Leistritz in Somerville, N.J., believes it is the first OEM to offer an oil-sealed vacuum pump as a standard option for venting a twin-screw extruder. Typical water-sealed vacuum pumps use the water once and then dispose of it, unless a closed-loop system is installed. A 3-hp pump for a 60-mm-diam. extruder running about 1000 lb/hr uses roughly 125 gal/hr of water. The oil-sealed pump adds only slightly to the cost of the extruder but saves water disposal charges, which can be significant in some states. Oil is cooled by a fan driven by the pump motor. The pump can be mated to multiple vents and used with a three-way valve so that processing can continue while the filter trap is being changed. Oil may need to be changed every two to six months, Leistritz says, depending on the quantity and type of volatiles being drawn off. Oil-sealed pumps are available for twin-screws up to 135 mm diam.
Leistritz Extruder Co
169 Meister Ave Somerville, NJ 08876
Phone (908) 685-2333 Fax (908) 685-0247