Spiral steel pipe is a spiral seam steel pipe, which is made of strip coil plate as raw material, often formed by warm extrusion, and welded by automatic double-wire and double-side submerged arc welding process. 

Cangzhou Shenlong Pipe Manufacturing Co., Ltd. produces large diameter spiral steel pipe, straight seam welded pipe, the company has passed the ISO9001R certification, the whole product is tested according to the standard, recently our company has just delivered a batch of spiral steel pipe, used in the Philippines water supply project, the specification is DN300-DN1200, hope that more customers choose our products. We will try our best to serve every customer and deliver every order.

Manufacturing method of spiral steel pipe

(1) The hot rolled steel strip is used for pipe damage, and the spiral seam is welded by automatic submerged arc welding method. The internal and external submerged arc welding seam is no less than one.

(2) The steel pipe is allowed to have steel belt butt weld, and the distance between the steel belt head and the pipe end shall not be less than 300mm. After negotiation between buyer and manufacturer, the head weld is allowed to be located at the pipe end, but there should be at least 150mm annular spacing between the head and the corresponding pipe end spiral candle seam.

(3) The butt steel pipe is allowed to be a steel pipe with two short retaining surfaces of the same specification and model. The length of each short steel pipe shall not be less than 2m. The spiral joints on both sides of the circumferential weld shall be staggered, and the circumferential distance shall not be less than 150mm.

Hydrostatic pressure test of spiral steel pipe

Each steel pipe shall be subjected to hydrostatic test without leakage, and the test pressure shall be calculated according to P=2ST/D S - hydrostatic test stress Mpa, and the test stress of hydrostatic test shall be selected according to 60% of the small yield value specified in the corresponding steel strip standard (Q235 is 235Mpa). Voltage stabilization time: D< 508 test pressure holding time not less than 5 seconds; D≥508 test pressure holding time not less than 10 seconds

Non-destructive testing of helical steel pipe

The repair weld of steel pipe, the head weld of steel belt and the ring seam shall be inspected by X-ray or ultrasonic. 100% SX-ray or ultrasonic inspection shall be carried out on the spiral welds of the steel direction used for the transport of combustible common fluids, and X-ray or ultrasonic inspection shall be carried out on the spiral welds of the steel pipes used for the transport of water, sewage, air, heating steam and other common fluids (20%).

Treatment of spiral steel pipe defects

(1) The defects can be removed by grinding wheel, but the remaining wall thickness must be within the permissible range

(2) The small length of the repair weld is 50mm; Base metal shall not exceed 1.5mm after welding and grinding

(3) The defective pipe segment shall be removed within the allowable length range

(4) judged as unqualified