On-site forming method for bent pipe of steel large-diameter pipeline

Abstract

The invention belongs to the technical field of bent pipe machining, and particularly relates to a steel large-diameter pipeline bent pipe on-site forming method which comprises the steps that the bending angle is measured through a rope and a protractor; the outer perimeter of the pipe is measured by a tape; the bending radius is calculated, and the back height and the belly height of the end joints are calculated according to a given formula; after the steel pipe is horizontally and stably supported, popping up two axial center lines by using the ink box, popping up a bus at equal division points of the circumference, sequentially marking flush opening intersection points of end joints and middle joints according to calculated sizes, and connecting to form a closed cutting line; cutting along a line by using oxygen-propane neutral flame, numbering and assembling, controlling an alignment gap, cutting a V-shaped groove on site, remeasuring the angle by using a protractor after spot welding, correcting distortion, and turning, welding and forming. The bent pipe can be manufactured on the steel pipe feeding and discharging without a material paper sample plate, material paper sample plate manufacturing can be omitted, sample plate errors are avoided, bent pipe manufacturing precision is improved, meanwhile, the method can adapt to the field construction environment, the technology is simplified, rework and material waste are reduced, cost is reduced, and construction efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pipe bending processing, and particularly relates to a method for on-site forming of a steel large-diameter pipe elbow. BACKGROUND

[0002] In pipe construction, the manufacture of an elbow is very important, and the accuracy of blanking directly affects the quality and construction effect. In the traditional method, an unfolding drawing is obtained by experience or reference to lofting and calculation, and blanking is performed by projection lines. This method is suitable for small-diameter pipes, but there are the following problems for large-diameter pipes: 1. The construction environment is mostly in the wild, and there is no flat site, so there is no condition to unfold the lofting, and it is impossible to unfold and blank; 2. The required paper for unfolding and blanking is large in size, and the drawing rule has a limited span, and after the paper is spliced for blanking, there are many wrinkles, and the error of the second drawing rule is large; 3. The error of the material paper template affects the pipe fitting assembly speed and welding quality, and increases the subsequent work burden.

[0003] When the traditional method is used to manufacture a steel large-diameter pipe elbow, the unfolding of the lofting is limited by the site and tools, and the error of the material paper template is large, which leads to low manufacturing precision, low efficiency, and high rework rate. SUMMARY

[0004] The purpose of the present application is to provide a method for on-site forming of a steel large-diameter pipe elbow to solve the problems in the background art.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0006] A method for on-site forming of a steel large-diameter pipe elbow, comprising the following steps:

[0007] 1) A line is pulled tight at both ends of the laid pipe or at both ends of the pipe trench, so that it coincides with the center line of the pipe or the pipe trench, and the required bending angle a is directly read out by a protractor;

[0008] 2) The circumference of the steel pipe is measured by a tape measure, and the bending radius is calculated according to R=mD, wherein D is the outer diameter of the pipe, and m is 1-3 times the outer diameter of the pipe;

[0009] 3) The steel pipe is horizontally supported and fixed by a rolling lever, and the circumference is equally divided by a line cone, and two axial center lines that are 180° to each other are popped out by a cartridge, and the circumference is equally divided and the corresponding generatrix is popped out;

[0010] 4) The length of the end section straight pipe segment, the end section back height, and the abdominal height are sequentially measured and marked on the outer wall of the pipe by a ruler, and the joint line is drawn by a joint paper, the intersection of the joint line and each generatrix is obtained, and the intersection points are connected to form a closed cutting curve;

[0011] 5) An oxygen-propane neutral flame or a slightly oxidizing flame is used to cut the end section and the middle section along the closed cutting curve once, and the cutting speed is adjusted to ensure that the cutting is complete and there is no adhesion.

[0012] 6) The cut segments are numbered, and in-situ assembled with one end segment as the reference, the center lines of the middle segment and the other end segment are aligned, the control gap between the aligned ends is 1-3mm, and the misalignment is ≤1mm / m, and the segments are fixed by spot welding;

[0013] 7) For the pipe opening with a diameter ≥DN100, a V-shaped groove is cut on site: the back part is 20-25°, the two sides are 30-35°, the abdomen part is 40-45°, and the blunt edge is 2-3mm;

[0014] 8) The center line angle of the bent pipe is re-measured by a string, and after correction of the distortion, the pipeline is leveled and the final connection is completed by rolling welding, and the entire manufacturing process does not require paper templates.

[0015] m is 1.5-2 times the outer diameter of the pipe.

[0016] The back height of the end segment of the pipeline is:

[0017] The abdomen height of the end segment of the pipeline is:

[0018] In the formula the back height of the end segment is h, the abdomen height of the end segment is H, R is the bending radius of the bent pipe, D is the outer diameter of the pipe, α is the bending angle, and n is the number of segments of the middle segment.

[0019] The nominal diameter of the steel pipe is ≥500mm, and the wall thickness is 3-26mm.

[0020] The measurement accuracy of the bending angle α is controlled within ±0.5°, and the angle deviation of the finished bent pipe is ≤0.5°.

[0021] As described above, by adopting the technical scheme, the present application has the following beneficial effects:

[0022] The present application can manufacture a bent pipe on a steel pipe without a paper template, which can save the manufacturing of a paper template, avoid template errors, improve the manufacturing precision of the bent pipe, ensure the assembly speed and welding quality, adapt to the field construction environment, and does not require a flat site and large-scale paper, thereby simplifying the process, reducing rework and material waste, reducing the cost, improving the construction efficiency, and effectively solving the problems of existing steel large-diameter pipeline bent pipe field manufacturing, such as difficulty in unfolding a sample, large error caused by dependence on a paper template, and low construction efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 It is a schematic diagram for calculating the bending radius of the present application.

[0024] Fig. 2 It is a schematic diagram of the dimensions of the pipeline of the present application. DETAILED DESCRIPTION

[0025] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0027] The method for forming a steel large-diameter pipe elbow on site, according to the present application, comprises the following steps:

[0028] 1) Measurement

[0029] If the two-end pipe has been laid, two persons stand at the two ends of the connecting pipe, lay the string flat on the center line of the pipe, the middle person pulls the string tight to make it coincide with the center line of the pipe, and measures the included angle of the string with a protractor.

[0030] If the pipe has not been laid and only a pipe trench is available, two persons lay the string on the center position of the pipe trench at the two ends of the pipe trench, the middle person pulls the string tight to make it coincide with the center line of the pipe trench, and measures the included angle of the string with a protractor.

[0031] 2) Calculation

[0032] Steel pipe circumference: due to the rust on the surface of the steel pipe and the influence of the spiral weld, etc., the actual size is obtained by measuring the pipe skin with a steel pipe ruler or a tape measure, instead of calculating the circumference with the circumference calculation formula, as shown in the following formula. Figs. 1-2

[0033] Bending radius: R = mD formula: R - bending radius (mm) D - pipe outer diameter (mm) m - required multiple. m is generally 1-3 times of the pipe outer diameter, and 1.5-2 times is most commonly used.

[0034] Back height of end piece:

[0035] Abdominal height of end piece:

[0036] In the formula, back height of end piece (mm) abdominal height of end piece (mm) R - bending radius of elbow D - pipe outer diameter (mm)

[0037] R - bending radius of elbow D - pipe outer diameter (mm)​​​

[0038] a - bending angle, n - number of segments of the intermediate piece.

[0039] 3) Scribing

[0040] The bottom of the steel pipe is supported by two rollers at the front and back ends and is fixed on the left and right sides to ensure its static stability and prevent it from swinging. Then, the outer diameter of the pipe is measured with a steel tape, and the center point is determined by vertically bisecting the outer diameter with a line cone. The center point is then divided into two symmetrical center lines using a cartridge, and the center lines are gently punched with a center punch to facilitate subsequent assembly. The circumference of the pipe is then divided into equal arcs at the outer diameter of the two ends using a tape measure, and the arcs are labeled with a stone pen. The arcs are then connected into an axial straight line using a cartridge. The welding size (i.e., the distance between the end segments of the straight pipe) is measured from either end of the straight pipe using a ruler, and the point is marked with a stone pen. The back height and the abdominal height of the pre-bent pipe end segment are then measured from the marked point using a ruler, and the points are marked with a stone pen. The last point of the paper is then used as a reference to draw a joint line that intersects the axial straight line at each equal division point. The intersection points are then marked with a stone pen, and the actual templates of the intermediate piece and the end piece are obtained by connecting the points into a smooth curve.

[0041] 4) Cutting

[0042] The torch cutting flame temperature is selected according to the wall thickness of the pipe. The intermediate piece and the end piece are cut using a welding tool along the line. During cutting, the preheating flame is either neutral or slightly oxidizing, and carbonizing flame cannot be used because the remaining carbon in the carbonizing flame will cause the cutting edge of the cut piece to be carbonized. The flame should be adjusted when the cutting oxygen jet is turned on to prevent the preheating flame from changing. The cutting speed should be slow to ensure cutting penetration, prevent sticking, and reduce iron oxide. After cutting is complete, the pipe end slag is removed.

[0043] 5) Assembly

[0044] The cut pipe is labeled and placed on the ground. One end piece is fixed to ensure its static stability and prevent it from swinging. The other end piece is then assembled with the intermediate piece using the fixed end piece as a reference. The center line must be aligned during assembly to prevent the bend from twisting. To ensure the quality of the weld joint and meet the butt joint requirements, the gap between the two pieces is carefully adjusted using a welding cutter until it meets the specification requirements. The gap between the large-diameter pieces is determined by the pipe wall thickness. When the wall thickness is about 3mm, the gap is 2-3mm. When the wall thickness is less than 3mm, the gap is 1-2mm. The misalignment rate should not exceed 1mm / m. After confirming that the assembly is appropriate, the pieces are reinforced by spot welding using a welding machine.

[0045] 6) Grooving

[0046] According to the pipeline process installation requirements, the welding of pipe orifice with diameter above 100mm must have a groove to ensure the strength and service life, when the pipe wall thickness is 3-26mm, V-shaped groove is adopted, the general groove angle is 20-25° at the back of the elbow, 30-35° at both sides, 40-45° at the abdomen of the elbow, the bevel size is required to be 2-3mm, the groove is required to be smooth, and there should be no defects such as cracks and interlayer on the surface of the groove.

[0047] 7) Correction

[0048] One person at each end of the pipe orifice puts a string in the center of the pipe, and the middle person adjusts it to coincide with the center line of the elbow, measures the angle with a protractor, and observes whether it is on the same axis from the side, and corrects it in time if there is distortion and skew.

[0049] 8) Welding

[0050] The elbow is welded flat, and it should not be moved, suspended or affected by external force, and the welding strength and quality are improved by using flip welding to reduce overhead welding.

[0051] In the field pipeline construction site of our company, 90° elbow pipes need to be made, and the bending radius is 1.5 times the outer diameter of the pipe. By using the present application, the center line angle of the pipe trench is measured to be 90°, the circumference of the steel pipe, the back height and the abdomen height of the end section are calculated, and the steel pipe is marked, cut, assembled, grooved and corrected before welding. The angle of the elbow pipe made is accurate, without distortion and skew, and the welding quality meets the requirements, the construction efficiency is improved by 40% compared with the traditional method, and there is no rework phenomenon.

Claims

1. A method of field forming a steel large diameter pipe bend, characterized in that, The method comprises the following steps: 1) Pull a string at both ends of the laid pipe or trench to coincide with the center line of the pipe or trench, and directly read the required bending angle a with a protractor; 2) Measure the circumference of the outer wall of the steel pipe with a tape measure, and calculate the bending radius R = mD, where D is the outer diameter of the pipe and m is 1-3 times the outer diameter of the pipe; 3) Horizontally support the steel pipe with a rolling lever and fix it left and right, bisect the circumference with a wire cone, and pop out two axial center lines that are 180° to each other with an ink cartridge, then equally divide the circumference and pop out the corresponding generatrix; 4) Measure and mark the length of the end section straight pipe segment, the end section back height and the abdominal height on the outer wall of the pipe in sequence with a ruler, draw the joint line with a joint paper, obtain the intersection of the joint line and each generatrix, and connect each intersection to form a closed cutting curve; 5) Adopt oxygen-propane neutral flame or slightly oxidizing flame to cut the end section and the middle section along the closed cutting curve once, and the cutting speed is determined to ensure that the pipe is cut through and not adhered; 6) Number the cut sections, and assemble them in place with one end section as a reference, align the center lines of the middle section and the other end section, control the gap between the joints to be 1-3 mm and the misalignment amount to be ≤1 mm / m, and point weld to fix; 7) For pipe joints with a diameter of ≥DN100, cut a V-shaped groove on site: 20°-25° at the back, 30°-35° on both sides, and 40°-45° at the abdomen, with a blunt edge of 2-3 mm; 8) Measure the center line angle of the bent pipe with a string, correct the distortion, pad the pipe, and complete the final connection by turning and welding, and the entire manufacturing process does not require a paper template.

2. A method of field forming a steel large diameter pipe bend according to claim 1, characterized in that: m is 1.5-2 times the outer diameter of the pipe.

3. A method of field forming a steel large diameter pipe bend according to claim 1, characterized in that: Wherein, The back height of the end nipple of the pipe is: The end socket of the pipe has a height of: wherein is the back height of the end node, is the back height of the end node, R is the bending radius of the bend, D is the outer diameter of the pipe, a is the bending angle, and n is the number of nodes of the middle node.

4. A method of field forming a steel large diameter pipe bend according to claim 1, characterized in that: The nominal diameter of the steel pipe is ≥500 mm, and the wall thickness is 3-26 mm.

5. A method of field forming a steel large diameter pipe bend according to claim 1, characterized in that: The measurement accuracy of the bending angle a is controlled within ±0.5°, and the angle deviation of the finished bent pipe is ≤0.5°.

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