Twin-shaft pumps

A twin shaft pump comprising two rotors 12 each attached to a shaft 10 which is mounted on a bearing 20 is disclosed. The shafts extend beyond the pumping chamber to a support member 30 which comprises mounts for the bearings. The bearing holder 30 defines the distance d between the two shafts. A thermal break 33 in structural elements, such as the pump body or the shafts, connecting the pumping cavity and the support is present to impede thermal conductivity between them, allowing the cavity and the support to operate a different temperatures. The physical properties of the thermal barrier 33 are different to that of the support material, such that the thermal conductance of the barrier is lower than the support. The rotors may be formed from a material with a lower coefficient of thermal expansion than the support material. The invention allows higher internal pump temperatures to be used whilst maintaining the bearings at their operating temperature and takes the differential expansion of components into account.