Sealing technology manual for the process industry - PTFE bellows

PTFE BELLOWS Bellows are components which are primarily used to pro- tect moving machine parts from external influences. Wherever reciprocating mechanical parts need to be protec- ted from environmental influences or aggressive media, bel- lows serve as reliable sealing components. They can also be used to compensate for movements, expansions, as well as axle offset, misalignments and vibrations. When used in combination with check valves, they can also be used to cir- culate or pump gases and liquids utilizing volume changes in the bellows, provided the installation space allows it. Application range of bellows • Virgin PTFE: Broad application range throughout the chemical industry • Modified PTFE: Low-porosity variant for the food, bever- age and pharmaceutical industries • Conductive PTFE: Designed to prevent static electrical buildup • Filled PTFE: Reinforcement with glass fibers or carbon fib- ers of those parts of the bellows under the most stress, e.g. where the bellows are mounted on a pump head Function • Protection of piston rods, linkages and other machine parts involving axial and in some cases radial motion • Compensation of movements and displacements be- tween two connecting components • Circulation and pumping of gases and liquids using vol- ume changes Dimensions • Smallest standardized internal diameter: 10 mm (smaller diameters available on request) • Largest external diameter: theoretically unlimited Installation and assembly Please refer to page 94 for general installation and assembly instructions. Applications of bellows as compensators • Compensation for expansion and vibration • Compensation for axle offset, misalignments and dis- placements in pipes • Fluid circulation in chemical, food and beverage industries • Rod protection in chemical, food and beverage industries • Protection from dust and contamination, e.g. for weigh- ing equipment in filling plants Applications of valve and pump bellows • In feed pumps and metering pumps • For control and shut-off valves in chemical, pharmaceuti- cal and food and beverage industries THE ADVANTAGES AT A GLANCE • Highly resistant to nearly all chemicals • Dependable sealing to prevent media contamination • High cost effectiveness thanks to production by machining • Special variants, made-to-order and small batches are possible • Compensator bellows in nominal widths of DN 10 to DN 500 available in stock TYPES FBA-9000 Compensators for low pressures FBC-9002 Compensators for moderate pressures FV-series Individual solutions for pump and valve bellows FBAX-9001 Variant of FBA-9000 available on request, as well as an extensive range of customer-specific variants DESIGN NOTES Compen- sators Standard bellows, as well as metal-reinforced special variants possible Valve and pump bellows Design guidelines based on individual experience in development and testing Special installation notes • The flange contact surfaces must be smooth and clean • PTFE bellows should not be over-expanded • PTFE flanges should be handled carefully due to their ductility • It may be advisable to use soft packings between flange and bellows • The screw holes and flange thickness listed for types FBA-9000 and FBC-9002 are smaller than those indica- ted in the DIN standard sheets Product portfolio 88

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