Spiral steel pipe temperature control

Spiral steel pipe welding temperature is mainly affected by the high-frequency eddy thermal power, high-frequency eddy current heating power is mainly affected by the frequency, power and thermal eddy current excitation frequency is proportional to the square; but also by the current excitation frequency excitation voltage, current and capacitance, inductance.

When the lack of heat input, the weld edge is heated up to a temperature of less than welding, metal structure remains solid, the formation of incomplete fusion or penetration; insufficient when the input heat, weld edge over the heated soldering temperature, resulting in burnt or droplet, so that the weld formation Caverns.

Welding multilayer of spiral welded steel pipe also considers inter-layer temperature to control the cooling rate near the weld zone. Interface temperature and preheat temperature are generally similar. Under avoid overheating premise near seam zone between the higher layer prevents cold crack temperature during multi-pass welding. After the heat treatment and welding heat pipeline construction is not usually performed after heat treatment after welding and heat treatment. But for construction in the alpine region, when the inter-preheat and interface temperature control is difficult to play a greater role, it is necessary to take certain joints after welding heat and heat treatment measures.

Spiral steel pipe installation process

Spiral pipe into operation to the site, first according to equipment and fittings position exhaust pipe, and in the field will be specific length of each pipe of measurement is good, mark the specific size and arrangement position in order to facilitate an interface condemnation, under the use of the crane tube, down tube during hoisting nylon sling to protect the pipe insulation.

1：repair mouth

Repair ports concentrated in the factory pipeline processing is completed, in order to ensure the quality of welding, before welding underwent a comprehensive inspection, correction, make pipe end, bevel angle, blunt edge, roundness, etc., are in line with their counterparts in joint size requirements, the need for individual pipe done in the field beveling process, the use of gas welding cutting, remove the slag and then use the wheel polished smooth.

Counterpart operating procedures: Check the interface connector size → clear breech → determine and adjust the position of the steel pipe longitudinal welds staggered → first conduit looking straight counterparts adjust gap dimension → pipeline cable counterparts leveling looking straight → spot welding

2：Welding

Interface welding using arc welding, again backing, survived two times, and each time the welding seam are finished, each arc welding point lead to be staggered. Repair welding pipe joints should be preceded by mouth, slag, bevel angle pipe end to end face, blunt edge, the gap should be consistent with specification; clip can not help strip welding or heating counterparts gap narrowing gap welding. Counterparts should be flush with the inner wall, with a long 300mm ruler in order around the inner wall abutting the interface, the wrong port allows partial check should be 0.2 times the difference between the wall thickness, and no greater than 2mm.