What are the types of the gear pumps? With neat sketch discuss construction working of any type of gear pump.

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 There are four types of gear pump

  • External Gear Pump
  • Internal Gear Pump
  • Screw Pump
  • Lobe Pump
The basic principle of external gear pump is that a pair of gears being driven by an external means. The gear motion generates suction at inlet by creating a partial vacuum which causes fluid to be drawn into the pump housing. The fluid is drawn through the pump and is displaced as the teeth mesh on the outlet side.


Construction:

External gear pump have two mating gear that are turned in a closely fitted casing. Each gear is mounted on a shaft which is supported on bearing in the end covers. In this drive shaft is coupled to the prime mover. Two ports inlet and outlet are provided directly on the opposite side of the mesh point of the gears. The larger and straight ports are preferred for better performance. The driving shaft is usually connected to the upper gear of the pump. The rotation of the driver gear cause the follower gear to turn.

Operation:

When the pump starts rotating the rotation of gear forces air out of the casing and into the discharge pipe. This removal of air from the pump casing produces a partial vacuum on the suction side of the pump.




Fluid from an external reservoir is forced by the atmospheric pressure into the pump inlet. Here the fluid is trapped between the teeth of the upper and lower gear and the pump casing. Continuous rotation of the gear forces the fluid out of the pump discharge.

A vacuum is formed in the cavity between the teeth as they un-mesh causing more fluid to be drawn into the pump. Pressure rise in the pump is produced by the squeezing action of the fluid as it is expelled from between the meshing gear teeth and the casing.

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