Are used mainly in chemical process pipelines and chemical equipments.
Basic types:
■ Pointed folds : large expansion for low pressures up to 1 bar,max 150ºC.
■ Round folds : Medium expansion for medium pressures up tp aprox 5 bar,max 150ºC.
■ Square folds : Low expansion for higher pressures,max 150ºC.
Special versions, including metal reinforcing rings,are available for high pressures and temperatures.The bellows can be supplied with and without steel or GRP- flanges.
Special versions of PTFE bellows are used in glandless valve and pump installations where they act as shut-off,volume control and sealing elements mostly with fibreglass-reinforced bottom plates or cones and with moulded-in threaded steel bushes.