Technical requirements for spiral tubes

1. Manufacturing method
(1) The use of hot-rolled steel belt to do billet, often temperature spiral molding, spiral seam using automatic submerged arc welding, internal and external submerged arc welds are not less than one.
(2) Steel pipe on the allowable to the head of the weld, steel and the end of the pipe end of the distance of not less than 300mm. The purchaser negotiates with the manufacturer to allow the head weld to be at the pipe end, but there should be a circumferential distance of at least 150 mm between the head and the corresponding tube end screw candle.
(3) Docking pipe allows the same specifications and the same type of two short section of a steel pipe, each section of the length of short steel pipe shall not be less than 2m, both sides of the ring weld seam should be staggered, the ring distance Less than 150mm.

2. The type of steel
The scope of the standard steel pipe should be used GB / T700-1988 in the Q195, Q215, Q235 steel welding. Note: Q refers to the yield strength of the letter, the value of the back of the yield strength value.

3. Hydrostatic test
Each pipe should be hydrostatic test without leakage phenomenon, the test pressure by the test P = 2ST / D where the S-hydrostatic test test stress Mpa, hydrostatic test test stress according to the corresponding strip standard. The minimum value of the yield (Q235 235Mpa) 60% of the selected. Regulator time: D <508 test pressure holding time of not less than 5 seconds; D ≥ 508 test pressure retention time of not less than 10 seconds

4. Nondestructive testing
Spiral tubes welding seam, steel strip weld and ring joints should be X-ray or ultrasonic inspection. For helical welds of steel for combustible ordinary fluid delivery, a 100% SX-ray or ultrasonic test shall be carried out. The spiral welds of steel pipes for general fluid delivery such as water, sewage, air, heating steam shall be subjected to X-ray or Ultrasonic examination checks (20%).


5. Defect handling
(1) Defects can be worn with a grinding wheel, but the remaining wall thickness must be within the allowable range.
(2) The minimum length of welding seam 50mm; base metal was welded after grinding shall not exceed 1.5mm.
(3) Remove defective pipe sections within the permissible length range.
(4) Judged to be unqualified.