Pumps

1. Pumps Because of the wide variety of requirements, many different types are in use including centrifugal, piston, gear, screw, and peristaltic pumps. The two main forms are the positive displacement type and centrifugal pumps. In the chemical and petroleum industries the centrifugal type is by far the most important.

2. I. In the positive displacement pumps the volume of liquid delivered is directly related to the displacement of the piston and therefore increases directly with speed and is not influenced by the pressure. Commonly used for delivery against high pressures and where nearly constant delivery rates are required. - reciprocating pumps - rotary gear pumps II.In the centrifugal type a high kinetic energy is imparted to the liquid, which is then converted into pressure energy.

3. 1. Positive-Displacement Pumps A definite volume of liquid is trapped in a chamber, which is alternately filled and emptied at a higher pressure through the discharge. Positive displacement pumps are used when higher head increases are required. Generally they do not increase velocity. A fixed quantity of liquid is pumped after each revolution. So if the delivery pipe is blocked, the pressure rises to a very high value, which can damage the pump. Widely used for pumping fluids other than water, mostly viscous fluids 1.a. Reciprocating pumps: the chamber is a stationery cylinder that contains a piston. 1.b. Rotary pumps: the chamber moves from inlet to discharge and back to the inlet.

4. 1.a. Reciprocating piston pump

5. Double acting piston pump

6. 1.a. Diaphragm or membrane pump For handling corrosive liquids The piston operates in a cylinder in which a non-corrosive fluid is displaced

7. 1.b. Gear pump

9. 1.b. Lobe pump

10. Peristaltic pump The tube is flattened and these "flats" move the fluid by positive displacement The flow can be precisely controlled by the speed of the motor. These pumps have been particularly useful for biological fluids where all forms of contact must be avoided. They are being increasingly used and are suitable for pumping emulsions, creams, and similar fluids in laboratories and small plants.

12. Screw pump

13. 2. Centrifugal Pumps The most widely used type in the chemical industries. It will pump liquids of very wide range of properties and suspensions with a high solids content including. There’re no valves, it may be directly coupled to an electric motor. Liquid is forced into an impeller. The vanes of impeller pass kinetic energy to the liquid, thereby causing the liquid to rotate. The liquid leaves the impeller at high velocity. The impeller is surrounded by a volute casing which converts the kinetic energy into pressure energy. Centrifugal pumps are generally used where high flow rates and moderate head increases are required.

14. The fluid is fed to the centre of a rotating impeller and is thrown outward by centrifugal action. The liquid acquires a high kinetic energy and the kinetic energy is converted into pressure energy.

15. Open impeller Closed impeller Double impeller

17. 3. Axial flow pump An axial-flow pump, or AFP, is a common type of pump that essentially consists of a propeller (an axial impeller) in a pipe. The fluid is pushed in a direction parallel to the shaft of the impeller, fluid particles do not change their radial locations.  Centrifugal Axial

18. One of the most common applications of AFPs are in handling sewage. In the chemical industry, they are used for the circulation of large masses of liquid, such as in evaporators and crystallizers. They operate at much lower pressures and higher flow rates than radial-flow (centrifugal) pumps.