The range of eccentric reductions and concentric reductions

The primary attention also for these fittings that may seem standardized is concentrated on some main factors, first of all the manufacturing process which must always be controlled and able to replicate the results, and then the materials that according to the type of application are selected from the best raw materials.
These two not indifferent factors must be combined with each other through another fundamental component which are the trained people in the company and who put their great experience into play in order to provide the best possible product on the market.
But let's analyze in an orderly way how INTERTUBI can make a difference for the market.

Which standards to refer to and the measures available


In the catalog for eccentric reductions and concentric reductions we find two reference standards that the market relies on:
The standard that regulates the American and Anglo-Saxon markets in general is ASME B16.9. In this section we find both stainless and carbon steel fittings. The maximum dimensions are 16 inches while the minimum manageable dimensions are equal to 3/4 of an inch. In this case, reference is made to homologous materials to those mentioned above, but designated according to American legislation.
Instead in the rest of the world the regulation is given by the EN 10253 standard, whose supported measures are defined based on the DN or nominal diameter which indicates the external diameter of the pipe and which can reach up to the important dimension of 500mm reaching minimum values of 10mm. In both cases of equal diametrical dimensions we can find a range of thicknesses available among the most common, also present in the pipes that can be combined.
We remind you that every detail is shipped accompanied by the EN10204 certification as a minimum of level 2.2 which, upon the customer's request, can be raised with the execution of specific tests prior to shipment agreed with the customer.

Technology for the production of eccentric reductions and concentric reductions

As reported in the catalog, also available online, many of these figures are obtained from welded tube or sheet metal, this tells us that the eccentric reductions and concentric reductions are obtained starting from a metal cylinder or purchased as the tube or created as in the case in which is obtained from sheet metal.
The next part involves a plastic deformation operation of the material to give the characteristic shape to the piece and this can be done in different ways: both hot (and in this case we get a more ductile and not work hardened product), and cold (a process that is preferred where greater yield strength is required).
The main processes used are:
- Cold drawing, in which the material is deformed using a press using a special mold
- Hot forging, very similar to deep drawing but done hot
These processing methods are particularly consolidated and are the first step, mechanical processing is then always carried out to prepare the ends of the fitting for its final use. In fact, most of the eccentric reductions and concentric reductions are already supplied with a bevel at the ends to facilitate subsequent welding operations.

The materials used for eccentric reductions and concentric reductions

There are two important families of materials used when talking about welded fittings and therefore of eccentric reductions and concentric reductions, and they are stainless steels and carbon steels.
When we talk about stainless steels we mean those alloys based on iron, chromium and carbon, which combined with other elements such as nickel, molybdenum, or silicon, for example, create a combination capable of counteracting surface corrosion. This is due to the fact that the surface generates a thin layer of oxide that is generated and above all self-regenerates in case of damage if the material is in contact with oxidizing environments including simple air.

Those mainly used in the production of welded fittings are of the family of austenitic steels which have a consistent percentage of chromium, the main element that makes them stainless, but also of nickel and molybdenum which make it resistant to intergranular corrosion but they also make it mechanically resistant to high temperatures.
The types of steel that are usually used are:

-    AISI 304

-    AISI 304L

-    AISI 316

-    AISI 316L

The suffix L indicates materials with a lower carbon content which consequently have better weldability.


But there are also carbon alloyed steels, which allow an even greater choice in the realization of eccentric reductions and concentric reductions. The legislation has recently been updated and carbon steels are designated according to three classes:
1. Carbon steels for construction, they are classified mainly on the basis of mechanical characteristics, indicating the yield strength in the initials of the steel itself

2. Low alloy steels, in whose initials the main alloy and the relative percentages are reported

3. High alloy steels, whose initials are preceded by an X and which, like the previous ones, show the alloy elements and the relative percentages


Usually the choice is not made in this field based on the classification but on the fields of use, therefore we find three main categories to refer to:
- High yield steels, such as L290NB, L360NB

- High temperature resistant steels, such as P235GH, P265GH, 16Mo3

- Low temperature resistant steels such as P265NL

But there are also more generic materials typical of ordinary mechanical constructions.

Another production technology for reductions: calendering

The eccentric reductions and concentric reductions, as seen above, can be made according to various production methods and deformation processes, from cold drawing to hot forging. Another possibility is provided by the calendering process of suitably prepared and shaped metal sheets, for example, through processes such as blanking. What is it about? Calendering is an industrial production method of plastic deformation that allows you to transform sheets or plates of material into a product. The characteristic components of this type of operation are the calenders, or cylinders, generally two or more rollers with opposite rotation to each other and arranged with the correct distance and inclination on the basis of the product to be produced. It is important to correctly set the main parameters, such as the rotation speed, not only on the basis of the material, but also as regards the desired surface finish.

The advantages of this process are many but the main ones are given by the possibility of obtaining constant thicknesses, flat surfaces and different types of surface finish. Designing both the product and the process correctly allows to obtain eccentric and concentric reductions that are excellent from a qualitative point of view, while errors both upstream and during the production process can compromise the correct outcome of the final product.

The use of TIG welding to create reducers

Welding is a fundamental operation to join the edges of the metal sheet and allow the creation of reducers, both concentric and eccentric.
In particular, TIG welding, an acronym for Tungsten Inert Gas, takes on significant importance. As the name suggests, it is welding with an infusible tungsten electrode carried out under the control of an inert gas. Furthermore, it can be carried out with or without filler material depending on the application and the specific case.
It is a very precise welding method but it requires a good level of preparation on the part of the operator who is responsible for this phase. In fact, the precision required to follow the welding bead and the coordination with any filler material must be carried out with technique.

The main benefits are:
- independence from the heat input of the welding, contrary to what happens with traditional welding;
- possibility of automating the process;
- possibility of welding small thicknesses;
- realization in any position and inclination;
- possibility of creating continuous or spot joints;
- possibility of using filler material to improve the characteristics.

On the other hand, however, there may be defects due to:
- tungsten inclusions in the bath;
- localized lack of gas protection;
- porosity, lack of fusion and cracks: that is, classic defects of each type of welding.