Advantages and disadvantages of
spiral welded pipe unit and spiral welded pipe
Spiral welded pipe unit
The spiral welded pipe unit is used to produce large-diameter steel pipes with a diameter of (89-2450)mm×(0.5-25.4)mm and a length of 6-35m. Its production methods are continuous and discontinuous. The unit adopts spiral forming, and the welding adopts two steps of pre-welding and final welding. Forming and pre-welding (spot welding) takes place on a spiral former, followed by internal and external submerged arc welding on the final welding machine.
The spiral welded pipe is formed by a spiral former, which can be divided into two types: upper coil forming and lower coil forming. Recently, there are three basic forms of the structure of the former of the
spiral welded pipe:
Sleeve-type spiral former. It is only suitable for the forming of small-diameter welded pipes. It is low in cost and easy to operate.
Roller spiral forming and deleting device. The roll former is made according to the working principle of the three-roller bending machine. The contact surface between the former and the steel strip is rolling friction, which has low resistance, long tool life, and almost no scratches on the product surface.
Mandrel screw former. This former is suitable for forming small-diameter, thin-walled high-quality spiral welded pipes. However, the inner surface of the steel pipe may be scratched due to friction.
Advantages of
spiral welded pipe:
Steel pipes of different diameters can be produced by using strip steel of the same width, especially steel pipes of large diameter can be produced by narrow strip steel.
Under the same pressure conditions, the stress of the spiral welded seam is smaller than that of the straight seam, which is 75% to 90% of the straight seam welded pipe, so it can withstand greater pressure. Compared with straight seam welded pipes with the same outer diameter, the wall thickness can be reduced by 10% to 25% under the same pressure.
The size is accurate, the general diameter tolerance is not more than 0.12%, the deflection is less than 1/2000, and the ellipticity is less than 1%. Generally, the sizing and straightening process can be omitted.
It can be produced continuously. In theory, it can produce infinitely long steel pipes. The loss of cutting head and tail is small, and the metal utilization rate can be increased by 6% to 8%.
Compared with the longitudinal welded pipe, it is flexible in operation and convenient in changing varieties and adjustments.
The equipment is light in weight and low in initial investment. It can be made into a trailer-type mobile unit to produce welded pipes directly on the construction site where the pipelines are laid.
It is easy to realize mechanization and automation.
The disadvantage of the
spiral welded pipe is: because the coiled strip steel is used as the raw material, there is a certain crescent bend, and the welding point is in the edge area of the strip steel with elasticity, so it is not easy to align the welding torch, which affects the welding quality. To do this, complex seam tracking and quality inspection equipment is set up.
