ABSTRACT
Couplings in a system are rarely fitted initially with a thought to their effect on noise. The most common requirement is that the coupling must accommodate misalignments which may be due to manufacturing or assembly errors but are often due to the effects of differential thermal growth, which can be surprisingly large. A temperature difference of 40°C can easily occur between a turbine casing and a gearbox and if the centre height is 1 m the corresponding differential expansion is 0.4 mm (16 mil). Axial growth can also present problems since a motor gearbox combination in a medium-sized (400 kW) installation with a distance of 4 m between foundation attachment points and a temperature rise of 50°C can expand axially by 2 mm.
