Because of Langley’s long experience in casting techniques, Langley impellers have built up a fine reputation for a very good ‘as cast’ finish on the vanes which, due to their inaccessibility, cannot normally be machined. But for high-speed pumps operating at 6000 rpm of more, dimensional accuracy of the vane profiles and their finish becomes increasingly critical. To meet these parameters Langley now use ceramic cores in the castings of high-speed impellers. Besides ensuring an even better ‘as cast’ finish to the vanes, their much-improved profile uniformity makes final balancing of the impeller somewhat easier with considerably improved hydrodynamics.
The vane finish achieved by the ceramic core technique is to be seen in the illustration of a 13” diameter double-shrouded impeller for duty in a high-speed sea water pump. It is cast in FERRALIUM 255 (UNS S32550, Alloy 255, DIN 1.4507, ASTM F61) processing, amongst other properties, anti-cavitation advantages which, combined with fine vane finish, ensure maximum resistance to that form of attack.
If you’d like more information regarding Ferralium 255, please get in touch with a member our expert team today.