When talking about quality judgement, we would conclude pressure taking into account. Today, we would talk about the formula for pressure calculation of spiral welded pipe, which would give us advice once we need to consult for this kind of steel pipe.

Internal pressure means the two main application of the force in the wall. And this step would give influence on steel tube’s quality. The formula is here:

Weld resultant stress δ = δY (l/4sin2α + cos2α) 1/2, which, α is the helix angle of the spiral weld pipe.

And for the δY and stress δ, they are the radial stress δY and axial stress δX. Thus, we can figure out that the helix angle of the spiral weld pipe is generally 50-75 degrees. Under this situation, the spiral weld large resultant stress. In the same work under the pressure of the same diameter spiral welded pipe wall thickness can be reduced a lot, spiral pipe plant can be made into a small caliber.