Section 3 Design Section 3 Design of Typical Chemical of Typical Chemical

Vessels Vessels

Chapter 7 Design ofChapter 7 Design of Shell-and-Tube Heat Shell-and-Tube Heat

ExchangerExchanger

7.1 Classification of Shell-and-7.1 Classification of Shell-and- Tube Tube （（ TubularTubular ） ） Heat Heat

ExchangerExchanger

4.U Tube Type Heat Exchanger

2.Float Head Heat Exchanger

3.Stuffing Box Heat Exchanger

1.Fixed Tube Sheet Type Heat Exchanger

Fixed Tube Sheet Type Heat Exchanger

接管法兰

管箱

容器法兰 排气管 膨胀节管板拉杆 定距管

折流板 换热管

壳程接管

支座排污口

管程接管

Nozzle Flange [Pipe Connecting F.] —— 接管法兰

Vessel Flange —— 容器法兰Tube Sheet [Plate] —— 管板(Air) Vent Nozzle —— 排气管Expansion Joint —— 膨胀节Shell Nozzle —— 壳程接管Tie Rod —— 拉杆(Pipe) Spacer —— 定距管

Header [Channel (head)] —— 管箱Baffle —— 折流板Heat Exchange Tube —— 换热管Inner Pipe Nozzle —— 管程接管Drain (Outlet) —— 排污口Support —— 支座

7.2 Contents7.2 Contents of Machine Designof Machine Design

1.1.Materials’ Selection Materials’ Selection

(Shell, Heads, Tube Sheets, Tubes, etc.)(Shell, Heads, Tube Sheets, Tubes, etc.)

2.Structure Design2.Structure Design

Confirming the fabric type, position, Confirming the fabric type, position,

connecting mode, etc. of each unit connecting mode, etc. of each unit

3.Strength Design

i. Confirming the strength dimension (wall thickness S) of units like shell, heads, etc.

ii. Opening reinforcement computation

4.Tube Sheet Design

5.Calculation of Thermal [temperature (difference)] Stress

6.Calculation of Tube-to-Tubesheet Joint Load [pulling-out force of tube]

7.3 Structure of Shell-and-7.3 Structure of Shell-and-

Tube Heat ExchangerTube Heat Exchanger

1.1. Type of Shell-and-Tube Type of Shell-and-Tube

Heat Exchanger Heat Exchanger

Main

Parts

Cylinder (Shell)

Heats

Tube Sheet (Plate)

Tube (Pipe) Bundle

Baffle, Tie Rod, (Pipe) Spacer

Pass Partition (Plate)

2.2.Structure of Heat Exchange Structure of Heat Exchange TubeTube

i. Type of commonly used tubesi. Type of commonly used tubes

—— —— Bare tube (Bare tube (光管光管 ), ), Profiled tube (Profiled tube (异型管异型管 ), ),

Fin (Finned) Tube (Fin (Finned) Tube (翅片管翅片管 ))

ii. Material of commonly used tubesii. Material of commonly used tubes

—— —— Carbon Steel (10 Carbon Steel (10 、 20)20)

Low Alloy Steel (Low Alloy Steel (16Mn、 15MnV))

Alloy Steel (Alloy Steel (1Cr18Ni9Ti))

CopperCopper

3.Connection of Tube and Tube Sheeti. Expansion Joint

Before Expansion After Expansion

ii. Welding [Soldered Joint]

iii. Expanded and Welded Joint

Advantages:

(1)Strengthening the Resistance to Fatigue

at the joint

(2)Eliminating the Stress Corrosion ( 应力腐蚀 ) and Gap Corrosion ( 间隙腐蚀 ),

then raising the lifetime

Methodology:

(1)Welding before expanding ( 先焊后胀 )

(2)Expanding before welding ( 先胀后焊 )

4.Structure of tube sheet and the connection of it with shell

Depending on types of heat exchanger

Tow Types

Non-movable (Fixed) Tube Sheet

—— used to fixed Tubesheet Heat Exchanger

Detachable (Non-fixed) Tube Sheet

—— used in Float Heat, Stuffing Box, U Type Heat

Exchanger

i. Fixed Tube Sheet

—— used in Fixed Tube Sheet Type Heat Exchanger

ii. Non-fixed Tube Sheet

—— the connecting structure of Float

Head, U Type and Stuffing Box

Heat Exchanger

5.The Sealing between Tube

Sheet and Header

Taking the Double Tube Side (Pass)

as the example:

Partition of Channel Head:

Structure of Channel Head:

6.Structure of Shell Side (Pass)

Main Units in Shell Pass Baffle Supporting Plate- 支承板 By-pass Baffles (Sealing Strip)- 旁路挡板 Impingement Plate (Baffle)- 防冲板 etc.

i. Baffles and Base Plate

Function: (1)Increasing the flow velocity of fluid in shell pass and changing the flow direction ——Improving the Heat Transfer Efficiency(2)Bearing the heat exchange tubes

Types:Arcuate, Disc and Doughnut Type, Fan Shaped.

ArcuateDisc and

Doughnut TypeFan Shaped

ii. By-pass Baffles

While there has clearance large enough

between shell and tube bundle, we set the

plates along the longitudinal direction and

force the fluid across the tube bundles in

order to avoid the fluid flow into the shortcut.

iii. Function of Impingement Plate

—— Preventing the fast flowing media

rushing ( 冲刷 ) the tube bundles at the

porch of shell pass

iv. For Steam Inlet Tube

—— Making as Bugle Type to decrease

the flow velocity and fulfil the buffering

function

7.4 Thermal [Temperature 7.4 Thermal [Temperature

Difference] StressDifference] Stress1.1.Thermal [Temperature Thermal [Temperature

Difference] Stress in Heat Difference] Stress in Heat ExchangerExchanger

i. Generation of Thermal T.D. Stressi. Generation of Thermal T.D. Stress

Conditions:

(1)Rigid connection between tube bundle and shell

(2)Thermal T.D. Stress occurs between tube and shell

ii. Calculation of Thermal T.D. Stress

Assumption:

Cold fluid flowing in shell pass, wall T of shell is ts

Hot fluid flowing in tube pass, wall T of tube is tt

In the course of installation tt = ts = to

In the course of operation(1)If the tube and shell can elongate freely

s = s （ ts – to） L

t = t （ tt – to） L(2)If the elongation is limited rigidly, both of them only elongate at the same length difference

Ls

t

At this moment:

Tube is compressed by compressive force Fcomp.

—— Compressive Stress (压应力 ) t occurs on the tube wall

Shell is pulled by tensile force Ftensile

—— Tensile Stress (拉应力 ) S occurs on the shell wall

This kind of stress caused by temperature

difference is called Temperature Difference

Stress or Thermal Stress.

Calculation of Thermal [Temperature

Difference] Stress:

If the deformation caused by temperature

difference is among the range of elasticity,

according to the Hook’s Law:

E E LA

F LA

F

(1) EA

FL

(2) tt

tt AE

FL

(3) ss

ss AE

FL

(4) )( ottt tt

(5) )( osss tt

And ∵

Compressive Length of

tube:Stretched

Length of shell:

Equ. (2) + Equ. (3), and putting Equ. (4) and (5) into it, working up:

(6) 11

)()(

sstt

ossott

AEAE

ttttF

(7) t

t A

F

(8) s

s A

F

∴ Thermal Stress on tube wall

Thermal Stress on shell wall

In these equations:

At —— Total sectional area of heat

exchange tubes, mm2

As —— Area of intersect surface on shell

wall, mm2

Et 、 Es —— Materials’ Modulus of

Elasticity of tube and shell

respectively, MPa

2.Calculation of Tube-to-Tubesheet Joint Load [Pulling-out Force]

Pulling-out Force q is the force that is endured

by the surface of per square meter expanding

perimeter of tubes, MPa

i. Pulling-out Force q p caused by pressure of media

ld

fpq

op

ofArea

Acting

perimeter expanding

media of force

In this equation:

P —— Design Pressure, choosing the larger

value between pressure in tube pass Pt and

pressure in shell pass PS, MPa

l

Pt

PS

do —— Outside Diameter of tube, mm

l —— Expanding Length of tube, mm

f —— Area among per four tubes, mm2

f

In-line Triangular Pitch( 三角形排列 )

a f

Square Pitch Arrangement[In-line Square Pitch]

正方形排列

a

2222

4866.0

460sin oo dadaf

22

4 odaf

In-line Triangular Pitch

In-line Square Pitch

ii. Pulling-out Force qt caused by Thermal Stress

t —— Thermal Stress inside tubes, Mpa

at —— Area of intersect surface of tube wall per tube, mm2

ld

aq

o

ttt

Area

StressThermal

Perimeter Expandingof

ld

dd

ld

dd

o

iot

o

iot

4 4

2222

iii. Superposition of qp and qt

Total pulling-out force

equal to their algebra sum: q = qp + qt

iv. Allowable Pulling-out Force [q] [q] depends on the joint type of expansion joint between tube and tube sheet.

Expanding Structure Type of tube and tube sheet [q] MPa

Non-flanged pipe end and non-notched tube

sheet holes 2.0

Flanged pipe end and notched tube sheet holes 4.0

v. Strength Conditions of Expanding

To assure the expanding joint undamaged and locked, should satisfying:

q —— Pulling-out Force of tubes, MPa

[q] —— Allowable Pulling-out Force, MPa

[q] q [q] q

3.Thermal Stress CompensationCompensation Measures:i. Decreasing the temperature difference

between tube and shell wall(1)Letting the fluid with larger Film

Coefficient of heat transfer flow across the shell pass

(2)When shell wall T tS < tube wall T tt, the insulating measures should be taken to shell wall in order to increase the temperature of it and then to decrease the temperature difference between tube and shell wall.

ii. Eliminating the rigid restriction between shell and tubes

(1)Erecting baffling units ( 挠性构件 ) on shell

—— Expansion Joint

Used in: Fixed Tube Sheet Heat Exchanger

(2)Making the shell and tube bundles expand

freely

Heat Exchangers with this kind of structure

—— Stuffing Box Heat Exchanger

Float Head Heat Exchanger

U Type Tube Heat Exchanger

Chapter 8 Machine Chapter 8 Machine Design ofDesign of

Tower Equipment Tower Equipment (( 塔设备塔设备 ))

7.1 Structure of Tower Set and 7.1 Structure of Tower Set and

Calculating Methods of LoadCalculating Methods of Load

1.Structure of Tower Set

i. Tower Body ( 塔体 )

—— (Cylindrical) Shell Section ( 筒节 )、Heads

( 封头 )、 Connecting Flange ( 连接法兰 )

ii. Internal Parts ( 内件 )

—— Tray ( 塔板 )、 Packing ( 填料 )、 Supporting

Sets ( 支撑装置 )

iii. Support (Saddle) ( 支座 )

—— Skirt Support

iv. Attachments ( 附件 )

—— Manhole ( 人孔 )、 Nozzle of input and

output ( 进出料接管 )、 Apparatus

Nozzle ( 仪表接管 )、 Distributor ( 分布 器 )、 Ladders outside the tower ( 塔外的扶 梯 )、 Platform ( 平台 )、 Insulation ( 保温

层 )

2.Loads and their Calculation Methods

Loads

Media Pressure ( 介质压力 )

Eccentric Load ( 偏心载荷 )

Wind Load ( 风载荷 )

Seismic Load ( 地震载荷 )

Dead Load ( 自重载荷 )

i. Dead Load

m01 —— The mass of shell and skirt support

of tower set

m02 —— The mass of internal parts of tower

set (trays or packing and supporting sets)

m03 —— The mass of insulating materials

m04 —— The mass of platform and ladders

m05 —— The mass of feed in tower

in course of operation

ma —— The mass of attachments such as

manholes, flanges, nozzles, etc.

mw —— The mass of liquid in tower in course

of hydrostatic pressure test

me —— Eccentric mass

Operation Mass:

m0= m01+ m02 +m03 +m04 +m05 +ma +me

Hydrostatic Pressure Test Mass:

mmax= m01+ m02 +m03 +m04 +mw +ma +me

Lifting (Hoisting) Mass [ 吊装质量 ]:

mmin= m01+ 0.2m02 +m03 +m04 +ma +me

ii. Seismic LoadD

ispe

rsin

g th

e M

ass

Model

—— Cantilever （ overhanging beam ） with

multi-mass system

Main factors effecting seismic force:

(1)Types and structure of tower

(2)Basis of tower ( 塔的基础 )

(3)Vibration Mode ( 振型 )

Seismic loads must be considered when design seismic intensity is larger than 7 grade

●

●

●

●

●

●

Mode I (Basic Mode)

●

●

●

●

●

●

Mode II

(1)Horizontal Seismic Force FK ( 水平地震力 )

In tower body, at the position where the

height is hK, the horizontal seismic force

caused by central load ( 集中载荷 ) mK:

(N) 1 gmCF kkzk

mk —— The mass of the section of column

at height hk, kgCz —— combined influent coefficient of structure ( 塔体结构综合影响系数 ) For cylindrical perpendicular equipments: Cz = 0.51 ——seismic influence coefficient ( 地震影响系

数 ) under the basic natural vibration period ( 基本自振周期 ) T1of equipments, confirming its value according to P237 Fig.8-5

T1 —— Basic natural vibration period of equipments under Basic Mode (Mode I), S To equipments with equal diameter and wall thickness:

k —— Mode Factor (Parameter) at the

position whose height is hk, its value is confirmed according to P238 Equation 8-7.

(s) 1033.90 3-31 ie

o

DES

HmHT

(2) Vertical seismic force FV ( 垂直地震力 )

To columns lie in the region with 8 or 9

degree seismic intensity, the vertical seismic

force should be taken into account.

FV of Section 0-0

at the bottom of tower:]

FV of random position

with quality i:

gmF eqvV max00

,2,1(

00

）ni

Fhm

hmF Vn

ikkk

iiIIV

●

●

●

●

●

●

●m1

m2

mi

mn

FV

hi

In these equations:

αV.max. —— Vertical seismic effecting coefficient ( 垂直地震影响系数 )

αV.max= 0.65αmax

meq —— Equilibrium quality of columns ( 当 量质量 ), kg

meq= 0.75 mo

hk —— Height of the functional point with

concentrated quality mk which is above Section I—I referring to the ground(??), mm

The Axial [Longitudinal] Stress σV ( 轴向应力 )

caused by vertical seismic force FV:

ei

VV SD

F

(3)Seismic Bending Moment ( 地震弯矩 )

*Moment that horizontal

seismic force FK acts

on random section:

* section I-I:

●

●

●

●

●

●

●m1

m2

mk

mn

F1

F2

Fk

Fn

hhk

hn

I I

)(

)(...)()( 11

hhF

hhFhhFhhFM

i

n

kii

kknnnnII

E

iii. Wind Load

10)( 6..21

ieioiii DlqfKKp

o o

1 1

2 2

i i

i+1 i+1

n n

l nl i+

1l i

l 2l 1

l o

qo

q1

q2

q3

Pn

Pi+1

Pi

P2

P1

Po

In the equation:Pi —— Wind load N between two neighboring sectionsqo —— Wind Velocity Pressure ( 基本风压值 ) of the position at the height of 10 meter, N / m2, checking the value according to P240 Table 8-4

li —— Distance between the two neighboring

calculating section, m

De.i —— Effective diameter of each portion, m

fi —— Coefficient of height variation

( 高度变化系数 ), checking the

value according to P240 Table 8-5

K1 —— Type??? Coefficient ( 体型系数 ),

K1 = 0.7

K2.i —— Wind Vibration (force) Coefficient

( 风振系数 )

If H ≤ 20 m, K2.i =1.7

If H ＞ 20 m, calculating it from

the following equation:

i

ziii f

K

12

In the previous equation:ξ —— Accretion Coefficient of Fluctuation ( 脉动增大系数 ), checking from P241 Table 8-6

νi—— Effecting Coefficient of the portion No.i Fluctuation (第 i 段脉动影响系数 ), checking from P241Table 8-7

φzi——Mode Coefficient of the portion No.i (第 i 段振型系数 ), checking from P241 Table 8-8

Computation of Wind Bending Moment

( 风弯矩 )

Wind bending moment at random section

of tower:

)2

...(

...)2

()2

(2

21

212

11

niiin

iiii

iii

ii

iiw

llllP

lllP

llP

lPM

4.Eccentric Load When some attachments are

hinging on the top of the tower,

their weight will affect the

tower body generating the

Eccentric Load.

The eccentric moment ( 偏心矩 )

is:

egmM ee

e me g●

Me —— Eccentric Bending Moment

( 偏心弯矩 ), N. m

me —— Eccentric Mass ( 偏心质量 ), kg

e —— Distance from the C.G. (center of

gravity) of eccentric units to C.L.

(center line) of tower, m0

7.2 Stability of Tower its 7.2 Stability of Tower its

Strength VerificationStrength Verification

1.1.Stress inside the tower bodyStress inside the tower body

i. Axial (Longitudinal) Stress i. Axial (Longitudinal) Stress m ( ( 轴向轴向 // 经向应力经向应力 ) )

and Hoop Stress and Hoop Stress (( 环向应力环向应力 ) ) caused by caused by

media pressure (media pressure ( 介质压力 )

ie

i

ie

im

S

PD

S

PD

.

.

2

4

ii. Axial Stress caused by weight loadii2

iei

iiii

SD

gm

.2

iim —— Mass of the part in tower body above random calculating section i-i, Kg

At Section i-i of tower:

iii. Axial Stress caused by bending moment ii3

Section i-i of tower:iei

iiii

SD

M

W

M

.2

max3

4

maxiiM —— Maximum bending moment at

the calculating section

max

max25.0

eii

wii

E

eii

wii

MMM

MMM

2.Stress Combination on sections of tower

There are three types of stress on tower body,

considering various dangerous situation,

combining 1 、 2 、 3, and calculating the

maximum combined stress value to verify the

strength and stability of tower body.

To internal pressure tower ( 内压塔 )

i. The maximum combined axial tensile stress

( 最大组合轴向拉应力 ) (comb.tensile)max is on the

surface toward wind ( 迎风面 ) of tower on

operation.

ii. The maximum combined axial compressive

stress ( 最大组合轴向压应力 ) (comb.comp.)max is

on the leeward side ( 背风面 ) of tower in time

of shut-down.

To external pressure tower ( 外压塔 )i. The maximum combined axial

tensile stress (comb.tensile)max is on the surface toward

wind of tower in time of shut-down.ii. The maximum combined axial

compressive stress (comb.comp.)max is on the leeward

side of tower on operation.

3.Conditions for the stability and strength of tower bodyi. Condition for stability

crcom ][max

min][

][

tcr

K

KB

In the previous equation:

[]cr —— Axial allowable compressive stress

( 轴向许用压应力 ), Mpa

B —— checking from the method on P183

[]t —— Allowable stress of material in design

temperature, Mpa

K —— Coefficient of load combination

( 载荷组合系数 ), K=1.2

ii. Condition for strength

In the above equation:

K —— Coefficient of load combination

( 载荷组合系数 ), K=1.2

—— Weld joint efficiency ( 焊缝系数 )

t

tensile K ][max

Dangerous sections of columns:

0-0 section —— Basis ( 基底 )

1-1 section

—— Sections on the position

of skirt supports and manholes

2-2 section

—— Section on the joint of

cylinder and skirt support

4.Calculating steps for stability and strength of columns

i. Confirming the effective thickness Se and Seh of cylinder and heads according to the calculating pressure

To cylinder:

To heads:

P

DPS

tic

][2

P

DPS

tic

h 5.0][2

valueofround

valueofround

12

1

2

CCS

CSS

CSS

dn

d

CSS ne .

ii. Calculating various loads

According to the location and various work

conditions (Installation, normal operation,

shutdown and hydrostatic pressure test, etc.)

of columns, checking some calculating section

(containing all dangerous sections) to

calculate various loads:

(1)Dead Load; (2)Seismic Load;

(3)Wind Load; (4)Eccentric Load.

iii. Assuming the effective thickness Sei of all

sections in cylinder (can be referred to Se)

Sei >= Se

Assuming the effective thickness of skirt

support shell is Ses

Ses >= 6mm

iv. Calculating the axial stress under various

loads of tower

(1)Axial stress 1 caused by media pressure

(2)Axial stress 2 caused by weight load

(3)Axial stress 3 caused by bending moment

v. Calculating the combined axial stress of tower

under the combined effect of multiplicate loads

should satisfy:

Condition for strength

Condition for stability

Else the thickness must be reassumed until satisfying all the verification conditions.

( and ( max.comb.compmaxlecomb.tensi ））

tK ][maxlecomb.tensi

cr][maxcomb.comp.

iv. Calculating the base ring and anchor

bolt according to the loads under the

above-mentioned work conditions.

5.Verification of stress in hydrostatic pressure

test ( 水压试验 )i. Testing pressure

tT Pp][

][25.1

ii. Calculating all stresses

(1)Hoop stress caused by testing pressure

(2)Axial stress caused by testing pressure

ie

ieiTT S

SDP

.

.

2

)(P)-static liquid(

ie

ieiT

S

SDP

.

.1 4

)(

(3)Axial stress caused by gravity

(4)Axial stress caused by wind bending

moment and eccentric bending moment

iei

ii

SD

gm

.

max2

iei

eii

w

SD

MM

.2

3

4

3.0

iii. Strength condition in hydrostatic pressure test

(1)Hoop stress

(2)Maximum combined axial tensile stress

(3)Maximum combined axial compressive stress

sT 9.0

sK9.0321maxlecomb.tensi

crcomp ][32max

min

9.0][

KB

K scr

7.3 Design

of Skirt

Support 1. Structure of skirt support

Exhaust opening —— 排气孔Access opening of outgoing tube —— 引出管通

孔Bed body —— 座体Manhole —— 人孔Anchor Bolt —— 地脚螺栓Bolt Base —— 螺栓座Base ring —— 基础环Bed —— 基础

2.Design of skirt supporti. Enactment an effective thickness Ses

according to the tower body

ii. Verifying the strength and stability

of dangerous sections on skirt support

Dangerous sections:

(1)Basis section ( 基底截面 )(0-0)

(2)manhole section ( 人孔截面 ) (1-1)

Dangerous Sections is illustrated like the picture:

Checking of longitudinal Checking of longitudinal stress of cylinderstress of cylinder

Longitudinal stress produced by internal or external pressure

Longitudinal stress produced by dead-weight under operating or non-operating condition

Longitudinal stress produced by bending moment

ei

ipD

41

eii

II

D

gm

14.32

eii

II

D

M

2max

3 14.3

4

Checking of stability of cylinderChecking of stability of cylinder Allowable longitudinal compressive stress

of cylinder take the lesser value Maximum combined compressive stress of

cylinder For vessels under internal pressure σ2 +σ3≤[σ]cr MPa For

vessels under external pressureσ1+σ2 +σ3≤[σ]cr MPa

KBKcr t

Checking of tensile stress of Checking of tensile stress of cylindercylinder

Maximum combined tensile stress of cylinder For vessels under internal pressure

σ1-σ2 +σ3≤KФ[σ]t MPa For vessels under external pressure -σ2 +σ3≤KФ[σ]t MPa

OK ?OK ?

When conditions specified can not be satisfied, it is necessary to reassume a new value for effective thickness δe or δei, and the above-mentioned calculations are repeated until requirements are fulfilled.

Checking of stress during Checking of stress during hydrostatic test of vesselhydrostatic test of vessel

Circumferential stress due to hydrostatic pressure of testing liquid

ei

eiiT Dheadliquidof

pressurestaticp

2

Longitudinal stress due to Longitudinal stress due to hydrostatic pressure of testing liquidhydrostatic pressure of testing liquid

Longitudinal stress due to dead-weight during hydrostatic test

Longitudinal stress due to dead-weight during hydrostatic test

Longitudinal stress due to bending moment

ei

iTDp

41

eii

IIT

D

gm

14.32

eii

eII

W

D

MM

23 14.3

3.04

Checking of stressesChecking of stresses

Allowable longitudinal compressive stress

KB

K s

cr

9.0

s9.0 sK9.0321

cr 32

Thickness of SkirtThickness of Skirt

Let the effective thickness of a skirt be , stresses at various selected dangerous sections should be checked according to following Articles.

Bottom sectionBottom section stress at bottom section should be

checked with following equations

tsK

KB

Asb

gmoZ sb

M oo

max

sK

KB

Asb

gmoZ sb

M w9.0

3.0 00

Section at opening on skirtSection at opening on skirt Stress at section 1-1 of man-hole or opening

for larger outlet piping on skirt should be checked with equations

tsK

KB

Asm

gm

Z sm

M

11

0

11

max

s

e

K

KB

Asm

gm

Z sm

M w9.0

3.0 11

OK?OK?

When the above-mentioned conditions can not be satisfied, it is necessary to reassume a new value for effective thickness , and the above-mentioned calculations are repeated until requirements are fulfilled.

Bearing RingBearing Ring

mm

mm

DDDD

isib

isob

400~200

400~200

Dib

Dob

DobDib

Dib

Dis Dis

δesδes

Maximum compressive stress acting Maximum compressive stress acting on concrete foundationon concrete foundation

Thickness of bearing ring without ribs (see Figure)

Thickness of bearing ring with ribs (see Figure)

Am

ZMMAm

ZM

bb

e

oo

W

b

o

b

oo

b gmax

max

max 3.0

bb

bb

max73.1

bs

b

M

6

Calculations of anchor bolts Calculations of anchor bolts

Maximum tensile stress sustained by anchor bolts in foundation should be calculated with equation

take the greater value

bb

eWE

bb

eW

B

A

gm

Z

MMMA

gm

Z

MM

00000

min00

25.0

When ＜ 0,vessel is stable by itself. However, for the purpose of fixing the vessel at a specific position, it is still necessary to provide the foundation with a certain number of anchor bolts.

When ＞ 0,it is imperative to use anchor bolts for the vessel. The thread root diameter d1 of anchor bolts should be calculated with equation

where C4－ corrosion allowance, generally C4=3mm;

n － the number of anchor bolts is first assumed as a multiple of 4;

41 ][14.3

4C

n

Ad

bt

bB

Welded Joint Between Skirt And Welded Joint Between Skirt And ShellShell

Checking 0f lap－

welds between

skirt and shell

Shearing stress of lapShearing stress of lap－－ welds welds should be checked with equation should be checked with equation

tw

W

JJ

W

JJ

A

gm

Z

M][8.00max

tw

W

JJ

W

eJJ

W

A

gm

Z

MM][8.0

3.0 max

buttbutt－－ welds between skirt and welds between skirt and shellshell

Checking of buttChecking of butt－－ welds welds between skirt and shellbetween skirt and shell

Tensile stress of butt－ welds should checked with equation

tW

esit

JJ

esit

JJ

D

gm

D

M][6.0

14.314.3

4 02

max