Hydraulic Machines And Systems

Hydraulic Machines and Systems 1. What do you mean by NPSH? A. The quantity used to determine if the pressure of the liquid being pumped is adequate to avoid cavitations in centrifugal pumps is called Net Positive Suction Head. 2. Define static head? A. The sum of suction head and delivered head is known as static head. It is represented by Hs. 3. Define manometric head? A. The manometric head is defined as the head against which a centrifugal pump has to work. It is denoted by Hm. 4. Define manometric efficiency? A. The ratio of manometric head to head imparted by the impeller to the water is known as manometric efficiency. 5. Define mechanical efficiency? A. The ratio of power available at the impeller to the power available at the shaft of centrifugal pump is known as mechanical efficiency. 6. Define overall efficiency? A. The ratio of power output of the pump to the power input to the pump is known as overall efficiency. 7. Basic components of centrifugal pump and their purpose? A. The following are the basic components of centrifugal pump, a.) Impeller: An impeller is a rotor inside a tube or conduit to increase the pressure and flow of a fluid. b.) Casing: It is an air tight passage surrounding the impeller and is designed in such a way that the KE of water discharged at outlet is converted into pressure energy before the water leaves the casing and enters the delivery pipe. c.) Suction pipe: A pipe whose end is connected to the inlet of the pump and other end dips into water in a sump is known as suction pipe d.) Delivery pipe: A pipe whose end is connected to the outlet of the pump and the other end delivers the water at a required height is known as delivery pipe. 8. Configuration of pumps in series? A. For high head or pressure requirement Flow rate remains same as the individual pump Head or pressure is the summation of two pumps.

9. Configuration of pumps in parallel? A. For high flow rate requirement. Head or pressure developed is same as the individual pump Flow rate is the summation of the individual pumps 10. Cavitation in centrifugal pumps? A. Cavitation in CFP may occur at the inlet of the impeller of the pump, or at the suction side of the pumps, where the pressure is considerably reduced. The cavitation in a pump can be noted by a sudden drop in efficiency and head. 11. Purpose of diffuser ring in CFP? A. Diffuser ring converts some of the velocity head into static head. 12. Diff b/w single suction pumps & multi suction pumps? A. Single suction pumps: These pumps are used for low to medium flow rates and low to very high pressure. Multi suction pumps: These are designed by placing two pumps parallel in one casing. These are used for medium to high flow rates at low to medium pressure.