaded ends.
When assembling pipe with ASME B16.11 socket welding fitting, the pipe is inserted into the fitting before welding. Inside the socket-weld fitting is a collar that prevents the pipe from being inserted too deeply into the fitting. A short amount of pipe is lost when the socket-weld connections are made. Before the weld is made, the pipe fitter will back the pipe off the collar approximately 1/8″ to allow for heat expansion during the welding procedure. 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 central long axis.
The threaded end (TE) connection for joining pipe is generally referred to as screwed connection. With tapered grooves cut into the ends of a run of pipe, screwed fittings and screwed pipe can easily be assembled without welding or other permanent means of attachment. The ASME B16.11 threaded fittings will have threads that are either male or female in accordance with ASME B1.20.1. Male threads are cut into the outside of the fitting, while female threads are cut into the inside of the fitting. As threaded fittings are assembled with threaded pipes, a short length of pipe is drawn into the fitting. This connection is called a thread engagement.
ASME B16.11 forged fittings can be made of materials consisting of forgings, bar, seamless pipe, or seamless tubular products. These materials shall conform to the requirements for the WP seamless construction materials of ASTM specifications A234, A403, A420, A815, or B366, or ASTM forging specifications A105, A182, A350, B462, or B564. Tees, elbows, and crosses shall not be machined directly from bar stock. Both threaded and socket-welding fittings of ASME B16.11 are made in small sizes and have high pressure-temperature ratings. They are used primarily for high-pressure steam.
|ASME B16.11 Forged Fittings (SW & THD)|
|90° Elbow||45° Elbow||Cross|
The dimensions and masses for each type of ASME B16.11 forged fittings (both socket welding and threaded) can be viewed in Table-2. Minimum body wall thickness, socket wall average thickness and minimum thickness, and minimum socket depth of socket welding fittings are specified. The minimum body and end wall thickness of threaded fittings are specified. Internal threads and external threads shall be threaded with American National Standard Taper Pipe Threads in accordance with ASME B1.20.1. End collars of both socket welding and threaded fittings shall be such that they overlap the crotch area.