Centrifugal pump | mechanical seal | Overhauling | Maintenance

The centrifugal pump defines as a hydraulic machine which converts the mechanical energy into hydraulic energy by means of a centrifugal force acting on the fluid.

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.These pumps are using to raises the water or liquid from a lower level to a higher level.

Parts of Centrifugal Pump

The different parts of the centrifugal pump are listed below.

Shaft

Impeller

Casing

Suction Pipe

Delivery Pipe

1. Shaft

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.

2. Impeller

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.

3. 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.

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 the suction pipe.

Types of Casings in Centrifugal Pump

Volute casing.

Vortex casing.

Casing with guide blades.

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. 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 a case, there is better conversion has done that is velocity energy into pressure and it has good efficiency than the volute casing.

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.

Working Principle of Centrifugal Pump

The pump works on the principle of the forced 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.

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.

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.

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 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 the reciprocating pump has high efficiency and cannot run at a higher speed.

Centrifugal pump has less maintenance cost compared to a reciprocating pump.