Welding method of steel pipe in diversion pipeline engineering

A. Pipeline engineering pipe material for spiral welded pipe, wall thickness 20mm, according to the design documents and construction site of the specific circumstances, welding using manual arc welding, submerged arc welding method, under normal circumstances, steel plate and pipeline longitudinal seam welding using submerged arc welding, manual arc welding, pipe ring seam and stiffening ring using and manual arc welding, the rest of the use of manual arc welding

　　。

　　B. Prefabrication of groove processing:

　　(1) When the pipe groove processing, because the wall thickness is less than 25mm, it is used V-groove (25°~30°).

　　(2) pipe groove using oxygen-acetylene semi-automatic cutting knife processing, semi-automatic cutting knife can not be machined special parts can be used by hand cutting processing.

　　(3) After the Groove processing must remove the groove surface of the oxide skin, slag and the impact of the quality of the joint surface, and should be uneven place grinding flat. C. Welding process: Engineering pipeline weld is divided into three categories according to its importance.

　　which：

　　A type of weld: A．

　　All welds in bifurcated tubes. B．

　　longitudinal seam of pipe wall. C．

　　Steel pipe ring seam. D．

　　The joint of the joint is folded. E.

　　The connection seam between the bulkhead and the pipe wall.

　　This type of weld if ultrasonic flaw detection rate is 50%, radiographic inspection rate of 5%, quality requirements for the B1 level qualified.

　　Two types of weld: A．

　　Steel pipe Tibi seam; B． The butt weld of the sealing ring and Gagen and the combined weld seam with the pipe wall.

　　This type of weld if ultrasonic flaw detection rate of 50%, quality requirements for the B2 level qualified.

　　Three types of weld: small force, and repair does not stop the power generation or water supply of the accessory components weld.

　　(1) The Weld group should be before the groove and its inner surface is not less than 10mm range of oil, paint, dirt, rust, burrs and other clear clean, and no cracks, interlayer and other defects.

　　(2) when the pipe or pipe fitting butt weld Group pair, the inner wall should be flush, the inner wall error margin should not exceed 10% of the pipe wall thickness, and should not be greater than 2mm; (3) The welding rod should be dried according to the stipulation before use, and should keep dry during the use. The surface of the wire should be removed before use of oil, rust and so on.

　　The welding electrodes, welding wires and fluxes of all kinds of welded joints can be selected according to the table below. (4) Welding materials should be baked and kept in accordance with the following requirements: welding electrodes, solder should be placed in the ventilation, drying and room temperature not less than 5 ℃ of the dedicated warehouse, set up special custody, baking and distribution, and should be in good time to test the temperature and electrode release records. Baking temperature and time should be strictly according to the specifications of the manufacturer. After baking the welding rod should be kept in 100-150 ℃ of the incubator, the drug skin should not fall off and obvious cracks. The use of the welding rod should be installed in the insulation tube, the electrode in the insulation tube time should not exceed 4h, more than, should be baked, repeated baking should not exceed 2 times.

　　Rust and grease should be removed before the wire is used.

　　(5) In case of drafts or wind speed exceeding 8m/s wind and rain, snow and ambient temperature under 5 ℃, relative humidity in 90%, welding place should be reliable protection measures to ensure that the welding department has sufficient temperature, welder skills will not be affected, can be applied welding.

　　(6) Before the welding, should be the groove and its two sides of the 50-100mm range of rust, slag, grease, water traces, etc. clear clean.

　　(7) Weld (including positioning welding) welding, should be in the groove on the arc, extinguish arc, strictly prohibited on the base of the arc, arc pits should be filled, multi-layer welding layer indirect head should be staggered.

　　(8) Positioning welding should comply with the following provisions: One or two welding seam positioning welding process and to welder requirements and main seam (that is, one or two types of welds, the same as the same) for the need to preheat welded steel plate, welding position welding should be the center of welding, at least in the 150mm range of preheating, preheating temperature than the main seam preheating temperature of 20-30 ℃

　　Positioning welding position should be more than 30mm from the weld end, its length should be above 50mm, spacing for 100-400mm, thickness should not exceed the official weld height of one-second, the thickest should not exceed 8mm, welding should be inspected before the quality of welding, such as cracks, pores, slag and other defects should be cleared.

　　(9) When the tool is welded, it is strictly prohibited to draw and extinguish the arc on the base material. (11) double-sided welding, the single side of the welding after the use of carbon-arc air gouging or angular grinding machine for the back clearance, will be welded to the root side of the positioning weld metal removal.

　　When using carbon-arc air planer, the Qinggen is used to trim the groove after clearing the root.

　　(12) Weld Assembly of the local gap of more than 5mm, but not longer than the length of the weld seam of 15%, allows for surfacing on either side of the groove, but should comply with the following provisions:

　　A, strictly prohibited in the clearance to fill in metal materials;

　　B, after surfacing the application of grinding wheel dressing;

　　C, according to the welding length and clearance size, the weld seam of the surfacing area should be carried out NDT inspection as appropriate.

　　(11) Longitudinal seam submerged arc welding at both ends of the weld set ARC plate and ARC-extinguishing plate, ARC plate and extinguish arc plate shall not be shot down, the application of oxygen-B flame or carbon arc air gouging, and grinding wheel to repair the original Groove shape. (12) Welding finished, welder should carry out self-test. One or two welding seam self-test after qualified, should be in the vicinity of the weld with a steel seal code, make good records.