Manufacturing Butt-Welding Fittings

The most appropriate manufacturing process for each product will be decided with consideration of its material, sizes, shape, use, standards and special properties.

There are numerous methods for manufacturing Elbows alone, several examples are listed as follows.

ELBOWS

Mandrel method (Hot Forming)

One of the most common manufacturing methods for manufacturing Elbows from pipes. After heating the raw material, it is pushed over a die called a "mandrel" which allows the pipe to expand and bend simultaneously. Applicable to a wide size range.

Extrusion method (Cold Forming)

Using raw material with the same diameter as finished product, pipe is pushed through a die and formed into its desired shape. Usually applied to stainless steel, small to medium sizes.

"UO" method

After raw material plate is cut out into a specially designed shape, it is shaped first into an U-shape using a die and then into an O-shape (tubular form) using another die, finished with a single weld. Usually applied to stainless steel and non-steel material, small to medium sizes.

"Monaka" method

One of the most used methods for manufacturing Elbows from plates. After two pieces of raw material plates are cut out symmetrically, each piece are press formed and welded together, which somewhat reminds us of the Japanese delicacy, "Monaka." This method is applicable to various materials and can even be applied to large items with diameters over 1 meter. It has two seams and special welding technology in use to meet various standards required by our clients (electricity, gas pressure vessels, etc.,) from whom BENKAN KIKOH Corporation products continue to receive high acclaim.

Hot Forming Die Bending method

After heating raw material pipe, it is press formed and corrected using different dies. The process may be repeated as needed to obtain the required shape, size, wall thickness, etc. Usually applied to thick-wall items that cannot be bent on a mandrel die.

TEES

Hydraulic Bulge method (Cold Forming)

After cutting and placing raw material into a die, the pipe is pressed as hydraulic pressure pushes out the branch. The Tee is pressed against the die, leaving the finished product to have a truly smooth outer surface.

Extrusion method (Hot Forming)

Using raw material with a bigger diameter than the finished product, the branch outlet is extruded from pipe while the main body is being pressed. The outlet's wall thickness can also be adjusted as needed. Applied to Tees with large diameters, heavy wall thickness and/or special material with challenging workability that cannot be manufactured using the hydraulic bulge method.

Steel Plate Welding method

Manufacturing methods are similar to Elbows, using steel plates as the raw material. Includes the UO-method, Monaka method and Throat-welding method.

"UO" method: After raw material plate is cut out into a specially designed shape, it is shaped first into an U-shape using a die, then the branch pipe is formed and then shaped into an O-shape (tubular form) using another die, finished with a single weld on the opposite side of the branch pipe. Usually applied to large diameter items used in severe conditions.

"Monaka" method: Two pieces of raw material plates cut out symmetrically are press formed and welded together. Usually applied to large-diameter items.
Throat-welding method: Mainly used for stainless and non-metal items, this method is similar to UO-method but with the weld on the same side as the branch pipe and the "branch throat." Usually applied to low-pressure, corrosion-resistant items.

 

REDUCERS

Outer Die method

One of the most common method for manufacturing Reducers, using an outer die. Raw material pipe is cut and pressed in an outer die, compressing one end of pipe into a smaller size.

 Plate Forming method

Plates can also be used to manufacture Reducers. In an UO method, plate is cut in a specially designed shape which is formed into an U-shape and an O-shape respectively, then finished with a single weld seam. The "Monaka" method is also available and is similar to that of Elbows and Tees, using two symmetrically cut plates formed and welded together with two seams. Both methods are used for large diameter items.

CAPS

 Deep Drawing method

One of the most common manufacturing methods for caps, where plate is cut out in a circle and formed by deep drawing.

LAP JOINTS / STUB ENDS

Flare method

One of the most common manufacturing methods of Lap Joints / Stub Ends. One end of the raw material pipe is spread out to form the brim. There are other methods, where the brim is welded onto the end of a cut pipe or where the whole product is machined from block.