Mr. Diermayer invents and patents a hingeless, bimetallic strip controlled isolating damper for gas-fired instantaneous water heaters; production and sale of the "Diermayer dampers". This flue gas damper is licensed by a number of gas works in Germany. 




The hingeless Diermayer damper is licensed by the Deutscher Verein von Gas- und Wasserfachmännern (DVGW - Association of German Gas and Water Engineers).






Manufacture of Diermayer dampers by the Franz Weber company, Munich. Subsequent incorporation in the Technical Rules for Gas Systems, expansion of the dampers to include gas furnaces and introduction of the product range in Austria and Switzerland (1960).





Continued development of the Diermayer dampers for instantaneous gas water heaters, publication of the DVGW Technical Standard G 654 as a Technical Rule for thermally controlled flue gas dampers - further technical modifications and adaptation to reflect developments in appliances.




The Franz Weber company relocates from Munich to a new building in Gröbenzell.





Publication of DIN 3388 Part 1 as a standard for thermally controlled flue gas dampers for gas appliances. This was also the basis for corresponding regulations in foreign markets.




1st energy crisis, increasing the range of applications for energy-saving flue gas dampers. The development of motor-controlled Diermayer dampers followed.







Further development and upgrading of KW products. Production under licence starts in the USA. Motorised Diermayer dampers used for liquid fuels as well as solid, expansion for use as positively operated draft regulators for the drying of chimneys.




The company relocates to new premises in Maisach.




Development and production of the KW draft restrictor.




Takeover of Servo Instruments Deutschland SID - the flue gas damper range is expanded accordingly.




Introduction of the first range of flue gas silencers.






Development and sale of a wide range of solutions for the boiler industry, also function-assisting and energy saving products for heating and flue gas engineering.




The company is taken over by the Raab Group.




Specialisation in the field of flue gas noise, further development of solutions for the market.





Integration of Servo-Instruments (SID) into the KW licence partnership with the Fraunhofer Institute for Building Physics (IBP) in Stuttgart as our scientific partner in the development of specialist silencer solutions. Work starts on the development of integrated solutions for the boiler and flue gas industry.




Modernisation and adaptation of the flue gas damper range. New foreign markets are opened up.




Rolf Wagenfeld accepts the group Raab. A native of Bremen knows the Raab Group since 2001 as a board member. From 2007 he was the Deputy Council Chairperson, held the Council Presidency since 2009.




The Raab Group expanding its product range by purchasing a recovery specialists: The NET Neue Energie-Technik GmbH in Puchheim near Munich, is more than 20 years in the heat exchanger business operates and brings industry knowledge in the design, manufacture and servicing of the heat recovery systems with.