DESIGN CALCULATIONS OF STORAGE TANKS

10 Pages·2010·0.08 MB·English

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 23 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

A. Cylindrical Tank, Fixed-Roof with Rafter & Column (cont.)

9. Seismic Design. [APPENDIX E, API 650]
9.1. Overturning Moment due to Seismic forces applied to bottom of tank shell,
M = Z I (C1 Ws Xs + C1 Wr Ht + C1 W1 X1 + C2 W2 X2)
10488643 Ft-lb
Kg-M

where,
Z = Seismic force factor, depends on seismic zone [Table E-2]
0.15

Seismic zone of site
2A
I = Importance factor
1

C1 = Lateral earthquake force coefficient [Para. E.3.3.3]
0.6
C2 = Lateral earthquake force coefficient [Para. E.3.3.3]
= 0.75 S / T when T <= 4.5
0.203019

= 3.375 S / T2 when T > 4.5
0.164867

S = Site coefficient [Table E-3]
1.5
T = Natural period of the 1st sloshing mode = k (D0.5)
5.541355
Sec.

k = Factor depends on ratio D/H
[Figure E-4]
0.625
D = Nominal tank dia.
78.60892
Ft
23.96
M

H = Max. design liquid level
40.28858
Ft
12.28
M
Ratio D/H
1.951147

Since T > 4.5 seconds, Use C2
0.164867

Ws = Total weight of tank shell
180760.5
lb
81.9917
Ton

Xs = Height from bottom of tank shell to shell's center of gravity
15.6939
Ft
4.7835
M

Wr = Total weight of tank roof (fixed or floating) + portion of the
106077.9
lb
48.1162
Ton
snow load, if any, specified by the purchaser
Ht = Total height of tank shell
40.28858
Ft
12.28
M

W1 & W2 = Weight of effective mass of tank contents that move
in unison with tank shell [Para. E.3.2.1 & Figure E-2]
D/H
1.951147

- Find ratio W1 / WT by knowing D/H
[Figure E-2]
0.38

- Find ratio W2 / WT by knowing D/H
[Figure E-2]
0.52

WT = Total weight of tank contents = Tank volume x specific gr.
12206584 lb
5536.82
Ton

(specific gravity of the product to be specified by the purchaser)
Tank volume
5.99E+12 Ft3
5536.82
M3

W1 = Ratio ( W1 / WT ) . WT
4638502
lb
Kg
W2 = Ratio ( W2 / WT ) . WT
6347424
lb
Kg

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 24 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

9. Seismic Design. (cont.) [APPENDIX E, API 650]

X1 = Height from bottom of tank shell to the centroid of lateral
Ft

seismic force applied to W1 [E.3.3.2 & Figure E-3]

X2 = Height from bottom of tank shell to the centroid of lateral
Ft

seismic force applied to W2 [E.3.3.2 & Figure E-3]

D/H
1.951147

- Find ratio X1 / H by knowing D/H
[Figure E-3]
0.375

- Find ratio X2 / H by knowing D/H
[Figure E-3]
0.56

X1 = Ratio ( X1 / H ) . H
15.10822
Ft
4.60498
M
X2 = Ratio ( X2 / H ) . H
22.5616
Ft
6.87678
M

9.2. Resistance to Overturning Moment at bottom of tank shell, WL
[Para. E-4]

Resistance to the overturning moment at the bottom of the shell
may be provided by the weight of the tank shell and by the anchorage
of the tank shell,
or, for unanchored tanks, the weight of a portion of the tank contents
adjacent to the shell.

For unanchored tanks, the portion of the contents that may be
used to resist overturning depends on the width of the bottom
plate under the shell that lifts off the foundation and may be
determined as follows : wL = 7.9 tb ( Fby G H )0.5
lb/Ft

However, wL shall not exceed 1.25 G H D
lb/Ft

Where, wL = max. weight of the tank contents that may be used
to resist the shell overturning moment,

wL1 = 7.9 tb ( Fby G H )0.5
5470.978
lb/Ft
wL2 = 1.25 G H D
3958.802
lb/Ft
Use wL = Min ( wL1 , wL2 )
3958.802
lb/Ft

tb = Thickness of the bottom plate under the shell
0.629921
INCH
MM

Fby = Min. specified yield strength of the bottom plate under the shell
30000
PSI

G = Design specific gravity of the liquid to be stored
1

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 25 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

9. Seismic Design. (cont.) [APPENDIX E, API 650]

9.3. Shell Compression . [Para. E-5]
9.3.a. Unanchored Tanks
[Para. E.5.1]

Value of M / [ D2 (wt + wL)]
where,
b = max. longitudinal compressive force at the bottom of the shell
lb/Ft

(lb/Ft of shell circumference)
wt = weight of tank shell and the portion of the fixed roof
731.9506
lb/Ft

supported by the shell (lb/Ft of shell circumference) = wt / 3.14 D

I. When M / [ D2 (wt + wL )] <= 0.785
0.361854

b = wt + 1.273 M / D2
2892.698
lb/Ft

II. When 0.785 < M / [ D2 (wt + wL )] <= 1.5
0.361854

b may be computed from the value of (b + wL )/ (wt + wL )

obtained from Figure E-5.
Value obtained from Figure E-5
2

b = ( wt + wL ) . Value from Figure E-5 - wL
5422.703
lb/Ft

III. When 1.5 < M / [ D2 (wt + wL )] <= 1.57
0.361854

6415.053
lb/Ft

VI. For M / [ D2 (wt + wL )] > 1.57
0.361854

or when b / 12 t > Fa
Value b / 12 t
478.3498
PSI
< Fa

Value Fa
6410.684
PSI
OK

In case b/12 t > Fa, the tank is structurally unstable.
It is necessary to take one of the following measures :

a. Increase the thickness of the bottom plate under the shell,
tb, to increase wL without exceeding the limitations of
E.4.1 and E.4.2.
b. Increase the shell thickness, t (see Item 9.5 for shell courses).

c. Change the proportions of the tank to increase the dia.
and reduce the height.
d. Anchor the tank in accordance with E.6.

b
w
w

M
D
w
w

w
t
L

t
L

L
=
+

−
+







−
1490

1
0 637

2

0 5
.
(
)

.
(
)

.

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 26 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

9. Seismic Design. (cont.) [APPENDIX E, API 650]

9.3.b. Anchored Tanks
[Para. E.5.2]

For anchored tanks, the max. longitudinal compressive force at
the bottom of shell, b = wt + 1.273 M / D2
2892.698
lb/Ft

9.4. Max. Allowable Shell Compression [Para. E.5.3]

The max. longitudinal compressive stress in the shell, b / 12 t,
shall not exceed the max. allowable stress, Fa determined by
the following formulas for Fa, which take into account the effect
of internal pressure due to the liquid contents.

G H D2 / t2
980331.9
> 106

- When G H D2 / t2 >= 106, Fa = 106 t / D
6410.684
PSI

- When G H D2 / t2 < 106, Fa = 106 t / 2.5 D + 600 (G H )0.5
6372.671
PSI

However, Fa shall not be greater than 0.5 Fty
0.5 Fty
15000
PSI
OK

where, t = thickness of the bottom shell course, excl. any corr. allow.
0.503937
INCH

Fa = Max. allowable longit. compressive stress in the shell
6410.684
PSI

Fty = Min. specified yield strength of the bottom shell course
30000
PSI

9.5. Upper Shell Course [Para. E.5.4]
If the thickness of the lower shell course calculated to resist the
seismic overturning moment is greater than the thickness required
for hydrostatic pressure, both excluding any corrosion allowance,
then the calculated thickness of each upper shell course for
hydrostatic pressure shall be increased in the same proportion,
unless a special analysis is made to determine the seismic overturning
moment and corresponding stresses at the bottom of each upper
shell course.

9.6. Anchorage of Tanks [Para. E.6]
When anchorage is provided, it shall be designed to provide the
following min. anchorage resistance in lb/Ft of shell circumference :

Min. anchorage resistance = 1.273 M / D2 - wt
1428.797
lb/Ft

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 27 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
0
Item : TK-01A

9. Seismic Design. (cont.) [APPENDIX E, API 650]

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 28 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

A. Cylindrical Tank, Fixed-Roof with Rafter & Column (cont.)

10. Overturning Moment due to Wind, Mw.
Mw1 = P (Ar Xr + As Xs)
549994.2
lb-ft
76089.4
Kg-M
Where, P = Wind pressure
PSI
50
Kg/M2

Ar = Projected area over roof = 0.5 Do (Ht - H)
INCH2
8.994
M2

Xr = Height from bottom of tank shell to center of gravity
Ft
12.5049
M
of roof = H + 0.3 (Ht - H)
As = Projected area of shell = Do H
INCH2
294.621
M2

Xs = Height from bottom of tank shell to shell's center of gravity
Ft
4.7835
M
= (H1+H2)/2 + (H2+H3)/2 + x
where x (see next page)
-0.0165
M
Do = D + 2 t1
23.992
M

( Up- lift for wind ) = 4 Mw / 3.14 D2
113.3247
lb/ft
168.757
Kg/M

Total load, W (operating: full liq. p = 1+ wind)
116.672
Ton

( Dead Load ) = W / 3.14 D
lb/ft
2098.53
Kg/M

where W = weight of tank exc. weight of floating roof & bottom
157.962
Ton

Ratio of Up-lift load / Dead load
0.080417
< 1

Since Up-lift (128 Kg/M) < Dead load (2838 Kg/M)
Not necessary of Anchor Bolts.

11. Anchor Bolt Strength.
11.1. Wind Load, Pw = 0.7 x P x Do x H
lb
10311.7
Kg
Where, P = Wind Pressure
50
Kg/M2

Do = Tank diameter
23.992
M
H = Tank Height
12.28
M
Wt = Total Tank Weight (excluding corrosion allowance)
151746
Kg
Wt' = Tank Weight except Bottom Plate (excl. corr. allow.)
126369
Kg

Design pressure
atmospheric

11.2. Overturning Moment, Mw2 = Pw . Xs
356542.5
lb-ft
49326.2
Kg-M
Overturning moment, Mw = Max. (Mw1 , Mw2)
549994.2
lb-ft
76089.4
Kg-M

11.3. Anti-Overturning Moment, Rw = Wt' . D/2
10957504 lb-ft
1515925 Kg-M

Ratio of Mw / Rw
0.050193
< 1
Since Mw < Rw
Anchor Bolts are not required.

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 29 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

A. Cylindrical Tank, Fixed-Roof with Rafter & Column (cont.)
To find tank shell's CG : Take Moment about CG :

W1 [(H1+H2)/2 + (H2+H3)/2 + x] + W2 [(H2+H3)/2 + x] + W3 [x]
= W4 [(H3+H4)/2 - x]
+ W5 [(H3+H4)/2 - x + (H4+H5)/2]
+ W6 [(H3+H4)/2 - x + (H4+H5)/2 + (H5+H6)/2]
+ W7 [(H3+H4)/2 - x + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2]
+ W8 [(H3+H4)/2 - x + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2 + (H7+H8)/2]

W1 [(H1+H2)/2 + (H2+H3)/2] + W1 x + W2 [(H2+H3)/2] + W2 x + W3 x
= W4 [(H3+H4)/2] - W4 x
+ W5 [(H3+H4)/2 + (H4+H5)/2] - W5 x
+ W6 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2] - W6 x
+ W7 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2] - W7 x
+ W8 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2 + (H7+H8)/2] - W8 x

x (W1 + W2 + W3) + W1 [(H1+H2)/2 + (H2+H3)/2]
= W4 [(H3+H4)/2]
+ W5 [(H3+H4)/2 + (H4+H5)/2]
+ W6 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2]
Figure (13)

+ W7 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2]
+ W8 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2 + (H7+H8)/2]
- x (W4 + W5 + W6 + W7 + W8)

x (W1 + W2 + W3) + x (W4 + W5 + W6 + W7 + W8)
+ W1 [(H1+H2)/2 + (H2+H3)/2]
+ W2 [(H2+H3)/2]
= W4 [(H3+H4)/2]
+ W5 [(H3+H4)/2 + (H4+H5)/2]
+ W6 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2]
+ W7 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2]
+ W8 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2 + (H7+H8)/2]

x =[W4 [(H3+H4)/2]
-0.054127 Ft
-0.0165
M
+ W5 [(H3+H4)/2 + (H4+H5)/2]
+ W6 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2]
+ W7 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2]
+ W8 [(H3+H4)/2 + (H4+H5)/2 + (H5+H6)/2 + (H6+H7)/2 + (H7+H8)/2]
- W1 [(H1+H2)/2 + (H2+H3)/2]
- W2 [(H2+H3)/2]]

/ (W1+W2+W3+W4+W5+W6+W7+W8)

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 30 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

A. Cylindrical Tank, Fixed-Roof with Rafter & Column (cont.)

11.4. Sliding.
Sliding force by wind, Ps = 0.7 x P x D x H
lb
10311.7
Kg

Frictional Resistance Force by wind, Rs = 0.3 Wt
lb
45523.9
Kg

Ratio Ps / Rs
0.226512
< 1

Since Ps < Rs
Anchor bolts are not required.

11.5. Anchor Bolts Provided.
Number of anchor bolts, n
12

Size of anchor bolts (UNC)
0.75
INCH
MM
Anchor bolt sectional area, A
2.36
CM2

Allowable load (for 3/4" bolt) :
- Tensile, fat
4299.009
lb
1950
Kg
- Shearing, fas
2976.237
lb
1350
Kg

11.6. Anchor Bolt Load.
Tensile load per each bolt, ft = (4 Mw / n D) - Wt' / n
-9845.45 Kg/Bolt
Since ft < fat
The anchor bolt is sufficient

Shearing load per each bolt, fs = (Ps - Rs)/n
-2934.35 Kg/Bolt
Since fs < fas
The anchor bolt is sufficient

12. Fixed-Roof Inspection Hatches. [API-650, Appendix H.65.3]
Inspection hatches shall be located on tank fixed roof to permit
visual inspection of the seal region.
- Max. spacing of inspection hatches per code
75
Ft
22.86
M
- Min. spacing of inspection hatches per code
4
Ft
1.2192
M

Circle dia. of inspection hatches = D - 6, Ft
72.60892
Ft
22.1312
M
Calculated No. of inspection hatches = 3.14(D-6)/75
3.041435

Assume actual No. of inspection hatches
6

Actual spacing of inspection hatches
38.01794
Ft
11.5879
M

< 75 Ft
OK

> 4 Ft
OK

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 31 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

A. Cylindrical Tank, Fixed-Roof with Rafter & Column (cont.)

13. Total Weight of Tank.
a. Weight of Shell
1st Course, W1 = 3.14 D t H p
22.6902
Ton

2nd Course, W2
19.8539
Ton

3rd Course, W3
15.5995
Ton

4th Course, W4
12.7632
Ton

5th Course, W5
9.92695
Ton

6th Course, W6
1.15797
Ton

7th Course, W7
0
Ton
8th Course, W8
0
Ton

Sub-Total (a)
180760.5
lb
81.9917
Ton

b. Weight of Bottom Plate, R1 = D/2 - Annular width, Rw
11.366
M
L1 = 2 R1 Sin (O/2)
1.82917
M
h1 = L1 / 2 R1 Tan (O/2)
11.3291
M
Total Bottom plate Area, A = 0.5 L1 . h1 . n
404.096
M2

Total bottom Plate Weight, W = A. ta . p Sub-Total (b)
69933.98
lb
31.7216
Ton

Figure (14)

c. Weight of Annular Bottom Plate
9593.336
lb
4.35147
Ton

d. Weight of Roof Plate = Roof area * t p
62546.89
lb
28.3708
Ton

Roof conical area = 3.14 * (D/2) * sq. root ((D/2)2 + h2)
451.765
M2

'where, h = Ht - H = Cone height = Rafter Slope * Do/2
0.74975
M
Rafter slope = 1/16 [see Figure (2)]
01:30

DESIGN CALCULATIONS OF STORAGE TANKS
According to API 650 Code, Edition Sept. 2003
Page : 32 of 34

Designed by : Eng. Abdel Halim Galala, Design General Manager
REV. : 0

Project : Design & procurement of storage tanks
Date : 26.9.2008

Job Name : El-Gamil Plant Storage Facilities
Location : Port Said

Service : Crude Oil Storage Tank
Client : PETROBEL

Capacity : 5000 M3
Item : TK-01A

A. Cylindrical Tank, Fixed-Roof with Rafter & Column (cont.)

e. Weight of Rafters
13.3577
Ton

Total length of rafters (H beam 250x125x6/9)
467.22
M
Weight of one meter of beam
28.5897
Kg

f. Weight of Column, Pipe 20" NPS, Sch. 40
4.46457
Ton

g. Weight of Top Wind Girder
3.07263
Ton

Circumferential length of 2 angles 6x4x3/8" (160x100x10mm)
150.545
M
Weight of one meter of angle
20.41
Kg
Total area of top wind girder, A
60.7712
M2

Weight of top wind girder, W = A * P * t
3.02929
Ton

h. Weight of Intermediate Wind Girder
5
Ton

Wind Girder ID
M
Wind Girder OD
M

i. Weight of Manholes, Cleanout Doors & Nozzles
6
Ton

j. Weight of Ladders & Platforms
5
Ton

k. Weight of brackets (cooling system supports)
3.32338
Ton

No. of brackets per level = 3.14 D / 4000
20
Support
Total brackets for two levels of cooling system + level for foam
84
Support
Bracket dimensions 400x850x100x8
600x850x8

Weight of one bracket
39.564
Kg

l. Weight of Inspection Hatches.
Ton

No. of inspection hatches, Nih
6

Weight of nozzle
Weight of flange (or loose cover)

m. Weight of Manways (for fixed-roof tanks).
Ton

At least one manhole, min 24" ID shall be provided for access to
the tank interior. [API-650, Appendix H.6.5.1]
No. of manholes located at fixed roof, 24" NPS
2

Weight of nozzle
Weight of flange

Total Tank Weight
189.683
Ton