Tube flaring is the process of tube fabricating, or tube end forming, used to form an extremely tight seal at the end of a pipe or tube. Many industries require the use of pipes and tubing in a flow system and therefore the ability to connect pipes and tubes without leakage is important.
Flaring creates a funnel shape at the end of the tube, which is designed to exactly match the dimensions of what the tube is being fitted against in order to create a tight seal. During the installation of the tube, the flare is matched exactly with a threaded fitting. The inside of the tube’s flare fits against the cone-shaped end of the fitting.A flare nut then screws the fitting together and brings the flare flush against the joining component. This creates a tight seal between the two pieces and eliminates the need for a gasket between the tube and fitting.
Flaring is a similar process to tube swaging in that a seal is created between two previously unattached tubes and tube components. After joining, liquids and gases are then able to pass through the tube system securely. For tubes that are subject to more wear and tear and are used in rougher environments, double lap flaring can be implemented to make the tube end stronger and give the inner surface of the flare a slightly thicker diameter.
A common flaring tool is used to make both single and double flares, and the most used angle for both is 45°. A die block with holes in it is used for the process. The holes allow different diameters of tubing to be handled correctly. A clamp then locks the ends of the tube into the holes, and makes a clean cut at the end in order for the most precise flaring.
A yoke with a cone-shaped compressor is attached to the die block and fits over the top of the clamped tube end. A t-shaped handle is used to move the compressor screw into the tube under great pressure, forcing a single flare at the end of the tube. The size of the flare depends on how far the end of the tube extends beyond the clamp of the die block.
To create a double lap flare, the process is the same; however the tube is turned slightly by adapters to create the double lap. The process of flaring can be time consuming as the resulting flare has to be big enough to fit snugly against the fitting, but small enough to fit the flare nut threads accurately.
Tube Flaring Informational Video