Butt Weld Elbow Fitting

butt weld elbow fitting

Buttweld pipe fittings comprise of long radius elbow, concentric reducer, eccentric reducers and tees. They are an important part of industrial piping systems to change direction, branch off or to mechanically join equipment to the system. Buttweld fittings are sold in nominal pipe sizes with specified pipe schedule. BW fitting’s dimensions and tolerances are defined as per ASME standard B16.9.

Butt Weld fittings are also called Welded Pipe fittings. These welded fittings in carbon steel and stainless steel offer many advantages compared to threaded and socket weld fittings. The latter are only available up to 4-inch nominal size whereas butt weld fittings are available in sizes from ½” to 72”. Some of the benefits of Buttweld fittings are mentioned below. 

Types of Butt Weld Pipe Fittings

Welded pipe fittings in carbon steel and stainless steel are the joining components that make possible the assembly of valves, pipes and equipment onto the piping system. Welded fittings compliment pipe flanges in any piping system and allows:

• Change direction of flow in a piping system
• Connect or joint pipes and equipment

• Provide branches, access and takeoffs for auxiliary equipment

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A common example using welded pipe fitting is a pipe reduced by concentric reducer, welded to a weld neck flange and connected to equipment. The figure below represents a complete collection of butt welded pipe fittings.

Seamless Elbow Manufacturing Process (Heat Bending & Cold Bending)

One of the most common methods for manufacturing elbows is using hot mandrel bending from straight steel pipes. After heating the steel pipe at a elevated temperature, the pipe is pushed, expanded, bended by the inner tools of mandrel step by step. Applying hot mandrel bending can manufacture a wide size range seamless elbow. The characteristics of mandrel bending are strongely depend on the intergrated shape and dimensions of the mandrel. The using advantages of hot bending elbows include smaller thickness deviation and stronger bending radius than other bending methond type. Meanwhile, using bending instead of prefabricated bends substantially reduces the number of welds needed. This reduces the amount of work required and increases the quality and usability of pipes. However, cold bending is the process to bent the straight steel pipe at normal temperatures in a bending machine. Cold bending is suitable for pipes with an outer diameter of 17.0 to 219.1 mm, and wall thickness 2.0 to 28.0 mm. The recommended bending radius is 2.5 x Do. Normally at a bending radius of 40D. By using cold bending, we can get small radius elbows, but we need to pack the internals with sand to prevent wrinkling. Cold bending is a quick and inexpensive bending method. It is a competitive option for making pipelines and machine parts.

Welded Elbow Manufacturing Process (Small & Large)

Welded elbows are made from the steel plates, so it is not seamless steel elbows. Use a mould and press the steel plate to the shape of the elbow, then weld the seam to be a finish steel elbow. It is the old production method of the elbows.  Recent years the small sizes elbows are almost manufactured from the steel pipes now. For the big size elbows, for example, it is very difficult to produce elbows over 36” OD from the steel pipes . So it is commonly made from the steel plates,  pressing the plate to the shape of half elbow, and welding the two halves together.  Since the elbows are welded in its body , the inspection of the welding joint is necessary . Commonly we use the X-Ray inspection as the NDT.

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