Rotary Pump | Types And Configuration

Rotary pump is a type of positive-displacement, used primarily for pumping fluids with high viscosity without abrasive impurities. The rotary pump works on the principle of expulsion of the fluid from the pump housing by the working part, a cam rotor. The most common types of rotary pump is double-cam pumps, which have delivery capacity of  6–160 m3/hr at a delivery pressure ranging up to 0.6–1.6 mega Newton’s per sq m(MN/m2), with a rotor speed of up to 300–400 rpm. Rotary pumps are common applications in the chemical and petroleum-refining industries. A rotary pump with its working members which move in a rotary motion or in both rotary and reciprocating motion to relocate a liquid medium; the displacement is a result of episodic changes in the volume of chambers or cylinders filled by the liquid. Rotary pumps include rotary vane pump, rotary vacuum pump, screw pumps, lobar pumps, labyrinth pumps, vane pumps, gear pumps, and radial-plunger and swash-plate pumps.

Due to their unique performance and simplicity in design, Rotary pumps make up about 10% of the pumps we use in industry. A rotary pump is positive displacement (PD) pump with several advantages. A rotary pump will discharge a constant volume of liquid regardless of the pressure they encounter. They put out the constant volume with each rotation of the shaft. Rotary pump do not convey velocity to the liquid they are pumping. The most important feature of rotary pump is that discharge pressure is controlled by resistance, and not affected by the specific gravity of the fluid. There is no radial thrust transferred to the shaft as you move on the pump curve.

The head of a centrifugal Rotary pump was restricted by the diameter of the impeller and its revolutions number or speed. How much pressures will a rotary PD pump produce? It is limited only by the strength of the pump casing and the internal components. Unlike centrifugal pumps, there is very less options you can adopt to do to modify a rotary pump to increase their performance. A rotary pump is a basically a spare parts business, where the performance of the pump is directly related to how well you maintain their internal clearances. Rotary pumps come in various configurations. There are several different Rotary pump configurations being introduced to industry. The most commonly used Among them are the External gear, Internal gear, Lobe, Progressive cavity, Three screw, Two screw, One screw, Flexible tube, Sliding vane, Flexible vane. Rotary pumps of both radial and axial types are being manufactured to offer fixed and variable delivery. Radial rotary pump is preferred for low rotational kinematics and large torque values while axial rotary pumps are preferred for high rotational speeds and small torque values.

Suction and forced discharge of the liquid occur with the reciprocating motion of the plungers as a result of centrifugal forces and spring stroke. Rotary pumps of this sort may have as many as 72 plungers arranged in multiple rows, provide a delivery of approximately 400 liters/min, and build up a pumping pressure of 100 mega newtons/m2.

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