The E-SL (Shuttle Block) pump employs an unique pumping principle – a combination of Rotary and Piston pump. Two double acting pistons in their respective slots at right angles to each other, accomplish this, while the rotor turns without the need for any valving. The Shuttle block pump is a self priming rotary pump. There are only three pumping elements – Rotor, Piston and Shuttle. Rotor is keyed to a single shaft and runs concentric in pump casing. It has a rectangular slot across its face. The channel-shaped piston reciprocates within this slot. A rectangular block, shuttle, fits liquid tight in piston slot and reciprocates. The rotary action of rotor combined with the eccentrically mounted shuttle creates reciprocating motion among the pumping elements.