Manufacture of a boiler

Manufacture of a boiler

  • What is the best sheet metal thickness for a boiler? Open or Close

    The E.U.’s EN303-5:2012 regulation determines that the thickness of the sheet metal in the interior of the combustion chamber must be 5mm; the surface where there is only the presence of smoke must be 4 mm thick; and as far as the surface that is in contact with water is concerned, it should be 3 mm thick. The inner sheet metal is reinforced (5mm) because it contacts the flame from the one side and water from the other side. When using thicker sheet, the life of the boiler is prolonged. The external sheet metal which gets in contact with water only is thinner (3mm). There is no need to use thicker sheet metal for the external parts. This would only be a waste of money in the production cost and a waste of material as well.

    CAUTION!!! Besides thickness, full attention must be given to the specifications and quality of the sheet metal. It would be a problem to have the projected thickness when the material is of poor quality!

  • Welded or cast construction? Open or Close

    Cast iron is not suitable for tensile stress and thermal shocks. Unlike an oil boiler which operates in a steady way, in a wood boiler’s chamber where solid fuel is burnt, the following occur at the same time: flame at 700°C, carbon at 1200°C and the fresh fuel we have just added. All these conditions lead to the use of cast construction for a solid fuel boiler.

    In addition, a cast construction has to be a least 10 mm thick in order to be durable, whereas a welded construction must be 5mm thick. That makes a cast boiler much heavier. Practically a cast boiler is 2.5 times heavier because we use material inappropriate for pressure vessel such as a boiler. However, as far as production is concerned, it was easier to construct a cast rather than a welded boiler during the past century.

  • MMA welding is the best. Welding with MIG isn’t appropriate for pressure. Open or Close

    MMA welding with electrode is necessary to refineries and in the steam boilers of the Electric Power Organization where the pressure is over 300 bars and the temperature exceeds 600°C. However for the welding of domestic boilers we use MIG because it covers the standards for domestic boilers. The excess in standards practically increases only the total cost of the boiler and not its lifetime.

  • Mannesmann and hollow Sections Open or Close

    Tubes or welded hollow sections are not suitable for alternating thermal loads and corrosive environments. That is why the regulation explicitly prohibits the use of tube or hollow section. The use of tube or hollow section is allowed only if the material is compatible, if the seam has been totally cut and reattached by an acceptable method. The reason that many boiler tubes are seamed is because the price of seamless pipe (Mannesmann) is 1.8 times higher.

  • My boiler is made by fireproof sheet metal not a simple one. Open or Close

    The fireproof sheet metal is suitable for special constructions (e.g. salt boilers) and has a resistance up to 900 degrees Celsius, which is why the cost is very high (about 10 euros/kilo). This means that the sheet metal of the boiler will cost about 2,000 euros. Find thecommercialerror!

    In the case of simple combustion, it is not required to use such strong materials. The metal of the boiler cannot raise above 130 degrees due to the water which continuously cools the panel. Of course, in a highly corrosive environment where there is fire, tar acids and water, we cannot use just any kind of material. The regulation defines the use of about 20 types of steel. The most "simple" category that can be used is steel E235 (1.308) or S235JR (1.0037).

    Caution! The quality of steel is not visible to the eye or caliper but in the laboratory with chemical analyses and controls of mechanical strength. All reliable manufacturers like Axinar use only materials accompanied by quality certificates and have passed as many sampling inspections as possible.

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