1. 1
PROJECT TRAINING REPORT
ON
2016
“DESIGN OF STORAGE TANK”
As Per IS:803-1976
Dissertationsubmittedforpartialfulfillmentof3rd
YearoftheDegreeB.Techin
MECHANICAL ENGINEERING”
under
“Kalinga Institute of Industrial Technology”
2013-2017
By:
Anandaroop Ghosal &Udayan Biswas
Under the guidance of:
Development Consultants Private Limited (D.C.P.L)
B L O C K - D G 4 , S E C T O R - 2 , S A L T L A K E , K O L K A T A - 7 0 0 0 9 1

2. 2
PROJECT TRAINING REPORT
ON
“DESIGN OF STORAGE TANK”
As Per IS:803-1976
NAME : ANANDAROOP GHOSAL &
UDAYAN BISWAS
COLLEGE : KALINGA INSTITUTE OF
INDUSTRIAL TECHNOLOGY
VENUE : DEVELOPMENT CONSULTANTS
PRIVATE LIMITED
DURATION : 2.05.2016 TO 15.06.2016
PREPARED BY REVIEWED BY APPROVED BY

3. 3
Dedicated to…..
Department of
School Of Mechanical Engineering

4. 4
KalingaInstitute of Industrial
Technology
ACKNOWLEDGEMENT:-
We would like to thank Development Consultants Private
Limited, Kolkata for giving us the opportunity to do our project
training and all the employees who have directly or indirectly
extended their kind support throughout the training period and
developmentof the “Project Training Report”.
Our sincere thanks to Mr. D.S. Mallick, Executive Director and
Head of Mechanical Engineering of DCPL for providing us with
all the help and resources for the project.
Thanks to Ms Arpita Das, of DCPL for providing us with all the
help and resources for the project.

5. 5
We would also like to thank to all concern department of
Development Consultants Private Limited, who directly or
indirectly helped us to make the training complete in all respect.
It is needless to say that we have really enjoyed the environment
of DCPL, cooperation of their staff, it's fantastic lunch, etc. We
will be grateful to DCPL for ever.
Anandaroop Ghosal
&
Udayan Biswas

6. 6
Development Consultants is a transnational engineering conglomerate
with over 5000 employees and 1000+ major engineering projects completed in 50
countries over it's 60 years of adherence to engineering excellence and technological
innovation. In India, the DC Group has been an integral part of the nation's
development since independence, particularly in the Energy Sector (Thermal and
Nuclear power plants) Paper Plant, Water Treatment Plant, Material Handling Plant
and Process Plant like Cement Plant where it has designed and managed
construction of most of India's major plants. The foundation of this far-reaching
organization was laid by its Founder and Chairman over it's first fifty years, Dr.
Sadhan C. Dutt. Our Mission is inextricably linked to his philosophy to offer state-of-
the-art engineering services and to remain in the forefront of the profession by
continuously aspiring for improved technology. It rests on the following principles.
 To offer services of the highest quality to ensure customer satisfaction.
 To achieve continuous self improvement through research & development,
training and human resource development.
 To meet social objectives by seeking the highest standard of business ethics,
ensuring a harmonious work environment and working for the welfare of the
community
KIIT UNIVERSITY :AN ILLUSTRIOUS HISTORY
1992(June)
 KIIT Society registered
 KIIT-ITI set up
1995
 KIIT Polytechnic Set-Up
1997

7. 7
 Took shape as an institution
 Degree Engineering programme started
2004
 Declared Deemed University By Ministry of HRD, Govt. of India
2007
 Kalinga Institute of Medical Sciences (KIMS) set up
2009
 Conferred Category 'B' status By Ministry of HRD, Govt. of
India
2014
 Conferred Categoty 'A' status By Ministry of HRD, Govt. of
India
 Achieved 'Tier 1' Accreditation (Washington Accord)by NBA of
AICTEfor Engineering
 KIIT University is also accredited by NAAC of UGC in 'A' Grade
KIIT UNIVERSITY, formerly known as Kalinga Institute Of Industrial
Technology, is a co-educational, autonomous university located at
Bhubaneshwar in the Indian state of Odisha. The university offers under-
graduate & post-graduate courses in Engineering, Biotechnology,
Medicine, Management, Law, Computer Application, Rural Management,
Fashion,Film Studies, Journalism and Sculpturing. It was one of the
youngest institutions to be awarded the deemed university status(under
the section 3 of UGC act 1956) in India and then the university status in
2004.
KIIT college of engineering has been ranked among 5th among all
national level Self-Financing Universities in India and Kalinga Institute of
Medical Sciences(KIMS), a constituent of KIIT University features among
the top 30 medical colleges of the country, according to the survey by
Mumbai-BasedMain-line media, The Pioneer in 2012.

8. 8
The School of Mechanical Engineering possesses highly qualified and
experienced faculty members from various IITs, NITs ,and other reputed
institutions. Current consultancy and research and development areas of
the school include Jet and Spray impingement Heat Transfer, Droplet
and Spray combustion, Computational Fluid dynamics, Mechanical
Systems Design and Optimization, Bio-mass and Bio-fuels (Synthesis,
Analysis & Optimization),Vibration & machine condition monitoring,
Meta-Machining, Metal Matrix/Polymer Matrix composites(Fabrication
and characterization), Metal Forming. Research & Development efforts of
the school are supported by bodies like AICTE , DST,DRDO, Institution of
Engineers(IE), Govt. of India.
CONTENTS

9. 9
SL.NO. DESCRIPTION PAGE
1.0 Introduction 9-11
2.0 Input Data 12
3.0 Design Basis 13-18
4.0 Design of Storage Tank as per IS Code 19-25
5.0 Results 26

10. 10
1.0) : Introduction
STORAGE TANK:
A storage tank is a construction or a container, usually holding liquids, sometimes for
gases. Liquids and gaseous products must be stored during intervals between
production, transportation, refining, blending and marketing. In general, the storage
of liquid or gaseous products is done in large sized vessels. Various parts of the
vessels are made in sizes which can be conveniently transported. The most common
material used is Mild Steel. Vessels are also made of stainless steel, aluminium and
Clad Steel, where the cladding may be either stainless steel, Nickel, Monel, or Inconel.
Such tanks are builds in two basic design – the Fixed roof design & External
floating roof design.
The design of bulk storage tank governed principally by safety requirements
and need to operate economically when tank is in service.
TYPES OF TANK:
According to the height of tank it is of two types:-
1)Tank which have a maximum height of 10m:
 above ground storage tank
 underground storage tank
2)Tank which have a height in excess of 10m.
According to the construction of roof it is of three types:
 fixed roof tank
 floating roof tank
 fixed roof tank with internal floating deck
DESCRIPTION OF TANKS:
According to the height of tank:-
 Above ground storage tank: Many tanks are installed in connection with fixed
heating equipment, e.g., as small tank up to 3.5m3
capacity which supply domestic
fuel installations and tanks over 3.5m3
capacity are used for large industrial
application of fuel-oil heating in boiler, furnace. Emergency venting is necessary to
protect the tank from over pressure.

11. 11
 Underground storage tank: It is used to keep petroleum spirit at public filling
station and similar private installation in underground tanks. Its advantage is to
allow the freedom of movement of vehicles. Where available space at filling site is
limited, burying the tank may be the only solution. But it may cause water
pollution.
According to roof of tank-
 Fixed roof tank: The main constructional feature of non-pressure and pressure
fixed roof are similar, but because of slightly higher internal pressure, the pressure
fixed roof is limited to diameter of 35m and top curb angle of the shell. It consist
of cylindrical shell, design may vary from cone or dome shaped to flat shaped.
Normal venting of non-pressure fixed roof tank takes the form of open or free
flow atmospheric vent. Pressure roof tanks are provided with breather vent which
have two important features are:-
a) they minimize the vapour losses for volatile liquids that would have occured
by free venting.
b) they protect the tank from excessive pressure.
 Floating roof tank: It has a vertical cylinder tank having a roof floats on the liquid
product surface. It significantly reduces the evaporation loss and hazards
associated with having a large, possibly combustible, vapour surface, consist of
cylindrical shell. This tank is widely used for storage of volatile petroleum product.
It reduces the product side corrosion and minimize evaporation. It provides an
extended service life with minimal maintenance.
 Fixed roof tank with internal floating deck: A plastic membrane floating on the
liquid inside a fixed roof tank conceived as a means of giving to existing fixed roof
tanks vapour loss characteristics comparable with those floating roof tanks.
Membrane covers the free surface of liquid, except for a small annular space
between the periphery of the membrane and shell of tank, to permit the
installation of vapour seal consist of a Z-shaped raised flexible skirt.
This type of tank reduces internal corrosion and permit highly volatile product to
be stored at atmospheric pressure.
Constructional features of tank:
1. Roof may be cone or dome shaped.
2. Roof may be supported or unsupported at the periphery.
3. The usual construction of roof is by lap welded mild steel plate of minimum
thickness of 5mm. Roof plate may sometimes be butt welded.

12. 12
4. Bottom plates are generally lap welded and the plate should have minimum
thickness of 6mm.
5. Tank should be designed with ladder, which operate automatically, for full roof.
6. Deck plate should have 5mm thickness and minimum height of 200mm and
should be joined by continuous fillet welding.
7. The primary drainage should be adequate to drain the maximum rainfall in 24
hr, without flooding the deck. The minimum capacity of drain is 75mm.
8. Venting should be provided to over stressing of the roof deck and should be
adequate to evacuate air and gases from underneath the roof.
9. Roof manhole is provided for access to tank interior and for ventilation when
tank is empty. It should be provided with diameter of 600mm.
10. Gauge hatch is provided to indicate the level of the liquid inside the tank.

13. 13
2.0) :INPUT DATA:-
Design of a Cone Roof Tank of Capacity 200m3
S No Parameters Input Values
1 Diameter : 6.0 m
2 Height : 7.5 m
3 Design Liquid Height : 7.5 m
4 Design Pressure : Hydrostatic+ 150 mmWC, and
50mmWC(vacuum)
5 Design Temperature : 750
C
6 Operating Pressure : Ambient, Hydrostatic
7 Operating Temperature : 40
C-500
C
8 Design Specific Gravity : 0.85
9 Product Stored : Crude Oil
10 Corrosion Allowance : 1.6 mm for Shell and Bottom, 0mm
for roof
11 Basic wind speed : 47 m/s
12 Seismic loads : IS 1983 Zone III
13 Joint Efficiency : 0.85
14 Test Pressure : Full of water
15 Material for Shell, Bottom & Roof : IS 2062 Gr A
16 Yield Strength : 250 MPa
17 Tensile Strength : 410 MPa
18 Roof slope : 1:5
19 Shape Factor : 0.7

14. 14
3.0) :DESIGN BASIS:-
Deign of Steel Storage Tank as per IS 803- 1976:-
Primary Considerations:
As per clause 5 : Permissible Stresses:
[5.1]:Maximum allowable working stresses shall not exceed the following.
[5.1.1]: In the design of tank shells, maximum tensile steel before applying the factor
for joint efficiency shall be 165N/mm2
(1680 kgf/cm2
) in case of steel conforming to
IS-2062 and IS : 226. For other grades of steels, maximum allowable stress shall be
0.7 of the minimum yield stress of each grade or 0.4 of the minimum ultimate tensile
stress, whichever is less.
[5.1.3]: The above stresses are permissible for design temperature of (-)100
C to
(+)2000
C.
[5.2]: The permissible stress for welds and welded connections shall conform to the
values as per IS : 816-1969.
Design of Shell Plate as per clause 6.3
[6.3.1.1]: Stresses in the tank shell shall be computed on the assumption that the
tank is filled with water of specific gravity 1.0 or the liquid to be stored, if heavier
than water.
[6.3.1.3]: Wind and internal vacuum loads shall be considered together to check the
stability of the tank shell. Internal vacuum in the tank shall be considered as
minimum 500 N/m2
(50 kg/m2
) if nothing is mentioned. Otherwise actual value to be
taken.
[6.3.2]: Joint Efficiency Factor :
This shall be taken as 0.85 for double welded butt joints, to determine minimum shell
plate thickness computed from the stress on vertical joints, subject to all vertical and
horizontal butt welds being spot radio graphed. Where, welds are not to be
radiography, the joint efficiency factor considered for design shall be 0.70
[6.3.3]: Plate Thickness:
[6.3.3.1]: The minimum thickness of shell plates shall not be less than the calculated
value from the following formula or as specified in 6.3.3.2 whichever is greater:
t= {4.9(H-0.3)DG}/(SE) if S is in N/mm2
or
={50 (H-0.3)DG}/(SE) if S is in kgf/cm2
where,
t=minimum thickness in mm

15. 15
D=nominal diameter of tank in m;
H=height from the bottom of the course under consideration to top of top curb
angle or to bottom of any overflow which limits tank filling height in m;
G=specific gravity of liquid to be stored , but in no case less than 1.0;
S=allowable stress; and
E=joint efficiency factor.
[6.3.3.2]: In no case shall the nominal thickness of shell plates (including shell
extensions for floating roof) be less than the following:
Nominal Tank Diameter(m) Minimum Nominal Thickness(mm)
Less than 15 : 5.0
Over 15 up to and including 36 : 6.0
Over 36 up to and including 60 : 8.0
Over 60 : 10.0
[6.3.3.3]: The nominal thickness of shell plates refers to the tank shell as constructed
and is based on stability rather than stress. Any required corrosion allowance for the
shell plates shall be added to the calculated thickness of 6.3.3.1, unless otherwise
specified by the purchaser.
[6.3.3.6]: Stability of tank shells against external loads shall be checked by
determining the maximum height of the shell from the top curb angle or wind girder
that does not buckle under this loading and providing stiffening to the shell if
required.
The maximum height of unstiffened shell, in metres, shall not exceed H1 as
determined by the following equation:
H1= (14700t)/p*√(t/D)3
, if p is in N/m2
or
= (1500t)/p*√ (t/D)3
, if p is in kgf/m2
Where,
H1= vertical distance between the intermediate wind girder and top angle of the
shell or the top wind girder of an open top tank in m;
t= average shell thickness in height H1in mm determined from the actual thickness of
plates used unless the purchaser specifies that the net thickness( actual thickness
used minus corrosion allowance specified) shall be considered;
D= nominal tank diameter in m; and
P= sum of all external pressures acting on the tank shell, that is, wind pressure
and internal vacuum.

16. 16
[6.3.6.2]:Minimum sizes of top curb angle shall be:
a) Tanks up to and including 10 m diameter 65 × 65 × 6.0 mm
b) Tanks over 10 m and up to and including
18 m diameter 65 × 65 × 8.0 mm
c) Tanks over 18 m and up to and including
36 m diameter 75 × 75 × 10.0 mm
d) Tanks over 36 m diameter 100 × 100 × 10.0 mm
NOTE — Thickness specified above includes corrosion allowance required for
petroleum service. Special consideration should be given for severe service.
[6.3.6.3]:For tanks having internal pressure, cross-sectional area of curb
angle provided shall not be less than the area required to resist the
compressive force at the roof shell junction minus the participating shell
and roof area.
Area of curb angle required is given by:
Ac=(PD2
)/(117500*tanθ) - (0.1Ws.ts) - (0.1WR.tR), where P is in N/m2
or,
Ac=(PD2
)/(12000*tanθ) - (0.1Ws.ts) - (0.1WR.tR), where P is in Kgf/m2
where
Ac= area of curb angle in cm2;
D= tank diameter in m;
P = upward force due to internal tank’s pressure minus weight of
roof plates;
θ= angle between the roof and a horizontal plane at the roof shell
junction in degrees;
Ws = width of the shell in the compression region in cm;
= 0.19√Rstswhere, Rs = radius of tank shell in cm;
ts= nominal shell thickness in mm;
WR = width of the roof in the compression region in cm;
= 0.095√ RRtR;
RR = radius of roof at roof shell junction in cm; and
tR = nominal roof thickness in cm.

17. 17
7.3:SHELL NOZZLE
[7.3.2]: Details and dimensions specified herein are for nozzles installed with their
axes perpendicular to the shell plate. Nozzles may be installed at an angle of other
than 90° to the shell plate in a horizontal plane, provided that the width of the
reinforcing plate is increased by the amount that the horizontal chord of the opening
cut in the shell plate increases as the opening changes from circular to elliptical in
making the angular installation. In addition, nozzles not larger than 75 mm nominal
pipe size, for insertion of thermometer wells, sampling connections, or other
purposes not involving the attachment of extended piping, may be installed at an
angle of 15° or less off perpendicular in a vertical plane, without modification of the
nozzle reinforcing plate.
7.4 Roof Manholes
[7.4.1]: They shall be suitable for attachment by welding to the tank roof sheets and
shall be positioned close to roof sheet supporting members.
[7.4.2]: The manhole cover may be hinged with single or multiple bolt fixing as
required by the purchaser.
[7.4.3]: Openings made for fixing manholes on self supporting roofs and roofs
subjected to internal pressure shall be reinforced by a plate ring having the same
thickness of roof plate and outer diameter equal to twice the diameter of the
opening.
7.5 Roof Nozzles
[7.5.1]: Flanged roof nozzles shall conform to Fig. 15 and Table 12,
installation of threaded nozzles shall be as shown in Fig. 15.
[7.5.2]: All nozzle openings greater than 150 mm diameter, shall be
reinforced by a plate ring having the same thickness as roof plate and outer-
diameter equal to twice the diameter of the opening.

18. 18
FIG-1: TYPICAL FIXED ROOF TANK SHOWING
STANDARD APPURTENANCES

19. 19
STORAGE TANKS

20. 20
4.0): Design Calculation as per IS-803-1976;
NOMENCLATURE
S. NO SYMBOL VALUES DESCRIPTION UNIT
1 D 6 Nominal diameter of tank m
2 r 3 Radius of tank m
3 H 7.5 Design liquid height m
4 C.A 1.6 Corrosion Allowance mm
5 Sut 410 Ultimate Tensile Strength MPa
6 Syt 250 Yield Strength MPa
7 S to be calculated Allowable Stress MPa
8 E 0.85 Joint Efficiency Factor -
9 G 0.85 Design Specific Gravity -
10 t1 to be calculated Thickness of 1st shell course from bottom mm
11 t2 to be calculated Thickness of 2nd shell course from bottom mm
12 t3 to be calculated Thickness of 3rd shell course from bottom mm
13 t4 to be calculated Thickness of 4th shell course from bottom mm
14 t5 to be calculated Thickness of 5th shell course from bottom mm
15 h 1.5 Height of each shell course m
16 ρ 7850 Density of Carbon Steel IS 2062 Gr.A Kg/m3
17 tanθ 0.2 Roof Slope -
18 Ar to be calculated Area of roof plate m2
19 tr to be calculated Roof plate thickness mm
20 tb to be calculated Bottom plate thickness mm
21 Pi to be calculated Upward force due to internal pressure N/m2
22 Pr to be calculated Pressure due to wt. of roof plate and structure N/m2
23 Peff to be calculated Effective pressure N/m2
24 Ws to be calculated Shell width in compression region mm
25 ts to be calculated Shell thickness mm
26 Wr to be calculated Width of roof in compression region mm
27 Ac to be calculated Area of curb angle m2
28 Vb 47 Basic Wind speed m/s
29 Pwind to be calculated
External pressure acting on tank shells i.e.,
wind pressure
N/m2

21. 21
30 Pvacu to be calculated Internal vacuum pressure N/m2
31 P to be calculated Pwind+Pvacu N/m2
32 H1 to be calculated Maximum height of unstiffened shell m
33 l to be calculated Slant height of roof m
34 K1 1.06 Probabilityfactor(Riskcoefficient) -
35 K2 0.91 Terrainand heightfactor(Forcategory3) -
36 K3 1.00 Topographyfactor -
37 K4 1.15 Importance factorfor industrial structure -
DESIGN STEPS:
Calculation of allowable stress(S):
As per IS-803 C.L. 5.1.1 :
Maximum allowable stress shall be 0.7 of the minimum yield stress of each grade or
0.4 of the minimum ultimate tensile stress whichever is less. Hence after calculating
we get S=164 N/mm2
Calculation of thickness of shell:
As per IS-803 C.L. 6.3.3.1:
 Thickness of 1st Shell Course from bottom
From the NOMENCLATURE TABLE and INPUT DATA, we get:
t1 = (4.9 (H-0.3) D.G / S. E) + CA
= (4.9 (7.5-0.3) 6 x 1)/( (164). (0.85)) + 1.6
= 3.19 mm
 Thickness of 2nd Shell Course from bottom
H 2= H-h=7.5-1.5= 6.00 m
From the NOMENCLATURE TABLE and INPUT DATA, we get:
t2 = (4.9 (H2-0.3) D.G / S. E) + CA

22. 22
= (4.9 (6.00-0.3) 6 x 1 / (164). (0.85)) + 1.6
= 2.80 mm
 Thickness of 3rd Shell course from bottom
H 3 =H-(2*h)= 7.5-(2*1.5) = 4.5 m
From the NOMENCLATURE TABLE and INPUT DATA, we get:
t3 =(4.9 (H3-0.3) D.G / S. E) + CA
= (4.9 (4.5-0.3) 6 x 1/ (164). (0.85)) + 1.6
= 2.49 mm
 Thickness of 4th Shell course from bottom
H4 = H-(3*h)=7.5-(3*1.5) = 3.0 m
From the NOMENCLATURE TABLE and INPUT DATA, we get:
t4= (4.9 (H4-0.3) D.G / S. E) + CA
= (4.9 (3.0-0.3) 6 x 1 / (164). (0.85)) + 1.6
= 2.17 mm
 Thickness of 5th Shell course from bottom
H5=H-(4*h)= 7.5-(4*1.5) = 1.5 m
From the NOMENCLATURE TABLE and INPUT DATA, we get:
t5= (4.9 (H5-0.3) D.G / S. E) + CA
= (4.9 (1.5-0.3) 6 x 1 / (164). (0.85)) + 1.6
= 1.85 mm
As per Cl. 6.3.3.2 Shell thickness provided are above minimum nominal thickness
recommended.
Refer IS 803 Cl. 6.2 for bottom plate uniformly resting on foundation or ground.
Min. thickness = 6 mm + CA
= 6 mm + 1.6 mm
= 7.6 mm

23. 23
Provide 8 mm thick bottom plate (next higher size)
Self Supporting Conical Roof Curb angle
 As per IS 803 CI: 6.3.6.2, minimum size of top curb angle required is 65 x 65 x
6 mm.
 Area of Curb angle, Ac provided = 2*(6.5*0.6)-(0.6*0.6) cm2
=7.44 cm2
 Area of Curb angle, Ac required = (Peff*D2
/117500 tan θ) – (0.1Ws.ts) -
(0.1Wr.tr)
 Where Peff=(Upward force due to internal pressure - Pressure due to weight of
roof plate)=(Pi-Pr)
 Internal Pressure of Tank, Pi = 150 mm WC = 150*9.81=1471.5 N/m2
 Roof Slope from horizontal, θ deg = tan -1
(0.2) =11.3 deg
 Thickness of roof plate, tr=D/5sinθ in mm [As per C.L-6.4.5]
 tr=6/5*10sin(11.300
) =0.61 in cm
 Slant height, l =√((D/2*tanθ)2
+r2
) =3.06 m
 Area of roof plate, Ar=π*r*l=28.84 m2
 Volume of roof plate, Vr=Ar*tr=0.1764 m3
 Mass of roof plate, mroof =Vr*ρ=1385.12 Kg
 Weight of Roof Plate, Wroof=mroof*9.81=13588.08 N
 Pressure due to weight of roof plate, Pr= (13588.08 N)/ 28.84 m2
= 471.20
N/m2
 Effective Pressure, Peff = (1471.5 – 471.20) N/m2
= 1000.29 N/m2
 Tank Diameter, D = 6 m, r=3 m
 Thickness of shell adjacent to top curb angle, ts= Shell thickness =0.5 cm
 Ws = Shell width in compression region = 0.19 √(r*100*ts)= 0.19 √(300 cm x
0.5cm) = 2.33 cm
 Wr = Width of roof in compression region = 0.095 √(r*100*tr) = 0.095 √(300
cm x 0.5 cm) = 1.29 cm

24. 24
 Ac (required) = ((1000.29 x 36 / 117500 x 0.2) –( 0.1 x 2.33 x 0.5) –( 0.1 x 1.29 x
0.61) cm2
= 1.34 cm2
 Basic wind speed (Vb) = 47 m/sec
 Design wind speed, Vz= (Vb*K1*K2*K3*K4)=(47*1.06*0.91*1*1.15)=52.14 m/s
[IS-875 Part 3]
where,
K1 =Probability factor(Risk Coefficient) [IS-875 C.L-5.3.1 Table-1]
K2 =Terrain and height factor[IS-875 C.L-5.3.3.2 Table-2, category 3] K3
=Topography Factor=1 [IS-875 C.L-5.3.3.1 Appendix-C]
K4 =Importance factor for cyclonic region, for industrial structures=1.15 [IS-
875 C.L-5.3.4]
 Wind pressure at any height above mean ground level,
Pwind=0.6*Vz
2
[IS-875, C.L-5.4]
=1630.94 N/m2
 According to Input Data, Internal vacuum pressure,
Pvacu=50 mmWC
=50 *9.81=490.5 N/m2
 Sum of all external pressures acting on the tank shell, i.e., wind pressure and
internal vacuum,
P=Pwind + Pvacu
=2121.44 N/m2
[IS-803 C.L-6.3.3.6]
 Maximum height of unstiffened shell ,
H1=(14700((ts- C.A)/P))* √((( ts -C.A)/D)3
)
=(14700(5-1.6)/2121.44)*√(((5-1.6)/6)3
)
=10.05 m [IS-803 C.L-6.3.3.6]

25. 25
CALCULATION TABLE
Parameter
Description
Clause No Formula Symbol Value Unit
Allowable stress
IS-803 C.L
5.1.1
0.4*Sut or 0.7*Syt whichever is less
S
164 N/mm2
0.4* Sut 164 N/mm2
0.7*Syt 175 N/mm2
Thickness of first
shell course from
bottom
IS-803 C.L
6.3.3.1
t1={4.9(H-0.3)D*G}/(S*E) +C.A t1 3.12 mm
Thickness of
second shell
course from
bottom
IS-803 C.L
6.3.3.1
t2={4.9(H2-0.3)D*G}/(S*E) +C.A t2 2.80 mm
Thickness of third
shell course from
bottom
IS-803 C.L
6.3.3.1
t3={4.9(H3-0.3)D*G}/(S*E) +C.A t3 2.49 mm
Thickness of
fourth shell
course from
bottom
IS-803 C.L
6.3.3.1
t4={4.9(H4-0.3)D*G}/(S*E) +C.A t4 2.17 mm
Thickness of fifth
shell course from
bottom
IS-803 C.L
6.3.3.1
t5={4.9(H5-0.3)D*G}/(S*E) +C.A t5 1.85 mm
Thickness of
bottom plate
IS-803 C.L
6.2.1
tb=6+C.A tb 7.6 mm

26. 26
Min. size of top
curb angle as per
dia. of tank
IS-803 C.L
6.3.6.2
- - 65*65*
6.0
mm
Area of top curb
angle
IS-803 C.L
6.3.6.2
Acpro =2*(6.5*0.6)-(0.6*0.6) Acpro 7.44 cm2
Area of curb
angle(required)
IS-803 C.L
6.3.6.3
Acreq= (Peff*D2
/117500 tan θ) –
0.1Ws.ts - 0.1Wr.tr
Acreq Calcula
ted
later
cm2
Thickness of roof
plate
IS-803 C.L
6.4.5
tr=D/(5*10sinθ) tr 0.61 cm
Volume of roof
plate
- Vr=Ar* tr Vr 0.18 m3
Area of roof plate - Ar=π*r*l Ar 28.84 m2
Slant height - l =√((D/2*tanθ)2
+r2
) L 3.06 m
Mass of the roof
plate
- mroof= Vr*ρ mroof 1385.1
3
Kg
Weight of roof
plate
- Wroof= mroof*9.81 Wroof 13588.
08
N
Pressure due to
wt of roof plate
- Pr= Wroof / Ar Pr 471.20 N/m2
Upward force due
to internal
pressure
Input data
Pi=150mmWC
Pi
150 mmWC
Pi =150*9.8 1471.5 N/m2
Effective pressure IS-803 C.L
6.3.6.3
Peff= Pi- Pr Peff 1000.3
0
N/m2
Thickness of shell
adjacent to top
curb angle
IS-803 C.L
6.3.6.3
ts=0.5 ts 0.5 cm
Shell width in
compression
region
IS-803 C.L
6.3.6.3
Ws=0.19* √(r*100*ts) Ws 2.33 cm
Width of roof
plate in
compression
region
IS-803 C.L
6.3.6.3
Wr=0.095*√(r*100* tr) Wr 1.29 cm
Area of curb
angle(required)
IS-803 C.L
6.3.6.3
Ac= (Peff*D2
/117500 tan θ) – 0.1Ws.ts
- 0.1Wr.tr
Ac 1.34 cm2
Top Angle - θ=tan-1
(0.2) θ 11.31 Degree
Maximum height
of unstiffened
shell
IS-803 C.L
6.3.3.6
H1=(14700((ts- C.A)/P))* √((( ts -
C.A)/D)3
)
H1
10.05 m
Wind Pressure IS-875 C.L
5.4
Pwind=0.6*Vz
2
Pwind 1630.9 N/m2

27. 27
Design wind
speed
IS-875 C.L
5.3
Vz=(Vb*K1*K2*K3*K4)
Vz 52.14 m/s
Internal vacuum
pressure
Input data
Pvacu=50mmWC
Pvacu
50 mmWc
Pvacu=50*9.81 490.5 N/m2
Sum of Pwind
&Pvacu
IS-803 C.L
6.3.3.6
P=Pwind+Pvacu P 2121.4 N/m2
5.0) RESULTS:
The storage tank was designed according to IS 803(1976).The thicknesses of different
shell course from bottom were calculated and were found as below:
SUMMARY OF TANK PLATES
SHELL PLATE:
No of shell
course from
bottom
Height of
course (mm)
Calculated
thickness(mm)
Thickness
required as per
design(mm)
Thickness
provided(mm)
t1 1500 3.12 5 6*
t2 1500 2.80 5 5
t3 1500 2.49 5 5
t4 1500 2.17 5 5
t5 1500 1.85 5 5
*Note:
The thickness provided for the 1st shell course from bottom is generally more than
the thickness provided for other shell courses for design considerations.
CONSIDERATION OF STIFFENER:
We had calculated the maximum height of unstiffened shell,

28. 28
 Maximum height of unstiffened shell ,
H1=(14700((ts- C.A)/P))* √((( ts -C.A)/D)3
)
=(14700(5-1.6)/2121.44)*√(((5-1.6)/6)3
)
=10.05 m [IS-803 C.L-6.3.3.6]
Design Tank Height, H= 7.5(given)
Since the value of H1>H, hence no stiffener is required.
PROVIDING CURB ANGLE:
As per CL 6.3.6.2 , Area of top curb angle=2*(6.5*0.6)-(0.6*0.6)=7.44 cm2
As per C.L 6.3.6.3, Area of top curb angle= ((1000.29 x 36 / 117500 x 0.2) –( 0.1 x 2.33
x 0.5) –( 0.1 x 1.29 x 0.61) cm2
= 1.34 cm2
Since the value of the top curb angle as per CL 6.3.6.2 is greater hence the provided
area of top curb angle will be Acpro =7.44 cm2