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Leakproof and resistant to chemicals and fouling

Butterfly valves for flue gas cleaning
Leakproof and resistant to chemicals and fouling

Type 4100 butterfly valves made from duroplastics withstand temperatures up to 200 °C and are resistant to aggressive gases and liquids. These valves have been certified by independent associations as 100 % leakproof according to EN 12266–1 (leakage rate A). In flue gas cleaning processes, they are gas-tight at a positive pressure of about 0.8 bar on the gasket.

Butterfly valves for flue gas cleaning

Leakproof and resistant to chemicals and fouling
Type 4100 butterfly valves made from duroplastics withstand temperatures up to 200 °C and are resistant to aggressive gases and liquids. These valves have been certified by independent associations as 100 % leakproof according to EN 12266–1 (leakage rate A). In flue gas cleaning processes, they are gas-tight at a positive pressure of about 0.8 bar on the gasket.
Today, environmental criteria and process control systems are placing ever higher demands on butterfly valves and fittings for sealing gases. Angenstein’s Type 4100 butterfly valves are suitable for applications where absolute tightness and reliability are crucial. They are used to shut off, control and redirect exhaust air, flue and process gases. Flue gas desulphurising, denitrification and cleaning in waste incineration plants are just a few typical applications.
The boilers, stoves and flue gas cleaning systems in waste incineration plants work 24 hours a day, seven days a week. These systems are divided into several different stages. Flue gas cleaning systems downstream of a waste incineration process generally consist of the following stages: filtration at high temperatures of about 900 °C or more to remove particles from the flue gas, then absorber stages and denitrification using SCR and SNCR (selective (non)-catalytic reduction). Following this, an activated carbon filter cleans the flue gas at much lower temperatures. Angenstein’s hermetically sealed Type 4100 butterfly valves are installed in the final stages, where they work at temperatures from 50 to 200 °C in a gaseous, acidic environment with wet SO2 gas in the presence of several chlorides and fluorides. The pressure in the pipes there varies between –90 mbar and 150 mbar overpressure.
The valves are used to redirect the flue gas (bypass) if the cleaning system is faulty, in other words they remain idle in the same position for most of the year but need to fulfil their function at any time without failure. Type 4100 butterfly valves have proven their ability to meet these requirements during many years in use.
For critical applications such as these, damper materials that are capable of withstanding the high chemical load are vital. The plastic butterfly valves made by Angenstein for this purpose are made from Derakane 470 FRP (Ashland) by manual or press lamination. The material for the inflatable seal is FPM based. All fittings used in the flue gas cleaning process are custom built and equipped with pneumatic actuators and different fail-safe positions, in order to ensure maximum safety if the pressure or possibly the entire system fails.
Special sealing technology
Type 4100 butterfly valves are characterised by 100 % leakproofness according to EN 12266–1 (leakage rate A) and ANSI Class IV to V as well as by their considerable flexibility in terms of materials and design. The continuous operating temperature range of the FRP valves extends up to 180 °C. The technical know-how necessary to achieve this required tightness is based on the special design of the sealing system, with a circumferential seal ring in combination with the pressure-vacuum-system.
The pressure vacuum system guarantees absolute leakproofness. The circumferential seal ring inside the valve body is inflated or contracted by this system. When the valve opens, the evacuated seal ring moves away from the disc. The valve is able to move virtually without any friction because of the shaft design and also the special PTFE bearing bush. Furthermore, the gasket and the valve disc are not exposed to major mechanical wear by friction. This technology means that even valves which are incrusted or stuck due to debris or dirt can still be opened. The valve is also closed with the seal ring deflated. After it has moved into the closed position, the ring is re-pressurised and hugs the disc to provide a tight seal.
Safety
Type 4100 butterfly valves are TÜV-tested for leakproofness according to DIN 3230, Part 3, B0, leakage rate 1 (04/1982) (superseded by EN 12266–1 06/2012). The tightness of the shaft bushing has also been tested with helium (leakage rate) and compliance with German clean air regulations is ensured. The valves can be custom built from different materials, e. g. thermoplastics (PE, PP, PVC PVDF), duroplastics (FRP), duroplastic lined (PVC, PVDF, E-CTFE, FEP, PFA), steel lined (PVDF, E-CTFE, FEP, PFA), stainless steel or nickel-based alloys, depending on the application and the customer’s requirements as well as their intended use and the mechanical, thermal and chemical loads. Seals made from elastomers such as EPDM and FPM meet the demands of a variety of processes. Butterfly valves are normally manufactured with nominal diameters from DN 300 to DN 3000. Smaller and/or larger sizes and rectangular valves can be supplied on request.
www.cpp-net.com search: cpp0116angenstein

Sascha Paul
Sascha Paul
Head of Project Management and Order Processing,Angenstein
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