1. Assignment # 4
Pumps:
A pump is a device used to move fluids (liquids or gases) or sometimes slurries by mechanical
action. Pumps can be classified into three major groups according to the method they use to move
the fluid: direct lift, displacement, and gravitypumps. Pumps must have a mechanism which
operates them and consume energy to perform mechanical work by moving the fluid.
The activating mechanism is often reciprocating or rotary. Pumps may be operated in many
ways, including manual operation, electricity,a combustion engine of some type, and wind action.
There are mainly two types of pumps
Positive displacement pumps
Variable displacement pumps
Positive Displacement Pumps:
It operates with the alternately filling a capacity and displacing a given volume of the liquid. It
delivers a constant volumes against varying heads. A Positive Displacement Pump cannot be
operated against a closed valve on the discharge side of the pump. If a Positive Displacement
Pump is allowed to operate against a closed discharge valve it will continue to produce flow
which will increase the pressure in the discharge line until either the line bursts or the pump is
severely damaged or both.
Reciprocating pumps:
Reciprocating compressors are either single- or double-acting. In single-acting machines the
compression takes place on only one side of the piston; double-acting machines use both sides of
the cylinder for compression.

2. A hand pump that moves fluids during both strokes of the pump handle. A wobble pump is an
example of a double-acting hand pump.
Axial piston Pump:
An axial piston pump is a positive displacement pump that has a number of pistons in a circular
array within a cylinder block. It can be used as a stand-alone pump, a hydraulic motor or an
automotive air conditioning compressor. An axial piston pump has a number of pistons (usually
an odd number) arranged in a circular array within a housing which is commonly referred to as a
cylinder block, rotor or barrel. This cylinder block is driven to rotate about its axis of symmetry
by an integral shaft that is, more or less, aligned with the pumping pistons (usually parallel but
not necessarily).
Double Acting Reciprocating pumps:
This type of pump operates in exactly the same way as the single acting with respect to its action.
The difference is, that the cylinder has inlet and outlet ports at each end of the cylinder. As the
piston moves forward, liquid is being drawn into the cylinder at the back end while, at the front
end, liquid is being discharged. When the piston direction is reversed, the sequence is reversed.
With a double acting pump, the output pulsation is much less than the single acting.
Variable displacement pumps:
It is the type of pumps in which volume is changed with by changing pressure, discharge and
head.
Centrifugal pump:
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to 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 or volute chamber, 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 rot dynamic
pumps including the radial, axial and mixed flow variations.

3. Radial flow pumps:
Often simply referred to as centrifugal pumps. The fluid enters along the axial plane, is
accelerated by the impeller and exits at right angles to the shaft (radially). Radial flow pumps
operate at higher pressures and lower flow rates than axial and mixed flow pumps.
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.
Mixed flow pumps:
Mixed flow pumps, as the name suggests, function as a compromise between radial and axial
flow pumps, the fluid experiences both radial acceleration and lift and exits the impeller
somewhere between 0–90 degrees from the axial direction. As a consequence mixed flow pumps
operate at higher pressures than axial flow pumps while delivering higher discharges than radial
flow pumps. The exit angle of the flow dictates the pressure head-discharge characteristic in
relation to radial and mixed flow.
jet pumps:
This uses a jet, often of steam, to create a low pressure. This low pressure sucks in fluid and
propels it into a higher pressure region
Submersible pump:
A submersible pump (or electric submersible pump (ESP)) is a device which has a hermetically
sealedmotor close-coupled to the pump body. The whole assembly is submerged in the fluid to be
pumped.

4. The main advantage of this type of pump is that it prevents pump cavitation, a problem associated
with a high elevation difference between pump and the fluid surface. Submersible pumps push
fluid to the surface as opposed to jet pumps having to pull fluids.
Gear pump:
A gear pump uses the meshing of gears to pump fluid by displacement. They are one of the most
common types of pumps for hydraulic fluid power applications. Gear pumps are also widely used
in chemical installations to pump fluid with a certain viscosity.
There are two main variations; external gear pumps which use two external spur gears, and
internal gear pumps which use an external and an internal spur gear. Gear pumps are positive
displacement (or fixed displacement), meaning they pump a constant amount of fluid for each
revolution. Some gear pumps are designed to function as either a motor or a pump.
Ram Pumps:
A ram pump requires hydraulic pressure to operate the pump (Not electricity!), so a drop or
"head" is mandatory to make the pump work. The ram pump then uses the energy generated by
the weight of the water to continuously pump a fraction of it uphill up to 10 times the "head" or
fall feeding the pump. When the ram pump's poppet valve (the only moving part) is open, water
flows downhill through the supply pipe to the pump and escapes out the open valve. That is waste
water, and is utilized to generate the kinetic energy required to pump some of the water up the
delivery pipe. As the water gains velocity in the supply, or drive pipe, it causes the poppet to snap
shut, which causes hydraulic pressure to peak immediately (a "water hammer" effect), which
forces some water through a check valve, and into the delivery pipe. This cycle repeats itself
about once a second.