The range of tubular heating elements

Tubular electric resistances are components that play a major role in heating liquids in open water heaters, pressure water heaters, pressurized and free boilers. It is fundamental, for the correct functioning of these machines, that the materials used for the realization of the resistances respect these three points:
They appropriately chosen, to overcome the problems, already during the selection phase, that may arise in operation.
They are derived from controlled supply chains and, therefore, are qualitatively excellent for construction and chemistry.
There are elements, even sacrificial, that protect the component from the main criticality, which means corrosion.
An important mention must also be made for the specific power that must not exceed the value of 9 W / cm2 for not having noise problems, but above all not to cause the dissociation of the minerals dissolved in the fluid that create calcareous deposits that may be the cause of corrosion problems. For this reason it is important to respect the aforementioned limit: overcoming it means making the correct choice of materials to be useless, constituting a waste in terms of money and time.
 

The tubular electric resistances have two main elements:

* The tube, containing inside the real resistances, that is the heating part.
* The fitting, which can be made either with a thread, calling it "plug", or without and in this case is called "flange".
 



The sheath, the container element of the resistance, is a fundamental element for the correct realization of these components. High temperatures, in water containing high quantities of minerals, therefore in hard waters, or in highly chlorinated waters, create the right conditions for the occurrence of corrosion phenomena. To overcome this, the choice falls first on the material to be used and, subsequently, it is necessary to intervene to extend as much as possible the life of use of the component with alternative solutions. The basic material is copper, with a purity close to 100% so as to constitute, with the initial choice, a corrosion barrier. The choice of copper as a constituent element of these tubes is to be attributed, as mentioned, to the extraordinary ability to resist corrosion, but also to its chemical-physical characteristics that make it a formidable electrical and thermal conductor. Why is it highly resistant to corrosion? Because on its surface spontaneously forms an adherent patina first of brown color and then of green or blue-green color, which protects it from corrosion.
Subsequently, sacrificial anodes can be installed that corrode instead of copper, usually made of magnesium. Anodes of this element are used because, being less noble than copper, it tends to wear out in its place, thus protecting the tube. Inside the tube, the resistance is present, which constitutes the actual heating element of the component and the separation between it and the external copper is constituted by the introduction of a layer of magnesium oxide. Although copper is one of the most used materials, it is not the only one and you can use other more or less complex alloys, to overcome the same problems: thermal stress and corrosion. Among the most used are certainly the stainless steel, resistant to corrosion, the inconel, alloys made of nickel and chrome that resist well to oxidation at high temperature and corrosion, and other materials such as titanium and carbon steel.


The fitting is one of the two main elements of the resistances. The copper tubes are fixed on it, the thermostat probes arrive and other elements are also connected, such as the sacrificial magnesium anodes. The type of attachment can be of various types: it can be threaded and called "plug", or it can be smooth and made by means of a flange. The material usually used to make this element is brass, with the addition of alloy elements such as:

There are also various types of gaskets, made of EPDM, a type of rubber characteristic for thermal insulation applications.
 

The company Gnali Bocia presents a wide range of tubular electric resistances in its catalog, and also deals with the production of spare parts of the elements making up these components. In fact, being specialized in the production of brass (particularly CW617N brass is used), it allows to obtain fittings of various types: threaded fittings, made with an ISO 228/1 M 1 "1/4 GAS thread, or flanged fittings or with Aniston connection. The exceptional quality from the point of view of the chosen material is one of the company’s strengths, which only relies on certified suppliers that guarantee a level of quality suitable for the required performance. Each item is checked before being put on the market and, by complying with ISO 9001, the production process is controlled and repeatable.

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