Butt weld pipe fittings

Butt-welded pipe fittings usually refer to components that connect the ends of pipes and pipe fittings through butt welding. Their ends are beveled or flat, and the weld seam is fully penetrated after beveling on the end face, which can form a firm, reliable and non-permeable connection. Butt-welded pipe fittings are a type of pipe fittings made of welded pipes of relatively high quality, mainly made of carbon steel, stainless steel and alloy steel.

Classification of welded pipe fittings
The commonly used butt-welded pipe fittings can mainly be classified into elbows, tees, reducers, pipe caps, crosses, etc.

Butt-welded elbow
The main function of the butt-welded elbow is to change the flow direction of the fluid in the pipeline system. According to the difference in size, it can be divided into long radius elbows (LR = 1.5D) and short radius elbows (SR = 1.0D). According to the manufacturing method, it can be further classified into pushed elbows, extruded elbows and welded diagonal elbows, with Angle ranges of 45°, 90° and 180°.

Butt-weld tee
Butt-weld tees can provide a connection point, facilitating the welding of other equipment onto the pipeline. According to the different diameters, they can be classified into equal diameter tees and reduced diameter tees. The 90° branch diameter of the reduced diameter tee is smaller than that of the straight pipe, allowing for the installation of smaller-sized pipes or pipe fittings.

Butt-welded reducer
Butt-welded reducers can regulate the flow and speed of fluids. One end is used to connect large-diameter pipes, and the other end is used to connect small-diameter pipes. It can mainly be divided into two types: concentric and eccentric.

Common standards

The most commonly used standard for butt-weld pipe fittings is ASME B16.9, which is applicable to the manufacture of metal butt-weld pipe fittings in factories ranging from NPS ½ "to NPS 48" (DN 15 - DN 1200), specifying the total dimensions, thickness tolerances, test methods and marking, etc. Other standards include EN, DIN, JIS, GOST, MSS, Different types of butt-welded steel pipes have different standard numbers, such as ASME B16.5 pipe flanges and flange fittings, MSS SP-43 forged stainless steel butt-welded pipe fittings, MSS SP-83 socket welding and threaded union joints, etc.

Common materials for welded pipe fittings

The type of material is usually consistent with the requirements of the pipeline to ensure the mechanical properties, corrosion resistance and thermal expansion consistency of the welded pipe fittings. Common materials include:

Carbon steel/low alloy steel: such as ASTM A234 WPB/WPC, A420 WPL6, etc.
Stainless steel and duplex steel: such as ASTM A403, WP304/316 or A815, etc.
Nickel-based alloys: such as Hastelloy, Inconel, Monel, Alloy 20, etc., are used in high-temperature and highly corrosive environments.
Other metals: such as aluminium alloy (ASTM B361), titanium alloy (ASTM B363), depending on the specific application requirements.

The size range of the welded pipe fittings

The dimensions of butt-welded pipe fittings are based on the pipe size standards ANSI B36.10 and B36.19.
Nominal size (NPS or DN) range: The common range is NPS ½ "to 48" (DN 15-1200), with a maximum of 72 ".
Wall thickness (Schedule) : According to ANSI B36.10 / B36.19 standards, common schedules include 10, 40, 80, XS, XXS and SCH 160, etc. Stainless steel is commonly thinner to SCH 10S, while carbon steel and high-pressure fittings are often scheduled  40 or  80.
Elbow radius: SR = 1 × D, LR = 1.5 × D, 3R = 3 × D.

What are the functions and roles of welded pipe fittings

Butt-welded pipe fittings have multiple important functions in pipeline systems, and the functions of different types of pipe fittings also vary:
Butt-welded elbow: Mainly used to change the direction of pipelines.
Butt-weld three-way fittings: They can be branched or connected to auxiliary equipment.
Butt-welded reducer: It is used to adjust the pipe diameter to adapt to different processes or equipment interfaces.
Butt-weld pipe cap: Used to seal the pipe end.

Summary

Butt-welded pipe fittings have become the leading role in industrial pipeline systems due to their high connection strength, wide range of applicable working conditions, and high degree of customization. When designing and selecting the type, it is necessary to comprehensively consider the type, standard, material, size and actual function in order to achieve a safe, efficient and economical pipeline solution.