Centrifugal Pump Working

By April 30, 2021Technology Blog

The Centrifugal pump is one of the most critical components of the process plant. Proper selection from different types of centrifugal pumps is crucial for plant performance. It is used in all facilities such as refinery, oil production platform, petrochemical plant, power plant, etc. they also used in other industries such as agriculture, food processing, and even in residential buildings to supply water.

In the process plant, a centrifugal pump transport the fluid from one equipment to another. Pumps are also used to transport liquid at a long distance through cross country pipelines. It is also used to achieve the desired pressure for certain high-pressure process applications such as boiler feed water pump.

How Centrifugal Pump Works?

The working principle of the pump is the conversion of energy. Refer to the chart that makes it easier for this entire energy conversion process easy to understand.

  • Liquid enters the pump suction nozzle.
  • It enters inside the rotating impeller vane through the eye. – Impeller gets it energy from the driver (Motor, Engine or Turbine)
  • Rotating impeller forces liquid outward by centrifugal force. The liquid will get velocity and pressure during this process.
  • Now, liquid enters insider the volute casing (sometimes with diffuser), which reduced its velocity and further increased the pressure. It also directs fluid towards the discharge nozzle.
  • You can check the animation below for the fluid movement from suction to discharge of the pump.
  • Impeller and casing are the main parts that do all the works of the conversion of energy. Impeller transfers the power to fluid, and casing helps to convert the same liquid head.

Factors That Impact Centrifugal Pump Working

Suction Pressure – If pressure at pump suction is less than required, it may lead to cavitation. Cavitation will severely impact pump performance and can damage the impeller permanently.

Flow at suction – Constant flow of fluid is required at pump suction; otherwise, it will not operate at the design condition. If flow reduces at suction, discharge flow will get reduced accordingly. If there is no flow at suction, it will seriously damage pump internals. You cannot dry run this type of pump. Furthermore, you have to prime the pump before you start if it is emptied after the last use.

Viscosity of the fluid – Centrifugal pumps are an excellent choice for a clean and low viscous fluid. Usually, liquid with less than 500 Centistoke is the right choice. However, you can design a pump to hand more viscous fluid, but that be more power hungry and inefficient.

Vapor Pressure of the Fluid – Process fluid will very low vapor pressure is not suitable as it may lead to cavitation. If you are working with such liquid, make sure you have enough pressure in your system all the time.

Density of the fluid – Liquid with high density will not work with the pump. As higher the density more, work has to be done by a pump to push the liquid. Again, this will create less than ideal situations for operation and maintenance due to increased power and maintenance requirements.

Factors That Impact Centrifugal Pump Working

Suction Pressure – If pressure at pump suction is less than required, it may lead to cavitation. Cavitation will severely impact pump performance and can damage the impeller permanently.

Flow at suction – Constant flow of fluid is required at pump suction; otherwise, it will not operate at the design condition. If flow reduces at suction, discharge flow will get reduced accordingly. If there is no flow at suction, it will seriously damage pump internals. You cannot dry run this type of pump. Furthermore, you have to prime the pump before you start if it is emptied after the last use.

Viscosity of the fluid – Centrifugal pumps are an excellent choice for a clean and low viscous fluid. Usually, liquid with less than 500 Centistoke is the right choice. However, you can design a pump to hand more viscous fluid, but that be more power hungry and inefficient.

Vapor Pressure of the Fluid – Process fluid will very low vapor pressure is not suitable as it may lead to cavitation. If you are working with such liquid, make sure you have enough pressure in your system all the time.

Density of the fluid – Liquid with high density will not work with the pump. As higher the density more, work has to be done by a pump to push the liquid. Again, this will create less than ideal situations for operation and maintenance due to increased power and maintenance requirements.

There are multiple ways to classify the centrifugal pump. Refer to the chart given below:

Depending on flow type: Radial, Axial and Mixed Flow Types Centrifugal Pump

Radial Flow Pump

In radial flow, fluid take a 90-degree turn from the suction. The most centrifugal pump comes under this category. Fluid enters through the horizontal suction flange and leaves through a vertical discharge flange. That means discharge is perpendicular to the pump shaft. This design is used when you want to increase discharge pressure with a limited flow of the fluid. You can simply say that it is high pressure – low flow rate pump. Most pumps used in oil and gas will fall into this category.

Axial Flow Pump

When the fluid flows parallel to the pump shaft, it is called an axial flow pump. In this type of pumping liquid moves parallel to the pump shaft. This action resembles working or propellant. This pump is useful when handling a large amount of fluid with very little pressure head. Dewatering pumps, water circulation pumps are everyday use cases of axial flow pumps.

Mixed Flow Pump

As the name suggests, when the fluid flow is mixed of both radial and axial, it is called a mixed flow pump. It is a trade off between radial and axial type pump. It can handle a high flow rate with a decent increase in pressure head.

For further details on Grundfos pumps please click here.

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