Spiral welded pipe: low-carbon carbon structural steel or low-alloy structural steel strip according to a certain angle of the spiral (called molding angle) rolled into the tube, and then welded together to make the pipe, it can use a narrow Strip production of large diameter steel pipe. Spiral welded pipe is mainly used for oil and natural gas pipeline, its specifications with diameter * wall thickness. Spiral welded pipe with single-sided welding and double-sided welding, welded pipe pressure test should ensure that the weld tensile strength and cold bending performance to meet the requirements.
Spiral welded pipe helix angle is generally 50-75 degrees, so the synthesis of spiral welded seam stress is 60-85% of the main stress. In the same working pressure, the same diameter spiral welded pipe than the straight seam welded pipe wall thickness can be reduced.
Spiral welded pipe burst, due to the normal stress and the weld stress is relatively small, the blasting usually does not originate in the spiral weld, its safety than the straight seam welded pipe high.
According to the shape of the end is divided into round pipe and shaped (square, flat, etc.) pipe.
Spiral welded pipe in accordance with a certain method can be divided into different types and models, according to the pipe material and the use of different and divided into:
GB / T14291-1992 (mining fluid spiral welded pipe), mainly used for mining pressure air, drainage, gas discharge shaft with straight seam welded steel pipe. Its representative material Q235A, B grade steel. GB / T14980-1994 (Large Diameter Electric Welded Steel Pipe for Low Pressure Fluid Transportation). Mainly used for conveying water, sewage, gas, air, heating steam and other low-pressure fluid and other purposes. Its representative material Q235A grade steel.
GB / T12770-1991 (mechanical structure with stainless steel spiral welded pipe), mainly for machinery, automobiles, bicycles, furniture, hotel and restaurant decoration and other mechanical parts and structural parts. The representative material 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb and so on.
GB / T3091-1993 (low pressure fluid conveying galvanized welded steel pipe), mainly used for conveying water, gas, air, oil and heating water or steam and other general low pressure fluid and other purposes. Its representative material Q235A grade steel.
GB / T12771-1991 (stainless steel spiral welded pipe for fluid transport), mainly used for conveying low-pressure corrosive media. Representative material is 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2 and so on.
When the spiral weld near the existence of defects parallel to it, because the spiral weld stress is small, so the risk of expansion is not as large as the direct weld.
Since the radial stress is the maximum stress present on the pipe, the weld is subjected to the maximum load in the direction of vertical stress. That is, the maximum load to bear the straight seam, ring weld to bear the minimum load, the spiral gap between the two.
