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- Technical standards and monitoring the quality of carbon steel pipe manufacturing
A. Cutting carbon steel pipe production
Carbon steel pipe longitudinal seam and around the groove, designed using the "V" shaped and "U" shape. Based on the detailed situation of the existing processing equipment of the construction units, design units in favor of the submerged arc welding initiative symmetrical "X" shape, the site manually changed to "partial X"-shaped welding groove instead - circumferential seam degree of centerline medial lateral and extent of the center line of the following to open a large "V" shaped groove, corresponding to the opposite direction to open a small "V" shaped groove.
Partial X "groove to facilitate the first welding the welding of the small slope of the mouth lift up His countenance, then arc gouging positive clear root welding the upper part of the weld.
Steel plate using active flame gas cutting gun cut, first cut a straight edge, coupled with cutting groove. Cutting oxygen pressure O.6MPa acetylene gas pressure O.5MPa. And then apply a high-speed angle sander to get rid of the groove within the slag, burrs, iron oxide, polished weld groove.
Rolling Machine Coil capacity of plate thickness 25mm × plate width 4000mm.
The first rolling machine pressure to the curvature of the steel plate at both ends of the head, and then roll the center part. The general volume grind 4 to 5 times, continue to model check the curvature of the curvature of the pass, spot welding the longitudinal seam interface.
Request in order to meet the standards, roundness, every details of the interface longitudinal seam welding finished and later again into the rolling machine was held Winder, to ensure quality standards.
3. Carbon steel pipe section assembly
Consider the site lifting and transport capacity, reducing the site welds, three short sections assembled into a long section, ie, wall thickness of 24mm, length 6000mm, weight 11094kg; wall thickness of 30mm, length 5400m, the weight of 12625kg.
The assembly is held in the length of the arc 7m to turn the trolley. Restraint adjacent pipe section longitudinal seam staggered 1800mm, the assembly of the amount of the wrong side of weld longitudinal seam restraint within 2mm girth does not exceed 3mm tack welding the length of each 250mm weld 50mm.
Inspection after the steel tube assembly
After examination, the plane of the nozzle 2mm, roundness 3D ‰ = 9mm, perimeter <3D ‰ = 9mm, have reached a standard request.
Fourth, the welding of steel pipe
A. Excellent line of the carbon steel pipe welding procedure qualification
30mm thick steel plate for welding procedure qualification. Q235 killed steel is steel plate, active submerged arc welding wire grade H08A, wire diameter 5mm, flux grade the HJ43 ring seam and longitudinal seam are used for docking flat welding groove type is symmetrical "X"-shaped, while the first open slope altercation 60 °, groove depth of 8mm, the blunt edge 14mm, welder for the MZ-1-1000A active arc welding machine, welding current 900 ~ 950A, arc voltage of 38V, welding speed of 200 250mm/min. Positive after welding, back seam arc gouging clear the root, re-welding. Weld by visual inspection and internal non-destructive testing, were a class of weld standard mechanical function to try to effect request for GB700-88.
Two. Welding of carbon steel pipe
Buried Steel: Material Q23 thickness t = 24mm. Welding parameters for voltage 36V, Current 850 ~ 900A, speed 35mm/min.
Welding sequence: every detail of length 2m, longitudinal seam the inside of the first opening 60 ° bevel depth 6mm the weldment fixed by the welding arm stretching to hold the initiative welding; longitudinal seam lateral arc gouging, open 60 ° groove, the depth of 6mm, clear what the root, and then high-speed angle sander get rid of slag, burrs and heat layer, held the initiative welding.
Details of three put together a large section of the length of 6m. Welding the inside, and after welding the outside. Direction as above. The difference is, when the steel pipe on the roll welding car as swing activities, but pretends to welding wire feed welder for the welding arm.
Welded pipe: pipe the Q23 thickness t = 30mm. Assessed strictly in accordance with the welding process welding electrical characteristics identified in the report to implement voltage of 38V, current 900 to 950A, speed 200 250mm/min.
3. Carbon steel pipe weld quality inspection
The weld visual inspection: basis DL/T5017-93 steel pipe fabrication and installation and check standards, workplace welding the longitudinal seam and girth, belongs to a class I and II weld points to check for cracks, holes, not welded full not up to standard requests, ash and other defects in appearance, upon inspection, to be held to deal with.
The non-destructive testing of welds inside: the pipeline is a super-large steel pipe in water supply projects, outstanding is the thickness t = 30mm steel pipe is the pipe bridge, it is necessary to withstand the internal water pressure, have to bear by the steel pipe weight and water the moment, and thus the quality of the welding request outstanding high. Pipe bridge with t = 30mm thick steel pipe, longitudinal seam and circumferential seam belong to a class of weld, the request was held 100% of the X-ray film examination and 100% ultrasonic flaw detection; of thickness t = 24mm buried steel pipe, longitudinal seam belongs to a class welding, held 20% of the X-ray film examination and 50% of the ultrasonic flaw detection. X-ray flaw detector model is XXH-300 ultrasonic flaw detector model for the CTS-22.
Steel, carbon steel pipe steel pipe corrosion
A. Buried pipe external corrosion
Shot blasting: spray steel shot rust Sa5 restraint, rust, metal appearance of heavily exposed silver-white metallic luster, surface roughness of 40 ~ 70μm.
Spray coating: strengthen the special grade coal tar epoxy, or a primer, cheek 5, the center clip four layers of epoxy glass cloth, 0.9 ~~ 1mm thickness, coated with the paint painted on each paint the interval drying up the sticky subject.
Quality check: visual inspection: paint the appearance of uniform, smooth, no sagging, no bubbles, no wrinkles. Application thickness gauge, sampling 5 percent, fully measured to achieve the design thickness, or thicken up painting. Held at the 5000V spark pinhole leak detector, pinhole and insulation check for qualified non-sparking. Adhesion to check the coating cut triangular mouth, held tearing force should be difficult to pull up; if pulled up, but the first layer of primer must be attached to the pipe metal appearance, so to be qualified.
Two. External corrosion of carbon steel pipe out tube
Using the STIC heavy-duty coatings.
The shot blasting: all child pipe rust.
Spray anti-corrosion coatings: When rust qualified, using airless high pressure spray gun to spray the first layer of red primer until the paint to dry non-stick hand, and then spray the end of the second film thickness of 300μm.
Paint inspection: visual inspection, all child thickness measured using a magnetic thickness gauge held measurement, the total film thickness of more than 600μm.
Within the anti-corrosion of the steel pipe
Buried pipes and penstocks within the anti-corrosion, are used to hang galvanized barbed wire, spray compressive strength of not less than of 30N/mm2 the cement mortar lining. Cement mortar mix ratio, water: cement: sand = 22:200:270; use of domestic water; # 525 Portland cement; rigid, clean, well-graded natural sand, clay content is less than 2% particle size less than 2mm.
Rust: in the pipe installation, welding, backfilling overburden, vertical deflection, etc. find qualified wire wheel brush to completely get rid of the rust of the pipeline within the oxide scale, welding slag, oil.
Bang bar galvanized wire: the laying of 3mm diameter wire mesh size 50mm × 50mm, 10mm, mesh interval within steel pipe and the bottom of the arc length 1380mm, laying barbed wire, in order to spray the car to walk; barbed wire and the wall between the pad diameter φ long 7mm Q235 steel, spot welding, spacing of 350mm, the pipe wall from the wire appearance 9mm.
Mechanical spraying of cement mortar: two-tier spray, sprayed the first layer 10 ~ 12mm thick, the second layer of sprayed 8 ~ 10mm, to ensure smooth creamy abrasion.
Conservation: A section of steel pipe spraying immediately block all air vents, so that the tube be kept moist, held conservation.
Check check: measurement of anti-corrosion thickness, appearance and gentle, check for cracks, hollowing phenomenon, the grout compressive strength to achieve 30N/mm to be held in the excessive part of the process to meet the standard request.
Six, the entire steel pipe pressure attempts
According to the design request: try to pressure for 0.481MPa seepage request a total length of 827m is greater than 41/min. In April 2000, held to suppress leakage buck and suppression water buck try the effect of two steel pipe seepage, respectively for O.1051/min and 0.281/min for design requests.
Inverted siphon pipe from design to fabrication and installation, all in strict accordance with the design and standard request, overcome the problem of steel pipe production and construction and installation techniques, strict quality control. After quality check, the unit works fine product was 96%, reaching more to meet the effectiveness and lay a solid foundation for the safe operation of the project..