structural analysis and design of process equipment (t.l)

8/16/2019 Structural Analysis and Design of Process Equipment (T.L)

1/361


2/361

7

I

E

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t

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--1t. .

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N*w

York

Chichester

STRUCTURAL

ANALYSIS AND

DESIGN

OF

PROCESS

EQUIPMENT

Mqon H.

Jowod

Nooter

Corporation

St. Louis,

M

issouri

Jomes R. Fqrr

Babcock

&

Wilco.r

Company

Barberton,

Ohio

A

Wiley-lnterscience

Publicqtion

JOHN

WILEY

&

SONS

Brisbone Toronto

Singopore


3/361

Copyright

O

1984 by

hhn

Wilev &

Sons,

Inc

All

righis

reserve{].

Publishcd

simultaneously

in Canada

Reproduction

or

transiation

()f

any

part oi

this

work

hcyond that

permitted

by Secton

107

or

108

of

ihe

It)?6 linited States

Copyrighl

Act

wrthout

lhe

permrssron

,,1

rlr .i't)\rfi hl owner

is unl.rwlul

Requests

iot

|

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,,

lrrrhcr infomati,)n

sbould

be addrcssed

lo

'

|

',

L

,

, I'1

t,.,rlrjitrrl.

John

Wil'v

&

Sons,

lnc

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.r

, ,

,'r',

,

(

nitrl.'riins

in l\rhlication

Data:

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Farr.

James

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lrllc

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Barbara


4/361

PREFACE

We

wrote this book to serve three

purposes.

The first

purpose

is to

provide

structural

and mechanical engineers associated

with

the

petrochemical

industry

a

reference

book

for the analysis and design of

process

equipment. The second

is to

give

graduate

engineering

students a concise

introduction to

the

theory of

plates

and

shells and its

industrial

applications,

The

third

purpose

is to

aid

process

engineers in understanding the background of

some

of the design equa-

tions in

the

ASME Boiler

and

hessure

Vessel

Code.

Section

VIII.

The topics

presented

are

separated

into four

parts.

Part 1 is intended

to

familiarize

the designer

with

some

of

the

common "tools of

the

hade."

Chapter

I

details

the

history

ofpressure

vessels

and

various

applicable

codes from

around

the world.

Chapter 2

discusses

design specifications furnished in

purchasing

process

equipment

as

well

as

in various

applicable codes. Chapter 3

establishes

the strength criteria used in different codes and the theoretical background

needed

in developing

design equations in

subsequent

chapters.

Chapter

4 in-

cludes

different

materials of construction

and toughness considerations.

Part

2

is divided into three chapters outlining the basic

theory

of

plates

and

shells.

Chapter 5 develops the membrane

and

bending

theories

of cylindrical

shells. Chapter

6 discusses

various

approximate theories

for

analyzing

heads

and

transition

sections,

and Chapter 7 derives the equations

for

circular

and rectan-

gular plates

subjected

to various loading and support conditions.

These three

chapters

form

the basis

from which

most

of

the design equations

are derived in

the

other

chapters.

Part 3, which consists

of

flve

chapters,

details

the design and analysis of

components.

Chapters

8 and 9 derive the

design equations established

by

the

ASME

Code, VI[-l and

-2,

for cylindrical

shells as

well

as

heads and transition

sections.

Chapter 10

discusses

gaskets,

bolts, and flange design. Chapter ll

presents

openings

and their

reinforcement;

Chapter

l2

develops

design

equations

tor

support systems.

Part 4 outlines

the

design

and analysisof some

specialized

process

equipment.

Chapter

13

describes

the

design

of flat bottom tanks; Chapter

14

derives

the


5/361

cquations

for analyzing

hest

transfer

equipment.

Chapter

l5 describes

the

theory

of

thick

cylindrical

shells in high-pressure

applications.

Chapter

l6 discusses

the

stress

analysis

of tall

vessels.

Chapter

17

outlines

the

procedure

of

the ASME

Code,

VI[-l,

for designing

rectangular

presswe

vessels.

To

simplify

the use of

this

book

as a

reference,

each

chapter

is written

so that

it stands

on

its

own as

much

as

possible. Thus,

each

chapter

with

design or other

mathematical equations

is written

using

terminology

frequently

used in industry

for that

particular

type of equipment

or component

discussed

in the

pertinent

chapter.

Accordingly,

a summary of

nomenclature

appears

at the end

of

most

of

the chapters

in which

mathematical

expressions

are

given.

In

using

this book

as

a

textbook for

plates and shells, Chapters

3,

5,6

md7

form the basis for

establishing

the basic theory.

Instructors can

select

other

chapters to

supplement

the

theory

according

to the background

and

needs

of the

graduate

engineer.

In

deriving the background

of

some

of the equations

given

in the

ASME

Boiler

and

Pressure

Vessel Code,

attention

was

focused

on Section

VIII,

Di-

visions

1

and

2. Although these

same

equations do

occur

in

other

sections

of

the

ASME Code,

such

as the Power

and Heating Boilers,

no consideration

is

given

in this book regarding

other

sections

unless specifically

stated'

MAAN JAWAD

JAMES FARR

Saint

Louit,

Missouri

Barberton, Ohio

September

1983

ACKNOWLEDGMENTS

We are

indebted to many

people

and

organizations

for

their help

in

preparing

this

book. A

special

thanks

is

given

to

the

Nooter Corporation

for

generous

support

rluring

the

preparation

of the

manuscript.

Also

a special

thanks

is

given

to

the

American Society

of Mechanical

Engineers

for supplying

many of

the

illustra-

tions

used

in this

book and also

to the American

Petroleum

Institute

and the

Tubular

Exchangers

Manufacturers

Association.

We

also

give

thanks to

Messrs.

W.

D. Doty, G.

Hays, G. G.

Karcher, T.

W.

[,odes,

H. S. Olinger,

and

R.

F. O'Neill

for

reviewing

the

manuscript,

and to

Mr. W. H.

Schawacker

for supplying

many

of

the

photographs.

We would

also

like

to extend

our

appreciation to

Mrs' Y.

Batteast

for

typing

portions

of

the

manuscript.

M. J.


6/361

PART

I

Chopter

I

l.l

1.2

CONTENTS

BACKGROUND

AND

BASIC

CONSIDERATIONS

Hisiory

ond

Orgonizotion

of

Codes

Use

of

Process

Vessels

and

Equipment

History

of

Pressure

Vessel

Codes

in

the

United

States

Organization

of

the

ASME

Boiler

and

Pressure

Vessel

Code

Organization

of

the

ANSI

B31

Code

for

Pressure

Piping

Some

Other

Pressure

Vessel

Codes

and

Standards

in

tie

United

States

Worldwide

Pressure

Vessel

Codes

References

BibliograPhY

3

4

l3

14

14

l5

l5

t6

16

1.3

1.4

1.5

1.6

8

9

'r0

ll

Chopter

2

Selection

of

Vessel,

Specificotions'

Reports,

ond

Allowoble

Slresses

Selection

of

Vessel

Which

Pressure

Vessel

Code

Is

Used

Design

Specifications

and

Purchase

Orders

Special

Design

Requlrements

Design

RePons

and

Calculatjons

Materials'

SPecifi

cations

2.1

2.2

2.3

2.4

2.5

2.6


7/361

2.7

2.8

2.9

2.10

2.11

2.12

Chopter

3

Dcsign Data tbr

Ncw Materials

Factors

of Safety

Allowable

Tensile

Stresses

in

the ASME Code

Allowable

Extemal Pressure

Stress

and

Axial

Compressive

Stress

in

the ASME Boiler

and Pres-

sure Vessel Code

Allowable

Stresses

in

the

ASME

Code

for

Pressure

Piping B31

Allowable

Stress

in Other

Codes of the World

References

Strength Theories,

Design

Criierio,

ond

Design

Equotions

Strength

Theories

Design Criteria

Design

Equations

Stress-Strain Relationships

Strain-Defl

ection Equations

Force-Stress Expressions

References

Bibliography

Moteriqls of

Construction

Material

Selection

4,l.l

Corrosion

4.1.2

Strength

4. 1

.3

Material Cost

Nonferrous

Alloys

4.2.1

Aluminum Alloys

't7

17

t7

l9

22

22

26

3.1

3.2

3.3

3.4

3.5

3.6

29

30

3l

33

33

35

39

42

43

45

46

46

49

52

53

53

3J

56

56

60

6l

63

68

Chopter

4

4.1

4.2

4.2.2

Copper

and Copper Alloys

4.2.3 Nickel

and High-Nickel

Alloys

4.2,4

Titanfum

and

Zirconium Alloys

4.3

Ferrous

Alloys

4.4

Heat Treating

of

Steels

4.5

Brittle

Fracture

4.5.

I

ASME

Presssure

Vessel Criteria

4.6

4.7

4.5.2

'l'heory

ol' Brittle

Fracture

4.5.3

Hydrostatic

Testing

4.5.4

Factors Influencing

Brittle

Fracture

Hydrogen Embrittlement

Nonmetallic

Vessels

References

Bibliography

ANAIYSIS

OF

COMPONENTS

Slress

in

Cylindricol

Shells

Ends

5.3.3

Pressure

on Ends

Only

Thermal

Stress

5.4.1

Uniform

Change

in Temperature

5.4.2

Gradient in

Axial Direchon

5.4.3 Gradient

in Radial

Direction

Nomenclature

References

Bibliography

CONTENTS

xlll

70

74

75

76

77

78

79

8l

83

116

lr8

119

124

127

r30

137

r38

139

PART

2

Chopfer

5

5.1

5.2

5.3

5.4

Stress

Due

to Intemal

Pressure

84

Discontinuity

Analysis

92

5.2.1 Long

Cylinders

96

5.2.2 Short

Cylinders

lO7

Buckling

of Cylindrical

Shells

I

14

5.3.1

Uniform

Pressure

Applied

to

Sides

Only

114

5.3.2

Uniform

Pressure

Applied

to

Sides

and

Chopter

6 Anolysis

of

Formed Heods

ond

Tronsition

Sections

6.

I

Hemispherical

Heads

6.1

.

I

Various Loading

Conditions

6.1.2 Discontinuity

Analysis

6.1.3 Thermal

Stress

6.1.4 Buckling

Strength

141

142

146

r52

158

159


8/361

xiv

CONTENTS

6.2

6.3

6.4

Chopter 7

7.1

7.2

7.3

7.4

PART 3

Ellipsoidal

Heads

Torispherical

Heads

Conical

Heads

6.4.1

Unbalanced

Forces at Cone{o-Cylinder

Junction

6.4.2

Discontinuity

Analysis

6.4.3

Cones

Under Extemal

Pressure

Nomenclature

References

Bibliography

Stress

in Flot

Plotes

Introduction

Circular

Plates

Rectangular

Plates

Circular

Plates

on Elastic

Foundation

Nomenclature

References

Bibliography

DESIGN OF

COMPONENTS

163

167

r68

169

172

175

178

'r80

t8t

183

184

184

193

197

200

201

201

203

205

206

208

218

226

23r

235

238

240

240

241

Chopter

8

Design

of

Cylindricol

Shells

8.1

ASME

Design

Equations

8.2

Evaluation

of Discontinuity

Stresses

8.3

ASME hocedure

for Extemal

Pressure

Design

8.4 Design

of Stiffening

Rings

8.5

Allowable

Gaps

in

Stiffening

Rings

8.6

Out-of-Roundness

of Cylindrical

Shells under

External

Pressure

8.7

Design

for Axial Compression

Nomenclature

References

Bibliography

Chopier

9 Design

of

Formed

Heods

ond Tronsifion

Seclions

Introduction

ASME

Equations

for Hemispherical

Head

Design

ASME Design

Equations

for Ellipsoidal

and

Flanged and

Dished

Heads

9.3.1

Ellipsoidal

and

Torispherical

Heads

Analysis

due to Intemal

Pressure

9.4.2

Conical

Shells

under

External

Pressure

9.4.3

ASME Simplification

of Discontinuity

Analysis

due to

External

Pressure

Nomenclature

References

Bibliography

CONTENTS

xv

243

244

247

249

256

26r

261

265

266

267

9.1

9.2

9.3

under External

Pressure

255

9.4

ASME

Equations

for Conical

Head

Design

256

9.4.1

ASME Simplification

of Discontinuity

Chopter

l0

l0.l

ro.2

Bfind

Flonges,

Cover

Ploles, ond

Flonges

269

Introduction

270

Circular

Flat Plates and

Heads

with Uniform

Loading

ASME

Code Formula

for Circular

Flat

Heads

and

Covers

r0.3

10,4

Comparison

of Theory

and

ASME Code

Formula

for Circular

Flat

Heads and Covers

without

Bolting

10,5

Bolted

Flanged Connections

10.6 Contact

Facings

1O.7 Gaskets

10.7.1

Rubber

O-Rings

10.7.2

Metallic

O- and C-Rings

10.7.3

Compressed

Asbestos

Gaskets

10.7.4

Flat Metal

Gaskets

10.7.5

Spiral-Wound

Gaskets

274

276

278

278

279

281

281

281

282

283

285


9/361

CONTENTS

1O.7.6 Jacketed

Gaskets

10.7.7

Metal Ring

Gaskets

10.7.8 High-Pressure

Gaskets

10.7.9 Lens

Ring

Gaskets

'10.7.

I0

Delta

Gaskets

10.7.1I

Double-Cone

Gaskets

I0.7.

l2

Gasket Design

10.8

Bolting Design

10.9

Blind Flanges

10. 10

Bolted Flanged Connections

with Ring-Type

Gaskets

l0.l

I

Reverse Flanges

10. l2

Full-Face

Gasket Flange

10. l3

Flange Calculation

Sheets

10, l4

FlatFace

Flange with Metal-to-Metal

Contact

Outside

of

the Bolt Circle

10.15

Spherically Dished Covers

Nomenclature

References

Bibliography

285

285

285

286

287

288

290

292

294

298

307

310

317

317

324

330

332

332

335

336

338

343

346

349

359

368

379

383

Chopter

I I

Openings,

Nozzles, ond Externol

[oodings

General

Stresses and Loadings

at Openings

Theory

of Reinforced

Openings

Reinforcement

Limits

I I .4.

I

Reinforcement

Rules for ASME.

Section I

I I

.4.2 Reinforcement Rules

for ASME,

Section VIII, Division

I

l

l.4.3

Reinforcement

Rules for ASME,

Section

VIII,

Division 2

I I

.4.4

Reinforcement

Rules for

ANSUASME

831. I

I

L4.5 Reinforcement

Rules for ANSI/ASME

83 t.3

ll.l

I 1.2

I 1.3

'|

1.4

I I.5

I 1.6

1t.7

CONTENTS

xvii

Ligament Efficiency of Openings in

Shells

387

Fatieue Evaluation of

Nozzles

under

Internal

Chopter l2

12.1

12.2

Pressure

Extemal Loadings

11

.7.1 Local

Stresses

in the Shell or Head

I 1.7.2

Stresses

in

the

Nozzle

Nomenclature

References

Bibliography

Vessel

Supports

Introduction

Skirt and Base Ring Design

12.2.1

Anchor Chair Design

12.3 Design of Support Legs

12.4 Lug-SupportedVessels

12.5

Ring

Girders

12.6

Saddle Supports

Nomenclature

References

Bibliography

PART

4 THEORY

AND

DESIGN

OF SPECIAL

EQUIPMENT

Chopter l3 Flot Bottom Tonks

13.1

Introduction

13.2 API

650

Tanks

13.2.1 Roof Design

13.2.2

Shell

Design

13.2.3 Annular Plates

13.3

API

620

Tanks

13.3.

I

Allowable

Stress

Criteria

I 3.3.2

Compression Rings

13.4 ANSI

896.1

Aluminum Tanks

13.4.

I

Design Rules

392

394

394

407

415

416

417

421

422

423

434

438

442

443

449

456

456

457

459

461

462

462

462

470

476

482

487

490

496

496


10/361

-

xviii

coNTENrs

13.5

AWWA

Standard

D100

References

BibliograPhY

Chopter

14

Heql

Tronsfer

Equipmeni

l4.l

TYPes

of

Heat

Exchangers

14.2

TEMA

Design

of

Tubesheets

in

U-Tube

Exchangers

14.3

Theoretical

Analysis

of

Tubesheets

in

U-Tube

Exchangers

14.4

Background

of

the

ASME

Design

Equations

for

Tubesheets

in

U-Tube

Exchangers

14.5

Theoretical

Analysis

of

Fixed

Tubesheets

14.6

TEMA

Fixed

Tubesheet

Design

l4'6'l

Local

Equivalent

Pressure

l4'6'2

General

Equivalent

Pressure

14'6'3

Relationship Between

Local

and

Equivalent

Pressure

14.7

ExPansion

Joints

Nomenclature

References

BibliograPhY

Chopfer

15

Vessels

for

High

Pressure

15.l

Basic

Equations

15.2

Pres$essing

of

Solid

Wall

Vessels

15.3

Layered

Vessels

15.4

Prestressing

of

Layered

Vessels

Nomenclature

Biblio$aphY

Chopter

16

Toll

Vessels

l6.l

DesignConsiderations

16.2

Earthquake

Loading

16.3

Wind

Loading

16.3'1

Bxternal

Forces

from

Wind

Loading

498

499

499

501

502

505

508

514

519

523

523

527

533

537

537

538

539

541

541

543

547

558

562

563

565

566

567

573

573

CONTENTS

I

6.3.2

Dynamic

Analysis from

Wind Effects

16.4

Vessel Under Intemal

Pressure

Only

16.5

Vessel

Under Internal

Pressure

and Extemal

Loading

16,6

Vessel Under External Pressure

Only

16.7

Vessel

Under

External Pressure

and

External

Loading

References

Bibliography

Chopter

17

Vessels

of

Noncirculor

Cross

Section

17,1 Types

of

Vessels

17.2

Rules in

Codes

17.3

Openings in Vessels

with

Noncircular

Cross

Section

601

17.4

Ligament

Efficiency for

Constant

Diameter

Openings

601

17.5

Ligament Efficiency

for

Multidiameter

Openings

Subject

to

Membrane

Stress

603

17,6

Ligament

Efficiency

for

Multidiameter

Openings

Subject

to Bending

Stress

606

Design Methods

and Allowable

Stresses

610

Basic

Equations

612

Equations

in

the

ASME

Code, VIII-I

619

Design

of

Noncircular

Vessels

in

Other Codes

626

I 7.

10.

I

Method

in

Swedish Pressure

Vessel

Code

627

I

7.

10.2

Design by

Lloyd's

Register

of Shipping

Rules

630

References

633

Bibliography

633

577

581

595

596

601

585

588

591

593

593

17.7

17.8

17.9

t7.to

APPENDICES

635

Appendix

A

Guide to Various

Codes

636

Appendix

B

Sample of Heat Exchanger

Speciflcation

Sheet

U6

Appendix

C

Sample of an API Specification

Sheet

648


11/361


12/361

CHAPTER

HISTORY

AND

ORGANIZATION

OF

CODES

-OtD

TIMERS

[(lop)

Courtesy

Bobcock

&

Witcox

Compony,

(bol|or,)

(

iuroly

,",r,,, ,

,"r,,,,r,,,1

2


13/361

HISIORY AND

ORGANT/N

rION

Of

CODTS

].4

ORGANIZATION OF

THT

ANSI

83

CODI]

IOR

PRISST'RE 7


14/361

Irr

l(X)(r,

l'r.llre'cx;rkrsi.rr

irr

.

rlrr)c

llrel.ry

i'l,yrrrr.

Massirclrrtsc.s,

r.cs.ltcd

irr

dcalh,

injrlry,

a|ld

cxtcnsivc

propcrty

darragc.

Aticr

this

accidcnr,

the

Massa_

clrusctt$ governor

directed

the fbrmation

of

a Board

of Boiler

Rules.

The

first

set

of

rules

for

the

design

and

construction

of

boilers

was approved

in

Massachusetts

on

August

30,

l9O7

. This

code

was

three pages

long- -

In

1911,

Colonel

E.

D. Meier,

the president

of-the

American

Society

of

Mechanical

Engineers,

established

a

committee

to

write

a

set

of

rules

tbr

the

design

and

construction

of

boilers

and

pressure

vessels.

On

February

13,

1915,

the

first

ASME

Boiler

Code

was

issuid.

It was

entitled

,,Boiler

Construction

Code,

1914

Edition."

This

was

the

beginning

of

the

various

sechons

of

the

ASME

Boiler

and

Pressure Vessel

Code,

which ultimately

became

Section

1,

Power

Boilers.3

^

The

first

ASME

Code

for

pressure

vessels

was

issued

as

,,Rules

fbr

the

construction

ofUnfired

Pressure

Vessels,',

Section

VIII,

1925

edition.

The

rules

applied

to

vessels

over

6 in.

in diameter,

voiume

ove.

1.5

ft3,

and

pressure

over

30

psi.

In

December

1931,

a

Joint

API_ASME

Committee

wis

ibrmed

to

develop

an unfired

pressure

vessel

code

for

the petroleum

indusiry.

.l.he

first

edition

was

issued

in

1934.

For

the

next

17 years,iwo

separate

unfiied

pre;sure

vessel

codes

existed.

In

1951,

the

last

API_ASME

Code

;as

issued

as

a

separare

document.a

In

1952,

the

two

codes

were

consolidated

into

one

code_the

ASME

Unfired

Pressure

Vessel

Code,

Section

VIII.

This

continued

until

the

196g

edition.

At

that

time,

the

original

code

became

Section

VIII,

Oivislon

I

,

pres_

sure

Vessels,

and

another

new part

was

issued,

which

was

Seciion

VI

II, Division

2,

Alternatiye

Rules

for

pressure

Vessels.

The

ANSUASME

Boiler

and

pressure

Vessel

Code

is issued

by

the

American

Society

of

Mechanical

Engineers

with

approval

by

the

American'National

Stan_

dards

lnshtute (ANSI)

as

an

ANSI/ASME

document.

One

or morc

sections

of

the

ANSI/ASME

Boiler

and

pressure

Vessel

Code

have

been

established

as the

legal

requirements

in

47

of

the 50

states

in

the

United

Str,",

,,",f

in

all

the

prwinces

of

Canada.

Also,

in

many

other

countries

of

the

worlti,

the

ASME

Boiler

and

Pressure

Vessel

Code

is

used

to

construct

boilcrs

arrc

pressure

vessels.

In

the

United

States

most

piping

systems

are

built

to

the

ANSI/ASME

Code

for

P.ressure

Piping

B3l

. There

are

a

number

of different

piping

couc

sectrons

for

different

types

of

systems.

The piping

section

that

i"

,ir".i

tiu.

boiiers

in

combination

with

Section

I of

the

ASME Boiler

and pressure

Vcsscl

(ixle

is the

o09

fo1 -o1er

Piping,

831.1.5

The piping

secrion

thar

is olicn

uscrt

with

Section

VIII,

Division

I

,

is

the

code for

-Cheniical

piant

and

lretnricLrrrr

t{clinery

Piping,

831.3.6

I,3

ORGANIZATION

OF

THE

ASME

BOILER

AND

PRESSURE

VESSET

CODE

The

ASME

Boiler

ancl

pressure

Vessel

Code is

clivided

into

many

sectrons,

divisions,

parts,

and subparts.

Some

ofthese

sections

relat",u

"

ro"lrti.

tina

of

T

cqUipl

c|l{

irrrtl

ir;lrlielrliorr;

olllcrs

fctalc

lo

sl)ccilic

Illillcliltls

all(l tlrclll{xls

l()f

applicatiOn

rn(l cot)trol

ol cclt'tiprnctrt;

lnd

tlthcrs

rclate ttt

care

lnd

inspoctioll

()l

installed cquipnrctrt.

'l'hc

tirllowing

sections

specifically

relate to

boiler and

pressure vessel

design

and

constructlon:

Section

I.

Power

Boilers

(one

volume)

Section

III

Division

1.

Nuclear

Power

Plant

Components

(7

volumes)

Division 2.

Concrete

Reactor

Vessels

dnd Containment

(one

volume)

Code

Case

Class

I

Components

in

Elevated

Temperature

Service

(tn

N-47

Nuclear

Code

Case

book)

Section

IV,

Heating

Boilers

(one

volume)

Section VIII

Division

1.

Pressure

Vessels

(one

volume)

Division

2.

Alternative

Rules

for

Pressure Vessels

(one

volume)

Section

X.

Fiberglass-Reinforced

Plastic Pressure

Vessels

(one

vol-

ume)

A

new

edition of

the ASME

Boiler and

Pressure

Vessel

Code

is issued on

July

I

every

three

years and

new

addenda

are issued

every

six

months

on January

I

and

July

l.

A

new edition

incorporates

all

the

changes

made

by

the

addenda

to

the

previous

edition;

it does

not

incorporate,

however,

anything

new

beyond that

coniained

in the

previous

addenda

except

for some

editorial

corections

or a

change

in

the

numbering

system.

The

new

edition of

the

code

becomes

manda-

tory when

it appears.

The addenda

are

permissive

at

the

date

of

issuance

and

become

mandatory six

months

after that

date.

Code

CasesT

are also

issued

periodically after

each

code meeting

They

contain

permissive rules

for

materials

and

special

constructions

that

have not

been

sufficiently

developed

to

place them

in

the code

itself.

Finally,

there

are the

Code

Interpretations8

which

are

issued

every

six

months These

are

in the form

of

questions and

replies that

further

explain

items

in the

code

that

have

been

misunderstood.

I.4

ORGANIZATION

OF

THE

ANSI

83I CODE

TOR

PRESSURE

PIPING

In

the United

States

the

most

frequently

used

design

rules

for

pressure

piping

are

the

ANSI

83l

Code

for Pressure

Piping.

This

code

is divided

into

many

sections

for different

kinds

of

piping applications

Some

sections

are

related

to

specific

sections

of

the

ASME

Boiler

and

Pressure

Vessel

code

as

follows:


15/361


16/361


17/361

CHAPTE

R

2

SELECTION

OF

VESSEL,

SPECI

FICATIONS,

REPORTS,

AND

ALLOWABLE

STRESSES

l3


18/361

l4

SttECTlON

OF

VESSIL,

SPECIFICAIl()N".

rtlr",lrr'.,

nND

ALLOWABLE

STRESSES

2.1

SELECTION

OF

VTSSI

I

Although

nrlrrly

lttr

l t.

,,'rrlrl,rt,

1,,

llr(

\(

lL'clion

of

pressure

vessels,

the

two

basic

r.r;rrirr.rrfrrt,, tlr,rt

,rll,,

t tlr, ,( [.r

lion

are safety

and

economics.

Many

it(.Drs

i||r.

r

rr,,rrI

r,,l

rr,tr,r',

rrrrrtcrials'

availability,

corrosion

resistance,

lrltllrrl,,

rrr,

rrl,tlr r11,

.

.rr,l

rrrrrgnitudes

of loadings,

location

of installation

rr, lr,lprl,

(

rnl

I,r.r,l'rt'

,"r,t

r.rrr'(lrquake

loading,

location

of fabrication_(shoD

"r

1.,

l,lr

t",

rrr,,r ,,t

\i.,,s(.1

installation,

and

availability

of

labor

supply

at the

\l

rrt,

rrr,

r, ,r'.rrr1'

rrsc

of

special

pressure

vessel

in

the

petrochemical

and

other

rrr,lrr rl, ,

rtr. ;rvrilability

of

the proper

materials

is

fast

becomrng

a

maJor

1,r,,t,1,,,'

I

lr(.

nrost

usual

material

for vessels

is

carbon

steel.

Many

other

special_

r,,,

l

r

r,rr{

rlls

iLre also being

used

for

corrosion

resistance

or

the abilily

ro conmln

.r

tlrrrr I wrthout

degradation

of

the

material's

properties.

Substitution

of

materials

r'.

I

x

(.vl

lent

and cladding

and

coatings

are used

extensively.

The design

engineer

rrrrrst

lrc

in

communication

with

the process

engineer

in

order

that all

materials

rrsctl

will

contribute

to the

overall

integrity

of

the

vessel.

For

those

vessels

that

rctluire

field

assentbly

in

contrast

to

those

that

can

be

built

in the

shop, proper

(luality

assurancc

must

be established

for

acceptable

welding

regardless;f

ihe

adverse

condilions

under

which

the

vessel

is

made_

provisions

must

be

estab_

lished

for

ftrrliography,

stress

relieving,

and other operations required

in

the

field.

For

thost.

vcssels

that

will

operate in

climates

where

low

temperatures

are

encounlcr((l

r)f

contain

fluids

operating

irt

low

temperatures,

special

care

must

be

takc

rr

Ir

crrsure

impact

resistance

of

the materials

at low

timperatures.

To

ohlirirr

tlrs

l,r()l)crty,

the

vessel may require

a

special

high-alloy

steel,

nonferrous

rrrirlcrirrl,

rrr some

special

heat

treatment.

2.?

WHICH

PRESSURE

VESSEL

CODE

IS

USED?

'l

lrc

lrrst

consideration

must

be

whether

or not

there

is

a

pressute

vessel

law

at

llrc lo(

irt

ion

of

the

installation.

If

there

is,

the applicable

iodes

are stated

in

the

l:rw.

ll

thc

jurisdiction

has

adopted

the

ASME

Code,

Section

VIII,

the

decision

rrrly

bc

narowed

down

to selecting

whether

Division

I

or Division

2

is used.

.

I'here

are

many opinions

regarding

the

use of

Division

I

versus

Division

2,

but the

"bottom

line"

is

economics.

In the

article

,.ASME

pressure_Vessel

Code:

Which

Division

to

Choose?",r

the

authors

have

listed

a

number

of factors

for

consideration.

Division

I

uses

approximate

formulas,

charts,

and graphs

in

simple

calculations.

Division

2,

on

the

other

hand,

uses

a

complex

methocl

of

fbrmulas,

charts,

and

design-by-analysis

which

must

be describcd

in

ir stress

report.

Sometimes

so

many additional

requirements

are

addcd

lo tltc

rriuirnum

specifications

of

a

Division

I

vessel

that

it might

bc rnorc

ccorrorrrir.rrl

to supply

lu I)ivision

2

vcssel

and

lake

advantage

of thc

highcr

itlL)rvrl)l(.

strrsscs.

2.4

SPECIAL

DESIGN

REQUIREMENTS

2.3

DESIGN SPECIFICATIONS AND

PURCHASE ORDERS

Currently,

the

only

pressure

vessel

code, exclusive of

the

ASME

Code,

III-l-

NB, Nuclear Vessels, which specifically

requires

formal

design

specifications

as

part

of

the

code

requirements is the

ASME

Code,

VIII-2, Alternative Rules

for

Pressure

Vessels.

This

code

requires a

User's

Design

Specification to

be

pre-

pared

and

certified

by

a

registered professional

engineer experienced

in

pressure

vessel

design.

This certification

by

the professional engineer

is

given on

the

ASME Manufacturer's

Data

Report, Form

A-

1.

The manufacturer

is

responsible

for retaining

the

User's Design Specification

for five

years.

For

other

codes

and standards, design

specifications and

design requirements

are not

well

defined.

For

the

ASME

Code,

VIII-1,

there is no specific

statement

that any design

specifications

are

required. The

only

indication

of

some sort of

design specifications

is

the

list of minimum

loadings

in

UG-22

that

is

considered

for all

construction

.

Sectron

l,

Power

Eoilers,

is

less definitive

on what loadings

are

necessary

to consider

and what

shall be

included in

a design

specification or

purchase

order.

PG-22

of

Section I

states

that loadings that

cause stresses

to

go

higher than 107o

above those

stresses

caused by internal

design

pressure

shall

be

considered.

The Manufacturer's Data Report, Form

U-1

for

the

ASME

Code,

V I-1,

requires many items

to be

listed, which

means that most of the basic

design

information

must be given

in

a

design specification

or

purchase

order.

Although

some codes

help the

purchaser

regarding what data are

needed

for

inclusion in

the design

specifications,

this

is

usually

done

by

mutual

agreement

between the

purchaser

and

the

manufacturer.

"For

those

process

vessels

that

do

not

have

a

"suggested"

list of

items

in

design

requirements

and

specifications

as

part

of

code

requirements,

it

is

necessary to

establish

them

in

the

purchase

order or contract

agreement.

The contract infor-

mation is

supplied by

the

purchaser

or

user

with the manufacturer's help as

to

what

is

needed and

what shall be considered.

Some

design standards

help

the

user and

manufacturer by offering fill-in forms

that specifically list

the

require-

ments for designing

a

process vessel.

Design specification forms for a heat

exchanger

built to

the standards

of

the

Tubular Manufacturers

Associationz are

given

in

Appendix

B and

lor

an

API

Srandard

650

Storage

Tanki

are

given

in

Appendix

C. It is always

necessary

to maintain

a

document containing

design

speciflcations

so

that a

permanent

record is

kept for

reference.

Often on a

large

process

vessel, some loadings from

attached or supported

equipment are not

known

until after

the

job

has

started.

2.4

SPECIAL DESIGN REOUIREMENTS

In addition

to the

standard

information required on all units, such

as design

pressure,

design temperature,

geometry,

and size, many other items

of

infbrma-

tion

are necessary

and

must

be

recorded. The

(xrrrosion

and

erosion

amounts

arc

l5


19/361

16

sfl,tcTtoN

Ot

Vtssll,

st,tctt

tcaTtoNs,

RfpoRTs,

AND

AU-OWABLE

STRTSSES

l, lx'

*,u,.,,

rrrrrl

rr

srrrtirlrlt.

r'irlcri.l

uld

method

of

protection

are to

be

noted.

The

lyl)c

(,l

lllrirl

tlrrrl

will

lrc

t,0|llainctl,

such

as lethal,

must

be

noted

because

ofthe

rcqltitc(l

slx\.ili(.rk.sigrr

tlctaiis.

Supported

position,

vertical

or honzontat,

and

s[pl)oll

lor.rrtiorrs

rlusl

bc

listed

as well

as

any

iocal

loads

from

supported

crltip,rc,t

rrrrtl

piping.

Site

locatiorr

is given

so

that

wind,

*o*,

una

"u.tnquut"

cquircntcots

ctrn

lre

determined.

Impact

loads

and

cyclic

requirements

are

also

inclurlcd.

lirr

thc

ASME

Code,

VIII-2,

a

statement

as

to

whether

or

not

a tatigue

:::'.r,:::'.-"111r'llo

according.to

AD_160

is

given.

rf

u

rutilu"

analysis

is

rc(lurrc(t.

lhe

specitlc

cycles

and

loadings

will

be given.

In

addiiion,

the

design

spccilications

state

whether

or

not

certain

loadings

ire

sustained

or

transrent.

The

allowable

stresses

vary

with

the

type

of

loadinls.

2.5

DESIGN

REPORTS

AND

CATCULATIONS

T:,1YE

,C"1..

.VII.2.

requires

a formal

design

report

with

rhe assumptions

rn.the

User's

Design

Specification

incorporated

in

the

stress

analysis

calcu_

lations.

These

calculaiions

are prepared

and

certified

by

a

registered

professional

engrneer

experienced

in

pressure

vessel

design.

As

with

the

Usir,s

Design

Specification,

the

Manufacturer's

Design

Report

is

mandatory

and

the

certification

reported

on

the

Manufactu.".i

Datu

Repo.t.

This

is kept on

file by

the manufacturer

for

five

years.

-

For

vessels

not

requidng

design

reports,

the

manufacturer

has

available

for

the-

Authorized

Inspector's

review

those

necessary

calculations

for

satisfying

U-2(g)

or

other

design

formulas.

The pressure

vessel

design

sheets

should

contain

basic

design

and

materials

data

and

at

least

the

basic

calculations

of

pressure

parts

as

given

in

the

design

formulas

and procedures

in

the

applicable

:_od^.

onT.nd1d_fg.

a simple

vessel,

an

example

of

calculation

sheets

rs

given

ll ilp"yiT

D. This

example

depicts

only

those

calculations

that

are required

for

the

Authorized

Inspector

and

for

construction.

Other

vessels

may requre

rnuch

more

extensive

calculations

depending

upon

the

complexity

and

con_

(raclutl

greements.

2.6

MATTRIALS'

SPECIFICATIONS

All

crxles

itnd

standards

have

materials,

specifications

and requirements

de_

sclibirrg

whirl

rrralcrials

are permissible.

Those

material,

tirut

*"i"r_rtt"O

*itt

ir

sp(.(

rli(

((xlc

arc

cither

listed

or

limited

to

the

ones

that

have

aliowable

stress

vrrlrrts

liivcrr.

l)upcnding

upon

the

code

or

standard,

permitted

rnatenas

tor

a

pirrtit

rrliu

plxt.ss

vcsscl

are limited.

For

instan".,

o;i.;";;,

Jin

an

se

or

ljll

(lcsif

nirrior

crr

bc

uscd

in

ASME

Boiler

and

piersir"

V"rr"i-Cot

"rnr,_"_

:]:lil...Y:::,:t

l:,lf

::l',t

SI)

specifications

are

the

same

u';;;,

B

specifi-

flltlotl

rr

lltc

ASIM

Stirrrtlirltls

a

On specific

instances,

certain

materiais

that

Itttvc

lrt'rr

rr.rlrril(

r'r'r(r

to

sonrc

other

spccification,

such

as

the

DIN

standard..

2.9

ATLOWABLE

TENSITE

STRESSES

IN

THE

ASMI

CODE

17

may

be

recertified

to

an

SA

or SB specification

for

an

ASME

certified vessel.

Depending

upon the

contract

specifications, permissible

materials

for

construc-

tion

are

given

in lists

such

as that

shown

in

Appendix

E.

2.7

DESIGN

DATA FOR

NEW MATERIALS

When design data,

such as

allowable stresses, are requested for

a new

material,

that

is,

one not

presently

in

the

code,

extensive

information

must

be supplied

to

the

Code Committee for evaluation. The ASME

Code Committee lists

this

information

to develop allowable

stresses,

strength data,

and other required

properties

for

accepting a

new material into

the

code.

Each section

of

the

code

contains an appendix listing

these

requirements such

as

the one

for

the

ASME

Code,

VIII-I, in Appendix

F. The

code also

provides

data

to

establish

extemal

pressure

charts

for new

materials; this is

given

to

those

who want to

establish

new external

pressure

charts. The required information

is

given

in Appendix G.

It is

the

person's

responsibility requesting the

addirion to supply all the

data

needed

to

establish those

properties

required in

the

code.

2.8

FACTORS

OF SAFETY

In

order to provide

a

margin of

safety between exact

formulas, which

are based

on

complex

theories

and

various

modes

of failure

,

and the

actual design

formulas

used

for

setting the

minimum

required thicknesses

and

the

stress levels, a factor

of

safety

(FS)

is applied to various materials'

properties

that

are used to set

the

allowable

stress values. The factors

of

safety

are directly

related to

the theories

and modes of

failure,

the specific design criteria of

each

code,

and

the extent to

x.hich various levels

of actual stresses

are

determined

and evaluated.

2.9

ALLOWABTE

TENSILE

STRESSES IN

THE

ASME

CODE

As previously

discussed,

the basis

for

setting the

allowable stress

values

or

the

design

stress

intensity values

is directly

related

to many different

factors

de-

pending upon the section

of

the code

used. The

criteria

for setting

allowable

tensile

stresses

for

each

section

of

the

ASME Boiler

and

Pressure

Vessel

Code

are

as follows:

For

Section

I,

Power

Boilers,

the ASME

Code, YIll-l

,

Pressure

Vessels,

and

Section

III,

Division

1, Subsections

NC, ND,

and NE,

except

for bolting

whose

strength

has

been

enhanced

by

heat treatment,

the factors

used to

set the

allow-

able

tensile stresses

are

summarized

below.

At

temperatures

in

the

tensile

strength

and

yield

strength range,

the least

of:

1.

j

of the

specified

minimum tensile

strength.

2.

j

of

the

tensile strength

at

remperarure.

3.

of

the

specified

minimum yield

strength.


20/361

I8 SEI.TCTION

OI VESSEL,

SPECITICATIONS,

REPORTS,

AND

AttOWABtE

STRESSES

4.

r{

ol thc yicld

strength

at

temperature

(except

as noted

below

where

90Zo

is

uscd).

At

temperatures

ip

the

creep

and

rupture

strength

range,

the least

of:

l, l00qa

of

the

average

stress

to

produce

a

creep

rate

of 0.0l

per

l000

hours

(l7o

in

105

hour).

2. 67Ea

of

the

average

stress to

produce

rupture

at

the

end

of 100,000

hours.

3.

80Vo

of

the

rninimum

stress

to

produce rupture

at

the end

of

100,000

hours.

,_

In

the

temperature

range

in which

tensile

strength

or yield

shength

sets

the

allowable

stresses,

higher

allowable

stresses

are

permitted

for

austenitic

stainless

steels

and nickel-alloy

materi-als

where

gleater

deformation

is

not

objectionable.

9h:l*,the

criterion

of

I

yield

strength

at

lemperature

may

be

increased

to

9oVo,yield

strength

at

temperature.

However,

the factor

spicified

minimum

yield

strength

is

still

maintained.

For the

ASME

Code,

VIII-I,

bolting

material

whose

slrength

has

been

en_

hanced

by

heat

treatment

or

strain

hardening

have

the addition;

criteria

of

(l)

j

of

the specified

minimum

tensile

strength

and

(2)

t

of

the specified

minimum

yield

strength.

For the

ASME

Code,

VIII-2,

and

Section

III, Division

1,

Subsection

NB

and

NC-3200

of

Subsection

NC,

the factor

used

to set

the design

stress

intensity

values

for

all

materials

except

bolting

is

the least

of:

1.

i

of

the

specified

minimum

tensile

strength.

2.

]

of

the

tensile

strength

at

remperarure.

3.

.2

of

the

specified

minimum

yield

strength.

4.

J

of

the

yielded

strength

at temperature

except

as noted

in

the

tbllowing

paragraph.

Higher

design

stress

intensity

values

are

permitted

for

austenitic

stainless

steels

and

nickel-alloy

materi€ls

where greater

deformation

is

not

objectionable.

In

this_ case,

the

criterion

of

J

yield

strength

at temperature

may

be

increased

to

as

high

as 90Vo yield

strength

at

temperature

or any value

beiween

and

gOVo

yield

strength

at

temperatue

depending

upon

the acceptable

amount

of

defor-

mation.

However,

the factor

of

j

specified

minimum yield

strength

is

still

maintained.

There

are

two

criteria

for

setting

bolting

design

stress

intensity

values

in the

ASME

Code,

VIII-2.

For

design

by

Appendix

3,

the criteria

are

the

same

as

for

the

ASME

Code,

VI -1,

because

these

values

are

used

for

the

tlcsign

of

bolts

for

flangjs.

Ior

design

by Appendix

4

of

the

ASMII

(ixlc.

VIII_2,

and

by

Sectirrn

III,

Division

-l

,

Slbsdition

NB

ancl NC-32(X)

ot'

Sutiscc.riirn

IrtC.

the

crilcria

lirr

setting

bolting

design

stress

intcnsity

vitlucs

urc

thc

lesscr

of

the

2.IO

ALLOWABLE

EXTERNAI

PRESSURE STRESS AND AXIAI.

STRESS

I9

following:

(1)

|

of

the

specified minimum

yield

strength

and

(2)

j

of

the

yield

strength

at temperature.

For

Section IV, Heating

Boilers, the criterion

for

setting the

allowable

stresses

is

much more

simple:

(1)

I

/5

of

the specified

minimum

tensile

strength.

2.IO

ALTOWABLE

EXTERNAL

PRESSURE

STRESS

AND

AXIAL

COMPRESSIVE

STRESS

IN

THE

ASME

BOILER

AND

PRESSURE

VESSEL

CODE

Within

the

ASME Boiler

Code, simplified

methods

are

given

to

determine the

maximum

allowable external

pressure

and the maximum

allowable axial

com-

pressive

stress

on

a

cylindrical

shell without having to resort

to complex

ana-

lytical

solutions.

Various

geometric

values

are

contained

in

the

geometry

chart,

whereas

materials' properties

are used to

develop the

materials

charts.

Allowable

stresses in

the materials charts

are based

on the

followine

criteria

For

cylindrical

shells

under external

pressure,

the least

of:

l. 33Vo

of

the

critical

buckling stress with

a

factor of 807o for

tolerance.

2, 33Va

of

the specified

minimum yield

strength

and

yield

strength

at tem-

perature.

3. 67Vo

of

the average

stress

to

produce

a

creep rate

of 0.01%/1000

hours

(17ol

100,000

hours).

4.

IOOVo

of

the allowable

stress

in

tension.

-

For spheres

and spherical

portions

of heads

under

extemal

pressure,

the least

OI:

l. 25Eo

of

the

critical

buckling stress with

a

factor

of

607o

for tolerance.

2.

25Va

of

the specified

minimum yield

strength and

yield

strength at

tem-

perature.

3. 507o

of

the average

stress

to

produce

a

creep rate

of

0.017o/1000

hours

(17ol100,000

hours).

4. IOOVo of

the allowable stress in

tension.

For cylindrical

shells

under

axial

compression,

the least ol

l.

259o of

the

critical buckling

stress with a factor

of

5OVo

for

tolerance.

2.

50Vo of

the

specified

minimum

yield

strength and

yield

strength at

tem-

perature.

3.

1007o

of the

average

stress to

produce

a creep rate

of 0.017o/1000

hrs

(

l7ol

100,000 hours).

4.

ljQVo

of

the

allowable stress

in

tension.


21/361

(-)

z

-{

*s

Z *9.

.

d':

a

ov.

,. i

.:Y

: ir a

5d

.9-

E

E=

3. *

a

E

e

az

.;T .9ir^l$-

.

o6; tE ;c===-

? :

Eg

€Et5;;'

;€i :EH3;E6EE

'< ri :E l-.r' 55::-

6

O.

\:'

E-=

O

o o o

6.

=g+

P-+tstE333E,

.Eo,;

;.: do0EEEE

4t4il

i-oi.lR4

Eoo+ ,

'H;

i.g I.g

PF

H i.=.=.r

a

eEeEg,:EiEEfEEEE

E(aG6.6*d-EG?q

.g

oo

:,

.o

i;

=<

-.

E;

oo

n=

do

F>


22/361

22 STI.TCIION

Ot VTSSTI-,

SPTCIFICATIONS,

REPORTS,

AND

ALLOWABIE

STRESSES

2.I

I

ALLOWABLE

STRESSTS IN

THE

ASME

CODE

FOR

PRESSURE

PIPING 83I

'I'hc

ullowrrblc

sircsscs

given

in various

sections

of the ASME

831

Code for

l\'csnulc

I'ipirrg urc sinrilar

to the

corresponding

sections

of

the

ASME Boiler

nrtl l\'cssurc

Vcssel

Code;

however,

in some

sections, the

basis

is different.

In

thc

(lxlc

lirf Power

Piping

B31.l,

the

allowable

tensile

stresses

are

set by

the

srrrrrc

crilcria

as

used for ASME

Code, Section

I. In the

Code

for

Chemical

plant

rn(l

llctrolcum

Refinery

Piping B31.3,

the allowable tensile

stresses

for

other

th n

bolting

are

set

on a similar

basis

as used for ASME

Section

VIII,

Division

l,

sxcept a factor

of

i

is

substituted

for

j

on

the

tensile

strength.

The factor

of

i

on yield

strength

is

used

in both

codes.

This

makes

831.3 in

the

tensile

and

yield

strength

range

is

similar

to Division

2

and

in

the creep and rupture

strength

range

similar

to Division

1.

2.12

ALLOWABLE

STRESS

IN

OTHER

CODES

OF

THE

WORLD

Throughout the

world,

various

factors

of

safety

are

applied to

materials'

data

to

establish

allowable

shesses

for

the design

of

boilers, pressure

vessels,

and

piping.

For

the

temperature

range to that

temperature

where

creep

or rupture

sets

the allowable

stresses,

the

universal factor

for

setting

allowable

stresses

is

based

on

yield

strength.

In some

countries,

a factor

is

applied

to sets

of

data

that have

been

established

from

many

tests;

in

others, the

data

are

determined

by

the

low

yield

point

or the

high yield point.

In still other

countries,

the actual

data for

the

component

being

designed have

its

yield

strength

determined

by tests

. The actual

data

of

the

part

are

then factored

into

the design formulas.

Not

all

countries

choose

to

use

the ultimate

tensile strength

as

a criterion

for

setting

allowable

stresses.

When

they do,

the

factor of

safety between

various countries

rs

some-

times

very different.

In

order to show

these

differences,

a

discussion

follows

regarding

the

allowable

stress

basis

of

several

different

countries.

The ierms, symbols,

and

definitions

used are

as

follows:

UTS

:

ultimate

tensile

strength

(either

specified

minimum

or

data at design

temperature)

y5

=

yield

strength

(either

specified

minimum or

data

at

design

tem-

perature)

R

=

stress

to cause rupture

in 100,000

hours

C

:

stress

to cause total

creep

or

creep

rate

in 100,000

hours

na

:

not

applicable

n

:

none

or not used

2.12

ATLOWABTE

STREss IN

OTHER

CODES OF

THE

WORI.D

Australia

rs

23

The

rules

used

for

the

design

of boilers

ald

pressure

vessels

set by

the

Standards

Association

of Australia

are called

the

SAA

Standards

Series

AS

1200.

The

factors

of safety

used

to set

the allowable

stresses

for

the

various

sections

are:

R

TS

AS 1210_1977

Pressure

Vessels

Class lH-1979

AS

1228-1980

Boilers

Belgium

n

n

The Belgian

rules issued

by The Belgian

Standards

Institute

(IBN)

permir

a

mixture

of

code

rules

from

various other

countries.

The

allowable

stresses

depend

usually

upon

the codes used.

However,

the basic

allowable

smesses

are

set as follows:

4

2.4

2.7

1.6*

1.5

1.5

1.6

na

1.5

UTS

ys

'

Boilers

Liquid

gas

Air receivers

Pressure

vessels

Czechoslavakia

3.2

2.7

1.6

1.6

1.5

n

n

n

n

1.8

n

n

Various

factors

at designer's

choice

Czechoslovakian

rules

are extensively

detailed for

all

types

of vessels

with

different

allowable

stresses

used for

intemal

pressure

as compared

with

extemal

pressure.

For the

design

of

boilers

and

pressure

vessels,

the

allowable

stresses

are

established

by

the least

of:

*l.5

at

temDerature.


23/361


24/361

26 SETECTION

OF VTSSEI, SPTCIFICATIONS,

REPORTS, AND

ATTOWABI.E

STRESSES

Sweden

The Swedish

rules

for the

design

of

boilers

and

pressure

vessels

set the

allowable

stresses

using only

the

yield

strength

and the

rupture

strength

as follows:

UTS

ys

C

Unilctl Kingdom

The

British

rules

for the design of

boilers

and

pressure

vessels are collectively

called

British

Standards.

The

basis

for

settine the

allowable stresses

is

the least

of:

UTS

ys

1.5

.5

ll

R

Boilers-

BS 1113

Pressure

vessels

BS

5500

Carbon steel

Stainless steel

2.7

2.35

2.5*

1.5

I _.'

I _J

l.J

1.5

1.5

l.

RTTTR.ENCES

Srrrrlcn,

A. M.,

and J.

R.

Mase,

"ASME

Pressure-Vessel Code:

Which

Division

to

Choose?",

('hrt\k\tl

lit|ineering,

January ll,

1982.

lnrthorlt

oJ luhular

Exchanger Manufacturers.Asroc., 6th ed., Tubular Exchanger Manu-

lrrllrrrr

As$oci0lbn,

White Plains,

N.Y., 1978.

rl,JJ

[l

lcnr|t(rrlrtrr.

REFERENCES

ANSUAPI

Standard

650,

Welded

Steel

Tanks

for

Oil

Storage, 7th

ed.,

American Petroleum

Institute, Washington, D.C.,

1980.

1982

AnnuaL

Book

of

ASTM

Standards,

Afieican Society for Testing

and

Materials, Philadel-

phia,

Pa.,

1982.

DIN Standa

(Deutsche

Normen

Dll,lr,

Herausgegeben vom Deutschen Normeruusschu

(D,VA),

Berlin,

Gemany.

27


25/361

-

-

2f

l+u)

'Fxy

i,=#n(*

.,&*)

r1

=

-q.C-/afu*razn1

"

i

2

(l

-p'J

\ayz

,,'I

L. t" a_w

^J

i

211*u;

a*aY

Th6ori6s,

€riter;o,

ond

bosic

equorions.

29

CHAPTER

3

STRENGTH

THEORIES,

DESIGN

CRITERIA,

AND

DESIGN

EQUATIONS


26/361

3.4 STRESS-STMIN REIATIONSHIPS


27/361

32

STRTNGTH THEORIIS, DESIGN

CRITERIA,

AND

DESIGN

EQUATIONS

due

to a

stress

concentration

caused

by an abrupt

change

in

geometry.

This

stress

is

important in considering

a

fatigue failure

because of cyclic

load application.

In

general,

thermal

stresses

are

considered

only in the

secondary

and

peak

categories.

Thermal stresses that

cause

a

distortion

of

the structure

are

catego-

rized as

secondary

stresses; thermal

stresses

caused

by

suppression

of thermal

expansion,

but

may not

cause

distortion, are categorized

as

peak

stresses.

Potential

failure

modes

and the various stress

limits

categories

are related.

Limits

on

primary

stresses

are

set to

prevent

deformation and

ductile

burst. The

primary plus

secondary

limits

are

set

to

prevent

plastic deformation leading to

incremental

collapse and

to validate using

an

elastic analysis

to

make

a fatigue

analysis.

Finally,

peak

stress

limits are

set

to

prevent

fatigue

failure due

to

cyclic

loadings.

The basic

stress

iniensity limits

for various

categories

relating to

an analysis

according to

the

ASME Code, VIII-2,

and Section

III,

Division 1,

Subsection

NB,

and

optional

Part

NC-3200

of

Subsection

NC are:

Stress Intensity

Category

Allowable

Value

Factor

Based on

Yield

Strength*

Factor

Based

on

Tensile

Strength*

General

primary

membrane

(P,)

ks,

Local primary

membrane

(P")

UKS^

himary

membrane

plus

primary

bending

(PM

+

Pd liks.

Primary

plus

secondary

(PM+PB+Q)

3s,

- c

s)

+s"

s,

+s,

25,

S-

(

In

the

ASME

Code, VIII-2,

and

Section

III,

Division

1, optional

Part

NC-

3200

of Subsection

NC, a factor

of

ft

is applied

to

various

loading

combinations

somewhat related

to whether or not

the

loading

is

sustained

or transient.

The

laotors

are

k

=

1.0

for

sustained

loads including

dead loads and

pressure;

k

-

1.2

for

sustained

load

plus

wind

or

earthquake

loads; t

=

1.25

for hydro-

$tiltic

tcsts; and k

-

1.15

for

pneumatic

tests.

'I'hc

dcsign

criteria

for

Section

III,

Division

l,

Subsection

NB, are very

sinrillr

lo

thoso

for

the

ASME

Code,

VIII-2,

except there is

less use

of design

lirrrrrrrlrrs,

culvcs,

tnd

tables,

and

greater

use

of design

by analysis

in

Section IIL

'l'h(.

cfllcgorics

ol slrcsses

and stress

intensity limits

are the same in

both sec-

liorrs.

+AiiurriflI

lhrt I | .O. ,\,,,

(lcsiSn

strcss

intensity valuc fbr

Section

III, Division l,

Subsection

Nll,

n[(l

thc

|

't{

i',nrl

pIr

I {rl S hsr(.li()n

NC,

and thc

ASMts

Codc,

VIII-2

(psi),

S"

=

yicld

strength

(plri).

url ,\,

ultirrxrtc

k

nsil(. slfrJrgth

(psi)

3.3 DESIGN

EQUATIONS

Once

the allowable

stresses

are

set,

the

basic

design equations

must be

devef

oped. The

design

of

process

equipment is

based

on

the assumption that

the

material

generally

behaves

elastically at the design

pressure

and

design

tem-

perature.

Accordingly,

most

of

the equations

are derived from the theory

of

elasticity

and

shength

of

materials basis.

3.4

STRESS-STRAIN

RETATIONSHIPS

The

stress-strain

relationship

at

any

point

within

a homogeneous,

isotropic, and

linearly

elastic

body that is

subjected

to a

system

of

forces is obtained

from

the

theory of

elasticity. Referring

to

Fig.

3.1,

the stress-strain

relationship

is

given

by

1.

e,:

ELo,-

p(oy

+

ozl)

t.

er

=

ELor-

ploz

'r

o^)J

I

e,

:

;lo,- tt(o,

I

o)l

(3.1)

-

I1-

-

rs

2(1

+

1t)

,DGE

2(l

+

1t)

^lv

= ---V-

rn

2(1

+

1t)

.t/,-

=

-

i--

L

Or, in

a

different form.

(r+

tt)(1

-zp.)

(1,+p.)(1

-2tt)

[e,(l

-

pc)

+

[e,(1

-

p)

+

p,(e, +

e,)]

p.(e"

+

e")l

(l

+ p)(1

-

Ii^,

:

"

ltl

2(l +

1.t)

T,

-

[€,(1

-

LIL)

pr,)+p(e.+er)]

(3.2)

34

STRENGTH THIORIES, DTSIGN CRITERIA,

AND

DESIGN

EQUATIONS

3.5 STRAIN-DEFTECTION EQUATIONS

35


28/361

'

f1--->


29/361

Fisure

3.2

Cross

s€ction

of

o

sh€ll woll

subie€ted

to str€rchine

ond

bendins

lodds'

Substituting

the

values

of lr

and

lz

into the

above and

deleting all

small

terms

results

in

(

t l\

€.:

€or

_

,\,:_

i)

:

e0,_ z.

x\

where

1,

is change

in

curvature.

Similarly,

/

r

l\

€n

:

€ou

-,\4-

i)

=

es

-

z'

xt

Substitution

of

the

above

two

equations

into

Eq.

3.4

gives

F

o,:

,-:--Lr"

+

peo

-

z(y"

+

trt'yt)

t-lt-

ti

q-

,--l€vt

+

l"r*-

z(Xr+

PX')

t-

lL-

Nolr

llrirl

llr(' cx|)tcssirttt

f,

is

related

to

the

deflection

by

the expression

dzw

/

dx2

x'=tt+kt"4'hffn

(3.5)

However, because

the

quantity

dw

fdx

is

smal

compared

with

unity, the

expres-

sion

above becomes

d2w

.

d2w

X':

77

a;to

Xt

=

7F

Hence,

Eq. 3.5

may be

written

as

(3.6)

(3.7)

(3.8)

The shearing

strain-displacement

relationship

can

be obtained

from

Fig.

3 3.

The

quantity

7,"

is shown

in

Fig. 3'34

and can

be expressed

as

"l'Y:"loq+a+P

where

7qry

is the

shearing

stress

due

to in-place

forces

and

d

and

B

are

due

to

twisting

moments.

Also,

from the

figure,

.

(d/

d\'ldv

du

d-srna

-__6-:

dy

(dD/?x)dx

0a

IJ-srnP-

d,

=A

*=T+1^+

peo,-,(#.

-

*fu)l

E

I ldzw,

drr\'l

ot:

T7

*.leb

+

Pew

-

'\dy,

-

It

dr')

l

du 0a

f,t:

Ioq,

dy-

a,

and

From

Fig. 3.30, which

represents the

middle surface,

the

rotation

is

given

by

-@w

I

Ai.

The minus sign

indicates

counterclockwise

rotation.

As

a result

of

this rotation, any

point

at a

distance z from

the middle

surface will

have

a

deflection

of

dw

dx


30/361

40

STRENGTH

THEORITS,

DESIGN CRITERIA,

AND

DESIGN EQUATIONS

3.6

FORCE.STRESSEXPRESSIONS

4l


31/361

,/

N.

N,

Et

=

r r(€0r+

/,€q,

r-lJ'

Ft

:

.--------t

(€0)

+

p€0r.)

l-

lL'

1'u,Et

2(l

+

1t)

N,}

(3.1

r)

,.:&(#.#)

u,=ffi\(*tu.

,*tu)

,.

Eilt

-

tL)

drw

l2ll

-

lt2t

ax

dy

Example 3.1

Stresses are

to be

determined

at the

inside comer

of an

opening

in

a

cylindrical

shell by applying

strain

gages

at the

location.

The cylindrical

shell

is

carbon steel

with E

:

29.9

x

106

psi

and

p

:

0.3. The

strain

readings

from

the three

gages

are

€,:

+360

x

10-6;

€):

+180

x

l0

o

and

e'

=

-230

x

10-6.

What are the

stresses

in

the

three

principal directions

at

the

opening?

Solutian. Using

the equations

given

under

Eq. 3.2, the stresses

are

determined

AS

,oq

o,:

;#1Q60X0.7)

+

0.3(180

-

230)l

:

13'630

psi

(

r.Jrw.+.,

,qq

",:

-*l(180)(0.7)

+

0.3(360

-

230t1

=

9499

O.;

'

t

r.JJ(u.+,

?qo

o

=

"''

tr-?10rr0.7)

+

0.3(360

+

180)l

:

60

psi

I

(1.3x0.4)"

--""'

Exanple 3.2.

What are the stresses

in

the two

principal

directions

of the

cylindrical shell with

the

o,

=

gt

Solution.

Using

the

simplified

equations

given

under

Eq. 3.4,

the

stresses

are

determined

as

',

=ffioso

+

0.3

x

180)

=

13,6oo

psi

o,

=ffi{rto

+

0.3

x

360)

:

9460

psi

r

42

SIRTNOTH

THEORI€S,

DTSIGN

CRITERIA,

AND

DESIGN

EQUATIONS

BIELIOGRAPHY

43


32/361

Problems

3.1

Strain

gages

are

attached

to

the surface

of

a tube

subiected

to internal

pressure.

The

gages

lie along

the

circumferential

and

l,ongitudinal

axes.

The

tube

is

carbon

steel with

t

=

29.9

x

106psi,

1.r,

:

0.3,

and

the

stress

at the surface

in

the

circumferential

direction

is

17,500

psi.

What

are

the

strain

gage

readings

in the

two directions?

Answer:

e,: *498

x

10-6

€i: +117 x

10-6

3.2 In

the tube

of

Problem

3.1,

what

is

the

strain

in the

z

-direction

structural analysis and design of process equipment (t.l)

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