There is a wide variety of vessels in the environmental technologies that are used as collecting tanks, filter tanks, separators, cyclones and much more. In this particular project there are multiple processing cycles running parallel to each other that alternately operate and regenerate. The goal of the filter tank is to filter organic components out of the exhaust air. The tanks are operated unpressurised, that is under an operating pressure of 0,5 bar. Therefore, the tanks are not subject to the Pressure Equipment Directive (PED).
Hot exhaust gas from parallel oven shafts is extracted through 6-10 flexible and valve controlled branches and discharged through the main pipe. The manifold has a diameter of approx. 1 m, is continuous welded and can be assembled as one solid piece.
Throttle valves are used for air volume control in order, for example, to regulate various extraction points or to block off individual ducts. Welded throttle valves (shaft, flap, bearing) have to be adjusted to the mechanical requirements of the plant – pressure, speed, temperature, medium.
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.
Carbon steel can also be used for high temperatures, for example, S235JR for temperatures of up to 300°C. Heat resistant steels were developed for use in high temperatures, including 16Mo3 which, on account of its chemical composition, can be used for temperatures of up to 450°C. In contrast to stainless steel, it is more susceptible to corrosion; however, the purchase price is considerably lower. In the project pictured here, the section used for lifting the pipe is undergoing a complete dye penetrant inspection.
A material not only needs to function well, sometimes aesthetic reasons can also be decisive for using certain materials. Pre-ground stainless steel sheet material can be used. The pre-processed surface area is protected by a factory-applied foil suitable for lasers. In this project for exhaust air towers, the ground sheet metal is rounded and bolted together from the inside; welds are found only on the base plate and the tower head.