A Presentation on Centrifugal pumps Chemical Engineering Department Faculty of Engineering Technology & research Isroli-Bardoli. Prepared by:- (1) MEET DESAI (140840105023) (2) KARTIK MODI (140840105025) (3) MEET PATEL (140840105036) (4) BHAVIK SHAH (140840105051)

Pump A pump is a device used to move fluids, such as liquids, gases or slurries. It increases the mechanical energy of the fluid. The additional energy can be used to increase - Velocity (flow rate) Pressure Elevation

Positive Displacement Pump Classification Pumps Positive Displacement Dynamic Rotary Reciprocating Centrifugal Axial Single rotor Multiple rotor Diaphragm Piston, Plunger

Centrifugal Pumps How do they work? Liquid forced into impeller Vanes pass kinetic energy to liquid: liquid rotates and leaves impeller Volute casing converts kinetic energy into pressure energy A centrifugal pump is one of the simplest pieces of equipment in any process plant. The figure shows how this type of pump operates: Liquid is forced into an impeller either by atmospheric pressure, or in case of a jet pump by artificial pressure. 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 or in case of a turbine pump a stationary diffuser ring. The volute or stationary diffuser ring converts the kinetic energy into pressure energy.

Centrifugal Pump Volute Diffuser

Centrifugal Pump Open Semi-Open Closed Vanes Impellers

Centrifugal Pump Characteristic Total Head H m Theoretical Actual Discharge Characteristic Flow Q m3/h

Centrifugal Pumps - Key Performance Parameters

Head Head Head Head Used for Newtonian fluids or true fluids such as water and petrol like non-viscous liquids. It is the measurement of kinetic energy created by the pump. It measures the height of a liquid column which the pump creates. Head measures energy of the centrifugal pump. Here, head relates to the velocity gained by the liquid while moving through the pump.

Friction Head (hf) In pipes and fittings the head required to deal with resistance to flow is known as friction head. Depends on following: size of pipe condition of pipe type of pipe the number of pipe fittings type of fittings flow rate nature of the liquid

Velocity Head (hv) The energy created in a liquid due to its motion at some velocity is called the velocity head. It is insignificant and is ignored in high head systems while it is a significant factor in low head systems.

Pressure Head It is considered when a pumping system begins from or empties into a storage tank that is under some pressure. This pressure is converted to feet of liquid.

System Head What is added ? What is subtracted ? Vacuum in the suction tank Positive pressure in the discharge tank What is subtracted ? Positive pressure in the suction tank Vacuum in the discharge tank

Pump Head Total Head Static Delivery Head +ve Static Suction Head -ve

Suction Head Pumps do not SUCK. It is not possible to PULL a fluid A pump simply lowers the pressure at its inlet and the fluid is pushed in

Suction Head Static Head Ambient Pressure Providing the Static Head is less than the Ambient Pressure Head then the pump can (theoretically) lower the pressure sufficiently for the fluid to enter Pressure Head at pump = Ambient Pressure Head ± Static Head The Static Head is Positive if the level of the fluid is above the pump

Suction Head Static Head Friction Head Ambient Pressure Friction Head When the fluid is in motion further losses occur due to friction, obstructions, in the pipeline and fittings Pressure Head at pump = Ambient Pressure Head ± Static Head – Friction Head

Net Positive Suction Head The pump has a NPSH requirement in order to prevent cavitation damage occurring and causing severe damage. The NPSH increases with flow due to pump internal losses - friction, impeller losses etc.

Net Positive Suction Head The requirement is that: Otherwise (if NPSHA < NPSHpump), the pressure at the pump inlet will drop to that of the vapor pressure of the fluid being moved and the fluid will boil. The resulting gas bubbles will collapse inside the pump as the pressure rises again. These implosions occur at the impeller and can lead to pump damage and decreased efficiency. Cavitation

Advantages of centrifugal pump As there is no drive seal so there is no leakage in pump. It can pump hazardous liquids. There are very less frictional losses. There in almost no noise. Pump has almost have 100 efficiency. Centrifugal pump have minimum wear with respect to others. There is a gap between pump chamber and motor, so there is no heat transfer between them. Because of the gap between pump chamber and motor, water cannot enter into motor. Centrifugal pump use magnetic coupling which breakup on high load eliminating the risk of damaging the motor.

Disadvantages of centrifugal pump Because of the magnetic resistance there is some energy losses. Unexpected heavy load may cause the coupling to slip. Ferrousparticles in liquid are problematic when you are using magnetic drive.This is because particle collect at impeller and cause the stoppage of pump after sometime.

Summary: The pumps widely used in industry and by commercial buildings and municipalities, can almost all be classified as either centrifugal pumps. There are three indications that a centrifugal pump is cavitating. Noise fluctuating discharge pressure and flow fluctuating pump motor current steps that can be taken to stop pump cavitation include:Increase the pressure at the suction of the pump. Reduce the temperature of the liquid being pumped. Reduce head losses in the pump suction piping. Reduce the flow rate through the pump.Reduce the speed of the pump impeller. To avoid pump cavitation, the net positive suction head available must be greater than the net positive suction required head. Net  positive  suction  head  available  is  the  difference  between the pump  suction pressure and the saturation pressure for the liquid being pumped. Cavitation is the process of the formation and subsequent collapse of vapor bubbles in a pump.

References:  Shepard, Dennis G. (1956). Principles of Turbomachinery. McMillan. ISBN 0-471-85546-4. LCCN 56002849. Reti, Ladislao; Di Giorgio Martini, Francesco (Summer 1963). "Francesco di Giorgio (Armani) Martini's Treatise on Engineering and Its Plagiarists". Technology and Culture 4 (3): 287–298 (290). doi:10.2307/3100858.  Gülich, Johann Friedrich (2010). Centrifugal Pumps (2nd ed.). ISBN 978-3-642-12823-3.  Baha Abulnaga (2004). Pumping Oilsand Froth . 21st International Pump Users Symposium, Baltimore, Maryland. Published by Texas A&M University, Texas, USA.  Moniz, Paresh Girdhar, Octo (2004). Practical centrifugal pumps design, operation and maintenance (1. publ. ed.). Oxford: Newnes. p. 13. ISBN 0750662735. Retrieved 3 April 2015.  Larry Bachus, Angle Custodio (2003). Know and understand centrifugal pumps. Elsevier Ltd. ISBN 1856174093.

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