This document discusses cavitation, valves, and types of valves. It defines cavitation as the formation of vapor bubbles when liquid pressure drops below vapor pressure. The cavitation process involves gas bubble formation, compression, and implosion which can damage surfaces. Cavitation can be reduced by minimizing pressure variations, increasing part stiffness and material hardness/corrosion resistance. The document also defines a valve as a device regulating fluid flow and lists common valve types like ball, gate, plug, butterfly, and globe valves. It provides brief descriptions of each type.

1. CAVITATION,VAVLE AND
TYPES OF VAVLE
PRESENTED BY
GROUP 3
FAHEEM ULLAH

2. WHAT IS CAVITATION?
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 Cavitation is defined as the phenomenon of the
formation vapour bubbles of flowing liquid in a
region where the pressure of the liquid falls
below its vapour pressure.
 VAPOUR PRESSURE
Vapour pressure is a measure of the tendency
of a material to change into the gaseous or
vapour state, and it increases with temperature.

3. Cavitation Process
 Step 1:
Gas bubble formation, also known as boiling, is
dependent on the temperature and pressure of a
liquid.
Gas bubbles form as the pressure of the fluid
decreases during the cavitation cycle.
 Step 2:
At the next phase of the process, as the pressure of
the fluid increases, the gas bubble becomes
compressed.

4.  Step 3:
With a further increase in the fluid pressure, the
gas vapor pressure inside the bubble reaches the point
that it is unable to support the external pressure of the
surrounding fluid.
 Step 4:
When the gas bubble collapses, or implodes, a
high-velocity jet of fluid impacts the surface of the part.
The impact not only destroys the surface film at that
location, but also can damage the base material
beneath that layer.

6. What types of parts can be damaged by
cavitation?
All parts that are in contact with a high-velocity moving
fluid with changes in pressure have the potential to be affected
by cavitation. Some examples include...
 Piping systems... including orifices and valve components.
 Pump components... including impellers, pump housings, and
torque converters.
 Hydroturbine components... including turbine runners, stay vanes
and wicket gates.
 Engine housings and cylinder sleeves.
 Ship components... including hulls, propellers, stabilizers, and
rudders.
 Heat exchanger components.

7. Cavitation Effect
 Noise
 Damage to components
 Vibration and loss of efficiency

8. What can be done to help keep caviation
from occurring?
 Minimize pressure variations
Pressure variations in a fluid-flow process create the
gas bubbles that cause cavitation. To minimize
pressure differences, streamline the parts that are
exposed to the fluid flow. Eliminate protrusions,
irregular surfaces, discontinuities, and sharp corners to
minimize abrupt changes in fluid pressure.
 Increase part stiffness
Increasing the stiffness of a part exposed to the
fluid flow may help to reduce the potential for
cavitation.

9.  Increase material hardness
Part of the damage caused by cavitation is due
to mechanical fatigue. By using metals with
higher material hardness properties, the effect of
cavitation can be reduced or delayed.
 Increase material corrosion resistance
Because the effect of erosion-corrosion
accelerates the rate of pitting damage, the use of
more corrosion-resistant materials is helpful in
some applications.

10. APPLICATION
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 CHEMICAL ENGINNERING
In industry, cavitation is often used
to homogenize, or mix and break down,
suspended particles in a colloidal liquid
compound such as paint mixtures or milk.
Cavitating water purification devices have
also been designed, in which the extreme
conditions of cavitation can break down
pollutants and organic molecules.

11. BIOMEDICAL
 Cavitation plays a key role in non-thermal,
non-invasive fractionation of tissue for
treatment of a variety of diseases and can be
used to open the blood-brain barrier to
increase uptake of neurological drugs in the
brain.
 Cavitation also plays a role in HIFU, a
thermal non-invasive treatment methodology
for cancer.

12. CLEANING
 In industrial cleaning applications, cavitation has
sufficient power to overcome the particle-to-substrate
adhesion forces, loosening contaminants. The
threshold pressure required to initiate cavitation is a
strong function of the pulse width and the power input.
This method works by generating controlled acoustic
cavitation in the cleaning fluid, picking up and carrying
contaminant particles away so that they do not reattach
to the material being cleaned.

13. VALVE
 A valve is a device that regulates, directs or
controls the flow of a fluid (gases, liquids,
fluidized solids, or slurries) by opening,
closing, or partially obstructing various
passageways.

14. Uses of Valve
 Valves have many uses, including controlling
water for irrigation, industrial uses for
controlling processes, residential uses such
as on/off and pressure control to dish and
clothes washers and taps in the home. Even
aerosols have a tiny valve built in. Valves are
also used in the military and transport
sectors.

15. Types of Valve
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 BALL VALVE
 GATE VALVE
 PLUG VALVE
 BUTTERFLY VALVE
 GLOBE VALVE

16. BALL VALVE
 A ball valve is a form of quarter-
turn valve which uses a hollow, perforated and
pivoting ball to control flow through it. It is open
when the ball's hole is in line with the flow and
closed when it is pivoted 90-degrees by the
valve handle. The handle lies flat in alignment
with the flow when open, and is perpendicular to
it when closed, making for easy visual
confirmation of the valve's status.

17. GATE VALVE
 A gate valve, also known as a sluice valve, is
a valve which opens by lifting a round or rectangular
gate/wedge out of the path of the fluid. The distinct
feature of a gate valve is the sealing surfaces
between the gate and seats are planar, so gate valves
are often used when a straight-line flow of fluid and
minimum restriction is desired. The gate faces can be
parallel, but are most commonly wedge-shaped.

18. PLUG VALVE
 Plug valves are valves with cylindrical or conically
tapered "plugs" which can be rotated inside the valve
body to control flow through the valve. The plugs in plug
valves have one or more hollow passageways going
sideways through the plug, so that fluid can flow through
the plug when the valve is open. Plug valves are simple
and often economical.

19. BUTTERFLY VALVE
 A butterfly valve is a valve that
isolates or regulates the flow of a fluid.
The closing mechanism is a disk that
rotates.

20. GLOBE VALVE
 A globe valve, different from ball valve, is a type
of valve used for regulating flow in a pipeline, consisting of
a movable disk-type element and a stationary ring seat in a
generally spherical body.
 Globe valves are named for their spherical body shape with
the two halves of the body being separated by an
internal baffle.

21. REFFERENCES
 http://www.repairengineering.com/cavitation.html
 https://en.wikipedia.org/wiki/Valve
 https://www.quora.com/What-is-the-difference-
between-a-gate-and-a-globe-valve