Mtech Seminar Final

8/13/2019 Mtech Seminar Final

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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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Mtech Seminar Final

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