Pump
Submitted by:
Reginald S Oliveros
PUMPS
Apumpis a device that moves fluids (liquidsorgases), or sometimesslurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid:direct lift,displacement, andgravitypumps.[1]
Pumps operate by some mechanism (typicallyreciprocatingorrotary), and consumeenergyto performmechanical workby moving the fluid. Pumps operate via many energy sources, including manual operation, electricity,engines, orwind power, come in many sizes, from microscopic for use in medical applications to large industrial pumps.
Positive displacement pump
A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe.
Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation.
Gear pump
This is the simplest of rotary positive displacement pumps. It consists of two meshed gears that rotate in a closely fitted casing. The tooth spaces trap fluid and force it around the outer periphery. The fluid does not travel back on the meshed part, because the teeth mesh closely in the centre. Gear pumps see wide use in car engine oil pumps and in varioushydraulic power packs.
Screw pump
AScrew pumpis a more complicated type of rotary pump that uses two or three screws with opposing thread—e.g., one screw turns clockwise and the other counterclockwise. The screws are mounted on parallel shafts that have gears that mesh so the shafts turn together and everything stays in place. The screws turn on the shafts and drive fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal.
Centrifugal pump
Acentrifugal pumpis a rotodynamic pump that uses a rotatingimpellerto increase the pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pump used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward or axially into a diffuser orvolutechamber, from where it exits into the downstream piping system. Centrifugal pumps are typically used for large discharge through smaller heads.
Centrifugal pumps are most often associated with the radial-flow type. However, the term "centrifugal pump" can be used to describe all impeller type rotodynamicpumps[4]including the radial, axial and mixed-flow variations
.
Axial-flow pumps
Axial-flow pumps differ from radial-flow in that the fluid enters and exits along the same direction parallel to the rotating shaft. The fluid is not accelerated but instead "lifted" by the action of the impeller. They may be likened to a propeller spinning in a length of tube. Axial-flow pumps operate at much lower pressures and higher flow rates than radial-flow pumps.