Post on 04-Jun-2018
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PRESENTED BY
LOKENDRA SINGH
2013MT0344
M.TECH(DESIGN ENGG.)
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ESIGN OF PRESSURE VESSELS ONTENTS
iIntroduction to pressure vessels
Requirements in vessel design
Designing of pressure vessels Thin cylinder &Thick cylinder
Burst pressure of mild steel pressure vessels
Conclusion References
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BASIC REQUIREMENTS IN VESSEL DESIGN
Requirements:
i. Enough strength —— no breakage
ii. Enough rigidity —— limit deformation
iii. Enough stability —— no failureiv. Durability —— assuring certain usage life
v. Tightness —— no leakage
vi. Saving materials and easy to manufacture
vii. Convenient to be installation and transportation
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DESIGNING OF PRESSURE VESSELS
STRESSES IN A THIN CYLINDRICAL SHELL DUE TO AN
INTERNAL PRESSURE
The analysis of stresses induced in a thin cylindrical shell aremade on the following assumptions:
1. The effect of curvature of the cylinder wall is neglected.
2. The tensile stresses are uniformly distributed over the
section of the walls .
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From the equation of force equilibrium,
circumferential stress
In the design of engine cylinders, a value of 6 mm to
12 mm is added in above formula to permit reboring
after wear has taken place. Therefore
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In constructing large pressure vessels like steam
boilers, riveted joints or welded joints are used in
joining together the ends of steel plates. In case of
riveted joints, the wall thickness of the cylinder,
where ηl = Efficiency of the longitudinal riveted
joint.
In designing steam boilers, the wall thickness
calculated by the above equation may be compared
with the minimum plate thickness as provided in
boiler code as given in the
following table.
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Minimum plate thickness for steam boilers
LONGITUDNAL STRESS
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CHANGE IN DIMENSIONS OF A THIN C YLINDRICAL
SHELL DUE TO AN INTERNAL PRESSURE
The increase in diameter of the shell due to aninternal pressure is given by,
The increase in length of the shell due to an internalpressure is given by,
The increase in volume of the shell due to aninternal pressure is given by
δV = Final volume – Original volume
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THICK C YLINDRICAL SHELLS SUBJECTED
TO AN INTERNAL PRESSURE
The stress over the section of the walls cannot beassumed to be uniformly distributed. They develop
both tangential and radial stresses with values
which are dependent upon the radius of the
element under consideration.
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Lame’s equation.
Lame has shown that the tangential stress at
any radius x is,
Birnie ’s equation
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Barlow ’s equation According to this equation, the
thickness of a cylinder,
Clarion's equation This equation is generally used
for high pressure oil and gas pipes.
According to this equation, the thickness of a
cylinder,
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C YLINDER HEADS AND COVER PLATES
The heads of cylindrical pressure vessels and the
sides of rectangular or square tanks may have flat
plates or slightly dished plates. The plates may
either be cast integrally with the cylinder walls or
fixed by means of bolts, rivets or welds. The designof flat plates forming the heads depend upon the
following two factors:
(a) Type of connection between the head and the
cylindrical wall, (i.e. freely supported or rigidlyfixed);and
(b) Nature of loading (i.e. uniformly distributed or
concentrated).
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BURSTING PRESSURE OF MILD STEEL
CYLINDRICAL VESSELS
An accurate prediction of the burst pressure of
cylindrical vessels is very important in the
engineering design for the oil and gas industry.
Faupel’s bursting pressure formula is found to besimple and reliable in predicting the burst strength
of thick and thin-walled steel cylindrical vessels.
Being inexpensive and possessing high plasticity,
toughness as well as good weldablity, mild steels
have become the main production materials ofpressure vessels such as tower reactors and
exchangers or chemical equipment.
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BURST PRESSURE ESTIMATES OF CYLINDRICAL
PRESSURE VESSELS
The different theoretical solutions for the burstpressure (Pb) of thin-walled pipes can be expressed
in the general form Pb=(CZL/2)n+1(4ti*σult)/Dm ;where
ti is the initial wall thickness, Dm is the mean of the
inner (Di) and outer (Do) diameters; CZL is a yield
theory dependent constant having values
CZL=1 for the Tresca Theory
=2/√3 for the von Mises theory
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CONCLUSION
In the design of pressure vessels safety is the
primary consideration, especially for nuclear reactorpressure vessels, due to possible severe accident. In
general however, the design is a compromise
between consideration of economics and safety.
Faupel’s bursting pressure gives accurate result inpredictions of bursting pressure for vessels .
Design of pressure vessels is a very serious thing
because failure of these lead to heavy loss to life and
property so we have to take care of all aspect ofpressure vessel design.
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REFERENCES
[1] Harvey J.F.,‘Theory and Design of Pressure
vessels´,Van Nostrand Reinhold, New York 1985.
[2] American Society of Mechanical Engineers,
‘Boiler and Pressure Vessel Code’ , ASME, NewYork.
[3] Kenyon E., ‘Pressure Vessel Design´, The
McGraw-Hill Companies, 2004.
[4] ‘International Journal of Pressure Vessels andPiping’ 88 119 -122, 2011.
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THANKING
YOU
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