Centrifugal Pump: Maximizing Efficiency and Power [PDF]

Centrifugal Pump Definition:

The hydraulic machine which converts the mechanical energy into Hydraulic energy is called Pumps. The hydraulic energy is in the form of pressure energy, If the mechanical energy is converted into pressure energy by means of a centrifugal force acting on the fluid, the hydraulic machine is called a Centrifugal pump.

Centrifugal Pump Parts:

The main parts of the Centrifugal Pump are as follows:

• Impeller
• Casing
• Suction pipe with a foot valve
• strainer and
• Delivery pipe

Impeller:

An impeller is a rotating component of a centrifugal pump which transfers energy from the motor that drives the pump to the fluid being pumped by accelerating the fluid outwards from the center of rotation.

Casing:

The Casing receives the fluid that is being pumped by the impeller, slowing down the fluid’s rate of flow. A volute is a curved funnel that increases in area as it approaches the discharge port.

Suction pipe with a foot valve and Strainer:

A pipe whose one end is connected to the inlet of the pump and another end dips into the water in a sump is known as a suction pipe. A foot valve is found at the end of a pipeline in a suction lift application. They function as a check valve, but they also have a strainer affixed to their open end.

Delivery pipe:

A pipe whose one end is connected to the outlet of the pump and other ends delivers the water at a required height is known as a Delivery pipe.

Centrifugal Pump Working Principle:

The Centrifugal pump acts as a reverse of an inward radial flow reaction turbine. This means that flow in a centrifugal pump is in the radial outward directions. The centrifugal pump works on the principle of forced vortex flow which means that when a certain mass of liquid is rotated by an external torque, the rise in pressure head of the rotating liquid takes place.

The rise in pressure head at any point of the rotating liquid is proportional to the square of the tangential velocity of the liquid at that point. Therefore the rise in pressure head is v²/2g. Thus at the outlet of the impeller, where the radius is more, the rise in pressure head will be more and the liquid will be discharged at the outlet with a high-pressure head. Due to this high-pressure head, the liquid can be lifted to a high level.

Centrifugal Pump Application:

1. Centrifugal pumps are used in buildings for pumping the general water supply, as a booster and for domestic water supplies.
2. The design of a centrifugal pump makes them useful for pumping sewage and slurries.
3. They are also used in fire protection systems and for heating and cooling applications.
4. Beverage industry: Used to transfer juice, bottled water, etc.
5. Dairy industry: Used to transfer dairy products such as milk, buttermilk, flavored milk, etc.
6. Various industries (Manufacturing, Industrial, Chemicals, Pharmaceutical, Food Production, Aerospace, etc.): For the purposes of cryogenics and refrigerants.
7. Oil Energy: Pumping crude oil, slurry, mud; used by refineries, power generation plants.

Centrifugal Pump Advantages:

1. Their simplicity.
2. They don’t require any valves or moving parts. This makes it easy to produce with many different materials.
3. It also allows them to move at high speeds with minimal maintenance.
4. Their output is very steady and consistent. 
5. Most of all, they are very small as compared to other types of pumps that create the same output.

Centrifugal Pump Disadvantages:

1. They use rotation instead of suction to move water and therefore have almost no suction power.
2. This means that a centrifugal pump must be put underwater, or primed before it will move water.

Priming and why it is necessary.

Priming can be defined as the process in which the suction pipe, casing, delivery pipe up to the delivery valve, which is filled completely with liquid to be raised from an outside source before starting the motor. The main reason for priming in the pump is to remove the air from the pump.

Necessity of Priming:

If air is not removed from the pump then a small negative pressure is created at the suction pipe and it can not suck the water from the water sump or reservoir. So it is advised to fill the pump with water before starting it.