January 29th, 2019
It’s worth a mention firstly that there are two common terms used in industry, tube bending and pipe bending. Tube is measured by the outside diameter whereas pipe is measured by the inside diameter. Pipe sizing refers to the nominal inside diameter, sometimes called nominal bore, rather than the actual inside diameter.
Tube bending, or pipe bending, dates back over 100 years. There are dozens of different kinds of machines dependent on the desired shape, which can range from simple hand-operated tube benders through to a fully computerised numerically controlled machines.
Some of the most common forms of bending are:
• Compression pipe bending
• Draw pipe bending
• 3-roller tube bending
• Induction pipe bending
Barnshaws offers tube / pipe bending using all of the above methods of bending across our various branches, with a capacity of up to 60” (1524mm) at the top end and down to 1” (25.4mm) at the bottom end; our cold bending being the largest capacity worldwide.
When considering pipe bending or tube bending, there are many factors that need to be taken into account, all of which have a significant bearing on the end results. It’s always good practice to consult a specialist pipe bending sub-contractor who will offer advice on what material to use and which method will produce the best results. For example, compression pipe bending and draw pipe bending feasibility is limited to the tooling the specialist bending sub-contractor has in their stock, and even if they do have suitable tooling, the material grade of a pipe might render the production unfeasible. For instance, a draw pipe bending machine that can bend a 4” (101.6mm) pipe to a 3D (3 x Diameter) radius in mild steel would have difficulty bending the same size pipe to the same parameters in stainless steel due to the additional strength (torque) required to bend.
In the case of pipes used in fluid transfer of any kind, the wall thinning / thickening often plays a big part in the material and machine selection for pipe bending. Also, it is this sector that requires pipe bending to a relatively small radii, typically less than 5D radius on 90 degree elbows. Wall thinning will occur on the outside (extrados) of the bend and is measured as the amount of reduction from normal or nominal wall thickness, to the amount of wall thickness remaining on the extrados after forming.
Most specialist pipe bending sub-contractors will have detailed information listed on their website, along with trained internal sales teams who can assist designers with their enquiries to avoid any unnecessary re-designs during the production stage.