Spiral welded steel pipe is one of the most commonly used steel pipes at present. With its advanced technology and strong and durable characteristics, spiral welded steel pipe is widely used in various fields of manufacturing and transportation. Spiral welded steel pipe is a spiral seam steel pipe welded by automatic double-wire double-sided submerged arc welding process.
1.Bulging method
One is to place rubber inside the tube, and use a punch to compress it above to make the tube bulge into shape; the other method is hydraulic bulge forming, in which liquid is filled into the middle of the tube, and the liquid pressure bulges the tube into the required shape. Most production uses this method.
Use a swage forging machine to stretch the end or part of the pipe to reduce the outer diameter. Commonly used swage forging machines include rotary type, connecting rod type, and roller type.
There are three methods that are commonly used. One method is called the stretching method, the other method is called the stamping method, and the third roller method has 3-4 rollers, two fixed rollers, and an adjusting roller to adjust the fixed roller distance. The finished pipe fittings It’s just curved.
Use a tapered core on a punch to expand the pipe end to the required size and shape.
5.Rolling method
Generally, no mandrel is needed, and it is suitable for the inner round edge of thick-walled pipes.
6.Roller method
A core is placed inside the tube, and the outer circumference is pushed with a roller for round edge processing.
Spiral welded steel pipe coating method The processing method refers to chemical coating on the surface of the spiral welded steel pipe. Common anti-corrosion forms include 3lpe anti-corrosion, epoxy resin anti-corrosion, cement mortar anti-corrosion, and huanyangmei. The biggest purpose of this processing method is to extend the life of the pipe. service life.
Coating construction process: Pipe rust removal → Primer coating → First coat of topcoat → Second coat of topcoat → Wrap glass silk cloth → Topcoat → Topcoat
Before applying primer, the surface of the pipe should be free of grease, ash, rust, and oxide scale. The quality standard of sandblasting rust removal reaches Sa2.5 level.
Apply primer after removing rust from the surface of the pipe, with a time interval of no more than 8 hours. When applying primer, the base surface should be dry. The primer should be applied evenly and plumply without any clumping or bubbling. The primer should not be applied within the range of 150 to 250mm from both ends of the pipe.
The epoxy coal pitch coated steel pipe coating is a two-component, room temperature curing coating; the glass fiber cloth is dry, dewaxed, untwisted, edge-sealed, medium alkali, and has a warp and weft density of 1012/cm~1212. /cm glass fiber cloth. Immediately after the topcoat is applied, wrap the glass silk cloth. The width of the edge of the glass cloth is 30 to 40 mm. The overlap length of the joints is not less than 100 mm. The overlap joints of each layer are staggered from each other. The oil permeability of glass fiber cloth is over 95%, and there should be no gap larger than 50mm*50mm. A 150-250mm stepped gap should be left at the end of the pipe.
The construction of pipeline interfaces should be carried out after passing the welding pressure test. The old and new anti-corrosion edges should not be less than 50mm, the overlap length of the joints should not be less than 100mm, and the joints should be firmly and tightly bonded.
① Quality inspection shall be carried out by sampling inspection method according to planning rules.
② Check each root with your eyes. The surface of the covering layer should be uniform, flat, and free of defects such as bubbles, wrinkles, bulges, and uneven edge pressure.
③The thickness of the paint film is measured with a magnetic thickness gauge. Measure a point every 1.5 meters on the circumference of the ends and center of the single-section steel pipe. The thickness of the paint film should meet two 85%: that is, the thickness of 85% of the measuring points meets the planning requirements. For measuring points that cannot reach the thickness, the minimum value should be no less than 85% of the planned thickness;
④ Use a pinhole viewer to check for pinholes. If pinholes are found, use a sandpaper grinder to grind and re-coat;
⑤ If the paint film thickness is insufficient or there are pinholes, it should be re-examined after repair and solidification. If it is unqualified, it should be repaired again until it is qualified;
⑥ To check the adhesion, use a hard tool to make a cut at an angle of 60° on the coating for inspection. The coating should be cut through to the base material, and the cut part should be pasted with tape. After tearing off the tape, observe the scratched area and apply The layer should be free of peeling. You can also check it on a sample painted under the same conditions.
① During and after surface coating construction, the painted workpieces should be protected to avoid flying dust and other debris.
② Inspection after painting should ensure that the coating is consistent in color, bright and bright, and free of defects such as wrinkles, blistering, sagging, and missing paint.
③To measure the thickness of the coating film, use a contact-type paint film thickness gauge to measure the thickness of the paint film. The paint film thickness gauge generally measures the thickness at 3 points and takes the average value.
