Increasing the wall thickness on a tight radius bend generally improves the final quality of a rolled tube as well as lowers the minimum radius a piece can be rolled with minimal distortion issues. Another important factor to consider when looking at pipe or tubing is the wall thickness of the piece to be bent. In these cases, the minimum radius will likely need to increase beyond a 3D size.
While it may not be a minimum for every bender, a 3D bend radius is a commonly used starting point for minimum radius bends.Īs a piece size gets larger, pre-made tooling for tight bends will be less common. For tight rotary draw bending, maintaining a bend radius that is a whole number multiple may increase the capability of the steel bender to meet your needs. So, even though it may be possible to give a piece a 2D or 3D bend, a 3.5D bend may be more difficult because the tooling is not on hand. This type of bending is usually performed on a rotary draw bender for speed and precision, which requires specific tooling built for each bend. 2D = 4 inches, 3D = 6 inches, and 5D = 10 inches for a 2 inch diameter pipe. In these cases, the 2D would reference a centerline bend radius of two times the diameter. For example, on a 2 inch pipe elbow, common bend measurements may be referred to as 2D, 3D, or 5D. In some instances, a rough guide for minimum radius bending would be to use a multiple of the piece diameter. A 2” carbon steel pipe will have a different minimum radius from a thin wall 2” aluminum tube. There are many factors to take into account when determining the minimum radius such as the material composition, shape, and size. In some instances, an estimator can quickly say yes or no based on prior knowledge and bending experience. View information about bending conduit using a bender and the deducts and multipliers charts.Often, in the rolling and bending industry, we field requests asking about the minimum radius to which we can roll or bend a piece. Most scientific calculators (and even the calculators built into smart phones) have these functions. The relatively simple math formulas of sine, cosine, and tangent can be used to determine the angles of the triangle, and, therefore, the necessary angles of your pipe bend(s). No matter how the tube is bent in this configuration (or how the triangle is oriented), one of the angles of the triangle will be 90° the other angle will depend on the first angle (d), and can be calculated as (90 – d). The “d” represents the angle at which the pipe is bent. The lengths/sides of the triangle are labeled “a,” “b,” and “c”. The black line represents an offset bend in a tube the red triangle represents the triangular geometry this offset creates. Most bends other than 90° can be calculated using the geometry of a triangle. Then, use this formula:įor example, if your die creates a 2.2” radius, and you need to create a 35° bend, your calculations would look something like this:
TUBE BENDING RADIUS FULL
Using the same variables as above, the standard dimension ratio (SDR) of a pipe can be calculated thusly:Ĭalculating CLR (Center Line Radius) for Bend AngleĪfter you’ve selected the appropriate die for bending your pipe, based on the pipe’s outside diameter and wall thickness, you should be able to find the radius of the bend.Ī simple way to determine the center line radius of a bend of a specific angle is calculate a full circle, then divide that number by 360 to find the measurement of one degree.
TUBE BENDING RADIUS SERIAL
S = wall thickness (mm) | S = pipe serial (-) Σ s = hoop stress (N/mm 2) | PN = normal pressure (bar) | da = external pipe diameter (mm)
TUBE BENDING RADIUS ISO
ISO 161-1 uses the following formula to calculate the wall thickness of pipe: It is important to understand the different elements of a bend in order to make accurate calculations. This radius will vary depending on the outside diameter of the tube, the wall thickness, and the angle at which the tube is to be bent. When calculating bend allowances to determine the cut length of HDPE conduit or PVC pipe, one must calculate from the center line radius (CLR) of the finished, bent pipe. An inexpensive scientific calculator and an angle finder are the only additional tools required. Using just a few mathematical formulas allows you to properly calculate a bend of nearly any angle.