BLM GROUP
New laser tube bending macchines
[DYNAMO-ELE LR150 Electric in-process right and left tube bending machine]
[ELECT New generation full electric CNC tube bending machine]
New laser tube cutting macchines
[LT722D laser tube cutting system]
[LT823D laser tube cutting for non orthogonal cuts]
New laser tube endforming macchine
[TUBE FORM with indexing rotary table with a multi-station with auto-indexing pre-load system]
SITEMAP
NEWS & EVENTI
Tube Bending - when tube bending is used
Every fitting is a possible source for a future leak. Vibration, pressure, corrosion, and chemical breakdown of the fitting materials are causes of fitting failure. In some circumstances tubefitters and plumbers wish to have as few fittings and welds as possible to avoid future sources of leakage. This can be important in heating tubes which are to be buried in concrete, boiler piping inside boiler casings, hydraulic piping, and others. The best solution to these situations is often to substitute tube bends in place of fittings wherever possible. When a tube is bent , the outside of the bend is stretched and the inside is compressed. The stretched outside has safety considerations. When the tube wall is stretched it becomes thinner. The general practice, with standard weight tube , is to minimize this thinning by limiting the radius of the bend to no less than five times the tube size. A bending wheel is a steel or cast iron circle that is pressed into the tube to make the bend . A groove is machined into its perimeter to a depth of one-half the tube diameter. If the bending wheel is measured across its greatest width and this is divided by 2, the radius of the bend that this particular bending wheel will make is obtained. Tube bending on too short a radius will flatten the tube and reduce its carrying capacity.
There are two kinds of tube bending methods. In the first, the bending wheel is pressed into the tube , which is held in position by two “ bending blocks ”. The beginning contact point between the machine and the tube is the center of the arc of the finished bend.
The other kind of bending machine grasps the tube to the wheel at the beginning of the bend and then rotates the wheel, forcing the tube to bend with the wheel as it rotates. This makes all calculations start at the beginning of the arc of the bend. This is the type process found in small hand benders used for hydraulic, gas, and air pressure lines, but it is also used in heavy tube fabrication shops where tube sizes 8" IPS and more are bent on a machine weighing many tons.
If we make a 90° bend in the center of a piece of tube 24 inches long, how long will the tube tangents be? We can't be exactly sure, except to say that they will not be 12 inches long. We can't be certain because the size of the tube is not known and, therefore, the radius of the bending wheel is not known. But the reason that the length of the tube tangents added together is greater than 24 inches is that the tube takes a short-cut across the angle of the bend. This shortcut results in what tubefitters call gain.
The tube bending machine
This machine has been designed to bend tubes already cut and is especially suitable for bending long elements or those requiring multiple curves at both ends of the tube. The tube ending machine can bend tubes whose ends have already been worked (e.g., profiling, tapering, etc.), within the limits of compatibility with bending head dimensions.