The ‘specification’ is probably the easiest part of
the design process.
It is one that pupils tend to neglect or write
It is usually a list of points, with each point
referring to the research work.
Have been used historically in public
contracting for buildings, highways and other
Specification in Design
Needed for :
Transfer of liquid from one place to another
e.g. water from an underground aquifer into a
water storage tank.
Circulate liquid around a system.
e.g. cooling water or lubricants through
machines and equipment
Purposes of Pump
A sub-class of dynamic axisymmetric work-absorbing
Used to transport fluids by the conversion of rotational
kinetic energy to the hydrodynamic energy of the fluid
The rotational energy typically comes from an engine or
The fluid enters the pump impeller along or near to the
rotating axis and is accelerated by the impeller, flowing
radially outward into a diffuser or volute chamber
(casing), from where it exits.
It consists of a series of backward curved vanes. The impeller
is mounted on a shaft which is connected to the shaft of an
Provide a pressure boundary for the pump and contains
channels to properly direct the suction and discharge flow.
3. Suction pipe with a foot valve and a strainer
A pipe whose one end is connected to the inlet of the pump
and other end dips into water in a sump
4. Delivery pipe
A pipe whose one end is connected to the outlet of the pump
and other end delivers the water at a required height
Centrifugal pump works by the conversion of
the rotational kinetic energy, typically from an
electric motor or turbine to an increased static
Centrifugal pump works by spinning water with
propellers inside an housing or casing.
During the spinning, pressure builds outwards.
The pressure propels the water through the
How it work?
• Cavitation - The net positive suction head (NPSH) of the
system is too low for the selected pump
• Wear of the Impeller - Can be worsened by suspended
• Corrosion inside the pump caused by the fluid properties
• Overheating due to low flow
• Leakage along rotating shaft
• Lack of prime - centrifugal pumps must be filled (with
the fluid to be pumped) in order to operate