Slip-on flanges: characteristics and production

Flanges are a set of mechanical devices necessary to join different components together without using a welded joint but only by means of screws and bolts. As already explained elsewhere with regard to threaded connections, they present an important series of advantages relating to disassembly and assembly, in addition to the possibility of intervening more easily if maintenance is required. In addition, the use of screws allows the components to be kept separate from each other, avoiding, in the event of nucleation and growth of a crack, that it develops without any type of interruption between one component and another. The third non-negligible aspect is the maintenance of mechanical properties: in fact, by applying the heat necessary to form a welded joint, microstructural changes are created in the components, especially in the groove area and in the HAZ (heat affected zone) with changes in the mechanical properties which may be important.

On the other hand, this type of joint also has limitations as regards tightness: time, combined with the pressure generated for example inside the connected pipes, can lead to the development of vibrations caused by a loss of the thread seal and can also lead to consequences that can be dangerous.
Within this category of mechanical components there are slip-on flanges, which belong to the category of overlapping welded flanges: they are welded to the pipe or mechanical component and connect to each other through the use of bolts. Therefore, they have multiple advantages deriving from both techniques used:
- Welding allows them to be produced more easily and only later to be joined with the tube;
- The threaded joint allows, on the other hand, to guarantee maintenance and a greater possibility of intervention, if necessary.

The forging of slip-on flanges

The slip-on flanges are produced, as well as the other types of flanges available in the Intertubi catalog, through a production chain that requires forging operations. What is this technique? Forging consists of a plastic deformation process in which the component to be deformed is heated to a high temperature (without ever entering the liquid field) and then proceeds to work through a series of hammer blows or press, giving in this way the shape. The use of temperature represents a cost from a production point of view, but also greater ease in applying the deformation and obtaining the desired shape.
Generally the starting point is constituted by a billet or an ingot, semi-products prone to this type of processing. An important aspect to consider for this type of processing is that it only serves to produce partially roughened semi-finished products: all finishes and final dimensions will then be achieved through much more precise processes such as machining with machine tools.