Steel bending pipes can be divided into simmered steel bending pipes, stamped steel bending pipes, and welded steel bending pipes according to their different production methods. Simmering steel bending pipe is divided into two types: cold simmering and hot simmering.
General knowledge about steel bending pipe: A steel bending pipe is a pipe fitting that changes the direction of the pipe. Steel bending pipe can be seen where pipes intersect, turn, go around beams, etc.
Simmered steel bending pipe has the advantages of good elasticity, high-pressure resistance, and low resistance. Therefore, it is often used in construction.
The main forms of steel bending pipe are elbows at various angles, U-shaped pipes, back-and-forth bends (or B-bends) arc-shaped steel bending pipes, etc.
An elbow is a pipe fitting with an arbitrary bending angle, which is used at the turn of the pipe. The bending radius of the elbow is represented by R. When R is larger, the bending part of the pipe is larger, and the steel bending pipe is smoother; when R is smaller, the bending part of the pipe is smaller, and the bending is faster.
Back-and-forth bends are pipe fittings with two bend angles (usually 135°). The distance between the center lines of the bent ends of a steel bending pipe is called the height of the back-and-forth bend, represented by the letter h. Indoor heating vertical branch pipes are connected to main pipes and radiators. When the pipes are connected to joints that are not on the same plane, they generally need to be bent back and forth.
The U-shaped pipe is a semicircular pipe fitting. The distance d between the center lines of the two ends of the tube is equal to twice the bending radius R. U-shaped tubes can replace two 90° elbows and are often used to connect two circular wing-shaped radiators arranged one above the other.
A curved steel bending pipe is a pipe fitting with three bending corners. The middle angle is generally 90° and the side angle is 135°. Curved steel bending pipes are used to bypass other pipes. Curved steel bending pipes are often used when piping sanitary equipment with hot and cold water supplies.
The size of a steel bending pipe is determined by the pipe diameter, bending angle, and bending radius. The bending angle is determined based on the drawings and the actual conditions at the construction site. Then a template is made, simmered according to the template, and the bending angle of the simmered pipe fittings is checked according to the template to see if it meets the requirements. The sample can be made by simmering round steel. The diameter of the round steel is selected according to the diameter of the pipe to be simmered, 10-14mm is enough. The bending radius of steel bending pipe should be determined according to the pipe diameter, design requirements, and relevant regulations. It can neither be too big nor too small. Because the bending radius is too large, not only a lot of material is used, but the bent part of the pipe also occupies a large space, which will cause difficulties in pipe assembly; if the bending radius is too small, the pipe wall at the back of the elbow will be thinned due to excessive elongation. , reducing its strength, and the pipe wall on the inside of the elbow is compressed, forming a wrinkled state. Therefore, it is generally stipulated that the bending radius of hot-simmering steel bending pipe should not be less than 3.5 times the outer diameter of the pipe; the bending radius of cold-simmering steel bending pipe should not be less than 4 times the outer diameter of the pipe; the bending radius of welding elbow should not be less than 1.5 times the outer diameter of the pipe; the bending radius of the stamping elbow should not be less than the outer diameter of the pipe.
When steel bends a pipe, the metal on the inside of the elbow is compressed and the pipe wall becomes thicker; the metal on the back of the elbow is stretched and the pipe wall becomes thinner. The smaller the bending radius, the more serious the thinning of the pipe wall on the back of the elbow, and the greater the impact on the strength of the back. To prevent the original working performance of the pipe from being greatly changed after bending, it is generally stipulated that the pipe wall thinning rate after bending shall not exceed 15%. The pipe wall thinning rate can be calculated as follows:
In the formula, A——the thinning rate of the pipe wall at the outer busbar after the pipe is bent (%);
DW——Pipe outer diameter (mm);
R——bending radius of steel bending pipe (mm).
When steel bending pipe, due to the change in the thickness of the inner and outer pipe walls of the bending section of the pipe, the cross-section of the bending section changes from the original circle to an elliptical shape. Changes in the cross-sectional shape of steel bending pipes will reduce the flow cross-sectional area of the pipe, thereby increasing fluid resistance and reducing the pipe’s ability to withstand internal pressure. Therefore, the ellipticity of steel bending pipes is generally specified as follows: When the pipe diameter is less than or equal to 150mm, the ellipticity shall not be greater than 10%; when the pipe diameter is less than or equal to 200mm, the ellipticity shall not be greater than 8%.
The ellipticity of the pipe can be calculated as follows:
In the formula, T——Ellipticity (%);
d1——Major diameter of elliptical deformation (mm);
d2——Short diameter of ellipse deformation (mm).
When water, gas steel pipes, and straight seam welded steel pipes are used to make cold simmering steel bending pipes or hot simmering steel bending pipes, the welding seam of the pipe should be located at 45° from the center line of the side. To prevent the pipe weld from cracking when bending.
Wrinkles are generally not allowed in simmered steel bending pipes. If there are individual undulations, the height shall not be greater than the following regulations: when the pipe diameter is less than or equal to 125mm, it shall not exceed 4mm; when the pipe diameter is less than or equal to 200mm, it shall not exceed 5mm.
Post time: Mar-18-2024