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The wall thickness or diameter ratio and the specified pipe tolerances are the two mainly factors influence people choose in using seamless pipes or welded pipes. Next we will introduce some factors which influence whether using seamless or welded Pipe. Availability is the first factor which can influence people whether using seamless or welded steel pipe. Therefore, from wide material in stock we may only provide a limited number of alloys when manufacture the seamless hot rolled pipes. We may not use the steel plates or coils for they are shortage. These plates or coils are mainly used to produce welded pipes with numbers of different material grades. We can recover from special alloys and service stores with the small quantities of raw materials. Alloy C4 is also a kind of service stores or special alloys and we can cut them and get them from wide material which is in stock. This is the first factor which can influence people whether using seamless or welded pipe.

Tolerances are the second factor which can influence people whether using seamless or welded pipe. The hot rolled seamless pipes have f 12.5 percent of wall thickness tolerance. In ASTM A999 or EN ISO 1127 T2, the hot rolled seamless pipes are fundamentally specified. However, the manufacturing procedure can cause differences in thickness of the wall. We can use the wall thickness differences to lead a possible eccentricity. In the other word, we can use the wall thickness differences to form a deviation which is from symmetry. The tolerance of welded pipes wall thicknesses usually is ASTM A999 to EN ISO 1127 T3. In order to make sure that the wall thickness tolerance are very constant when pass through the entire mild steel pipe body and make sure that the wall thickness tolerance are the best tolerance, we should take the evenness of the coil thickness or the steel plate into consideration. They are the second factor which can influence people whether using seamless or welded pipe.

Pipe lengths and quantities are factors which can influence people whether using seamless or welded steel pipe. We may produce the length of seamless pipes relying on the weight a meter or a rod. From this, we can know that the lengths of pipe would maximum 13 meters when the lengths of pipe up to NB 100. While the lengths of pipe would maximum 4 meters when they are up to NB 200. Then we can produce the lengths of pipe with maximum 4 meters. Coil is the main material to make the minimum production. Those are factors which can influence people whether using seamless or welded pipe.

Spiral welded steel pipe is a steel strip coil plate of raw materials, often warm extrusion molding, with automatic double wire welding double-sided submerged arc welding technology with spiral steel pipe. (1) raw material namely strip coil, wire, flux. Have to pass strict physical and chemical inspection before investment. (2) the strip head to tail docking, use single or double wire submerged arc welding, after rolled steel tube adopts automatic submerged arc welding repair welding. (3) before shaping, strip after flattening, cutting edge, edge planing, transmission and cleaning the surface to the flanging process. (4) on both sides of the electric contact pressure gauge control conveyor under the pressure of oil cylinder pressure, ensure the smooth delivery of strip steel. (5) the use of external control or internal control roll forming. (6) spiral pipe weld gap control device is used to ensure that meet the requirements of welding seam clearance, pipe diameter, and quantity of the wrong side of weld gap are tightly controlled. (7) welding and welding are used within the United States Lincoln welding machine for single or double wire submerged arc welding, to obtain the stable welding specification. (8) after welding the weld passes the online continuous ultrasonic automatic meter check, ensure the spiral weld nondestructive testing coverage of 100%. If there are defects, automatic alarm and spray tags, production workers to adjust process parameters, in a timely manner to eliminate defects. (9) by air plasma cutting machine to cut the steel tube into single. After cut into single pole (10), the head of every batch of steel pipe should be strictly check system, check the weld mechanical properties, chemical composition, amalgamation, steel tube surface quality and the nondestructive flaw detection, ensure that qualified DSAW steel pipe process, can be formally put into production. (11) have continuous acoustic detection of weld mark parts, after manual ultrasonic and X-ray check, if there are defects, after repair, again through the nondestructive inspection, until defects have been eliminated. (12) strip steel butt weld and fellowship with spiral weld d joint in the tube, all pass X-ray films and television inspection. (13) each steel pipe after hydrostatic pressure test, radial sealing for the pressure. Test pressure and time are controlled strictly by welded steel pipe hydraulic microcomputer testing device. The parameters automatically printed out. (14) pipe end machining, make the end verticality, slope Angle and the blunt edge to get accurate control