Within any domestic or civil system it is possible to find pipes that have orthogonal axes to each other or with an angle that does not make them parallel such as, for example, at 45 °. For the realization of the connection, then, some fundamental components are chosen that allow the junction: the elbows. In particular, the austenitic stainless steel elbows
(in 304 / 304L and 316 / 316L) have a series of mechanical and resistance characteristics:
- Mechanical resistance: allows to avoid breakages in operation;
- Good ductility: useful in the component forming process;
- Resistance in temperature: allows to face severe working conditions that could lead to the premature failure of the structures;
- Corrosion resistance: a central aspect for devices that are in contact with particularly aggressive fluids and environments.
Within the Intertubi catalog there are numerous types of elbows that differ in some fundamental characteristics:
- Reference standard: the two main ones are the American standard ASME B16.9 and the European standard EN-10253;
- Characteristic dimensions: among which it is appropriate to remember the radius of curvature, the thickness and the diameter of the duct;
- The angle: that is, the inclination between the axes of the two pipes placed in connection.
As regards the first distinction, based on the reference standards, in the American case there are 45 ° elbows without welding, with a diameter from ½ " to 24" and a radius of curvature equal to 1.5 times the diameter, and 90 °, from 1" to 24" with a radius of curvature equal to the diameter.
For the European standard, however, the elbows are welded with an angle of 45 °, from 13.7 mm to 609.6 mm with a radius of curvature equal to 1.5 times the diameter, and at 90 °, from 21.3 mm to 114.3 mm with a radius of curvature equal to 2.5 times the diameter.
The fundamental distinction is the presence of the welding that derives from the different production method. Welding is a widely used joining technology for metallic materials with many benefits but also some limitations due to the microstructural change, the possible presence of defects and, in general, the quality of the product obtained.
The forging process of stainless steel elbows
In order to be able to create stainless steel elbows that comply with the regulations and quality requirements requested by customers, Intertubi uses, in addition to materials with excellent characteristics and properties, controlled production processes following the best procedures deriving from both study and experience in the field.
In particular, the forging process assumes considerable importance. This operation allows the transformation of stainless steel by bringing it to high temperatures and plastically deforming it to obtain a semi-finished product. The correct choice of the parameters to be set for the process is fundamental, in addition to the continuous maintenance of the systems, both to avoid subsequent damage during operation and not to produce an excessive number of rejects which represents damage from an economic point of view.
Among these are:
- Temperature of the starting steel;
- Form of the starting material;
- Type of material and chemical composition;
- Presence and intensity of tensions;
- Type of forging operation carried out;
- Type of lubricant used in the process.
Based on the foregoing, it is easy to understand how the study and analysis of the mutual influence of these parameters is an essential requirement. In addition to this, even the hammers or matrices used must be constantly maintained to prevent problems such as thermal fatigue and other types of failure from altering the quality of the product.
At the end of this operation, however, the stainless steel elbows must be finished and further processed before they can be put on the market.
How to choose the most suitable stainless steel elbow?
The strategy to follow for choosing the correct stainless steel elbow for the specific application is not unique. In fact, it depends not only on the design characteristics of the system in question, which means the geometry, the arrangement, the inclination of the pipes and the dimensions, but also on the surrounding conditions, such as the environment and the stresses present, which represent additional but certainly not secondary characteristics. The experience and quality of Intertubi allows us to meet the needs of the customer by supporting him in the most suitable choice for the specific case of study, avoiding inconvenience upstream of the project and reducing costs, maintenance and related times.