ProjectReportL&T

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L&T HEAVY ENGINEERING
POWAI CAMPUS
LARSEN AND TOUBRO
Design of Inner Door of a
12 m Spherical Pressure
Vessel
Submitted By:
Ishank Agarwal
P.S/S.S No. - 660270
Under the Guidance of:-
VIKRAM BIRADAR
MANAGER – DESIGN & ENGG.

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1. ACKNOWLEDGEMENT
Training at an industry gives a sophomore engineering student the opportunity to
understand the industry and its challenges, but more importantly a chance to find out
his interests for future. My experience at L&T was a relishing one, helping me clear a
lot of doubts and also teaching me a lot.
I would like to thank my institute, Indian Institute of Technology, Kanpur, for giving
me the opportunity to undergo this informative training period.
I’ll also like to thank Larsen and Toubro for giving me this opportunity
My whole hearted thanks to Mr. Vikram Biradar for his guidance and encouragement.
He ensured that I made the most of my stay here. I thank him for presenting me with a
project that in its course taught me the philosophy behind design and helped me to
hone my practical and engineering skills.
I would also like to thank Mr. Naveen Jaiswal for his constant guidance and support
throughout my stay here.
Last but not the least, I would thank all the people I met here who kept me motivated
and going on to complete the project that I was assigned. They made it very easy for
me to adapt to the department and constantly supported me to learn.

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2. ABSTRACT
This project report is based on the study of pressure vessels, and the study and
design of a spherical pressure vessel using various standards. Larsen & Toubro
Limited, also known as L & T, is an Indian multinational conglomerate with
headquarts in Mumbai, India. The company has business interests in engineering,
construction, manufacturing goods, information technology and financial services,
and also has an office in the Middle East and other parts of Asia.
My department was Nuclear Equipment and Systems in the Heavy Engineering
division. This group is concerned with design of the received product orders.
A pressure vessel is a closed container designed to hold gases and liquids at
pressures substantially different from the ambient pressure. The pressure
differential is dangerous, and fatal accidents have occurred in the history of
pressure vessel development and operation. A brief introduction to pressure vessel
is presented.
Pressure Vessels are commonly designed and manufactured to the standards set
forth by various associations or organizations. These bodies, in cooperation with
users, designers and manufacturers, establish a common set of guidelines for the
construction and design methods, tolerances and practices to be employed. ASME,
TEMA and AD-2000 MERKBLATTER codes have been used for pressure vessel
design.

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3. INTRODUCTION TO LARSEN AND TOUBRO
Larsen & Toubro Limited, also known as L & T, is an Indian multinational
conglomerate headquarted in Mumbai, India. It was founded by Danish engineers,
Henning Holck-Larsen and Soren Kristian Toubro. The company has business
interests in engineering, construction, manufacturing goods, information
technology and financial services, and also has an office in the Middle East and
other parts of Asia.
SALIENT FEATURES
- Public Company
- Conglomerate
- Headquartered in L&T House, Ballard Estate, Mumbai, Maharashtra, India.
- Areas served include India, Middle East, East Asia and Southeast Asia.
- Products include: Construction, Heavy equipment, Electrical equipment,
Power, Shipbuilding, Financial services, IT Services.
- 84,027 employees (2014)
- It comprises a large number of Subsidiaries & Associate companies spread
across the world. Its subsidiaries include L&T InfoTech, L&T Mutual Fund,
L&T Infrastructure Finance Company, L&T Finance Holdings, L&T IES,
L&T MHPS.
It's all about Imagineering

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World’s largest vacuum distillation column - weighing 975 MT - fabricated by L&T for Paradip refinery
(Orissa, India).
Image Source: http://www.larsentoubro.com/lntcorporate/common/Pdf/Annual_review_2013.pdf
4. L&T HEAVY ENGINEERING
L&T Heavy Engineering operates at the upper end of the technology spectrum, and
has been at the forefront of introducing new processes, products and materials into
the manufacturing sector. It is one of the world’s top five heavy engineering
manufacturers, earning global recognition for the size and complexity of the
equipment and systems that it designs and manufactures, and the speed with which
they have been successfully executed. The Company’s proven design and
engineering strengths give it a competitive edge in its domain. The business
manufactures and supplies a broad spectrum of custom designed, engineered
critical equipment and systems to core sector industries like fertilizer, refinery,
petrochemical, chemical, oil & gas, thermal power, nuclear power, aerospace, as
well as equipment and systems for defense.

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Many of the equipment manufactured by L&T Heavy Engineering are the world’s
largest, heaviest, first of its kind. These include the world’s largest vacuum
column, the biggest coke drum, the biggest EO reactor and the largest FCC
regenerator.

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5. DEPARTMENT
MARKETING GROUP PROJECT
MANAGEMENT
GROUP
DESIGN AND
ENGINEERING
MATERIAL
PROCUREMENT
My department is Design and Engineering division of the Nuclear Equipment And
Systems department. This group is concerned with design of the received product
orders. It designs independently or suggests the modifications in the design of the
products, jigs, fixtures, etc. of the various projects. This group also prepares and
supplies all the drawings and other documents required for the different projects.
BUSINESS UNIT

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6. INTRODUCTION TO PRESSURE VESSELS
A pressure vessel is a closed container designed to hold gases and liquids at
pressures substantially different from the ambient pressure. The pressure
differential is dangerous, and fatal accidents have occurred in the history of
pressure vessel development and operation.
Pressure vessels are everywhere in manufacturing and process equipment,
refineries and petrochemical plants, submarines, spacecraft and, more generally, in
all hydraulic and pneumatic systems. Most pressure vessels are welded steel
cylinders with convex or dished head closures.
Pressure vessel design and operation are tightly controlled by engineering
organizations. Their codes have the force of law. The mechanical design of most
pressure vessels is done in accordance with the requirements contained in the
ASME Boiler and Pressure Vessel Code, Section VIII. Section VIII is divided into
three divisions.

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7. MAIN PRESSURE VESSEL COMPONENTS
• Shells
The shell is the primary component that contains pressure. Pressure vessel
shells are welded together to form a structure that has a common rotational
axis. Most shells are either cylindrical, spherical or conical in shape.
• Heads
All pressure vessels shells must be closed at the ends by heads. Heads are
typically curved rather than flat. Curved configurations are stronger and
allow heads to be thinner, lighter and less expensive than flat head. Heads
can also be inside a pressure vessel. These “intermediate heads” separate
sections of the pressure vessel to permit different design conditions in each
design sections.
• Nozzles
A nozzle is a cylindrical component that penetrates the shell or heads of a
pressure vessel. The nozzle ends are generally flanged to allow for necessary
connections and to permit easy disassembly for easy maintenance or access.
Nozzles are used for the following applications:-
o Attach piping for flow in or out of the vessel.
o Attach instrument connections, (e.g. level gauges, thermowells, or
pressure gauges)
o Provide access to the vessel interior for manways.
o Provide for direct attachment of other equipment items (e.g., heat
exchanger or mixer).
Nozzles are sometimes also extended inside the vessel for some applications
for some applications, such as, inlet for distributions or to permit entry of
thermowells.
• Support
The type of support used depends primarily on the size and the orientation of
the pressure vessel. In all cases, the support must be adequate for the applied
weight, winds and earthquake loads. The design pressure is not a
consideration in the design of support as the support is not pressurized.
Temperature may be a consideration in support design from the standpoint
of material selection and provision for thermal expansion.
o Saddle Supports
Horizontal drums are usually supported at two points by saddle
support. A saddle support spreads the weight load over a large area of

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the shell to prevent an excessive local stress at the support points.
Width of the saddle, among other design details, is determined by the
specific size and design conditions of the pressure vessel. One saddle
support is normally fixed or anchored to its foundation. The other
support is normally free to permit unstrained longitudinal thermal
expansion of the drum.
o Leg Support
Small vertical drums are usually supported on legs that are welded to
the lower portion of the shell. The maximum ratio of support leg
length to drum diameter is typically 2:1. Reinforcing pads and/or
rings are first welded to the shell to provide additional local
reinforcement and load distribution in places where the local stresses
may be excessive. The number of legs needed depends on the drum
size and the loads to be carried. Support legs are typically used for
pressurized spherical storage vessels. The support legs for small
vertical drums and spherical storage vessels may be made of
structural steel columns or pipe sections, whichever provides a more
efficient design. Cross bracing between the legs is typically used to
absorb wind and earthquake loads.
o Lug Supports
Lugs that are welded to the pressure vessel shells may also be used to
support a vertical pressure vessel. The use of lugs is typically limited
to vessels of small to medium diameter (1ft to 10ft) and moderate
height to diameter ratios of 2:1 to 5:1. Lug supports are often used for
vessels of this size that are located above grade within structural
steel. The lugs are typically bolted to horizontal structural members
to provide stability against overturning loads. However the bolt holes
are often slotted to permit free radial thermal expansion of the drum.
o Skirt Supports
Tall, vertical, cylindrical pressure vessels are typically supported by
skirts. A support skirt is a cylindrical shell section that is welded
either to the lower portion of the shell or the bottom head. Skirts for
spherical vessels are welded near the mid plane of the shell. It is
normally not necessary for the skirt bolt holes to be slotted. The skirt
is normally long enough to provide enough flexibility so that the
radial thermal expansion of the shell does not cause high thermal
stresses at its junction with the skirt.

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Horizontal Vessel on Saddle Support
Vertical Vessel on Lug Support

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Spherical Pressurized Storage Vessel

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Tall Vertical Tower

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Vertical Drum on Leg Support

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Vertical Reactor

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8. MATERIALS OF CONSTRUCTION
The mechanical design of a pressure vessel can proceed only after materials have
been specified. The ASME code does not state what materials must be used in each
application. It specifies what materials may used for ASME code vessels, plus
rules and limitations on their use. But it is upto the end user to specify the
appropriate materials for each application considering various material selection
factors in conjunction with ASME code requirements.
A. Material Selection Factors
The main factors that influence material selection are:
- Strength
- Corrosion Resistance
- Resistance to Hydrogen Attack
- Fracture Toughness
- Fabricability
Other factors that influence material selection are cost, availability, and ease of
maintenance.
I. Strength
Strength is the materials ability to withstand an imposed force or stress.
Strength is a significant factor in the material selection for a particular
application. Strength determines how thick a material must be to
withstand imposed loads.
The overall strength of a material is determined by its yield strength,
ultimate tensile strength, creep and rupture strength. These strength
properties depend on the chemical composition of the material. Creep
strength (a measure of material strength at elevated temperatures) is
increased by the addition of alloying elements such as chromium,
molybdenum, and/or nickel to carbon steel. Therefore, alloy materials are
often used in elevated temperature applications.
II. Corrosion Resistance
Corrosion is the deterioration of metals by chemical action. A material’s
resistance to corrosion is probably the most important factor that
influences its selection for a given process. The most common method
that is used to address corrosion in pressure vessels is to specify a

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corrosion allowance. A corrosion allowance is supplemented metal
thickness that is added to the minimum thickness that is required to resist
the applied loads. This applied thickness compensated for thinning (i.e.,
corrosion) that will take place during service.
The resistance of carbon steel can be increased with the addition of
alloying elements such as chromium, molybdenum, or nickel. Alloy
materials, rather than carbon steel, are often used in application where
increased corrosion resistance is required in order to minimize the
necessary corrosion allowance.
III. Resistance to Hydrogen Attack
At temperatures from 300°F to 400°F , monotonic hydrogen gas diffuses
into the voids that are normally present the steel. In these voids, the
monotonic hydrogen forms molecular hydrogen, which cannot diffuse
out of steel. If this hydrogen diffusion continues, pressure can build up to
high levels within steel, and the steel can crack.
At elevated temperatures at over 600°F, monotonic hydrogen not only
causes cracks to form but also attack the steel. Hydrogen attack differs
from corrosion in that damage occurs throughout the thickness of the
component, rather than just at its surface, and occurs without a metal
loss. Also, once hydrogen attack has occurred, the metal cannot be
repaired and must be replaced. Hydrogen attack is a potential design
factor at hydrogen partial pressures above approximately 100 psia.
Material selection for these hydrogen service applications is based on
API 941, Steels for Hydrogen Services at Elevated Temperature and
Pressure in Petroleum Refineries and Petrochemical Plants. API 941
contains a family design curves (the Nelson Curves) that are used to
select the appropriate material based on hydrogen partial pressure and
design temperature.
IV. Fracture Toughness
Fracture toughness refers to the ability of a material to withstand
conditions that can cause a brittle fracture. The fracture toughness of a
material can be determined by the magnitude of the impact energy that is
required to fracture a specimen using Charpy V-notch test. Generally
speaking, the fracture toughness of a material decreases as the
temperature decreases (i.e. it behaves more like glass). The fracture

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toughness at a given temperature varies with different steels and with
different manufacturing and fabrication processes.
Material selection must confirm that the material has adequate fracture
toughness at the lowest expected metal temperature. It is especially
important for material selection to eliminate the risk of brittle fracture
since a brittle fracture is catastrophic in nature. It occurs without warning
the first time the necessary combination of critical size defect, low
enough temperature, and high enough stress occurs.
V. Fabricability
Fabricability refers to the ease of construction and to any special
fabrication practices that are required to use the material. Of special
importance is the ease with which the material can be rolled or otherwise
shaped to conform to vessel component geometry requirements.
Pressure vessels commonly use welded construction. Therefore, the
materials used must be weldable so that individual components can be
assembled into the completed vessel. The material chemistry of the weld
area must be equivalent to that of the base material so that the material
properties and corrosion resistance of the weld area will be the same as
those of the base material.
B. Maximum Allowable Stress
One of the major factors in the design of pressure vessels is the relationship
between the strength of the components and the loads (i.e., pressure, weight,
etc.) imposed upon them. These loads cause internal stresses in the
components. The design of a pressure vessel must ensure that these internal
stresses never exceed the strength of the vessel components.
Pressure vessel components are designed such that the component stresses
that are caused by the loads are limited to maximum allowable values that
will ensure safe operation. Maximum allowable stress is the maximum stress
that may be safely applied to a pressure vessel component. The maximum
allowable stress includes a safety margin between the stress level in a
component due to the applied loads and the stress level that could cause a
failure.

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I. Maximum Allowable Stress Criteria
The ASME Code Section II, Part D, Appendix 1 discusses the basis used to
establish maximum allowable stress values for materials other than bolting
for Division 1 vessels. A similar discussion is contained in Section II, Part
D, Appendix 2 for bolting, and Section VIII, Division 1, Appendix P for
low-temperature, cast or ductile iron materials. Refer to these appendices for
the specific safety margins and other considerations used in determining the
maximum allowable stresses.
Two sets of allowable stress values are provided in Division 1 for austenitic
materials and for specific non-ferrous alloys. The higher alternative
allowable stresses exceed two-thirds but do not exceed 90% of the minimum
yield strength of the material at temperature. The higher allowable stress
values should be used only where slightly higher deformation of the
component is not in itself objectionable (e.g., for shell and head sections).
These higher allowable stresses are not recommended for the design of
flanges or other strain-sensitive applications. In the case of flanges, for
example, the larger deformation that would be expected if the higher
allowable stresses were used could cause flange leakage problems even
though a major flange failure would not occur.
II. ASME Maximum Allowable Stress Tables
Tables in the ASME Code Section II, Part D contain the maximum
allowable tensile stresses of materials that are acceptable for use in 88
ASME Code Section VIII pressure vessels. The maximum allowable stress
varies with temperature because material strength is a function of
temperature.
The first part identifies the Spec. No. (i.e., material specification number),
the grade (a material specification may have multiple strength grades), the
nominal chemical composition, the PNo. and Group No., and the minimum
yield and tensile strengths in thousands of pounds per square inch (ksi). This
first part also helps identify similarities that may exist among the material
specifications (e.g., nominal alloy composition, yield strength, and tensile
strength). In some cases, these similarities may help select the material to
use for pressure vessel fabrication, given specific process conditions. The
maximum allowable stress values as a function of temperature are presented
in the second part.

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ASME Maximum Allowable Stress

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ASME Maximum Allowable Stress (Excerpt), cont'd

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9. CALCULATIONS
Dimensions:-
Hinge Support Rod
Connecting Rod

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Assumptions:-
- The material used for the construction of the door is SA 350 LF2.
- All calculations are done in matric units.
- All calculations are on the basis of ASME Section VIII Division
III, 2010.
- The Design Pressure is 3.3 MPa and external pressure 0.1 MPa.
- Inner door is a combination of a cut spherical portion and a
cylinder.
- Equations for sphere have been used on the cut-spherical portion.
Inner Door

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- Considered buckling in the cylindrical portion.
Required Values:-
- Design Pressure 3.3 MPa and external pressure 0.1 MPa.
- Yield Strength (Sy) is 250 MPa.
- Ultimate Tensile Strength (Su) is 485 MPa.
- Young’s Modulus for steel 210 GPa.
- Density of steel 7850 kg/m3
- Poisson’s Ratio for steel 0.27.
- Inner diameter of spherical part 2690 mm.
- Inner diameter of cylindrical part 2000 mm.
- Load supported by each latch = 3500 kgf = 34.34 kN
Some Equations Used:-
- Equation for thickness of cut-spherical portion:
where Y is the ratio of the outer diameter to the inner diameter of the sphere.
- Equation for thickness of cylindrical portion considering buckling:

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where Y is the ratio of the outer diameter to the inner diameter, E is the
Young’s Modulus, v is the Poisson’s Ratio.
Calculation of thickness:-
- Thickness of Spherical Part:-
PD = min ( 346.41 ln(Y) , 424.35 ln(Y))
Therefore, PD = 346.41 ln(Y)
Then Y = 1.00957
Then DO = 1.00975 * 2690 mm
Do = 2715.75 mm
Thickness t = 2715.75 -2690 = 25.75 mm.
- Thickness of Cylindrical Part:-
PD = 210 ( Y-1)3
/ (40*(1-0.272
)Y3
Y = 1.0911
Do = 1.0911*2000 mm
Do = 2182 mm
Thickness t = 2182-2000 = 182mm
Now, since the thickness of the door throughout would be same, let us assume the
thickness of the door to be 180 mm throughout.
Calculation of Weight:-
Then, Volume of spherical part( for ts= 25mm) = 0.0814m3
Volume of spherical part( for ts= 180mm) = 0.586m3
Volume of cylindrical part( for tc= 180mm) = 0.656 m3

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For thickness of Spherical part 180mm
Net Volume = 0.656 + 0.586 = 1.242 m3
Mass of Inner door ‘M’ = 1.242* 7850 kg
M = 9749.7 kg
Weight of Inner Door ‘W’= 9749.7 * 9.81 N
W = 95.65 kN
For thickness of spherical part 25mm
Net Volume = 0.656 0.0814 = 0.7274 m3
Mass of Inner door ‘M’ = 0.7274* 7850 kg
M = 5710 kg
Weight of Inner Door ‘W1’=5710 * 9.81 N
W = 56 kN
Calculation of Stress:-
Consider the supporting rods from hinge to be rectangular rod of
approximate length 1000mm, width 150mm and height 190mm.
Weight of rectangular rod ‘W2’ = 7850*1*0.15*0.19 *9.81 = 2.194 kN
Then,
Maximum bending moment for supporting rod will be at Hinge pin, thus
Mb,max = W1*L + W2L/2
Vb,max = W1 + W2
σmax = Mb,max * ymax / I = Mb,max * (h/2) / (b*h3
/12) = 6* Mb,max /(bh2
)
Mb,max = (95.65 + 2.2/2) * 1 = 96.75 kN-m
σb,max = 96.75 * 6 /(0.15 * 0.192
) = 107.2 MPa
since,
σb,max < σy thus it will not yield.

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Shear at Hinge Support
σs = VS / A = 97.85/(0.025 * 0.19) = 20.6 MPa < σy
Shear at Hinge pin Support
σs = VS / A = 97.85 / (0.07 * 0.01) = 139.78 MPa < σy
Bending of Hinge pin support
Mb = 0.4 * VS = 39.14 kN-m
σb,max = 39.14 * 6 / (0.31 * 0.072
) = 154.6 MPa < σy
Calculation for Number of Latches Required
Total curved area of the of the door spherical portion = 3.36 m2
External Pressure on inner door = 100 kPa
By considering the force
Net force external force on the inner door = 336 kN
Thus,
No. of Latches Required = 336/34.34 = 9.78 => 10
Considering Moment about the Hinge

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Taking the moment of an element particle of area r*dr*dθ, about the
hinge and integrating would give us
Monemt Md = 356 kN-m
Moment due to n latches symmetrically about Hinge =
68.6* Σi (sin(180*i/n))
Thus, Total Number of Latches required = 8 (calculated at
WolframAlpha.com)

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10. RESULT & ERRORS
Result
- The thickness of the inner door would be 180 mm.
- The specifications of Hinge dimensions would be able to handle the load of
the inner door.
- To latch the inner door, Toggle clamps can be bought from outside. Steel
Smith is a company in Mumbai that deals in such latches.
Errors:-
- The formula used to calculate the thickness of the cut-spherical part is for
spheres. Thus, a higher thickness would be required.
- Buckling for the cylindrical part will not be too dominant as the length to
diameter ratio is low. Then, the required thickness will not be so high.
- In my calculations, failures in the welded portions are not considered.

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