• The hydraulic machines which convert the mechanical energy into hydraulic energy are called pumps.
• A pump is a mechanical device that is used to transfer different fluids (gases or liquids) from one location to another by applying mechanical action.
✓ Classification of Pumps :
A) Positive Displacement Pump:
1) Reciprocating:
(i)Piston
(ii)Plunger
(iii)Diaphragm
2) Rotary
(i)Lobe
(ii) Vane
(iii)Gear
(iv)Screw
B) Dynamic Pump:
1)Centrifugal
(i)Axial flow
(ii)Mixed flow
(iii)Peripheral
2)Special effect Pump:
(i)Jet pump
(ii)Hydraulic Ram
(iii)Electromagnetic pump
A) Positive Displacement Pumps:
• The positive displacement pumps most commonly use moving parts (such as gears, lobes, plungers, pistons, or rotors) to transfer the fluids.
• The moving parts of these pumps discharge the fluid from the pump housing and increase the hydraulic pressure at the same time.
1) Reciprocating Pump :
• It uses a piston or plunger for pumping the fluid from one location to another.
• It is known as a positive displacement pump because it releases a positive amount of fluid.
• Ex- Hand pump, bicycle pump, syringe , etc.
(i)Piston Pumps :
The piston pump is a simple and powerful device. It uses a piston instead of a plunger. It has a piston, a cylinder, a casing, and a series of control units. The piston is connected to the crankshaft through a connecting rod. The piston of this pump gets power from an electric motor via a crankshaft.
2) Rotary Pumps :
In Rotary type positive displacement pumps fluid is moved with the help of rotating mechanism which results in creating a vacuum which traps and draws in the liquid.
The rotor of the rotary pump transfers the fluid by orbiting and rotatory movement.
The rotary pump mechanism consists of housing, vane, cams, runner, inlet, and outlet ports.
(i) Screw Pump :
These types of pumps use one or several screws to move the liquid along the screw axis. A screw pump generates pressure by using additional axial acceleration in the fluid within its clearance area.
It is a non-clog, large-capacity, atmospheric pressure device.
(ii) Rotary Vane Pump :
It increase the pressure of the flowing fluid using the vanes mounted to a rotor.
A vane pump is a positive displacement pump that delivers a constant flow rate under different pressure conditions. It is a self-priming pump. It is known as a “vane pump” because it pressurizes the fluid due to the impact of the vanes.
(iii)Rotary Lobe Pumps:
• The rotor of this type of pump does not touch the housing during its working. The liquid sucks in from the suction valve to the cavity between the chamber wall and the lobes. Due to the meshing of the rotors, the liquid can’t escape between them. Therefore, liquid exits from the nozzle along the rotation direction of the outer lobe.
These types of hydraulic pumps have various characteristics such as high reliability, hygienic quality, rust resistance, and excellent efficiency.
They are frequently used in the applications such as biopharmaceutical manufacturing, beverage & food processing, and hygienic processing industries.
(iv) Gear Pumps:
• The gear pumps use a series of gears to transfer the fluid.
• Gear pump usually has two gears:
• idler / driven gear
• power / driver gear.
• These gears mesh with each other.
• The power gear gets power from the prime mover or a mechanical power source.
• An internal combustion engine, electric motor, or manual labor is used to rotate the power gear.
B.) Dynamic Pumps:
• A dynamic pump transfers the fluid by increasing its pressure as it passes through the impeller and diffuser of the pump.
• In this type, the impeller increases the speed of the fluid and
the diffuser converts this speed into pressure energy.
• It uses centrifugal force to transfer the fluids.
• The energy transfer is continuous.
{1} Centrifugal Pump:
Schematic diagram of a centrifugal pump
(Reference: michael-smith-engineers.co.uk)
• Centrifugal pumps are used to transfer fluids by converting rotational kinetic energy to hydrodynamic energy. Rotational energy usually comes from an engine or motor.
• It uses an impeller and a diffuser for pumping the fluids. The impeller is connected to an electric motor via a crankshaft.
• The fluid enters the pump along to the rotating axis and then is accelerated by the impeller. Finally, it flows radially outward into the pump diffuser or volute chamber from which it exits.
{2} Special Effect Pumps :
(i)Jet Pump :
• For the efficient working of the jet pump, it must be completely filled with water.
When the system starts, the water is expelled by using a centrifugal pump.
(ii)Hydraulic Ram (Hydram) Pump :
A hydraulic ram is a cyclic water pump that is powered by hydropower.
This machine uses the effect of a water hammer to create pressure that allows a part of the input water to be lifted to a position higher than the original starting point of the water.
(iii)Electromagnetic Pumps :
In this type, the magnetic field is perpendicular to the direction of movement of the liquid and to the current flow. This creates an electromagnetic force that propels the fluid forward.
This type of pump is usually used to transfer liquid metal through cooling systems.
These types of pumps are used to move fluids such as brines, molten salts, liquid metals, or other conductive liquids using electromagnetic power.
