
147Melting Furnace Parts and Accessories
Most of the mechanical pumps in use for molten aluminum service are cen-
trifugal (see Figure 8.10) rather than positive displacement, due to the higher
discharge volumes and velocities of centrifugal designs. These pumps cost less
per unit capacity than other stirring devices and cost less to operate as well
(Henderson et al., 1996); maintenance costs are higher, but development work
has focused on improving their reliability (Bright et al., 2007b; Chandler, 2006).
Mechanical pumps are often portable and can be used on more than one furnace.
The newest pumps can circulate 20,000 kg/min of molten alum