Sealing technology manual for the process industry - Diaphragms

DIAPHRAGMS Diaphragms form a reliable but flexible separating wall between two component spaces. The volume changes of the separated media can be converted into force. Diaphragms are especially interesting sealing components for the food and beverage industry where they can perform a number of different functions. Available in all basic elas- tomer variants, or with application-specific modifications such as fabric reinforcements, metal inserts or foil layers, diaphragms are extremely dependable and resistant to me- dia. They are very affordable solutions, as the minimal re- quirements with regard to tolerances and surface qualities of the surrounding components make it possible to produce them inexpensively. Function • Regulation and switching using pressure that is converted into rod force • Separation of media in component spaces with nearly identical pressure levels • Pumping and compression of liquids and gases • Measuring volume flows • Actuation of valves Dimensions From 5 mm to maximum diameter of 1,000 mm (or larger for individualized applications). Installation and assembly Please refer to page 94 for general assembly and installation instructions. Applications Since diaphragms can be very closely tailored to specific ap- plications in terms of their shape and materials compo- sition, they can be used in a very broad spectrum of appli- cations. Typical areas are: • Actuators • Fittings • Water reservoirs • Pumps and compressors • Valves and controllers TYPES Diaphragm types • Flat diaphragms • Convoluted diaphragms • Plate-shaped diaphragms • Rolling diaphragms • Individual designs available upon request Materials composition • MB as pure rubber diaphragm • GMB with fabric insert or overlay • MBM with metal insert and/or film • GMBM with metal insert and fabric overlay or insert and/or film • Diaphragms with film overlay made of PTFE, modified PTFE, electrically conductive foils etc. • Diaphragms made of pure PTFE DESIGN NOTES Design • In designing diaphragms, it is advisable to use FEM calculations to reduce development and testing times • The diaphragm’s construction position (0 position) should be selected such that the diaphragm is not under load • The deflection of the diaphragm during operation should be designed in such a way that no overstret- ching and no excessive stress peaks can occur • The diaphragm’s mountings must in some cases be able to withstand considerable forces and should be designed accordingly. It is advisable to utilize FEM calculations here, too Choice of materials • The elastomer base material, as well as any applicab- le fabric, metal or plastic inserts, must be resistant to all media involved in operation • For applications in particularly aggressive media, it is advisable to add a layer of PTFE to the diaphragm THE ADVANTAGES AT A GLANCE • Good media resistance • Broad range of functions and applications • Economical • Highly dependable Product portfolio 74

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