CONTENTS
SR. NO.
DESCRIPTION
1
DESIGN DATA
2
CALCULATIONS FOR MINIMUM SHELL THICKNESS
3
BOTTOM PLATE DESIGN
4
INTERMEDIATE WIND GIRDER
5
VERIFICATION OF UNSTIFFENED SHELL
6
DESIGN OF ROOF PLATE
6.1
COMPRESSION AREA VERIFICATION AGAINST EXTERNAL PRESSURE
6.2
COMPRESSION AREA VERIFICATION AGAINST INTERNAL PRESSURE
7
TANK VERIFICATION AS PER APPENDIX F
8
ROOF THICKNESS AND COMPRESSION AREA VERIFICATION AS PER API 620
8.1
DESIGN DATA
8.2
ROOF DESIGN
8.3
COMPRESSION AREA DESIGN
9
STABILITY OF TANK AGAINST WIND LOADS
9.1)RESISTANCE TO SLIDING
10
STABILITY OF TANK AGAINST SEISMIC LOADS
10.1
RESISTANCE TO OVER TURNING
10.2
SHELL COMPRESSION FOR UNANCHORED TANKS
10.3
SHELL COMPRESSION FOR ANCHORED TANKS
11
ANCHORAGE FOR UPLIFT LOAD CASES
12
ANCHOR CHAIR CALCULATION
13
DESIGN OF INTERNAL FLAOTING ROOF (BOUYANCY CALCULATIONS)
14
FOUNDATION LOADING DATA
15
EVALUATION OF EXTERNAL LOADS ON TANK SHELL OPENINGS
AS PER P.3 OF API 650, ADD. 4, 2005
16
VRV AND VENTING CALCULATIONS (PENDING)
1) DESIGN DATA
Design Code
:
API 650, 10th Edition, ADD. 4, 2005, Appendices F, S & V
Client's Specs.
:
PIP VESTA 002
Item No.
:
TK-59301
Description
:
Acetone Storage Tank
Material
:
Dc
Density of Contents
A 240 Type 304L
=
791
G
Fym
=
0.791
=
148
Design Temperature
T
=
90
o
Operating Temperature
T
Pi
=
35
o
Design Internal Pressure
=
4.00
kPa
=
20.32
in. of content
Design External Pressure
Pe
=
0.90
kPa
=
4.57
in. of content
High Liquid Level
Hl
=
16.75
m
*HL1
=
17.587
m
Sd
=
132
MPa
(As Per Table S-2)
St
=
155
MPa
( As Per Table S-2)
Specific Gravity of Contents
Material's Yield Strength
( At Design Temp.)
Design Liquid Level
Allowable Design Stress
( At Design Temp.)
Allowable Hydrostatic Stress at Test Temp.
kg./m3
MPa
( As Per Table S-5)
C
C
Corrosion Allowance
Bottom
=
0.00
mm
Shell
=
0.00
mm
Roof
=
0.00
mm
Structure
=
0.00
mm
degree
Slope of Tank Roof

=
9.46
Outside Dia. of Tank
Do
=
20.930
m
Inside Dia. of Tank
Di
=
20.900
m
Nominal Tank Dia.= Di + Shell Thk. =
D
=
20.915
m
Height of Shell
=
18.00
m
Weight of Top Compression Ring
H
Wc
=
84.72
kN
Weight of Accessories on Shell (Stair, Ins., Clips & Nozzles etc.)
Wsa
=
100.00
kN
(Assumed)
Weight of Roof Attachments (Platform, Ins., Handrail & Nozzles etc.)
Wra
=
50.00
kN
(Assumed)
Design Wind Velocity
V
=
155
kph
Modulus of Elasticity @ Design Temp.
E
Fy
=
189000
MPa
Yield Strength of Steel Structure (Ladder, platform, etc.)
=
250.00
MPa
Live Load on Roof
Lr
=
1.20
kPa
*Including Static Head Due To Internal Pressure & Liquid Head due to rise of liquid in Rim Portion (in punctured condition).
2) CALCULATIONS FOR MIN. SHELL THICKNESS
The required shell plates thickness shall be greater of the values computed by following formulas.
The minimum thickness of shell plate as per App. S, Clause S.3.2, shall be computed using following formula.
Design Shell Thickness
td =
4.9D (HL - 0.3)G + CA
Sd*(E)
Hydrostatic Test Thickness
tt =
4.9D (HL - 0.3)
(St)* E
td = Design shell thickness, mm
tt = Hydrostatic test shell thickness, mm
G = Specific gravity of fluid to be stored
=
D = Nominal dia. of tank
HL1 = Design liquid level
=
20.915 m
0.791
=
17.587 m
CA = Corrosion allowance.
Sd = Allowable stress for design condition
=
=
132.00 MPa
St = Allowable stress for hydrostatic condition
=
155.00 MPa
E = Weld Joint Efficiency
=
0.00 mm
0.85
(As Per Table S-6)
(PIP VESTA002, 3.2.D)
1st Shell Course
Width of 1st course
W1
=
2.000
Design height for 1st shell course
HL1
=
17.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
12.490
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
13.447
mm
15.000
mm
m
Shell thickness provided t1 =
m
2nd Shell Course
Width of 2nd course
W2
=
2.000
Design height for 2nd shell course
HL2
=
15.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
11.045
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
11.891
mm
14.000
mm
m
Shell thickness provided t2 =
3rd Shell Course
Width of 3rd course
W3
=
2.000
Design height for 3rd shell course
HL3
=
13.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
9.600
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
10.336
mm
12.000
mm
m
Shell thickness provided t3 =
4th Shell Course
Width of 4th course
W4
=
2.000
Design height for 4th shell course
HL4
=
11.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
8.155
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
8.780
mm
10.000
mm
m
Shell thickness provided t4 =
5th Shell Course
Width of 5th course
W5
=
2.000
Design height for 5th shell course
HL5
=
9.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
6.710
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
7.224
mm
8.000
mm
m
Shell thickness provided t5 =
6th Shell Course
Width of 6th course
W6
=
2.000
Design height for 6th shell course
HL6
=
7.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
5.265
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
5.668
mm
6.000
mm
m
Shell thickness provided t6 =
7 Shell Course
th
Width of 7th course
W7
=
2.000
Design height for 4th shell course
HL7
=
5.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
3.820
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
4.113
mm
6.000
mm
Shell thickness provided t7 =
8th Shell Course
Width of 8th course
W8
=
2.000
Design height for 8th shell course
HL8
=
3.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
2.375
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
2.557
mm
6.000
mm
m
Shell thickness provided t8 =
m
9th Shell Course
W9
=
2.000
Design height for 9th shell course
HL9
=
1.587
m
Required Shell Thickness (Design Shell Thk.)
td
=
0.930
mm
Required Shell Thickness (Hydrostatic Test Thk.)
tt
=
1.001
mm
6.000
mm
Width of 9th course
(Inc. Comp. Ring)
Shell thickness provided t9 =
NOTE: Minimum shell thickness requirement is fulfilled for the top most shell course.
Shell Table - 1
Shell Course #
1
2
3
4
5
6
7
8
9
Shell Width (m)
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
Uncorroded Shell Thk. (mm)
15.00
14.00
12.00
10.00
8.00
6.00
6.00
6.00
6.00
Corrroded Shell Thk.(mm)
15.00
14.00
12.00
10.00
8.00
6.00
6.00
6.00
6.00
Uncorroded Shell Weight (KN)
154.70 144.39 123.76 103.13
82.51
61.88
61.88
61.88
61.88
Corroded Shell Weight (KN)
154.70 144.39 123.76 103.13
82.51
61.88
61.88
61.88
61.88
Total Shell Weight (KN) (Uncorroded)
=
856.0 KN
Total Shell Weight (KN) (Corroded)
=
856.0 KN
For calculation of compression area, please refer to Roof Design as per API 620, Section 8 of this document.
Total Cross-Sectional Area Provided
=
16430 mm2
Weight of Curb Angle ( Uncorroded)
=
84.72 KN
Weight of Curb Angle ( Corroded)
=
84.72 KN
3) BOTTOM PLATE DESIGN
As per API 650, Appendix S, Clause S.3.1
All bottom plates shall have minimum nominal thickness of 5 mm, exclusive of any corrosion allowance.
Required Bottom Plate Thickness tb =
Used bottom plate thickness
tb
=
tb
=
5 mm
=
6.00 mm
5+ CA
mm
Weight of BottomPlate (Uncorroded)
=
16672.84 kg
=
163.56 KN
Weight of Bottom Plate (Corroded)
=
16672.84 kg
=
163.56 KN
Low Liquid Level
=
0.6 m
Weight of Liquid Due to Min. Liquid Level
=
1597 KN
Total Design External Pressure Froce on the bottom Plate
=
313 KN
As the sum of force due to total design external pressure is less than the sum of the weights of the bottom plate
and min. liquid level in the tank, membrane stresses need not be evaluated (As per V.9.1 of API 650).
4) INTERMEDIATE WIND GIRDER
(API 650 Sec. 3.9.7)
The maximum height of the unstiffened shell shall be calculated as follows:
H1 = 9.47 t (t / D)3/2 * (190/V)2
As ordered thickness of top shell course (mm)
t
=
Nominal tank diameter (m)
D
=
Design wind speed
V
=
Maximum height of the unstiffened shell
H1
=
The reduction/modification factor calculated (As per S.3.6.7)
RF
=
Maximum height of the unstiffened shell (Modified )
H1
=
Height of Transformed Shell
6.00 mm
20.915 m
155 Km/hr
13.12 m
0.9793
12.85 m
(API 650 Sec. 3.9.7.2)
Transposed width of each shell course
Wtr
=
W x (tuniform/tactual)5/2
Where,
W = Actual width of each shell course (mm)
tuniform = As ordered thickness of top shell course
=
6.00
mm
tactual = As ordered thickness of shell course for which transposed width is being calculated (mm)
1st Shell Course
Thickness of 1st course
Wtr1 = W1 x (ttop/t1)5/2
t1
=
15.00 mm
Wtr1
=
202.4 mm
Thickness of 2nd course
Wtr2 = W2 x (ttop/t2)5/2
t2
=
14.00 mm
Wtr2
=
240.5 mm
Thickness of 3rd course
Wtr3 = W3 x (ttop/t3)5/2
t3
=
12.00 mm
Wtr3
=
353.6 mm
Thickness of 4th course
Wtr4 = W4 x (ttop/t4)5/2
t4
=
10.00 mm
Wtr4
=
557.7 mm
Thickness of 5th course
Wtr5 = W5 x (ttop/t5)5/2
t5
=
8.00 mm
Wtr5
=
974.3 mm
Thickness of 6th course
Wtr6 = W6 x (ttop/t6)5/2
t6
=
6.00 mm
Wtr6
=
2000.0 mm
Thickness of 7th course
Wtr7 = W7 x (ttop/t7)5/2
t7
=
6.00 mm
Wtr7
=
2000.0 mm
Thickness of 8th course
Wtr8 = W8 x (ttop/t8)5/2
t8
=
6.00 mm
Wtr8
=
2000 mm
Thickness of 9th course
Wtr9 = W9 x (ttop/t9)5/2
t9
=
6.00 mm
Wtr9
=
2000.0 mm
Htr
=
10328 mm
=
10.33 m
2nd Shell Course
3rd Shell Course
.
4th Shell Course
5th Shell Course
6th Shell Course
7th Shell Course
8th Shell Course
9th Shell Course
Transformed Height of tank Shell
[As Htr < H1, Intermediate Wind Girders are not required]
HTS =
5) Verification of Unstiffened Shell Against External Pressure
(As Per Appendix V of API 650)
For unstiffened shells elastic buckiling will occur if following criterion is satisfied as per V.8.1.1
(D/ts min) ^ 0.75 [ ( Hts /D) x ( Fy / E )^0.5 ] ≥ 0.00675
D
tsmin
=
Nominal Diameter of Tank, m.
=
Minimum thickness of thinnest shell course, mm .
HTS
=
Transformed Height of the tank, m.
Fy
=
Yeild Strength @ Design Temp., MPa.
E
=
Modulus of elasticity, MPa.
( V.8.1.1)
Therefore,
0.0353
>
0.00675
[Elastic buckling criteria is satified]
The design external pressure for an unstiffened tanks shell shall not exceed:
(V.8.1.2)
Total design external pressure, Ps
Ps
≤
Ps
≤
E
45609 ( HTS / D ) ( D/tsmin) 2.5
0.370 KPa
(Allowable External Pressure)
Where
Ps
=
Total Design External Pressure for design of shell, KPa
Greater of
1) Specified design external pressure excluding wind pressure
2) W + 0.4 Pe
W
Kg
=
0.0000333 ( V )2 x ( Kg ) x ( Kh )
=
Wind gust factor
=
1.1
(V.3.1)
Kh
=
Wind height factor
=
1.1
W
C1
=
0.968 kPa
=
Pe
=
0.900 kPa
C2
=
W + 0.4Pe
=
1.328 kPa
Ps
=
[Greater of C1 and C2]
=
1.328 KPa
So,
[As Ps exceeds the allowable external pressure, hence, shell must be stiffened.]
Minimum shell thickness required for a specified design external pressure is
tmin
>
73.05 x ( Hts x Ps)0.4 x D0.6
( E )0.4
(V.8.1.3)
tmin
=
10.005 mm
[The minimum shell thickness provided is not sufficient. Stiffeners are required.]
Maximum spacing of the intermediate stifferners
Hsafe
=
( tsmin )2.5 x ( E )
(V.8.2.1.2)
45609 x D1.5 x ( Ps)
tsmin
=
6
mm
E
=
189000
MPa
D
=
20.915
m
Ps
=
1.328
kPa
Hsafe
=
2.88
m
[Safe height is less than the transformed height, so, stiffeners are required]
Number of intermediate stiffeners required, Ns, based on Hsafe
HTS / Hsafe
Ns + 1
=
Ns + 1
=
3.59
Ns
=
2.59
(V.8.2.1.3)
Therefore, number of intermediate stiffener(s) required, Ns
=
3
Spacing of intermediate stiffeners on transformed shell
Spacing
=
HTS / ( Ns + 1)
=
2.58
(V.8.2.1.4)
m
Intermediate Stiffener Ring Design
Number of buckling waves, N
N2
=
N
SQRT (( 455x D3) / (tsmin x HTS2)) ≤ 100
=
80.65
≤
100
=
8.98
~
10
(V.8.2.2.1)
[Satisfactory]
Maximum spacing, Ls on minimum shell thickness, tsmin, = HTS / (Ns + 1)
Lsmax
=
HTS / ( Ns + 1)
(V.8.2.2.2)
2.58 m
Locate 1st Stiffener on 6 mm Shell at spacing
=
2.58 m
From Top
Locate 2nd Stiffener on 6 mm Shell at spacing
=
5.16 m
From Top
Locate 3rd Stiffener on 6 mm Shell at spacing
=
7.75 m
From Top
Radial load imposed on the stiffener by the shell, Q = 1000 x Ps x Ls
Q
=
1000 x Ps x Ls
=
3429 N/m
(V.8.2.2.3)
Required Moment of Inertia, Ireq'd = ( 37.5 Q D3 ) / ( E ( N2 - 1 ) )
The actual moment of inertia of the intermediate stiffener ring region will consist of the combined moment of inertia of the
intermediate stiffener and the shell within a contributing distance on each side of the intermediate stiffener.
Shell Contribution
wshell
=
13.4 x SQRT( D x tshell )
(V.8.2.2.4)
wshell
=
2 x 13.4 x SQRT( D x tshell )
For both sides
=
300.22
mm
where
tshell = actual thickness of the shell plate on which the stiffener is located.
Required moment of inertia of stiffener
Ireq'd
=
(37.5 Q D3 ) / ( E ( N2 - 1 ) )
=
78.2
cm4
=
781561
mm4
(V.8.2.2.5)
Required Cross-Sectional Area of the Intermediate Stiffener, Areq'd = ( Q D ) / ( 2 fc )
Areq'd
=
( Q D ) / ( 2 fc )
(V.8.2.2.6)
(V.8.2.2.6.1)
where
fc = smallest of the allowable compressive stresses of the roof , shell, bottom or stiffener ring material at design temperature
fc
=
0.4 x Fy
for intermediate stiffing regions but not less than 103 MPa.
=
100 MPa
Use fc
=
103 MPa
Areq'd
=
348.16 mm2
Required Cross-Sectional Area of the Intermediate Stiffener Structural Shape, Astiff = Areq'd - 26.84 tshell SQRT ( D tshell )
Astiff
=
=
Areq'd - 26.84 tshell SQRT ( D tshell )
-1456
(V.8.2.2.6.2)
mm2
The negative sign shows that the stiffening provided by the shell alone is sufficient and no additional structural shape is required.
But, as per API 650, Appendix V, Clause V.8.2.2.6.2, Astiff must be greater than or equal to 0.5 Areq'd.
So,
Astiff
=
0.5 x Areq'd
Astiff
=
174.08
mm2
Provided Stiffener
L
90
mm
90
mm
6
mm
Ireq'd
=
825869
mm4
[The provided moment of inertia is satisfactory]
Astiff
=
1044
mm2
[The provided area is satisfactory]
6) Design Of Roof Plate
Self Supported Externally Stiffened Conical Roof As Per API 650, Sec. 3.10.5
To avoid the higher thickness of roof plate, the roof is being designed as externally stiffeneed conical roof.
As the design of this type of roof is not directly addressed in API 650 due to its unconventional nature, therefore,
the roof design is carried out on FEA based engineering software STAAD PRO 2007.
Used Thickness
=
6
mm
Corroded Thickness
=
6
mm
Stiffening Members
=
W10x19
Inner Ring
=
40
Nos.
Outer Ring
=
20
Nos.
Intermediate Ring
=
1
Nos.
Weight of Roof Plate (Uncorroded)
=
164.23 KN
Weight of Roof Plate (Corroded)
=
164.23 KN
Estimated weight of the stiffeners for the roof structure
=
100 KN
Total roof weight including stiffeners
=
264.23 KN
Quantity
6.1)
Compression Area Verification Against external Pressure (As calculated above )
As per Appendix "R", greater of the following Two combinations:
Greater of
T1 = DL + (Lr or S) + 0.4 Pe
T2 = DL + Pe + 0.4 (Lr or S)
Dead Load
*DL
=
Roof Live Load
Lr
=
External Pressure
Pe
=
0.900 KPa
Snow Load
S
T1
=
0.000 KPa
Combination # 1
=
2.475 KPa
Combination # 2
T2
=
2.295 KPa
Pr
=
2.475 KPa
*Based on
6
0.915 KPa
1.2
KPa
Max [ T1 , T2 ]
mm thick roof plate + attachments + stiffeners
(Based on used thickness)
(As per Appendix V of API 650)
Required participating area in the cone roof to shell joint region for external pressure is:
Ar
=
Ar
=
V.7.2.2
125 * Pr * D2 / (f * tan θ)
6154 mm2
Length of Cone Roof participating in Compression Region (based on provided thickened plate)
Xcone
=
Xcone
=
V.7.2.3
13.4 x {( D tcone) / sinӨ)}0.5
741 mm
Based on
24 mm
Thk. Compression Plate
Length of Shell participating in Compresion Area
Xshell
=
13.4 x ( D x ts1 )
Xshell
=
300 mm
V.7.2.3
0.5
Based on
24 mm
Thk. Compression Plate
So, total provided compression area
A
=
Acompression plate + Ashell
=
(Xroof x troof compression plate) + (Xshell x tshell compression plate)
=
24978 mm2
[Provided compression area is adequate]
6.2 )
Compression Area Verification againt Internal Pressure
(As per 3.10.5.2)
Required Minimum Participating Compression Area
Ar
=
As per 3.10.5.1 of API 650
D2
( T / 2.2)
0.432 Sin Ө
Ar
=
6932
mm2
Ar
=
7063
mm2
wh
=
R2
=
(After Modifying with factor 1.019 as per S.3.6.6)
0.3 x (R2 x th)0.5
Rc
=
63580 mm
Sin
wh
=
371 mm
wc
=
0.6 X (Rc X tc)0.5
Rc
=
Inside Radius of Tank Shell
wc
=
300.48 mm
A
=
(wh x th) + (wc x tc)
=
Based on
=
Based on
mm2
16106
[Provided compression area is adequate]
7)
TANK VERIFICATION AS PER APPENDIX F
Corroded weight of shell
=
856 kN
Corroded weight of roof
=
264 kN
Corroded weight of Compression Ring & Plate
=
85 kN
Corroded weight of attachments
=
150 kN
Total weight of shell, roof & attachments
=
1355 kN
Net Uplift = Internal Pressure - (Corroded Weight of Roof, Shell, Curb Angle & Attachments)
=
1372.28
=
17.32
-
1354.96
KN
[Anchorage must be provided against internal pressure and F.7 is applicable]
24 mm
Thk. Compression Plate
10450 mm
24 mm
Thk. Compression Plate
9) Stability of Tank Against Wind Load
Wind velocity
V
HR
=
155 Km/hr
Roof Height Above Shell
=
1.74 m
Height of tank including roof height
HT
=
19.74 m
Shell Height
H
=
18.000 m
Effective wind gust factor
G
Cf
=
0.85
Force co- efficient
=
0.8
Wind directionally factor
Kd
=
1
Velocity Pressure Exposure Co-Eff.
Kz
=
1.16
Topo Graphic Factor
Kzt
=
1
Importance Factor
I
qz
=
Design Wind Pressure
Design Wind Load
P1
=
43.06 m/s
As per API 650 3.9.7.1 (a)
By interpolation (ASCE 7-05, Fig. 6-21)
B02-E03
ASCE 7-05, Chapter 6, Table 6-3
=
1.15
R-1910-0320 rev.0
0.613 x Kz x Kzt x Kd x V2 x I /1000 ASCE 7-2005, Chapter 6, Eq. 6-15, Clause 6.5.10
=
1.516 KN/m2
qz x G x Cf x Af
425.97 KN
ASCE 7-05, Chapter 6, Eq. 6-28, Clause 6.5.15
Tank Anchorage Requirements Against Wind
As per 3.11.2 of API 650
Unanchored tanks shall satisfy both of the following criterias:
Case 1:
0.6Mw + MPi < MDL / 1.5
Case 2:
Mw + 0.4MPi < ( MDL + MF ) / 2
Mw
=
P1xH/2
MPi
=
Pi x A X D/2
MDL
=
(Wt of shell + roof + bottom) x D/2
Mw
=
3833.8 KN-m
MPi
=
14371 KN-m
MDL
=
13435 KN-m
MF
=
0
=
2826798
ft-lbs
For empty condition (when tank contains no fluid)
Case 1:
16671
<
8957
[Unsatisfactory]
Case 2:
9582
<
6717
[Unsatisfactory]
[Anchorage against wind pressure is required]
9.1)Resistance To Sliding
API 650 3.11.4
The wind load presure on projected area of cylinderical surfaces =
0.86 kN/m2
=
18.0 psf
(API 650, Chapter 3, Clause 3.2.1 (f))
This presure is for wind velocity of 120 mph (190 Km/hr), for all other wind velocities the presure shall be adjusted in proportion of ratio (V/190)2
O.D. of Tank =
D0
=
Design Wind Velocity
V
=
(V/190)2
=
Vf
=
20.930 m
155 km/hr
0.666
(Vf = Velocity Factor)
Wind Presure on vertical plane surfaces
=
0.86 kN/m2
(API 650, Chapter 3, Clause 3.2.1 (f))
Wind Presure on vertical conical surfaces
=
1.44 kN/m2
(API 650, Chapter 3, Clause 3.2.1 (f))
Projected area of roof
=
18.25 m2
Projected area of shell
=
376.74 m2
Fwind
=
Vf (Wind Pressure on Roof x Projected Area of Roof + Wind Pressure on Shell x Projected Area of Shell)
=
Ffriction
=
233.11
kN
(API 650, Chapter 3, Clause 3.2.1 (f))
Maximum of 40% of Weight of Tank
=
541.98
kN
(API 650, Chapter 3, Clause 3.11.4)
[Anchorage against sliding is not required]
10)
Stability Calculations Against Seismic Load (As per API 650 Add. 4, 2005 )
D
=
20.915
m
Nominal diameter of tank
H
=
16.750
m
High Liquid Level
D/H
=
1.25
H/D
=
0.80
Site Class
=
E
Corroded thickness of bottom plate
tb
=
6.00
mm
Corroded thickness of 1st shell course
ts
=
15.00
mm
Mrw
=
SQRT[Ai(WiXi+WsXs+WrXr)]2 + [Ac(WcXc)]2
2.5 x Q x ( I / Rwi ) x Sa0*
Over turning ring wall moment
As per API 650 E.6.1.5
For site class 'E'
Acceleration-based site coefficient
Scaling Factor
Ai
=
Fa
=
2.5
=
1
=
=
0.19
0.4 x Ss
=
0.08
Sa*
=
0.0433
Rwi
=
4
From Table E-4
I
Ai
=
1.25
From Table E-5
=
0.148
Wi
=
Ss
=
Q
Sa0*
S0
=
SP
Effective impulse weight of the liquid
[1.0 - 0.218 (D/H)] W p
As per API 650 E.4.9.1, Equation E-9
From Table E-1
As per API 650 E.4.9.1
Based On UBC Response Spectrum
As per E.4.2.c
Based On UBC Response Spectrum
As per Equation E-4
(When D/H < 1.333)
As per Equation E-14
ANCHOR CHAIR DESIGN
REFERENCE:
AISI E-l, Volume ll, Part Vll (ANCHOR BOLT CHAIRS)
T-192 Steel Plate Engineering Data Series - Useful Information - Design of Plate Structures, Volumes I & II
NOMENCLATURE:
a
= top-plate width, in. along shell
b
= top-plate length, in., in radial direction
c
= top plate thickness, in.
d
= anchor-bolt diameter, in.
e
emin
= anchor-bolt eccentricity, in.
f
fmin
= distance, in., from outside of top plate to edge of hole
g
= distance, in., between vertical plates (preferred g = d + 1)
= 0.886d + 0.572, based on a heavy hex nut clearing shell by 1/2 in. See Table 7-1
= d/2 + 1/8
[Additional distance may be required for maintenance.]
h
= chair height, in.
j
= vertical-plate thickness, in.
k
= vertical-plate width, in. (average width for tapered plates)
L
= column length, in.
m
= bottom or base plate thickness, in.
P
= design load, kips; or maximum allowable anchor-bolt load or 1.5 times actual bolt load,
whichever is less
r
= least radius of gyration, in.
R
= nominal shell radius, in., either to inside or centerline of plate (radius normal to cone at
bottom end for conical shells)
S
= stress at point, ksi
t
= shell or column thickness, in.
w
= weld size (leg dimension), in.
W
WH
= total load on weld, kips per lin. in. of weld
WV
= vertical load, kips per lin. in. of weld
z
= reduction factor
= horizontal load, kips per lin. in. of weld
ILLUSTRATIVE FIGURES (NTS):
a
j
g
c
j
BOTTOM PLATE
BCD
TANK ID
f
e
t
BOTTOM PLATE
SHELL INSIDE
e
b
f
a
DATA
t=
0.236 in.
6 mm
R=
41.339 in.
1050 mm
P=
3.70 kips
16.46 kN
BCD =
90.551 in.
2300.0 mm
Bottom Plate Thickness, m =
0.236 in.
6 mm
Bottom Plate Projection from Shell OD =
1.969 in.
50 mm
Earthquake considered =
Y
Wind over 100 mph =
Y
Continuous ring at top =
N
Y = Yes, N = No
GEOMETRY
a=
6.000 in.
152.4 mm
b=
7.874 in.
200 mm
c=
0.315 in.
8 mm
d=
1.063 in.
27 mm
e=
* emin1 =
3.701 in.
94 mm [Satisfactory]
2.500 in.
50.0 mm
** emin2 =
1.514 in.
38.5 mm [Not Applicable]
f=
fmin =
1.969 in.
50 mm [Satisfactory]
*** g =
gpreferred =
3.937 in.
100 mm [Satisfactory]
2.063 in.
52.4 mm
**** h =
hmin =
12.000 in.
304.8 mm [Satisfactory]
12.000 in.
304.8 mm
hmax =
18.000 in.
457.2 mm
j=
*****jmin =
0.551 in.
0.500 in.
14.0 mm [Satisfactory]
12.7 mm jmin = Max [1/2 in., 0.04 ( h - c )]
k=
4.921 in.
125 mm
0.656 in.
16.675 mm
[jk >= P/25 ---- Satisfactory]
L=
0.551 in.
14 mm
*
based on minimum bottom plate projection
**
based on heavy hex nut clearing shell by 1/2 in. See table A.
***
must be adjusted in a way to allow welding margin
****
if chair height calculated is excessive then
i) reduce eccentricity
ii) use more anchor bolts of smaller dia.
iii) use a continuous ring at top of chairs
*****
this limits assure a max. L/r of 86.6 and max. avg. stress in the side plates of
12.5 ksi even assuming no load was transmitted into the shell through the welds
TOP PLATE
Critical stress in the top plate occurs between the hole and the free edge of the plate. For convenience
we can consider this portion of the top plate as a beam with partially fixed ends, with a protion
of the total anchor bolt load distributed along part of the span. See figure:
Using above philosophy, thickness of top plate can be calculated with the help of following expression:
Let
S=
25.00 ksi
[
172.37 MPa
P
c= ( 0. 375 g−0 .22 d )
Sf
c=
cused =
]
0. 5
0.31
in.
7.8
0.31
in.
8
mm
mm [Satisfactory]
The thickness of top plate has been calculated based on 25 ksi stress value.
Actual stress in the top plate which occurs between the hole and the free edge of the plate can be evaluated
using the following expression:
S=
S=
P
(0 . 375 g−0 . 22 g )
fc 2
11.56 ksi
79.72 MPa [Satisfactory]
MAXIMUM STRESS IN SHELL
Chair must be high enough to distribute anchor bolt load to shell without overstressing it. The difficulty lies in
the bending caused by eccentricity of the anchor bolt with respect the shell. Except for the case where a
continuous ring is used at the top of chairs, maximum stress occurs in the vertical direction and is a
combination of bending plus direct stress. Formula which follow are approximations, based on the work
of Bjilaard.
Hence, maximum stress (i.e., a combination of bending plus direct stress) in vertical direction can be
evaluated using following expression:
Z=
1. 0
0 . 177 am m 2
+1 . 0
t
√ Rt
( )
Z=
S=
0.926
[
Pe
1. 32Z
0.031
+
0 . 333
t 2 1.43ah 2
√ Rt
+ ( 4 ah2 )
Rt
S=
15.98 ksi
]
110.17 MPa [Satisfactory]
Maximum recommended stress is 25 ksi.
This is a local stress occuring just above the top of the chair, a higher than normal stress is justified but an
increase for temporary loads, such as earthquake or wind is not recommended
Assembly of Chair
For field erected structures, ship either the top plate or the entire chair loose for installation after the
structure is sitting over the anchor bolts.
Where base plate is welded to the shell in the shop, attach side plates in the shop and ship top plate loose
for field assembly.
Where base or bottom plate is not welded to shell in the shop, as for flat bottom tanks, shop attach side
plates to top plates and then ship the assembly for field installation.When you do this, weld both sides at
top of side plates so shrinkage will not pull side plate out of square. See figure:
WELDING
Welds between chair and shell must be strong enough to transmit load to shell. 1/4 in. minimum fillet welds
are nearly adequate, but should be checked if a large anchor bolt with a low chair height has been provided.
Seal welding may be desired for application in corrosive environments.
wmin =
0.25 in.
6.35 mm
wused =
0.24 in.
6 mm
Allowable Stress =
13.60 ksi
Allowable Load Per Lin. in. =
9.6wused =
9.62 kips per in. of weld size
2.27 kips per in. of weld size
W v=
Wv =
93.77 MPa
P
a+2 h
0.12
kips per lin. in. of weld
[Satisfactory]
W H=
WH =
Pe
ah+0 . 667 h2
0.08
√
kips per lin. in. of weld
W = W 2+ W
W=
0.15
V
H2
kips per lin. in. of weld
For an allowable stress of 13.6 ksi on a fillet weld, the allowable load per lin. In. is 13.6 x 0.707 = 9.6
kips per in. of weld size. For weld size w, in., the allowable load therefore is 9.6w >= W
8)
Roof Thickness and Compression Area Verification As Per API 620
Nomenclature
P
=
total pressure, in lbf/in.2 gauge, acting at a given level of the tank
under a particular condition of loading, = P1 + Pg,
=
pressure, in lbf/in.2 gauge, resulting from the liquid head at the
P1
=
level under consideration in the tank,
Pg
=
gas pressure, in lbf/in.2 gauge, above the surface of the liquid. The maximum
gas pressure (not exceeding 15 lbf/in.2 gauge) is the nominal pressure rating
of the tank. Pg is the positive except in computations used to investigate
the ability of a tank to withstand a partial vacuum; in such
computations; its value is negative,
T1
=
meridional unit force, in lbf/in. of latitudinal arc, in the wall of the tank
at the level of the tank under consideration.
T1 is positive when in tension,
T2
=
latitudinal unit force, in lbf/in. of maridional arc, in the wall of the tank
under consideration. T2 is positive when in tension.(in cylinderical
sidewalls the latitudinal unit forces are circumfrential unit forces.),
R1
=
radius of curvature of the tank wall, in in., in a meridional plane,
at the level under consideration. R1 is to be considered negative
when it is on the side of the tank wall opposite from R2 except
as provided in 5.10.2.6
R2
=
length, in in., of the normal to the tank wall at the level under
consideration, measured from the wall of the tank to the axis of the
revolution. R2 is always positive except as provided in 5.10.2.6
W
=
total weight, in lb, of that portion of the tank and its contents (either
above the level under consideration, as in figure 5-4, panel b, or
below it, as in figure 5-4 panel a) that is treated as a free-body in the
computations for that level. Strictly speaking, the total weight would
include the weight of all metal, gas, and liquid in the portion of the
tank treated as described; however, the gas weight is negligible and
the metal weight may be negligible compared with the liquid weight.
W shall be given the same sign as P when it acts in the same
direction as the pressure on the horizontal face of the free-body;
it shall be given the opposite sign when it acts in the opposite
direction,
At
=
cross-sectional area, in in.2, of the interior of the tank
at the level under consideration,
t
=
thickness, in in., of the sidewalls, roof, or bottom of the tank,
including corrosion allowance,
c
=
corrosion allowance, in in.,
E
=
efficiency, expressed as a decimal, of the weakest joint across which
the stress under consideration acts.
wh
=
width in in., of roof or bottom plate considered to participate in resisting the
circumfrential force acting on the compression-ring-region,
wc
=
corresponding width, in in., of shell to be participating sidewall plate,
th
=
thickness, in in., of the roof or bottom plate at and near the juncture of the
roof or bottom and sidewalls, including corrosion allowance,
tc
=
corresponding thickness, in in., of the cylindrical sidewalls at and near the
juncture of the roof, bottom, and sidewalls,
R2
=
length in in., of the normal to the roof or bottom at the juncture between
the roof or bottom and the sidewalls, measured from the roof or bottom to
the tank's vertical axis of of revolution,
Rc
=
horizontal radius, in in., of the cylinderical sidewall at its
juncture with the roof or bottom of the tank,
T1
=
meridional unit force (see 5.10) in the roof or bottom of the tank at its
juncture with the sidewall, in lbf/in. of circumferential arc,
T2
=
corresponding latitudinal unit force (see 5.10) in the roof or bottom,
in lbf/in. of meridian arc,
T2s
=
circumferential unit force (see 5.10) in the cylindrical sidewall of the tank
at its juncture with the roof or bottom, in lbf/in., measured along an
element of the cylinder,
a
=
angle between the direction of T1 and a vertical line ,
Q
=
total circumfrential force, in lb, acting on a vertical cross
section through the compression-ring region,
Ac
=
net area, in in.2 of the vertical cross section of metal
required in the compression-ring-region exclusive of
of all corrosion allowances.
Sts
=
maximum allowable stress value for simple tension, in lbf/in. 2,
as given in Table 5-1
8.1)
Design Data
Design Code
API 620, 10th EDD. 2002, ADD. 01
Item
TK-59301
Description
Acetone Storage Tank
Material
A 240 Type 304L
Design Density of Contents
=
791 Kg/m3
=
49.38 lbs/ft3
=
1000 Kg/m3
=
62.43 lbs/ft3
Specific Gravity Of Contents
=
0.791
Material Yield Strength
=
Density of Water for Hydrotest
=
148 MPa
21465.59 psi
Design Temperature
=
90 OC
Internal Pressure
=
4.00 kPa
Extrenal Pressure
=
0.58 psi
=
83.54 psf
=
Allowable Tensile Stress at Design Temperature
0.90 kPa
=
0.13 psi
=
18.80 psf
=
110.00 MPa
=
15954 psi
Corrosion Allowance
Shell
Bottom
Roof
Inside Dia of Tank
Nominal Dia of Tank
Outside Dia of tank
Height of Shell
D
Dn
D0
=
0.00 mm
=
0.00 in.
=
0.00 mm
=
0.00 in.
=
0.00 mm
=
0.00 in.
=
20900 mm
=
68.57 ft
=
822.83 in.
=
20915 mm
=
68.62 ft
=
823.43 in.
=
20930 mm
=
68.67 ft
=
824.02 in.
=
18000 mm
=
59.06 ft
Weight of Compression Ring & Plate
=
19047 lbs
Weight of Accessories
=
11240 lbs
Wind Velocity
=
155 km/hr
=
96.31 mph
Yield Strength of Steel Structure
=
36260 psi
Roof Angle
=
9.46 degree
8.2)
Roof Design
As this type of roof design is not directly addresses by API-620 due to its unconventional nature.
Due to this reason the elastic analysis of the roof needs to be performed to verify the induced
stresses for the conformance of roof reliability and strength. The comparison provided in the
analysis is based on Von Mises stresses which should be compared with material yield stress
as specified in table 5-1 and table 5-3 of API 620 whereas the compression area calculations
are provided based on art. 5.12.4 which have already been considered in our analysis.
(See report above)
Roof Plate Thk.
t
=
=
8.00 mm
0.315 in.
Joint Efficiency
E
=
0.70
Rise in Height of Roof
h
=
5.71 ft
1/2 Apex Angle

=
80.54 degree
Radius Of Cone
L
=
34.76 ft

=
At'
=
539477 in2
=
3746 ft2
Roof Area
9.46 degree
Roof Weight
W (Uncorroded)
=
70642 lbs
Roof Weight
W (Corroded)
=
70642 lbs
Hz. Projected Area
At
=
532523 in2
=
3698 ft2
=
6.00 mm
=
0.24 in.
=
6.00 mm
=
0.24 in.
Dn
=
823.43 in.

=
80.54 degree
=
0 mm
8.3)
Compression Area Design
th
tc
For Conical Roof (5.10.2.5.b)
c
0 in.
E
=
0.7
R1
=
Infinity in.
R2 = R3 / cos
=
2504.96 in.
R3 = Dn / 2
=
411.71 in.