The pumps are used all over the world for different industrial and household applications. There are multiple types of pumps. Centrifugal and positive displacement pumps are the most widely used types of pumps, and they all have a different working method. Positive displacement and centrifugal pumps are the best ideal devices for moving fluids through complex municipal and industrial systems. When pumping fluid from one housing to another, there are a few things to consider when selecting which pump to use.This article mainly explains the difference between the positive displacement pump and the centrifugal pump.
What is a centrifugal pump?
A centrifugal pump is a type of pump which transfers liquid from one location to another by converting rotational energy driven by a motor into energy that propels the liquid. It uses centrifugal force for the Too and FRO motion of the liquid inside the pump. The centrifugal pump works on the centrifugal force principle.
There are multiple types of centrifugal pumps, and all types work on the same principle.
The centrifugal pumps have housing, diffuser, impeller, and impeller blades. In this pump, the fluid enters the pump impeller through a rotating shaft, where it is accelerated towards the diffuser or vortex. When the fluid strikes the blades of the impeller, the blades deliver some energy to the fluid and increase the fluid speed.
After the impeller process, the high-speed fluid goes into the vortex casing or diffuser. The vortex casing has an increasing area from the inlet to the outlet side. This vortex reduces the fluid speed and increases the pressure. As the desired pressure is achieved, the pressurized fluid is sent to the desired area.
In a centrifugal pump, as the fluid viscosity increases, the pump efficiency decreases. In contrast, the efficiency of the positive displacement pump remains the same even with an increase in the fluid viscosity. This is a major difference between the centrifugal pump and the positive displacement pump.
What are the applications of a Centrifugal Pump?
Centrifugal pumps are used to pump thin fluids with low viscosity, such as chemicals, low viscosity fuels, and oils and water. They are most commonly used to pump high flow rates at low pressure. The most common applications of the centrifugal pumps are given below:
- Cooling towers
- To transfer light fuel and petrochemicals
- Water supply and municipal water applications
- Septic Tanks
- Water circulators and air conditioning systems
- Firefighting systems
- Boiler feeds
What is a Positive Displacement Pump?
A positive displacement pump pumps a liquid by taking a certain amount of fluid and pushing it into the desired area. A positive displacement pump uses a reciprocating component such as a piston, plunger, or diaphragm to pump the fluid.
These types of pumps offer high pressure with low flow rates. They are most commonly employed used in applications that require high-pressure fluids.
The motion is initiated by two or three main axes running in opposite directions of each other.
The obvious difference between the centrifugal pump and the positive displacement pump is how they work.
As shown above, a centrifugal pump accelerates the fluid and applies pressure to the outlet. A positive displacement pump sucks a limited amount of fluid and transports it from the inlet to the outlet pipe. In simple terms, centrifugal pumps build up pressure to build up the flow, and positive displacement pumps build up a flow to build up pressure.
What are the applications of the Positive Displacement Pump?
The positive displacement pumps are most commonly used when demand low flow rates at high pressure. They are employed to pump high viscosity fluids. The positive displacement pumps have the following applications:
- For processing crude oils
- Oil processing center
- Municipal sewage system
Centrifugal Pump Vs Positive Displacement Pump:
The main difference between the centrifugal pump and the positive displacement is given below:
|Centrifugal Pump||Positive Displacement Pump|
|A centrifugal works on the forced vortex flow principle.
|A positive displacement pump works on the positive displacement principle.|
|It is less expensive than the positive displacement pump.||These are costly.|
|The pump efficiency decreases by increasing the fluid viscosity.||This pump efficiency is not affected by the fluid viscosity.|
|This pump has priming issues. It needs initial priming.||These pumps don’t have priming issues. They don’t need initial priming.|
|The centrifugal pumps are not best suitable for fluids having more than 850 CST viscosity.||As viscosity doesn’t matter for this pump. You can use the positive displacement pump for all fluids.|
|It has fewer reciprocating parts than the positive displacement pumps.||It has more reciprocating parts.|
|It has a casing, impeller, and diffuser.||It has a piston, plunger, or diaphragm.|
|These are not best for high viscosity fluids.||They are best for high viscosity fluids.|
|They supply pulsating free flow.||They provide pulsating flow.|
|In this pump, the fluid flow rate changes with the variation in the pressure.||The fluid flow rate remains the same for all pressures.|
|It provides a high discharge rate at a low head.||This pump provides a low discharge rate at the high head.|
|It has the capability to handle a large amount of fluid.||It can handle a small amount of fluid.|
|This pump has a simple design.||This has a complex design.|
|They are less efficient than the positive displacement pumps.||These are the most efficient pumps.|
|The centrifugal pumps have the following major types:
· Radial centrifugal pump
· Axial centrifugal pump
|The positive displacement pumps have the following major types:
· Reciprocating pump
· Plunger pump
· Diaphragm pump