Working of boiler injectors and its advantages and disadvantages of injectors

The injector is the instrument used to feed water into the boilers. It is usually employed where space is not available to implement a feed pump. Used for vertical and locomotive boilers

In an injector, the water is delivered to the boiler by steam pressure, the kinetic energy of the steam is used to increase the pressure and velocity of the feed water.


The handle at the top of the injector is connected to a spindle. The lower end of the valve serves the purpose of the valve.

The lower part of the spindle has a screw which works in a nut which is an integral part of the steam cone. And the key checks the rotation of the steam cone.

There is a steam pipe through which the steam passes through, And there is water pipe for water inlet, Delivery cone through which the pressured water outflows.


With the rotation of the handle, steam cone moves up and down, The valve controls the steam flow through the steam pipe. Water entering through the water pipe. The water flow is controlled by the flow of steam. The sliding motion steam cone due to the steam pressure of the water flow is controlled.

The steam and water are combined with the combining cone. The mixture then passes through the delivery cone and there its kinetic energy is converted into pressure energy.


  • Low initial cost

  • simplicity

  • Compactness

  • Thermal efficiency very high


  • Pumping efficiency is low

  • Irregularity of operation under extreme variation in steam pressure

  • It cannot force very hot water

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