Spiral steel pipe
Spiral steel pipe standard name is "spiral seam double-side submerged arc welded steel pipe", is the use of hot rolled steel strip as pipe billet, at room temperature through spiral molding, spiral seam automatic submerged arc welding method welding, the inside and outside should have a submerged arc welding seam. In strict accordance with GB/ T9711-2011, SY/T 5037-2012 and API SPEC 5L standards, the company produces Ф 219mm-2020mm spiral steel tubes with length of 8-18m. The wall thickness of Q345B material is 5mm -- 25.4mm and the wall thickness of X80 material is 5mm -- 20mm. Mainly used for oil, natural gas and other pressure long distance transmission pipeline (such as the national west to east gas transmission and other key engineering fields), can also be used for gas, water, gas, fire, air and heating steam and other common fluid transport, and can be used in piling, structure and other construction fields.
Specification: 219 mm - 3020 mm Ф Ф
Application: it is used for oil, natural gas and other pressure long transmission pipe (such as the national key engineering field of west-east gas transmission), also can be used for gas, water, gas, fire, air and heating steam and other common fluid transportation, and can be used in piling, structure and other construction fields.
China Oil and Gas Industry Standard SY/T 5037-2000 "Spiral Slot Submerged Arc Welded Steel Pipe for Low-pressure Fluid Transmission Pipeline"
Nominal outer wall thickness and theoretical weight per meter
One. Butt-welding connection of steel pipe
(1) Place the two steel pipes that need to be connected on the same axis in the same plane.
(2) Keep the gap between the two pipe ends between 2-3mm. In order to ensure the welding gap distance, gaskets can be added between the two pipes.
(3) ensure the groove Angle of the butt steel pipe.
(4) Do not make the steel pipe move by any external force within 30 minutes after welding, otherwise it will crack the butt weld and affect the use effect of the pipe.
(5) If it is necessary to conduct non-destructive testing (X-ray or ultrasonic testing) on butt welds, it shall be conducted 24 hours after the completion of welding if conditions permit.
Two, flange connection
(1) the metal flange is set on the connector, and the corresponding connector is corrected so that the two flanges connected are perpendicular to the center line of the pipeline and the surface is parallel.
(2) Nuts of the same specification shall be used, and the installation direction shall be the same. The bolts shall be fastened symmetrically. Fastened bolts should be exposed outside the nut, and should be flush. The bolt cap should be galvanized.
(3) The length of the connecting pipe should be accurate. When tightening the bolt, the pipe should not produce axial tension.
(4) The flange connection part shall be provided with a bracket.
One. Matters needing attention during hoisting
(1) The transverse contact surface between the hook and the pipe end shall not be less than 40mm, otherwise it is easy to deform the pipe mouth and affect the pipe docking.
(2) Limitation on the number of hoisting roots. The maximum number of hoisting roots is 4-5 in diameter 219, 273, 325 and 377. Diameter 426, 478, 529 specifications, lifting up to 2-3 pieces at one time; Diameter 630, 720 specifications, one time up to 2 hoisting; One steel pipe with diameter above 820 shall be hoisted at one time.
Two. Matters needing attention in transportation
In the process of transportation, avoid collision between the steel pipe body or pipe end and other hard objects, resulting in deformation of the pipe orifice or pipe body, and such collision will also cause scratches of the steel pipe body.
Three. Matters needing attention in storage
(1) Stacking height: too high stacking may easily deform the roundness of the steel pipe, affecting delivery and use. Especially D/T (pipe diameter/wall thickness is greater than 150) pipe diameter of more than 1220 shall not exceed 2 layers; Pipe diameter between 820-1020 shall not exceed 3 layers; Other specifications, according to the requirements of the site.
(2) corrosion prevention: if there are corrosive liquids and gases near the storage place or near enterprises that use or manufacture such products, corrosion will occur to the steel pipes stored, and rainproof cloth shall be applied to protect them.
(3) The foundation of the stowed steel pipes shall be higher than the ground plane to ensure that part of the steel pipes will not be immersed in water due to rain.
(4) After stacking steel pipes, clamps should be made on the periphery steel pipes to prevent accidents caused by rolling stacking of steel pipes.
First, butt weld wrong side (radial dislocation) phenomenon
(1) to measure whether the pipe diameter or the ovality of the steel pipe exceeds the standard; to measure the circumference of the steel pipe and the diameter of the pipe end;
(2) If the pipe diameter or ellipticity exceeds the standard, our company will negotiate with you to solve the problem;
(3) If the diameter or ellipticity of the pipe does not exceed the standard, please turn one of the steel pipes and adjust it to the best position of the two steel pipes with the closest size (radial dislocation of both ends shall not exceed 3mm) for welding in order to ensure welding.
Two, steel pipe cutting phenomenon
(1) Whether the measurement tangent exceeds the standard;
(2) if the cutting deviation exceeds the standard, our company will negotiate with you to solve the problem.
(3) If the cutting Angle does not exceed the standard, in order to ensure welding, please turn one of the steel tubes and adjust to the best position of the two steel tubes with the closest size (the gap between the welding ports is 2mm) for welding.
Three, tube end remanence phenomenon
1. Measurement method of tube end remanence:
(1) Equipment: Gauss meter.
(2) When the steel tube remanent magnetic induction intensity is less than 40× 10-4t, the welding operation is basically not affected; When the remanence induction intensity is greater than 40× 10-4t, the welding operation and welding quality will be affected.
2. Demagnetization method:
(1) Use an Angle grinder to polish the inner tube end wall of the steel pipe, and polish it once counterclockwise to eliminate the magnetic remanence of the steel pipe.
(2) Coil demagnetization:
Use a 20mm2 wire to wind clockwise around the end of the pipe, and the number of winding turns should not be less than 10, no matter how many. Connect both ends of the coil directly to the DC welding machine, adjust the current to about 200 amperes, and it will take about 20 minutes after the power is switched on. Pay attention to the temperature of the wire, and then use the wire for 3mm and 120mm long. The 50mm and 20mm3 root wire sections were magnetic tested within a week of the pipe end, and it was found that the 120mm and 50mm wire could not be absorbed, which proved that it could be welded. 20mm wire can not be attracted to prove that there is no magnetic. If the magnetism does not decrease, it is proved that the positive and negative poles of the DC welding machine power supply are connected in reverse. The wiring plug of the welding machine is replaced. After the replacement, the same test is carried out according to the above operation, and the magnetic field is changed to reduce the magnetism.