Scrolling through the Intertubi catalog, it is possible to see a section dedicated to couplings and sockets. Both components are threaded and represent an important solution for making connections between pipes with threaded ends. The difference lies in the position and length of the thread required for coupling.
The material used is simple carbon steel, that is, a steel with a high C content that is very often compared with stainless steel. While the latter is generally chosen for its corrosion resistance characteristics, thanks to a very high presence of Chromium (Cr) and Nickel (Ni), carbon steel has high flexibility, low melting point and, therefore, a greater workability, even if it has a considerably lower resistance to aggressive environments.
The steel couplings
The
steel couplings are perfectly axially symmetrical threaded components with a constant section that act as ideal fittings for connecting pipes. The thread is present on the inner surface and the realization of the latter takes place by means of chip removal after obtaining the hollow cylinder by a welded tube and subsequently cut.
The fundamental dimensions for the choice of couplings are:
- L = length of the component and corresponds with the thread length;
- Φ1= outer diameter of the component;
- Thickness / th = wall thickness along the entire circumference.
In the Intertubi catalog there are couplings with Φ1 from 15 mm to 121 mm, L from 17 mm to 83 mm and thicknesses from 2 / 2.6 to 4.5 / 5.4 mm. The dimensions follow the EN 10241 standard and the thread conforms to the EN 10226 standard.
The steel sockets
The
steel sockets are perfectly axially symmetrical threaded components with a constant section that have an external thread only on one end. The production of the thread and of the component takes place according to the same methodology as the coupling.
The basic dimensions are the same as the coupling with the difference that the length L does not correspond to the thread length A.
In the Intertubi catalog there are sockets with Φ1 from 17.2 mm to 114.3 mm, A from 14 mm to 36 mm, L always equal to 100 mm and thicknesses from 2.2 to 4.0 mm. The dimensions and tolerances follow the EN 10255 standard and the thread conforms to the EN 10226-1 standard.
Both the couplings and the sockets are fundamental components in hydraulic fittings and their realization is essential to make the systems, in which they will operate, operate correctly. All components are made following the EN 10204 / 2.1 standard. Of course, for correct operation, correct implementation by trained operators and constant maintenance over time are necessary, thus avoiding problems both for people and for the environments in close contact.
The advantages of using carbon steel
As briefly introduced in the previous sections, carbon steel has very important characteristics for the production of couplings and welding nipples. The term "carbon steel" is used to distinguish alloys consisting mainly of iron and carbon from alloys with high content of elements such as chromium and nickel, or the so-called stainless steels.
Being a general term that indicates a multitude of different types of steels, it is commonly divided into groups and subgroups for both identification and designation at the regulatory level. The fundamental distinction is:
- Low-alloy steels: these are steels that have good resistance and toughness characteristics even if they are not easily heat treated. They are heavily used in production because the price is relatively low and the properties are acceptable in many types of applications. In fact, they can be used in various fields, including in the structural field, from the production of automobiles to the field of construction and hydraulic fittings, as in the case of couplings and welding nipples;
- High-alloy steels: they certainly have a higher cost but the mechanical characteristics and general properties are high, guaranteeing important performances in many areas. Usually, steels with alloying elements present between 0.30 and 1.70% belong to this category.
These categories are not the only ones in the world of metallurgy as regards the alloying elements present but there are also further divisions that introduce intermediate classes between the two. Furthermore, within, there are a number of further subdivisions, concerning:
- The main treatments to which they are subjected: in fact, the choice of a type of treatment during the production phase can considerably modify the characteristics of the product obtained, improving some aspects and solving critical issues that in operation can lead to failures and malfunctions, even of considerable entity. To do this, however, it is necessary that they be carried out accurately: summary or poorly cared for treatments can lead to worsening of performance and amplification of any problems arising from the production process previously carried out;
- The peculiar characteristics and the typical uses of each steel: in fact, some properties may be necessary for some applications but be degrading for others. Knowing how to identify these differences is a fundamental requirement to maximize performance and increase the useful life of the systems and structures in which the components are installed.
With regard to the carbon steel couplings and welding nipples produced by Intertubi, the experience and compliance with the regulations in the field of fittings allow to obtain high quality products, managing to meet the needs of customers both in terms of size and for the types of threads that can be made.
The importance of threading for couplings
Threaded couplings, as reported in the previous paragraphs, play a central role in plant engineering, allowing connections between different components, limiting losses to a minimum and promoting the general efficiency of the system.
The decision to make the connections via threaded joints is taken on the basis of some construction and structural requirements that arise during the design and installation phases:
- Versatility: regardless of the main construction characteristics, the threaded couplings are versatile and suitable components for numerous types of applications;
- Ease of installation: the systems on which they are mounted can be in awkward and difficult to reach positions for the welding process and this means that threaded joints are preferred;
- Disassembly and intervention: unlike welding, threaded connections allow rapid disassembly and facilitate intervention both in the case of ordinary maintenance and in the event of extraordinary maintenance.
- Transmission of cracks: if a break occurs in a pipe, the propagation tends to stop at the threaded couplings, limiting the damage and circumscribing it to a specific area.
Certainly, in addition to these favorable characteristics, there are also problems with threaded couplings, but by outlining a trade-off between the two situations it is possible to note that there are certainly more advantages than disadvantages in using these products.
