Introduction to ASME B16.11 Socket welded pipe fittings

Socket welding is a kind of pipe connection in which the pipe is inserted into the wall of the valve, pipe fitting or flange. In contrast to butt welding, socket welding is usually used for small diameter pipes of 2 inches and less.

Socket welding adopts fillet weld. When high structural strength requirements and high leakage risk become design considerations, socket welding welded joints are a better choice.

The fatigue strength of the socket welded joint is lower than that of the butt welded joint, because of the use of fillet welds and abrupt changes in geometry. However, socket welds are still superior to other mechanical joints.

Socket welded pipe fittings are a group of high-pressure pipe fittings used in various industrial production processes. Its characteristics are:

1) For conveying non-leaking flammable media, toxic or expensive media and 300PSI to 600PSI steam.

2) Only connected with ASME pipe, same caliber.

3) It is used for permanent work of pipelines and provides better flow characteristics.

4) Its material is ASTM material, and its manufacturing standard is ASME B16.11. B16.11 includes pressure-temperature ratings, dimensions, tolerances, marking and material requirements for carbon, stainless and alloy steels. The optional material forms are forgings, round rods and seamless tubes. Commonly used materials are ASTM A105, A182, or A350.

5) Socket welded pipe fittings have three pressure grades: CLASS3000, 6000 and 9000.

Type, pressure grade, size range and pipe wall thickness grade of socket welding fittings

Type of pipe fitting	Pressure grade
	3000	6000	9000
45°&90°Socket welding elbow	1/8--4	1/8--2	1/2--2
Socket welding tee, Cross and coupling	1/8--4	1/8--2	1/2--2
Half coupling	1/8--4	1/8--2	1/2--2
Cap	1/8--4	1/8--2	1/2--2
Suitable pipe wall thickness class	Sch80， XS	Sch160	XXS

Advantages of socket welded pipe fittings

1) The pipe does not need to be prefabricated groove.

2) It is not necessary to calibrate spot welding, because the pipe itself plays a calibration role.

3) The welding material will not penetrate into the pipe hole.

4) Can replace threaded pipe fittings, thus reducing the risk of leakage.

5) Fillet welds are not suitable for X-ray inspection, so correct pipe fitting and welding is very critical. Fillet welds are often inspected by magnetic particle inspection and penetration inspection.

6) Construction costs are usually lower than butt welded joints. The reason is that there is no need for groove alignment and groove prefabrication.

Shortcomings of socket welded fittings

1) The welder shall ensure the welding expansion gap of 1.6mm on the shoulder of the pipe and socket when welding.

2) The presence of cracks inside the welding gap and socket weld reduces the corrosion resistance or radiation resistance of the pipeline. When solid particles accumulate at the socket welding joint, it may cause faults in pipeline operation and maintenance. In this case, a fully welded butt weld is usually required for the entire pipe.

3) Socket welding is not suitable for ultra-high pressure food industry. Because it is not completely welded through, leaving overlap and cracks, difficult to clean, forming false leakage.

Our team at Hebei Zhongyan Pipeline Co., Ltd. is well trained and has extensive experience in maintaining and producing various types of steel. Whether you have a large construction project or need industrial machinery parts, our team of steel manufacturing consultants will ensure that your project has the parts you need, when you need them.