Process defects of spiral submerged arc welding pipe
Sources: this site Click: Date: 2015-9-12 18:22:26
Spiral welded pipe is generally hot rolled strip coil for tube by spiral shape, using high frequency resistance welding method or submerged arc welding molding. The process can narrow the billet production of large diameter pipe, you can also use the same width of the billet production of different pipe diameters.
1, spiral welded pipe in the oil and gas transportation in the reason being challenged because of its technology can not overcome the inherent shortcomings. Main features:
A weld length increased by 30% to 100% longer than the Longitudinal welds. Pipe major defects in the weld, the weld length means poor reliability, and simultaneously forming and welding, weld defects significantly higher chance of weld quality assurance is not easy.
2, spiral welded pipe production line generally do not have the flaring process, can not be reduced forming and welding residual stress, causing internal pipe has a larger residual stress, the residual stress is tensile stress (up to 200Mpa ~ 300Mpa), and after a pipe under internal pressure , the wall also produces hoop tensile stress, the two superimposed, so pipe pressure diminished capacity. And the residual tensile stress, especially in the presence of residual tensile stress weld location also greatly reduces the ability of resistance to stress corrosion pipe, oil and gas pipelines in the acidic medium must be strictly limited residual tensile stress.
3, on the surface of spiral welded pipe welding, weld poor shape, inside and outside the weld seam of the back saddle shape is difficult to overcome, it is difficult to avoid the stress concentration.
1, spiral welded pipe in the oil and gas transportation in the reason being challenged because of its technology can not overcome the inherent shortcomings. Main features:
A weld length increased by 30% to 100% longer than the Longitudinal welds. Pipe major defects in the weld, the weld length means poor reliability, and simultaneously forming and welding, weld defects significantly higher chance of weld quality assurance is not easy.
2, spiral welded pipe production line generally do not have the flaring process, can not be reduced forming and welding residual stress, causing internal pipe has a larger residual stress, the residual stress is tensile stress (up to 200Mpa ~ 300Mpa), and after a pipe under internal pressure , the wall also produces hoop tensile stress, the two superimposed, so pipe pressure diminished capacity. And the residual tensile stress, especially in the presence of residual tensile stress weld location also greatly reduces the ability of resistance to stress corrosion pipe, oil and gas pipelines in the acidic medium must be strictly limited residual tensile stress.
3, on the surface of spiral welded pipe welding, weld poor shape, inside and outside the weld seam of the back saddle shape is difficult to overcome, it is difficult to avoid the stress concentration.
