What is a centrifugal pump and how the centrifugal pump works? and what is a centrifugal pumps operating principle?
Let me tell you one thing that, it is one of the simple and interesting topics in fluid mechanics.What is the need of a pump? We require a pump to transmit water from a region of low pressure to a region of higher pressure.
In this, the pump uses a centrifugal force acting on the fluid surface to convert the mechanical energy. The centrifugal pump flows in a radial outward direction. therefore the pump acts like a reverse reaction turbine.
these pumps are using to raises the water or liquid from a lower level to a higher level.
Different Parts of Centrifugal Pump
The different parts of the centrifugal pump are listed below.
- Suction Pipe
- Delivery Pipe
- It is a central part of the pump which is rotating with the impeller is connected.
- the shaft coupled to the prime mover to get the power.
- the shaft fits with the ball bearing.
- It is consist of a series of backward curved vanes.
- It is mounted to the shaft of an electric motor.
- An impeller is a rotating part of the centrifugal pump.
- It enclosed in a watertight casing.
- It is an airtight passage surrounding the impeller.
- It is designed in such a way that the kinetic energy of the water discharged at the outlet is converted into pressure energy before the water leaves the casing and enters the delivery pipe.
- The casing works as a cover to protect the system.
1.4 Suction Pipe with a foot valve and strainer
- The suction pipe has two ends.
- One end is connected to the inlet of the pump and the other dips into the water in a sump.
- A foot valve fits at the lower end of the suction pipe. The foot valve is the one-way type of valve which only opens in an upward direction.
- A strainer is also fitted at the end of the suction pipe to prevent the entry of foreign bodies into suction pipe.
1.5 Delivery valve
- The delivery valve has two ends.
- One end is connected to the outlet of the pump and the other end delivers the water at a required height.
2. Different types of casings in Centrifugal Pump
- Volute casing.
- Vortex casing.
- Casing with guide blades.
2.1 Volute casing (Spiral casing)
It is surrounded by the impeller. Such a casing provides a gradual increase in the area of a flow thus decreasing the velocity of water and correspondingly increasing the pressure.
2.2 Vortex casing
Vortex casing is a circular chamber in which introduce between the impeller and casing. here the fluid from the impeller has to first pass through the vortex chamber and then through the volute casing. In such case, there is better conversion has done that is velocity energy into pressure and it has good efficiency than the volute casing.
2.3 Casing with guide blades
In casing with guide blades, the blades surrounding the impeller. these blades are designed and arranged in such a way that, the water from the impeller enters the guide vane s without shock and creates a passage of increasing area, through which the water passes and reaches the delivery to leave with pressure.
3. Working Principle Of Centrifugal Pump
The pump works on the principle of the force vortex flow. it means when a mass of liquid is rotating by an external torque, the rise in pressure head of the rotating liquid takes places.
The rises in pressure head at any point is directly proportional to the velocity of the liquid at that point.
Therefore the rise in pressure head is more at the outlet of the impeller and the liquid will discharge with a high-pressure head at the outlet.
Due to this, the high-pressure head the liquid can be lifted to a high level.
This pump is suitable for low head discharge. It develops normally at a head of 50m.
4. What is priming in a centrifugal pump
Priming is the operation in which the suction pipe, casing of the pump and a portion of the pipe up to the delivery valve is completely filled up from an outside source with the liquid to be raised by the pump before starting the pump.
5. Why priming is necessary for a centrifugal pump
The pressure developed by the impeller of a centrifugal pump is proportional to the density of the fluid in the impeller. If the impeller is running in the air, it will produce a negligible pressure which may not suck water through the suction pipe. To avoid this, the pump is first primed i.e., filled up with water.
6. Difference Between Centrifugal Pump and Reciprocating Pump
The centrifugal pump is simple in construction than the reciprocating pump. Because the centrifugal pump has less number of parts.
Centrifugal pump has more weight due to a given discharge. Where reciprocating pump has less weight of pump for a given discharge.
Centrifugal pumps are suitable for large discharge with a small head. Where reciprocating pumps are suitable for less discharge with a high head,
Centrifugal pump requires more floor space and heavy foundation. Reciprocating pump requires less floor space with a simple foundation.
Centrifugal pump has less wear and tear compare to reciprocating and it can handle dirty water.
Centrifugal pump delivery is continuous and needs priming. Whereas reciprocating pump delivery is pulsating and no needs priming.
Centrifugal pump has low efficiency and can run higher. Whereas reciprocating pump has high efficiency and cannot run at higher speed.
Centrifugal pump has less maintenance cost compared to a reciprocating pump.
7. Advantages of Centrifugal Pump
- The biggest advantage of centrifugal pumps is their simplicity.
- They are suitable for large discharge and smaller heads.
- They don’t require any valves or many moving parts.
- Centrifugal pump allows them to run at high speeds with minimal maintenance.
- Their output is very steady and consistent.
- Centrifugal pumps provide a lot of flexibility, are easy to move, and don’t take up a lot of space.
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