Centrifugal pumps

  • Aviinash 
  • 5 min read

Pumps are generally used to move a fluid from a low-pressure region to a high-pressure region and vice versa. To make this possible many types of pumps are invented around the world, out of which Centrifugal pumps is also one among them which works efficiently. The Centrifugal pump was first invented by an Italian scientist in the year 1475 for lifting muds. Until the 17th century straight vanes are used in centrifugal pumps. Later, curved vanes are introduced in centrifugal pumps to transport water.

Centrifugal Pump

Principle:

Centrifugal pumps work on the principle of converting the kinetic energy of water into hydrodynamic energy by the means of centrifugal force that acts on the water. The Kinetic energy will be provided by a rotational motor. The fluid will enter the pump through the impeller. Due to centrifugal force, the fluids are moved away in an outward direction and then they will exit through the volute chamber.

Construction:

Various parts of centrifugal pumps are impeller, vane, suction eye, volute chamber, and casing. The impeller was rotated by an electric motor. The suction eye is located at the centre of the impeller. One side of the suction eye is attached to the suction pipe through which the fluid enters. The vane is attached to the impeller which will create a centrifugal force to the fluid. All these parts of the pump are enclosed in a casing and it has the attachment of a volute chamber through which the fluid exits. The casing is designed in the way of increasing cross-sectional area because the pressure will increase as the velocity decreases. By increasing the cross-sectional area the velocity of the fluid will decreases so that the pressure of the fluid will increases.

Working:

The suction pipe will suck the fluid from the pump/reservoir and the fluid enters the pump through the suction eye. Then the fluid enters the impeller. As the impeller is rotating it creates a centrifugal force in it by pushing the fluid in an outward direction. The impeller consists of curved vanes the fluid is pushed outward radially and tangentially. As there was an increasing cross-sectional area in the casing, the pressure of the fluid was increased and it will exit the pump with the help of the delivery pipe. The two important components used for energy conversion are the impeller and casing. The efficiency of the centrifugal pump will depend on the input of the shaft and the output power of the water delivered.

Types of Centrifugal Pumps:

The centrifugal pump is divided based on the fluid flows on it and the designs it has. Some of them are:

Based on the number of impellers, they are divided into:

  • Single-stage: They are used in situations where we want a high flow rate and minimal pressure. They are also used in the case of high, moderate, and low Total Dynamic Head.
  • Multi-stage: It consists of two or more impellers connected in series. They are used for high Total Dynamic Head activities.
  • Two-stage: It consists of two impellers that are operated simultaneously. They are used for moderate Total Dynamic Head activities.

Based on the splitting of cases, they are divided into:

  • Axial split: The casing is divided in the axial direction and they are mounter in the horizontal direction for easy maintenance of it.
  • Radial split: The casing is divided in a radial direction.

Based on the design of impellers, they are divided into:

  • Single suction: The fluid is sucked into the blades only in one direction and it has greater axial thrust.
  • Double suction: The fluid is sucked into the blades in two directions and it has moderate axial thrust.

The centrifugal pumps are also divided into various types based on the alignment of shafts, types of bearing used, and so on.

Priming in Centrifugal Pumps:

Before the start of a centrifugal pump, the important factor that should be considered is Priming. As these pumps are not designed to pump air and gases hence they should contain the amount of water in them. So the pump is dipped in water to remove the air present in it before the start. There various techniques that are used in pumps for priming.

The Characteristic curve for a Centrifugal Pump:

This curve is used to make the hydraulic calculations of the pump. Various factors like flow head, pump input, head, and power output are calculated using this characteristic curve.

Applications:

  • They are used to transport water, mud, solvents, oils, acids, and bases from lower regions to higher regions.
  • They are used to transport low viscosity fluids.
  • They are used in high-pressure applications.
  • They are used as coolants.
  • They are used in draining mines, pits, and in construction sites.
  • They are used in air conditioning and ventilation.

Advantages:

  • They will transfer a large volume of liquid.
  • They are designed simply.
  • They are compact.
  • There is no transmission of heat.
  • There are no seals that will lower the leakages.

Limitations:

  • If it is not operated for a long time, there will be a formation of rust.
  • When the fluid vaporizes due to the speed at which it rotates, it will cause a bubble in the fluid which results in the corrosion of the casing.
  • The pump will be damaged when it is not primed properly.
  • When the load is heavy, it will damage the pump.

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