Before performing steel bending pipework, you must first calculate the unfolded length of the bent section of the pipe and mark the starting point of the bending so that the correct semi-finished product can be obtained after bending.
1. Calculation of 90°bending pipe
90°bending pipe is the most widely used in pipeline engineering, and its bending radius varies depending on the production method. For cold-simmered steel bending pipes, R=(4~6)D is often taken; for hot-simmered steel bending pipes, R=4D; for stamping elbows or welded elbows, R=(1~1.5)D is often taken. After the bending radius is determined, the cutting length of the bent part can be calculated, and the heating length during simmering can be determined. After the pipe is bent, the outer arc and inner arc of the bent section are not the actual length of the original straight pipe, but only the steel The length of the centerline of the bending pipe remains unchanged before and after bending, and its unfolded length is equal to the length of the original straight pipe section. Now assume that the starting and ending points of the curved section are a and b respectively. When the bending angle is 90°, the length of the curved section of the pipe is exactly 1/4 of the circumference of the circle drawn with r as the radius, and its arc length is represented by the bending radius. When bending U-shaped bends, reverse double elbows, or square telescopic joints if the center distance of two adjacent 90° elbows as required by the design drawing or actual measurement is used for marking and bending, then the bending will be The center distance between the two elbows will be larger than the original distance. This is due to the extension of the metal pipe when it is heated and bent. When blanking, this extension error should be subtracted from the center distance of the two elbows, and then the center line and heating length of the second elbow should be drawn so that after the two elbows are bent, the distance between the center lines will be exactly right. equal to the required size. In actual work, when making pipe fittings composed of multiple elbows, the marking work is completed several times. First, calculate the cutting length of each section on the sketch and select a straight pipe of appropriate length; then start from one end to make elbows one by one. After the previous elbow is made, draw the next one to facilitate the work on the steel bending pipe. dimensional error in.
2. Calculation of any steel bending pipe
Any steel bending pipe refers to a steel bending pipe with any bending angle and any bending radius. As long as the bending angle and bending radius are constant, you can easily calculate steel bending pipes at any angle and bending radius using Table 1-1. When simmering, the length of the heating pipe section should generally be slightly longer than the bending length to ensure uniform heating of the bending part. The increased length is generally stipulated as follows: for pipes with a large bending angle, the length of the outer diameter of the pipe can be increased; for pipes with a small bending angle, 20% of the bending length can be added.
3. Calculation of other steel bending pipes
① Back and forth bending at any angle There are two types of back and forth bending at any angle: equal bending radius and unequal bending radius. Bending back and forth at any angle with equal bending radius. This kind of steel bending pipe has five variable data: bending radius R, bending angle a, bending distance H, steel bending pipe length A, and straight pipe length L. In actual work, generally, three data (H, R, and a) can be determined based on the design or actual site conditions, and only two data (L, A) need to be determined by calculation.
② Calculation of arc-shaped steel bending pipe. Arc steel bending pipe is also called semicircle bend and hug bend. Common angles of arc-shaped steel bending pipes are 45° and 60°.
③Wrinkle elbow. The simmering method of the wrinkled elbow is different from the cold simmering and hot simmering steel bending pipe. Its characteristic is that the total length of the pipe wall on the back of the elbow remains unchanged before and after bending, while the pipe wall on the inner side of the elbow bends due to local heating, resulting in Regular wrinkles. Therefore, the method of drawing lines is also completely different. Marking dimensions for each part of a wrinkled elbow with a bending angle of 90°.
Post time: Dec-13-2023