Solids suspension using an angle-mounted axial-flow impeller in an unbaffled tank relies on proper placement of the impeller in the vessel such that swirling flow does not occur. Even with proper placement, the just-suspended speed of an angle-mounted agitator is often 75% higher than with vertical mounting on the centreline in a baffled tank, leading to torque and power requirements that average more than twice and five times higher, respectively. Angle-mounted turbulent power numbers of axial-flow impellers are generally similar to, but lower than the corresponding power numbers with vertical mounting on the centreline of a baffled tank.