Manufacturing method

  1. The use of hot-rolled steel pipe to do bad, often warm spiral shape, spiral automatic submerged arc welding method, internal and external submerged arc welding seam not be less than one.
  2. Allows the pipe from the strip end weld, steel head and pipe ends shall not be less than 300mm. After consultation with the manufacturer and purchaser, allowing end weld pipe end is located, but there should be at least 150mm hoop spacing between the head and the respective tube end seam spiral candle.
  3. Butt pipe allows the same specifications of the same model to stop two short faces a pipe, the length of each short pipe may not be less than 2m, on both sides of the weld joints should be staggered spiral ring, which ring the distance not less than 150mm.

Kind of scope of this standard steel pipe should be used in the GB / T700-1988 Q195, Q215, Q235 welded steel. Note: Q refers to the letters on behalf of the yield strength, yield strength values ​​behind the value.

 

hydrostatic test should be done each pipe hydrostatic test without leakage, pressure test press Calculate P = 2ST / D where S- hydrostatic test stress test Mpa, hydrostatic test stress test according to the corresponding steel with standard of minimum specified yield (Q235 is 235Mpa) 60% of the selection. Regulators time: D <508 test pressure holding time less than 5 seconds; D≥508 test pressure holding time less than 10 seconds 4 NDT pipe welding seam, strip end weld and circumferential joints should be X-ray or ultrasonic inspection. For ordinary combustible fluid transport spiral steel to weld should be 100% SX-ray or ultrasound test, used for water, sewage, air, heating steam and other general transmission fluid with spiral weld steel pipe should be X-rays or ultrasonic inspection checks (20%).

 

defect treatment

  1. Available defective wheel rubbed off, but the remaining wall thickness must be within an allowable range
  2. A minimum length of welding seam 50mm; shall not exceed 1.5mm base metal to be welded after grinding
  3. Within the allowable length of the defective tube resection
  4. As unqualified