API-650 design procedure example

CONTENTS:-

Sr.No. 1 2 3 4 5

6 7 8 9 10 11

DESCRIPTION DESIGN DATA CALCULATIONS FOR MINIMUM SHELL THICKNESS BOTTOM PLATE DESIGN INTERMEDIATE WIND GIRDER 4.1 AS PER API 650 SEC. 3.9.7 SUPPORTED CONICAL ROOF 5.1 DESIGN OF ROOF PLATE 5.2 DESIGN OF ROOF PLATE WITH STIFFENING 5.3 DESIGN OF COMPRESSION RING 5.4 DESIGN OF ROOF RAFTERS COMPRESSION AREA AT ROOF TO SHELL JOINT 6.1 DESIGN OF COMPRESSION AREA AS PER API 650 App. F STABILITY OF TANK AGAINST WIND LOADS 7.1)RESISTANCE TO SLIDING FOUNDATION LOADING DATA VENTING CALCULATIONS NOZZLE FLEXIBILITY ANALYSIS AS PER APPENDIX P SHELL TO ROOF RAFTER JOINT STRESS ANALYSIS

PAGE 3 4 5 6 7 7 8 10 11 13 14 16 19 20

1) DESIGN DATA Design Code Client's Specs. Fluid Material

: : : :

Density of contents Specific gravity of contents Material's yield strength Design Temperature Internal Pressure External Pressure High Liquid Level

DL

API 650, 10th Edition, Add.4 2005, Appendix F 32-SAMSS-005, BD-407062 Rev.00C FIRE / UTILITY / WASH WATER TANK SA-516 Gr 70. 1004.9 1.0049 260 71 0.747 0.245 8.560

kg./m3

T Pi Pe Hl

= = = = = = =

Design Liquid Level

HL

=

9.000

m

Allowable Design Stress at Design Temp.

Sd

=

173.00

MPa

API 650 Table-3.2

St

=

195.00

MPa

API 650 Table-3.2

D H

= = = = = = = = =

3.20 3.20 3.20 3.20 9.46 13.516 13.500 13.508 9.000

mm mm mm mm 0 m m m m

Wr Ws Wc V Fy Lr

= = = = = =

30.00 5.00 6.85 154 250 1.2

KN KN KN Km/hr M Pa = Kpa

Allowable Test Stress for Hydrostatic Test Condition Corrosion allowance Bottom Shell Roof Roof Supporting Structure Slope of Tank Roof Outside dia. of tank Inside dia of tank Nominal dia. of tank Height of Shell Weight of roof attachments (platform, handrail, nozzles, etc.) Weight of attachments (pipe clips, nozzles, etc.) Weight of curb Angle Design Wind Velocity Yield Strength of Steel Structure Live Load on roof

G dy

 Do Di

MPa o C Kpa Kpa m

API 650 Table-3.2 = =

3.0 1.0

inch of water inch of water

1:6

=

44.32 ft

36.259 Ksi API 650 Sec. 3.2.1d

2) CALCULATIONS FOR MIN. SHELL THICKNESS Calculations of Shell Thicknesses by Section 3 The minimum thickness of shell plate as per section 3.6.3.2, shall be computed using following formula; Design Shell Thickness td = 4.9D (HL1 - 0.3)G + CA Sd Hydrostatic Test Thickness

tt =

4.9D (HL1 - 0.3) St

Where, G = Specific Gravity of fluid to be stored D = Nominal dia. of tank HL = Design liquid level for course under consideration CA = Corrosion allowance on shell

= = = =

1.0049 13.508 9.00 3.20

1st Shell Course Width of 1st course Design height for 1st shell course

m m mm

W1 HL1

Required Shell Thickness Required Shell Thickness Shell thickness provided 2nd Shell Course Width of 2nd course Design height for 2nd shell course

= 2.500 m = 9.076 m (Including Equivalent head due to internal pressure) td = 6.57 mm tt = 3.36 mm t1 = 8.00 mm

W2 HL2 td tt t2

Required Shell Thickness Required Shell Thickness Shell thickness provided 3rd Shell Course Width of 3rd course Design height for 3rd shell course

W3 HL3 td tt t3

Required Shell Thickness Required Shell Thickness Shell thickness provided 4th Shell Course Width of 4th course Design height for 4th. shell course

W4 HL4 td tt t4

Required Shell Thickness Required Shell Thickness Shell thickness provided

Shell Course # Shell width (m) Shell Thickness (mm) Corroded Shell Thk.(mm) Shell Weight (KN) Shell Weight (KN)Corroded

= =

Shell Table -1 1 2.500 8.00 4.80 65.36 39.22

Total Shell Weight (KN) Total Shell Wt.(KN) (Corroded) Total weight of corroded shell + Shell attachments,

= 5.61 mm = 2.13 mm = 8.00 mm (As per Tank General Note 3 of Data Sheet) = =

1.880 m 4.08 m

= = =

4.65 1.28 6.00

= =

2.120 m 2.196 m

= = =

3.93 0.64 6.00

2 2.500 8.00 4.80 65.36 39.22

W'ST

2.500 m 6.576 m

mm mm mm

mm mm mm

3 1.880 6.00 2.80 36.86 17.20 = = =

Including Curb Angle

4 2.000 6.00 2.80 39.22 18.30 206.80 113.93 120.78

KN KN KN

3) BOTTOM PLATE DESIGN As per API 650 Sec. 3.4.1 All bottom plates shall have minimum nominal thickness of 6mm, exclusive of any corrosion allowance. tb Required Bottom Plate Thickness = 6+ CA mm tb = 9.20 mm Used bottom plate thickness = 10.00 mm Weight of bottom Plate = 11430.3 kg = 112.13 KN Weight of bottom Plate ( Corroded ) = 7772.6 kg = 76.25 KN

3.1) ANNULAR PLATE DESIGN Hydrostatic test stress for first shell course

Sh

= =

(API 650 Sec. 3.5) (4.9D (H1 - 0.3)/tsc) 119.97 M Pa

< 172 M Pa OK

If hydrostatic test stress for first course is less than 172 Mpa, lap welded bottom plates may be used in lieu of butt-welded annular bottom plates. tb

=

Max. design liquid level

HL1

=

Width of annular bottom plate

Wap

=

Required width of annular bottom plate

Wap

=

711.91

mm

Width of annular bottom plate provided

Wact

=

800.0

mm

Thickness of annular bottom plate

10.00

mm

9.08 m 215 x tb / (HL1 x G)1/2

(between shell ID & lap of bottom plate with annular plate)

4) INTERMEDIATE WIND GIRDER 4.1) As per API 650 Sec. 3.9.7 The maximum height of the unstiffened shell Where, t = As ordered thickness of top shell course

H1

=

t = As Per Article 3.9.7.1 of 32-SAMSS-005 D = Nominal tank diameter V = Design wind speed The maximum height of the unstiffened shell

=

= = = H1

=

9.47 t (t / D)3/2 x (190/V)2 6.00

API 650 Sec.3.9.7.1

mm

2.80 mm 13.508 m 154.00 Km/hr 3.81

m

Height of transformed Shell Wtr W x (tuniform/tactual)5/2 Transposed width of each shell course = 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)

API 650 Sec.3.9.7.2

1st Shell Course As ordered thickness of 1st shell course Actual width of 1st shell course

t1 W1

= =

8.00 mm 2500 mm

Transposed width of 1st shell course

Wtr1

=

1218 mm

2nd Shell Course As ordered thickness of 2nd shell course Actual width of 2nd shell course

t2 W2

= =

8.00 mm 2500 mm

Transposed width of 2nd shell course

Wtr2

=

1218 mm

3rd Shell Course As ordered thickness of 3rd shell course Actual width of 3rd shell course

t3 W3

= =

6.00 mm 1880 mm

=

1880 mm

= =

6.00 mm 2120 mm

=

2120 mm

Wtr3

Transposed width of 3rd shell course 4th Shell Course As ordered thickness of 4th shell course Actual width of 4th shell course

t4 W4 Wtr4

Transposed width of 4th shell course Htr

Height of transformed Shell

= =

Wtr1 + Wtr2 + Wtr3 + Wtr4 6436 mm

=

6.436 m

As Htr > H1 Intermediate Wind Girder is Required Intermediate Wind Girder The required minimum section modulus of an intermediate wind girder shall be calculated as follows. Zreq. = D2 H1 x (V/190)2

API 650 Sec.3.9.7.6

17 Where:

Z = Required minimum section modulus of intermediate wind girder. (cm3) H1 = Vertical distance (m) between the intermediate wind girder and the top angle of the shell =

3.218

m

D = Nominal Tank diameter =

13.508

m

Zreq. =

22.69 cm3 From Table 3-20 we provide one angle of 102*76*6 as intermediate wind girder as per fig. 3-20 detail c Zpro.= Section modulus provided = 50.2 cm3

(Including shell participating width & corroded thickness of 2.8mm)

As Apov.>Areq. The Intermediate Wind Girder Is Ok

5) Design of Roof Plate 5.1) Supported Conical Roof Minimum roof plate thickness

tR

D x √Tr/2.2

=

API 650 Sec.3.10.5.1

4.8 Sin

Where,

Tr = Greater of load combinations (e)(1) and (e)(2) as per App. R P1 = DL + (Lr or S) + 0.4 Pe Combination i, P2 = DL + Pe + 0.4 (Lr or S) Combination ii, DL Where, Dead Load of the roof, = 0.981 kPa Live Load on the roof, Lr = 1.200 kPa External Pressure, Pe = 0.245 kPa Snow Load, S = 0.000 kPa P1 = 2.279 kPa P2 = 1.706 kPa (Max. of P1 & P2) Tr = 2.279 kPa tR = 17.43 mm ≥ 5 mm tR + C.A. = 20.63 mm As per API Sec. 3.10.5.1 the Maximum thickness for self supported roof is 12.5mm (excluding corrosion allowance) but due to high value of calculated roof thickness, it is proposed to provide supported roof. Used thickness = Roof Plate Thickness tprov = Roof developed radius

Rr

10.00 10.00

= =

Ar

Roof developed Area Weight of Roof Weight of Roof (corroded)

mm mm

6.85

API 650 Sec. 3.10.5

(Including Corrosion Allowance)

m

147.5 114.72 77.22

= =

API 650 App. R (e)(1) API 650 App. R (e)(2)

m2 KN KN

Roof is designed as a supported cone roof. The system of rafters is provided to support the roof plate. The rafters are supported at tank shell and load is transferred to tank periphery. Maximum Spacing of Rafters at Outer Ring

= 0.6 * π = 1.88 m API 650 3.10.4.4 Maximum No. of Rafters Required N = π x D/0.6 X π = 22.51 ( Brownell & Young - 4.3b) 5.2) Design of Roof Plate and Stiffening Member Roof plate shall be designed as continuous beam with uniform load comprising of roof live load and self weight of roof plate. The maximum unsupported span of roof plate is equal to the spacing of stiffeners at tank outer dia. Number of Rafters N2 = 24.00 = 1.77 m = 69.7 inch Roof Plate Span l (Maximum spacing of Rafters at tank outer dia) Roof plate thickness

= = = =

tr

Assumed Plate width

b

Design Live Load Self Wt. of roof plate

Lr Wr

6.80

mm

1

inch

1.20

=

0.26772 inch

(corroded plate thickness)

6.851

KN/m2

0.78

KN/m2 Design load for roof plate shall be comprising of roof live load and the total dead load acting on the roof. Roof Plate Design Load wp = Lr + Wr = 1.98 KN/m2 = 0.29 psi Assuming width of roof plate 1 inch and calculating the bending moment for strip if roof plate 1 inch wide. = 69.7 inch Roof Plate Span l Design load/ length w = wp x b = 0.29 lbs/inch 2 wl = = Bending Moment At Mid Span Mc 58.035 lbs inch Bending Moment At Supports

Ms

=

24 wl2

Section modulus of Plate

Zp

=

b tr2/6

=

116.07 lbs inch

12

Allowable Bending Stress

Fb =

Allowable Bending Moment M allow

0.6 x Fy = Fb x Zp

22625.9 psi

=

0.012

in3

( As per API 650)

= 270.3 lbs inch Mallow>Ms Thickness Is Ok = + Therefore Plate Thickness Provided 6.80 CA = 10.00 mm (Including Corrosion Allowance)

147

5.3) Design of Compression Ring

 

Fig- 2 : Central Compression Ring Loading Diagram Live Load on roof Lr =

1.2

KN/m2

Load of roof plate Dr =

1.04

KN/m2 (including weight of rafters & accessories)

g = Lr + Dr =

2.24

KN/m2 (udl due to roof plate and live load)

Radius of tank R =

6.75

m

0.80

m

Radius of central compression ring

R2 =

Span of Rafter

Ls =

6.03

m

Self weight of Rafter

=

25.30

Kg/m

Total weight of Rafter Total weight of Rafter corroded

= =

3662.6 2444.8

Kg Kg

Total weight of Rafter/area Weight of Rafter Weight of Central Ring

= gr = Wr = N2 =

0.24 0.248 2.76

KN/m2 KN/m KN

h= R1 =

1.12

m

5.95

m

=

3.959

KN/m

=

0.469

KN/m

Number of rafter Height of Roof at center Radius of tank - radius of compression ring = g1 2Rg =

24.00

N2 g2

=

2R2g N2

Calculation of load transferred at joint of stiffener and central ring Wa = P1 + P2 Weight of Central Ring ,Wr per stiffener P1

=

Wr N

=

0.115 KN

= =

35.93 KN 23.98 KN

Load transferred to central ring by rafters,P2 =

g2 x R2

=

0.38

KN

Wa =

P1 + P2 =

0.49

KN

g 0 = gr + g2 = g3 = g1 - g2 =

0.72

KN/m

3.49

KN/m

Considering the equilibrium and taking Moments about point A. Ha = Wa x R1 +(g0 x R1) R1/2 + g3 (R1/2) ( R1/3) Ha Radial Load transferred to ring through stiffeners, H a = Number of Stiffeners Supported on central Ring, N2 = Radius of central compression ring, R2 = Moment transferred to ring,

Thrust T =

32.19 24 0.8

KN

=

7.24

Kips

m

=

2.624 ft

Ha R2 ( cot 180 - N2 ) = 2 N2 

M=

M

h 32.19 KN

=

=

0.41

Kip ft

=

0.562 KN m

27

Kips

=

122.25 KN

Ha Cot 180 = 2 N2

Fig -3 : Central Compression Ring PROPERTIES OF COMPRESSION RING (Corroded) b1 =

200

A1= b1h1 =

1360

mm2

A1y1 =

4624 mm2

h1 =

6.8

A2= b2h2 =

3400

mm2

A2y2 =

850000 mm2

b2 =

6.8

A3= b3h3 =

1496

mm2

A3y3 =

164560 mm2

h2 =

500

Location of Centroid ( See Fig) C = A1y1 + A2y2 +A3y3 =

b3 =

6.8

h3 =

220

y1=

3.4

y2=

250

y3=

110

A =

Moment of Inertia I = b1h13 + A1 (C-y1)2 +b2 h23 +A2(C-y2)2 + b3 h33 + A3 (C-y3)2 12

12

I =

6256 mm

Section Modulus =

162.91 mm

A

2

=

12

141451394.829

mm

4

0.00626 m

2

Z = I / (h2 - C) fb =

=

419628.8

mm3

M =

1340.28

KN/m

150000

KN/m2

19541.63

KN/m2 KN/m2

fb

125000 + fc

Fb

Fc

= 2

Z Allowable Bending Stress Fb = 0.6 Fy = fc = T = A Allowable Compression Stress Fc = 0.5 Fy =

=

0.17

0.0004196288 m3

As fb/Fb+fc/FcAmin, Therefore used Curb Angle is satisfactory 6.1) Tank Design As Per Appendix F Uplift on Tank as per F.1.2 Corroded Roof Thickness Nominal dia. of tank (Di + Shell thick)

tR D At

Area of tank Internal design pressure of tank Total upward lifting force acting on roof

Pi FR

Weight of roof (corroded)

WR

Weight of shell, roof and attached framing

107 D'L 107

F.2 through F.5 are applicable Internal design pressure is,

P

W'ST = Weight of shell and attached framing Max. design pressure, limited by uplift at base of shell is;

mm2

2

Amin

DLS

Ref: API 650 Fig F-2

mm2 231 Ah + Ac

Aprov. Minimum required participating area, Amin.

API 650 Sec. 3.1.5.9

API 650 App.F.5.1

mm

2

= = = = = = = = > = <

6.80 13.508  x R2 143 0.747 Pi x At

mm m

= = =

(1.1 x A x tanθ) / D2 + 0.08 x tR

m2 kPa

107 kN 77.22 kN 77.22 224.75 kN 224.75 API 650 F.4

2.85 kPa 120.78 kN

API 650 F.4.0 0.00127 x DLS / D2 + 0.08 x tR - 0.00425 x Mw / D3 = = 0.841 kPa Pi But, internal design pressure of tank is = 0.747 kPa 0.747

295.30 mm2 D2 x [0.4Pi-0.08th+0.72(V/120)2]/1.1(tan ) 973.7 mm2 973.7

Used Curb Angle is satisfactory

7)Stability of Tank Against Wind Load Wind velocity height of tank including roof height effective wind gust factor force coefficient wind directionally factor Velocity Pressure Exposure Co-Eff. Topo Graphic Factor Importance Factor Design Wind Pressure

V Ht

Design Wind Load

Overturning Wind Moment

G Cf Kd Kz Kzt I qz

= = = = = = = = =

P1

=

Mw

=

( Ref: ASCE-7) 154.0 Km/hr = 10.125 m = 33.2091 ft. 0.85 0.50 0.95 0.95 1.0 1.15 0.613 x Kz x Kzt x Kd x V2 x I/1000 1.164 KN/m2 qz x Do x G x Cf x Ht 67.711 KN

=

m/s

P1 x Ht 2 342.78 KN-m =

Resisting Moment Resisting Moment

42.78

252746.5

ft-lbs

Mr = 2 D (Ws' + Wr'-Uplift due to Design Pressure ) 3 2

Ws' = total weight of tank shell + Curb Angle = Wr' = total weight of tank roof

120.785 101.203 517.567

= = Mr

=

KN KN (Including Rafters) KN-m

As Mr > Mw Anchorage is Not Required 7.1)Resistance To Sliding

( Ref: API 650 3.11.4)

The wind load\ pressure on projected area of cylindrical surfaces =

0.86

KN/m2 =

18.0 psf

This pressure is for wind velocity of 100 mph (160 Km/hr) For all other wind velocities the pressure shall be adjusted in proportion of ratio (V/160)2 O.D of tank = D0

= =

13.516 m 154 Km/hr

=

0.926

(Vf=Velocity Factor)

Wind Pressure on vertical plane surfaces

=

0.86

KN/m2

Wind Pressure on vertical conical surfaces

=

0.72

KN/m2

Projected area of roof

=

7.601

m2

Projected area of shell

=

121.64 m2

Design Wind Velocity V (Ve/160)2

Fwind = = Ffriction = =

Vf(Wind Pressure on Roof X Projected Area of Roof + Wind Pressure on Shell X Projected Area of Shell) 101.985 KN Maximum of 40% of Weight of Tank 109.702 KN

Ffriction>Fwind No Anchorage Is Required To Resist Sliding

8) Foundation Loading Data The self weight of roof and live load will be transferred to tank shell Live load transferred to foundation Live Load on roof, Lr =

1.2

Area of Roof, Ar = Total Live Load, WL =

147.46 m2

Lr x Ar xD Circumference of Tank C = Live Load transferred to Foundation wL =

KN/m2

176.95 KN 42.5 m WL / C

4.2

KN/m

153.41 206.80 15.00 375.20 8.84

KN (Including Rafter & Compression Ring) KN KN (Including Curb Angle & Inter. Wind Girder) KN (Including Platform Weight) KN/m

Dead load transferred to foundation Self Weight of Roof Wr = Self Weight of Shell Ws = Self Weight of shell Attachments Wa = Total Dead Load acting on shell WD = Dead Load Transferred to Foundation Wd = WD / C

Operating & Hydrostatic Test Loads Self Weight of Tank = Weight of Fluid in Tank at Operating Conditions = Weight of Water in Tank at Hydrotest Conditions = Uniform Load at Operating Condition = Self Wt. + Fluid

Wf = Ww = Wo =

Uniform Load at Hydrotest Condition = Self Wt. + Water

Wh =

487.34 KN 12715 KN 12638 KN 92.12

KN/m2

91.59

KN/m2

70.3 0.6 342.8

KN KN/m KN-m

Wind Load Transferred to Foundation Base Shear due to wind load, Fw = Reaction due to wind load, Rw = Moment due to wind load, Mw =

Summary of Foundation Loading Data

Dead load, shell, roof & ext. structure loads

DL =

8.84

KN/m

Live Load

LL =

4.17

KN/m

Uniform load, operating condition

Wo =

92.12

KN/m2

Uniform load, hydrotest load

Wh=

91.59

KN/m2

Base shear due to wind

Fw =

70.32

KN

Reaction due to wind

Rw =

0.60

KN/m

Moment due to wind load

Mw=

342.78

KN-m

Note: 15% to 20% Variation will be consider while designing the Foundation.

Summary of Tank Major Parts Thickness and Weight Item Shell Plate Bottom Plate Roof Plate Roof Rafter & Compression Ring

Tank Capacity Calculations:

Plate Thickness (mm) 8.00 6.00 10.00 10.00 -

Weight (Kgs) 13,325 7,755 11,430 11,694 3,944

As per API 650 App. L

I. Nominal Capacity, Qmax.

Where:

Di = H =

Qmax. = x Di2 x H 4 13.500 m 9.000 m Qmax. = 1288 m3

II. Net Working Capacity, Qnet Qnet. =

m3

=

xDi2 x (H1-LL) 4

Where:

H1 = LL =

8.560 m 6.965 m Qnet. = 228.31

m3

=

45,459 ft3

m3

8,056 ft3

Bolt Connection Stress Analysis Ultimate Dead Load on the roof including Live Load + Self Weight of Roof + Weight of Accessories, g gu = =

Lr + Dr 2.24

Mpa

( Refer to 5.3. Design of Compression Ring)

Radial Load transferred to the end of the rafter gu x D2

Hr =

4Ls*N2

Where; D = Tank Diameter = N2 = Number of Rafter = Ls = Length of Rafter = Hr =

2.22

13.5 m 24 6.03 m KN/m

By applying this load on the rafter Max. Shear Force Induce,P =

6.12 KN

(from STAAD result)

Now, calculating the Shear Stress for 3/4"-10 x 1- 1/2" Hex. Head Bolt, A193-B7. F =

P/A

Where; A = Bolt Shear Area =

0.7854 ( D-(0.9743/n))2

A=

215.4834 mm2

0.334

in2 =

But there are two bolts in this connection, therefore, A = Induced Shear Stress on Bolt F = 14.20 As per ASTM 193 Min. Tensile Strength, Fu = Allowable Stress; Shear Stress

430.9669 mm2

Mpa

485

Mpa

(Ref. ASTM A193 Table 3)

( Ref. Table I-D AISC Allowable Stress Design, 9th Edition) Fv Fv

= 0.17 Fu = 82.45 Mpa

> Induced Stress

Allowable Stress of Bolt is greater than the required maximum stress for the connection. Therefore, the provided Bolt is SAFE and ADEQUATE.

ht of Accessories, gu

gn of Compression Ring)

Design, 9th Edition)