a type of positive-displacement rotary pump, used chiefly for pumping highly viscous fluids without abrasive impurities. The principle of operation of a rotary pump is based on expulsion of the fluid from the pump housing by the working part, a cam rotor. The most common types of rotary pump in the USSR are double-cam pumps, which deliver 6–160 m³/hr at a delivery pressure of up to 0.6–1.6 meganewtons per sq m(MN/m²), or 6–16 kilograms-force per sq cm (kgf/cm²), with a rotor speed of up to 300–400 rpm. Rotary pumps are used in the chemical and petroleum-refining industries.

a pump with working members that move in a rotary motion or in both rotary and reciprocating motion to displace a liquid medium; the displacement is a result of periodic changes in the volume of chambers or cylinders filled by the liquid. Rotary pumps include screw pumps, lobar pumps, labyrinth pumps, vane pumps, gear pumps (with only a rotary motion of the working members), and radial-plunger and swash-plate pumps (with rotary and reciprocating motion of the working members).

Figure 1. Diagram of a radial-plunger rotary pump: (1) rotor, (2) plunger, (3) case, (4) journal, (5) discharge cavity, (6) suction cavity

In a radial-plunger rotary pump, the axes of the plungers are perpendicular to the rotational axis of the rotor (Figure 1) or at an angle of not less than 45° to the axis; the rotor is located eccentrically with respect to the axis of the case.

Suction and forced delivery of the liquid occur with the reciprocating motion of the plungers as a result of centrifugal forces and spring action. Rotary pumps of this type may have as many as 72 plungers arranged in multiple rows, provide a delivery Q ≤ 400 liters/min, and build up a pumping pressure ρ ≤ 100 meganewtons/m² (1,000 kilograms-force/cm²).

In a swash-plate rotary pump, the rotational axis of the rotor is parallel to the axes of the cylinders or at an angle of less than 45° to the axes. In rotary pumps of this type, the rotor disk or the block carrying the plunger cylinders is inclined with respect to the axis of the shaft. Suction and forced delivery occur with the rotary motion of the rotor and reciprocating motion of the plunger. The movement of the plunger may be caused by, for example, the action of the inclined rotor disk (Figure 2). Rotary pumps of this type usually have seven to nine cylinders and provide a delivery Q ≥ 1,800 liters/min at a pressure ρ ≅ 20MN/m² (200kgf/cm²) or Q ≥ 1,000 liters/min at a pressure ρ ≅ 35MN/m² (350kgf/cm²).

Rotary pumps of both radial and axial types are being manufactured to provide fixed and variable delivery. Radial rotary pumps are preferred for low rotational speeds and large torque values; axial rotary pumps are preferred for high rotational speeds and small torque values. Rotary plunger pumps are used in hydraulic systems with liquids under high pressures.

Figure 2. Swash-plate rotary pump: (1) pump body, (2) plunger-carrying block, (3) plunger, (4) inclined disk, (5) shaft, (6) suction chamber, (7) pin, (8) slide valve, (9) discharge chamber