Pipe Manufacturing Process：Seamless And Welded Pipes

Seamless pipe manufacturing process

Seamless pipe is the strongest of all pipe types because it has a homogeneous structure over the entire length of the pipe.

Seamless pipe can be manufactured with very accurate dimensions and schedules. However, there are restrictions on the fabrication of large diameter pipes. Seamless pipe is widely used in the manufacture of pipe fittings such as elbows, bends, and tees.

Details of various manufacturing processes.

Mandrel Mill Process

In the Mandrel Mill pipe manufacturing process, the steel billet is heated to high temperature in the rotary furnace. A cylindrical hollow, which is also known as mother hollow, is produced with the help of a rotary piercer and set of roller arrangement that keeps the piercer at the center of the billet.

The outside diameter of the piercer is approximately that of the inside diameter of the finished pipe. With the help, secondary roller arrangement outside diameter and thickness are achieved.

Mannesmann Plug Mill Pipe Manufacturing Process

Mannesmann was a German engineer who has invented this pipe manufacturing process. The only difference between the Plug mill process and the Mandrel mill process is that in the mandrel method inside diameter is achieved in a single pass whereas in Mannesmann multi-stage reduction is possible.

Forged seamless pipe manufacturing process

In the forged pipeline manufacturing process, a heated billet is placed in a forging die with a diameter slightly larger than the finished pipe. Cylindrical forgings are made using a forging hammer hydraulic press with matching inside diameters.

Once the forging is complete, the pipe is machined to its final size. The forged pipe manufacturing process is used to make large diameter seamless pipe that cannot be made by conventional methods. Forged pipe is commonly used for steam manifolds.
Extrusion Process

In extruded pipe manufacturing, a heated billet is placed inside a die. A hydraulic cylinder pushes the billet towards the piercing mandrel and the material flows out of the cylindrical cavity between the die and the mandrel. This action produces the tube from the billet.

Sometimes the manufactured pipe produces a thick tube, which is called a hollow master pipe. Many of the secondary pipes manufactured use this female hollow to produce pipes of different sizes.

Welded Pipe Manufacturing Process

Welded pipe is made from sheets or continuous coils or strips. To manufacture a welded pipe, the first plate or roll is rolled into a circular cross section with the help of a plate winder or rolls in the case of a continuous process.

Once the circular section is rolled out from the plate, the pipe can be welded with or without filler material. Welded pipes can be manufactured in large sizes without any upper limit. Welded pipe with filler material can be used to manufacture long radius elbows and bends.

Compared to seamless pipes, welded pipes are cheaper and since the weld seam is also weak.

There are different welding methods used to weld pipes

ERW- Resistance welding

EFW- Electrofusion welding

HFW- High Frequency Welding

SAW- Submerged arc welding (long seam and spiral seam)

ERW pipe manufacturing process

In the ERW / EFW / HFW pipe process, the first plate is formed into a cylindrical shape and the longitudinal edges of the formed cylinder are welded by flash welding, low frequency resistance welding, high frequency induction welding or high frequency welding. Frequency resistance welding.

SAW pipe manufacturing process

In the SAW welding process, an external filler metal (electrode wire) is used to join the formed plates. Depending on the size of the pipe, SAW pipe can have a single longitudinal seam or a double longitudinal seam.

SAW pipe is also available with spiral seams, which are continuously rolled from a single sheet coil. Spiral SAW pipe has a very high productivity compared to straight SAW pipe. However, spiral SAW pipe is only used for low pressure services, such as water, non-critical process services, etc.

The source is from here.