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The filter vessel is considered a pressure vessel due to its operating pressure and falls within the scope of the Pressure Equipment Directive (PED) 2014/68/EU. First the design is made in accordance to the AD-Merkblatt, then drafting and a TÜV design review follow. The casing is welded in accordance to the regulations of the AD-Merkblatt. Testing, done in the presence of the TÜV, includes X-ray, pressure tests and final inspections. Complete documentation is provided which includes operating instructions and hazard analysis.

When designing filter tanks, not only pressure and temperature is considered, but also resistance to corrosion. Different types of stainless steel can be used for this, depending on the medium found in the exhaust air. First, stainless steel tanks are full-surface pickled – exterior and interior – by our experts in our own LBF-pickling facility. Next, passivation then ensures long-lasting corrosion resistance. For aggressive media, additional interior coatings can be applied.

These pressure vessels are filled with activated carbon and are used to clean pollutants in sewage. Activated carbon is particularly suitable for absorbing organic substances. As an alternative, the vessels are also suitable for the treatment of turbidity filtration during beverage processing. The vessels are construed designed for a maximum operating pressure of 5 bar.

The chamber for the special machine construction consists of 5-10mm thick walls. The metal profiles and ribbings are circumferentially welded for stabilization against negative pressure. The liquid-tight vacuum chamber is used for automated cleaning operations.

At operating temperatures above 400 °C, it is necessary to test which stainless steel can be used, taking into account both the components of the media and the operating conditions. 1.4541 or 1.4571 can be considered up to temperatures of approximately 500°C, e.g. during continuous operation and with a dry medium. Alternatively, 1.4828 and 1.4841 can be used (these are high temperature stainless steels that can be used for temperatures reaching up to approx. 800° – 900°C). Such temperatures occur for example in engine test stands or in furnace technologies.

Stainless steel 1.4541 is used in exhaust gas lines and stacks discharging furnace exhaust air with maximum temperatures of approx. 450° - 500°C. Depending on the type of fuel, exhaust gases contain among other things sulphur dioxide or nitrogen oxides (SO2 or NOX), which in water form sulphuric acid or nitric acid. Particularly facilities that are not in continuous operation are at risk of this, for example, through the build up of condensation. During the design process, the demands that the temperature place on the material must be considered as well as the protection needed to prevent corrosion.

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