Tank Design Sample as Per API 650

Steel Welded Tank Dia.:15.75 m 18.00 m Height DESIGN CODE : API 650 Tank Diameter : 18 m =18x3.2808 =59 ft Specific Gravity : G=1.0 Vapour Pressure :22.5 in H2O Sd=22700 psi (Material of onstruction is st 37) St=24900 psi Tank has internal pressure : P= 22.5 in H2O=5.55 kPa= 555 kg/m²

Weight of roof =0.006*0.5*(18*3.14)*(10^2+1^2)^0.5*8000=12283 =0.006*0.5*(18*3.14)*(10^2+1^2)^0.5*8000=12283 kg

Design of shell Height of tank shell =16.1 m Liquid filling level =15.78 m

C.A.= 1. 1 .2 mm

F.7 and 3.6.3.2

→

E=0.85 Design shell thickness td =2.6Dx(H+P/12G-1)xG/Sd+ 0.0472

→

Design shell thickness

→

td =0.00676*(H+22.5/12-1) +0.0472

Hydrostatic test shell thickness

Hydrostatic test shell thickness

→

tt= 2.6xD(H-1)/St

Height ( m) 2 4 6 8 10 11.5 13 14.5 16

(ft)

td ( in)

6.5616 13.1232 19.6848 26.2464 32.808 37.7292 42.6504 47.5716 52.4928

0.081767 0.126124 0.17048 0.230541 0.259193 0.29246 0.325728 0.358995 0.392262

tt=0.00616*(H-1)

( mm )

tt (i n )

( mm )

Cosidered

2.0768924 3.2035453 4.3301983 5.8557329 6.5835042 7.428494 8.2734837 9.1184734 9.9634631

0.034259 0.074679 0.115098 0.155518 0.195937 0.226252 0.256566 0.286881 0.317196

0.87019 1.896844 2.923499 3.950153 4.976807 5.746798 6.516788 7.286779 8.056769

6 6 6 6 8 10 12 14 16

Thickness

Wt - corr. kg 1176.7 1361.3 1840.0 2488.2 2797.5 3156.5 3515.6 3874.7 4233.7 Total in kg: 20210.5

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Steel Welded Tank Dia.:15.75 m 18.00 m Height Design of Roof  1) Acording to (3.10.2) the minimum thickness of roof plate is 5mm Take it 6mm 2) Roof structure design: To use 33 IPE200 this means each member will carry the following: Dead weight: 200 Kg Roof plate weight : 300 Kg Live weight :300 Kg Total :900 Kg Z= M/f =800x393.75/1650 =190.9 cm3 from steel table we will find : → IPE 200 is safe Zy=194.3 cm3 Maximum Design Pressure Permitted -Pf- API 650 APPENDIX F Pf =1.6xP- 4.8xth =1.6x22.5-4.8x0.1968= 35.05536 in of water  Pf >P OK Let us calculate the weight of the shell without any corrosion : td Wt (in) (mm) Kg 0.629921 0.551181 0.472441 0.393701 0.314961 0.23622 0.23622 0.23622 0.23622

16 14 12 10 8 6 6 6 6

Σ

9073.303 5954.355 5103.733 4253.111 3402.489 2551.866 2551.866 2551.866 5621.503 41064.09 Kg

=

90505.26 pd

Roof plate weight=12283 kg = 27072.7 pd Roof structure weight=4482 kg = 9878 pd

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Steel Welded Tank Dia.:15.75 m 18.00 m Height

73.4 kg/m2

→

Wind load on tank wind velocity =48m/s=108mile h → wind force 0-16=860 kPa=87.6 kg/m2 wind force 16-17.2=720 kPa=73.4 kg/m2 according to API 650 3.11.1 →

17.2 16

87.6 kg/m2

→ 8

87.6 kg/m2

→ 0

Load between 0-16 : F1=87.6x16x18= 25229 kg

Load between 16-17.2 F3=73.4xArea=73.4x1.2x18x0.5=792.7 kg Overturning moment due to wind load: M=F1x8+F3x(16.4)= 214832 Kg.m Overturning stability (3.11) W= shell weight to resist uplift less corrosion+dead weight supported by shell minus uplift from internal pressure

W= 20210+ 27072.7 +9878-555x(18x18/4xπ)=42851 kg Stability Moment = 2/3x(WD/2)=257106 kg.m > So, It does not need Anchor Bolts. Seismic Design of the Storage Tank:

M

(APPENDIX E)

M =Zx I (C1xWsxXs + C1xWrxHt + C1xW1xX1+C2xW2xX2) Z : seismic zone factor=0.2 I=1.0 E3.1 C1=0.60 (API 650 - E3.3)

D/H=18/16=1.1→ K=0.58 (Figure E-4) T(natural period of the first sloshing mode, in second)

=K√D =0.58x√59 =4.45 <4.5 Then C2=0.75*S/T S=1.5 (table E-3) C2=0.75x1.5/4.45 =0.25 REMARKS:

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Steel Welded Tank Dia.:15.75 m 18.00 m Height

Ws:total weight of the tank shell in pound =90505 pd

Xs=ΣMi.Xi/ΣMi Xi (m) 1 3 5 6 8 10.75 12.25 13.75 15.25

td (in) 0.629921 0.551181 0.472441 0.393701 0.314961 0.23622 0.23622 0.23622 0.23622

(mm) 16 14 12 10 8 6 6 6 6

Σ

Wt Kg 14201.691 12426.48 10651.269 8876.0571 7100.8457 3994.2257 3994.2257 3994.2257 3994.2257 69233.246

Mi xXi 14201.69 37279.44 53256.34 53256.34 56806.77 42937.93 48929.27 54920.6 60911.94 422500.3

Xs=6.1 m =20 ft Wr:Weight of roof structure and roof plates=27072.7+9878= 36950.7 pd H=52.5 ft

D/H=1.1→X1/H=0.4 (Figure E-3) →X2/H=0.71 (Figure E-3) → X1=21 ft X2=37.3 ft

WT:weight of tank content=(πD²/4)x15.68x1=3990 ton=8794123 pd W2/WT=0.27 (figure E-2)

→W2=2374413 pd W1/WT=0.78 (figure E-2)

→W1=6859416 pd M =Zx I (C1xWsxXs + C1xWrxHt + C1xW1xX1+C2xW2xX2) M=0.2x1x(0.6x90505x20+0.6x36950x52.5+0.6x6859416x21  + 0.25x2374413x37.3) M=22164005 pd .ft (overturning moment due to seismic loads)

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Steel Welded Tank Dia.:15.75 m 18.00 m Height Resistance to overturning (APPENDIX E.4) wL=7.9x tbx Fby xGxH tb=8 mm=0.315 in Fby=34000 psi (minimum yeild strength for st 37) G=1.0 H=52.5 ft

wL=7.9x0.315x 34000x1.0x52.5 =3324.7 pd/ft of circumference *1.25xGxHxD=1.25x1.0x52.5x59=3871.9 pd/ft WL shall be 3324.7 pd/ft

Ws1 :Tank shell weight /circumference =90505/πx59=488.3 pd/ft WL(total)=(WL+Ws1)xπxD =(3324.7+488.3)xπx59=616734 pd Mresistance= WL(total)xDiameter=616734x59=36387343 pd.ft Mresistance < Moverturning

→There is no uplift due to seismic loads

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Steel Welded Tank Dia.:15.75 m 18.00 m Height

Shell compression

Check the shell compression according to to API 650 - E.5.2

b:maximum longitudinal compressive force at bottom of shell  =Wt+(1.273xM/D²) where Wt: weight of shell tank and roof plates and structures

Wt=(Ws+Wr)/πD =(191091)/πx65.6 =927 pd b=927+(1.273x 24473031/65.6²) =8166.5 pd/ft of circumference b/12t=8166.5/12x0.63=1080 pd/in²  As per E.5.3 GHD²/t²=1.0x52.5x(65.6/0.63)² =569227 < 10 exp6 Then Fa:Maximum allowable stress =1000000xt/D =1000000x0.63/65.6 =9603.6 pd/in²

→

b/12t
→

No overstress in bottom shell

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