Strength characteristics of the spiral welded pipe under pressure

The helix angle of the spiral welded pipe is generally 50-75 degrees, the synthesis of spiral weld stress is longitudinally welded pipes of 60-85% of the principal stress. In the same work under pressure, spiral welded pipe of the same diameter than the straight seam welded pipe wall thickness can be reduced.

Since the radial stress is present in the maximum stress on the steel pipes, so that direction of the seam in a vertical stress to withstand the maximum load. That straight seam withstand load maximum circumferential welds to withstand the load minimum the spiral seam somewhere in between.
Solenoid blow suffered due to weld the normal stress and the resultant stress is relatively small, blasting mouth generally not originated in the spiral weld its security than longitudinally welded pipes.
Near the spiral weld defects corresponding parallel exists, due to the smaller force of spiral weld its extension risk than large straight weld.
Spiral welded pipe withstand the internal pressure, typically in the wall of two main stress, i.e., the radial stress δY and axial stress ΔX. Weld synthetic stress δ = Δy (l/4sin2α + cos2α) 1/2, where, α is the spiral weld pipe helix angle.