The Welding Process
---The welding of the spirally welded pipes is based on the Double-Sided Submerged Arc Welding (DSAW) process.

The principle

---Arc welding works by using electric current to produce an electric arc in a gas environment. The arc's heat brings the metal to fusion point. A key question is how to increase both the concentration
and energy intensity of the arc. DSAW's better penetration makes it possible to achieve higher weld travel speeds without impairing quality, thus improving productivity and lowering costs.

Multi arc welding
---The Spiral Mill combines the advantages of DC and AC arc combinations. Both on the inside and the outside the multi arc principle is used. The first welding pass is done by using a DC arc. Herewith a large and concentrated penetration can be achieved. The second pass is done by using an AC arc. Herewith better deposition rates can be achieved. The result of the multi arc welding on both sides of the coil is a full penetration weld of a very high quality produced in a cost effective way. The flexibility of the mill is very high because of the use of this system. A large range of coil thicknesses (between 10 and 25mm) can be transformed in spirally welded pipes in an economic way by choosing the right parameters.