ASME Section III NP Extract

7/24/2019 ASME Section III NP Extract

1/6

ASIIIE

2011a SECTION

IlI,

DMSION

1

-

NB

tJ

j

U

1

c{

(A

I

t$

\,

NB-3512.2 Alternative

Design

Rutes.

A

valve

design

may

not

satisfy

all of

the requirements

of NB-3512.1. A

design

may

be accepted

provided

it meets one

of

the

alternatives listed in

{a),

ib),

[cJ,

or

[d)

below,

faj

When

the

valve

design satisfies the rules of

NB-3530

through NB-3546.2 with thermal

stresses neglected,

the

rules

of

NB-3200 relative

to

accounting

for

thermal

secondary

stresses

and

fatigue anaiysis

[NB-37.22.2,

NB-3222,3,

and NB-3222.41 shall also

be

satisfied.

@l

When a valve is

exempted

from

fatigue analysis

by

the ruies ol NB-3222.4[d),

the

design

is

acceptable,

provided

that

the requirements

of

[1J

or

(2J

below are

met.

(1)The

rules ofNB-3530

through NB-3546 shall be

mel The

rules of NB-3200

may

be

substituted for

those

of NB-3545,2

for

evaluating secondary

stresses,

and

NB-3545,3

need

not be considered.

(Z)The

rules of NB-3530

and

NB:3541shall

be met.

An

experinrental stress analysis

is

periornred

in accor-

dance with

Appendix

ll,

and the rules

of

NB-3200

rvith

respect

to primary

and

secondary stresses

resulting from

pressure

and

mechanical

loads shall be mel.

Uniess

otherwise

specified

in the Design Specifications,

the

pipe

reaclions

shall be

taken as

those loads which

produce

a

stress

[NB-3545,2[b]l

of

0.5

times

the

yield

srrength

of

the

piping

in tension

for

the

direct or

axial

ioad

and

a

stress o[

1.0

times the

yield

strehgth of

the

piping in

bending

and

torsion,

Thernral

secondaty stresses shall

be accounted for

by

either the rules of NB-3200

or NB-3545,

(cJ

When

a

valve

design

sarisfies the rules

of

NB-3530

and

NB-3541,

and

when an experirnental

stress

analysis

has been

performed

upon

a

simiiar

valve in

accordance

with

Appendix II,

and an

acceptable

analytic

method has

been

established,

the results

may be

used

in

conjunction

ents

of

NB-3200

for

pressrtre

and

mechanical

ioads

lish

design

acceptability.

Accom-

stress

intensity

at

all

points,

including

all

other effects,

shall

be

used

for

the

analysis

to

satisfu

the

rules

ol NB-3200.

The

valve

Design

Specification

shall

provide

the

loadings

and

operating

requirements

to

be

considered

under

Level B,

C,

and

D

Service

Limits

[NCA-3252ta](5Jl

for which

a design

analysis

is

to

be

included in

the Design

Report.

(2)

ln

place

of using the values

of

S, to satisfy

the

rules

oF

NB-3200,

the

allowable

stress

intensity

values

for

ferritic

valve

body and

bonnet

materiais shall

be those

allowable

stress values

given

in

Section

II,

Part D, Subpart

1, Table

1A For

materials in Section

ll,

Parr

D, Subpart

1,

Tables

2A and

28, a reduced

allowable

stress

intensity

based

on

applying

a factor

ol A,67 to

the

yield

srrenEths

lisled in Section

li,

Part

D,

Subpart

1, Table

Y-1

shall

be

used.

(3J

The adequary

of the sh.ess

analysis

of the body

and

bonnet

shall be

verified by

experimental

stress

analysis

conducted

in

accordance

with the requirements

of Il-1100 through

II-1400,

lndividual

tests shdl

be

made

to

verify

the

adequacy

of

the

shress

analysis

of

internal

pressure

effects

and

pipe

reaclion

effects. Tests

shall

be

made

on

at

least

one

valve

model

of a

given

configuration,

but

a verified

analytical

procedure

may then

be

applied

to

other

valves

of

the

same

configuration,

although they

may

be of different

size

or

pressure

raring. The

geometrical

differences shal)

be

accounted

for

in

the extrapolation

stress

analysis.

The analytical procedure

shall

have

verified capability

of

providing

this

exrrapolarion.

(4J

A

Design

Report

shall

be

prepared

in

sufficient

detail to show

that the valve

satisfies

all applicable

requirements,

f5J

Prior

to

installation,

the valve

shall be

hydro-

stafically

tested

in

accordance

with

NB-3531.2,

For this

purpose, the

prinrary

pressure rating shall

be

determined

by

interpolation

in

accordance

with

NB-35a3[cJ.

NB-3513

Acceptabil,ity of

Small.

Valves

Valve

designs

having

an

inlet

piping

connecfion

NPS

4

(DN

100)

or

less

are

acceptable

when they

satisfy either

the

stanclard

design

rules

or

the

alternalive design

rules.

NB-3513.I

Standard

Design

Rules. The

design

shall

be

such

that

the

requirements

ol

NB-3530

and NB-3541

shall

be

met for

wall

thicknes.ses

corresponding

to the

applicable pressure-temperaftue

rating. When

the Special

Class

Ratings

of

ASlvlE

816.34 apply,

the

NDE

exemptions

of NB-2510

shall

not

be

used,

NB-35I:1.2

Atternative Design

Rul.es.

i

valve

design

shall

satisfy

the

requirements of NB-3512.2.

NB-3515

Acceptabllity

of Metat

BeLlows

and

Metal

Diaphragm

Stem

Sea[ed Valves

Valves

using metal

bellolvs

or metal diaphragm

stem

modation

of

thermal

se-Enqgly stresses and

pipe

reac-

tions

shall be

as

given

inlttXZ)f Requilements

for farigue

analysis of either

NB-3200 or NB-3550 shall

be met.

[dJ

When

permitted

by the

Design Specification,

a

weld

end

valve that

does

nol

meet

all of

the requirements

of NB-3540

may

be

designed

so that it

meets

the

requirements

of

NB-3200

for all

pressure-retaining palts

and

those

parts

defined

by

NB-3546.3[a),

and shall also

meet

all

of the foliowing requirements,

fI]

Pressure,

thermal,

artd

mechanical effects, sucb

as

those resulting

.from

earthquake,

maximnm

stem

force,

closure force,

assembly forces,

and others

tlut

nray

be

defined

in

the

Design

Specification,

shall

be inclucied in thc

design analysis.

For

l evel

A

Service

Limits,

the

pipe

reaction

effects

are to be

determined by considering

that

thc maximum

liber stress in

the connected

pipe

is at

one-half of its

yield

strength

in

direct tension

and

at

its

yielct

sh'ength

in

torsion

and

in

bending in

the

plane

of

the

neck and

run, and also in

the

plane

of the

run

perpencli-

seals shall

be constru*ed

in accorclance with

the

rules

of

individuai

pipe

reaction

eifects

thal rcsult in

the

maxinurnt or

diaphr-agms

do not retain

pressure,

and Design

BZ

D-6


2/6

Pa

h

tsr

Ps

Pt,

Pz

Qp

Qrt

Qrs

Sn,lntaxl

Spr

tr

-

P.

=

generai

primary

membrane

stress intensify

at

crotch region,

calculated according

to NB-

3545.1(a),

psi

(MPa)

=

Desigin Pressure,

psi

(MPaJ

=

Pressure

Rating Class Index,

psi

(MPa)

=

standard calcuiation

pressure

frorn

NB-3545.1,

psi

(MPa)

=

rated

pressures

from

tables

oi

ASNIE

81.6.34

corresponding

to

Pressure

RaEing Class

lndices

p.1

and

p,2, psi (MPa)

=

sum

of

primary plus

secondary stresses

at

crotch

resulting

from internal

pressure

[NB-35a5.2[a]1,

psi

(lvlPa)

=

maximum thermal

srress component caused by

through-wall temperafure

gradient

associated

with

100"F/hr

[56'C/hr)

fluid

temperanrre

change rate

[NB-3545.2(cJ],

psi

(]vlPaJ

=

maximum thermal secondary membrane

plus

bending stress resulting

from structural

discon-

tinuity

and

100'F/hr

(56'C/hr)

fluid

tempera,

ture

change

rate, psi

(MPaJ

=

mean radius of

body

wall at

crotch

region

[Fig.

NB-3545.2[c)-1],

in.

(mm)

=

inside

radius

of body

at crotch

region for

calculating

Qp

[NB-3545.2(a)J,

in.

[mmJ

=

fillet radius of external

surface

at

crotch

[NB-3545,1[aJ],

in.

(mmJ

=

assumed

maximum stress

in

connected

pipe

for

calculating the secondary

stress

due

to

pipe

reaction

INB-3545.2[bJ],

psi

(lvlPaJ

=

fatigue stress intensity range

at crotch

region

resulting

from step

change in

fluid

temperature

A?2

and

pressure

AP,

(NB-3550), psi

(MPa)

"

design

stress

intensity

(NB-3532),

psi

[MPa)

'

sum of

primary

plus

secondary

stress

lntenslfies

at crotch region

resulting

from

100"F/hr

(56"C/hr)

temperature change

rate

INB-

3545.2),

psi

(lvlPaJ

'

maximum range

of

sum of

primary

plus

second-

ary

sfress,

psi

(MPa)

,

fatigue stress intensity

at

inside

surface

in

crotch region resulting

frorn

100"F/hr

[56'C/hr)

fluid temperature

change rate

(NB-354s.3),

psi

[MPa)

,

fatigue

stress

intensity

at

outside

surface

in

crotch region

resulting

from 100"F/hr

(56'C/hr)

fluid

temperature

change rare

[NB-3545.3),

psi

(lvlPa)

,

thickness

ofvalve

rvall adiacent to

crotch

region

for

calculating

1,1

and

L7y

[Fig.

NB-35a5.1[a)-1],

in,

[mmJ

maximum

effective

metal

thickness

in crotch

region

for

calculating

thermal stresses

[Fig.

NB-35a5.2ic)-1],

in.

(mrnJ

thickness

of

bociy

(run)

rvall

adjacent

to

crotch

for calculating

1,1

and

Lp

[Fig.

NB-35a5.1(a)-1],

rn.

ImmJ

ASITIE 2011a

SETflON

lll, D|VISION

I

-

NB

te

=

minimum body

wall thickness adjacent to

crotch

for

calculating

thermal

stresses

IFig.

NB-

35a5.2[c]-11,

in.

(rnm)

fm

=

rninimum

body

wall

thiclsress

as determined

by

NB-3541, in.

(mm)

ty

t2

=

minimum

wall thicknesses

from

ASME

816.34

corresponding

to

Listed

Pressure Rating

Class

Indices

p71

and

pr2

and inside diameter dm,

itl.

Imm)

API

=

f1111

range

of

pressure

fluctuation

associated

wtth

At1,

psi

[MPa)

/Pi

=

5ps616ed

range

of

pressure

flucruation

asso-

ciated

with

A7,,

psi

[MPa)

ATtr

=

2

specihed step

change

in

fluid temperature,

oF

("C),

where I

=

,2,3,

...,

n;

used

to

determine

the

fatigue

acceptability

of a valve body

(NB-35541

ll"r

=

speclfied range

of fluid temperarure,

"F

("C),

where

i

=

7,7,3,..,,

n;

used to

evaiuate

normal

valve

usage

[N8.3553)

d?"'

=

maxirnum

magnitude

of the difference ln aver-

age

wall

temperafures for walis

of

thicknesses

t

and

I,, resulting

from

100"F/hr

(56'C/hrJ

fluid

temperature

change

rate,

"F

('C)

NB.354O

DESIGN OF

PRESSURE-RETAINING

PARTS

NB-354f

General Requirements

for

Body Wa[[

Thickness

The

minimurn

wall thickness

of

a

valve

body

is to

be

determined

by the rules of NB-3542

or

NB-3543,

NB-3542

Minimum WaLt

Thickness of

Listed

Pressure

Rated

Valvesz3

The

lvall

thickness requirements

for

listed

pressure

rated

valves

apply

also

to integral

body

venturi

valves. For

a

valve

designed

to

a listed

pressure

rating of

ASME

816.34,

the

minirnum thickness of its

body wall, including

the neck,

is

to be determined

from ASME

816.34,

except

that

the inside

diameter

d-

shall

be the

larger of the basic

valve

body inslde dianreters in

the region near

the

weldirrg

ends,

Highly

localized

variations

of

inside

diarneter

assoclated

wlth

rveld

preparation\lNB-3544.8(a)

and

-@f-,neeri

noi

be

consicie'Fedfir

esE#sin -

--ifrmiffiiimT-alTlhickness f,,. ln all such

cases,

however,

the

requiremenls

ol NB-3545.2[b)(6)

shall be

satisfied.

N8-3543

Minimum Watl

Thickness

of

Vatves

of

Nonl,isted

Pressure

Ratinga

To

design a

valve

for Design

Pressure

and

Design

Temperature

corresponding

to other

than

one of the

pressure

ratings

listed

in the tables of

ASivlE

816.34,

the

procedure

is

the

same as

that

of

NB-3542

except

that

interpolation

is

required

as foliows.

[oJ

Based on

the

Design

'l'emperature,

linear interpola-

-:lLoa errUeen,thelabulttgdJe1lp_Elatqre_j11tejaAiC.sXal_bq::=.,.

'-:

used

to

deterrnine

the iisted

pressure

rating

pl,

next

C

sr

sm

JN

Spz

16

f-'

L

sJ

t/J

r/l

+

c{)

n

T.

b

ly.

(-.

tt

L-J

*85

D-1


3/6

[eJ

For

socket

welding

ends,

valves

NPS

Z

IDN

50J

and

smaller for

which

the body

cavity

consists

of

rylindrically

bored

sections

shall meet

all

of

the following:

fIJ

d. shall

be

the

port

drill

diameter;

[2J

the

requiremenr

of NB'3542

shall

be

satisfied;

and

[3J

socket

welding

end

valves

greatet'than

NPS

2

(DN

50J

shall

not

be

used.

NB-3544,9

Openings

for Auxltiary

Connections.

Openings

for

auxiliary

connections,

such

as

for

drains,

bypasses,

and

vents,

shall

meet

the

requirements

of

ASME

816.34 and the

applicable

reinforcement

requirements

of NB-3330,

NB-3545

Body

Primary

and

Secondary

Stress

Limits

The limits

ol

primary

and

secondary

stresses

are

established

in

the following

subparagraphs.

NB-3545.1

Primary Membrane

Stress

Due

to

lnter-

nat

Pressure.

For

valves meeting

all

requirements

of this

Subarticle,

the most

highly

stressed

porrion

of

the body

under internal

pressure

is

at

the

neck

to

flow

passage

junction

and

is

characterized

by

circumierential

tension

normal

to the

plane

of

center

lines,

wlth

the

maximum

value at

the

inside surface.

The

rules

of this

paragraph

are

intended

to control

the

general

primary nrembrane

stress

in

this

crotch

region,

The

Standard

Calculation

Pressure

p"

to

be used

for

satisfoing

the requiremenls

of

NB-3545

is

found

either

directly

or

by

interpolation

from

the

tables

in

ASlvlE

815.34

as the

pressure

at 500oF

l25A'C)

for the

given

Pressure

Rating

Class

Index

p^

[aJ

ln

the crotch

region,

the

maximum

primary

mem'

brane

srress

is to

be

deterinined

by

the

pressure area

method

in

accordance

with

the

rules

of

[1]

through

[6J

beiow

using

Fig. NB-3545.1[aJ-1.

IIJ

From an

accurately

drawn

layoud

of

the

valve

body, depicting

the finished

section

of

the

rotch

region

in

the

muilal

plane

of

the bonnet

and flolv

passage

center

lines, deterrnine

lhe

fiuid

area

,4/alld

metal

area

A',

Aland

An

are to

be based

on

the

internal

surface

after

complete

Ioss

of

metal

assigned

to

corrosion

allowance.

f?)

Calculale

the

crotch

general primary

membrane

stress

intensity:

,^

=(+

+

o.s)p,

\An /

The

allolvable

value

of lhis

sEress

intensity

is

S.

for

the

vaive

body

material

at

500"F

(250"C) as given

in

Section

Il,

Part D,

Subpart

1, Tables

2A

and

2P,

(3)

The

distances

L1 and

Lp which

provide

bottnds

on

thc fluid

and

metal

areas

are determined

as

follows,

Use

the

larger

value

of:

ASME

2011a

SESTION

lll, DMSloN 1

'

NB

or

and

use

Le

=7,

L1

=0.5d-76

(

NB-3545,2 Secondarv Stresses.

In

addition to

salis-

I

tlns

tli

t;l;-=

.*t7

--'=

body shall

also satisfy

the

crlterion

that

the

range of

Lp

=

0.512

+

0.354

W-;6

where

the

dimensions

are as shown

in

Fig.

NB-3545.1(a)-1,

ln

establishing

appropriate

values for

the

above

parameters,

some

judgment

may

be

required

if

the

valve

body

is

irregular

as

it is

for

globe

valves and

others

with

nonsymmetric shapes.

ln

such

cases,

the internal bound-

aries

oflr.shall

be the lines that trace the

greatest

width

of

internal

wetted

surfaces

perpendicular

to the

plane

of

the

stem and

pipe

ends

[Fig.

NB-3545.1[a)-1

skelches

(b),

[d),

and

(eJl.

(4)

lf

the calcr.rlated

boundaries fot'

47

and

.4,,,

as

defined by

/,,1 and lp, fall

beyond

tire

valve

body

IFig.

NB'3545.1(a)-1

sketch

(bJ],

the

body surface

becomes the

proper

boundary

for

establishin

g

41 and A^,

No

credit

is

to

be taken

for

any

area

ol

connected

piping

which

may be

included

within

the

limits

of

1,4 and L,y.

lf

the

flange is

included

with An,

the area

of one

bolt hole is

to be.

subtracted for

determining the

net

value of rl.,

[5]

Except

as rnodified below web

or

fin-like

exten-

sions

of

the

valve body

are

to

be

credited

to

.4.

only

to

an

effective

length

from the wall

equal

to the average

thickness of the

redited

portion,

The remaining

web

area

is

to

be added to

+

[Fig.

NB-35a5.1[a)-1

sketch

(bJ],

However,

to the

extent

that

additional area wili

pass

the

following tesq

lt may

also

be

included

in

A-.

A

line

perpendicular

to the

plane

oflhe

stem and

pipe

ends

from

any

poitrts

in

r4. does

not break out

of

the

wetted

surface

but

passes

through a

continuum

of

metal

until

it

breaks

through

the

outer

surface

oi

the body.

[6J

ln.most cases, it is

expected

that the

portions

defined

by

A^ in the

several

illustrations

of

Fig,

NB-3545.1(a)-1

rvill

be

most

highly

stressed. However,

in

the

case

of highly irregular

valve

bodies,

it

is

recommended

that

all

sections

of the

crotch

be checked

to

ensure that

the

largest value of

P. has been

established

considering

both

open

and

fully

closed

condifions.

flrJ

ln

regions

than

the crotch,

while the

value

ol

P,

calculated

be

the

highest

value of

body

general primary

s

all

normal

valve

for

possible

higher

stress

regions.

Suspected

regions

and

28.

"\

J

Ul

-{'

,,

be

checked

by

the

pressure

area method

applied to

thti

particular

local

.body

contours.

I'he aliolvabie

vaiue of

this

stress

intensily is

S,n

lor

the

valve body

material at

500'F

(26O'Cl

as

given

in

Seclion

Il,

Part D, Subpart 1,

Tables

2A

89

o-E


4/6

,*?;;

fri,s,;tr

i

,Y

.t

0

t:

l

c

.J

ASJIIE 2011a

SECTION

lll,

DIVISION

L

-

NB

19 These requirements for the acceptability

of a valve design

are

not

intended

to

ensure the

functional

adequary

oithe

valve.

However,

for

pressure

relief

valves

the

Designer is

cautioned

that

the requirements of

NB-7000 relafive to

set

pressure,

lift,

blowdown, and ciosure

shall be

meL

tu

--

i

20

|

CAUTTON:

Fertain

types

of

double

seated valves

have tire

capabillty

of trapping liquid

ln

the

body or bonnet cavlty

in

the closed

7

position,

If

such

a carrity

accunrulates

liquid

and

ls

ln the closed

position

at

a

time

wlren

adjacent

system

piping

ls lncreasing

ln

temperature,

a

substantial

and

uncontrolled

increase

In

pres.sure

ln

the body or bonnet cavlty may result. Where such

a

condltlon

is

posslble,

lt

i.s

the

responsibllity

of the Owncr

or

the Orvner's

dcsignee

to

provlde,

or

require

to

be

proulded,

protection

agalnst

harmfirl

overpressure ln such valves.

21

The

severity and

frequency

of

specified

fluid

temperarure

variations

may

be

such

that

the

period

of

calculated

pressure

integrity is

less

than

plant

design

life.

In

such

cases

it is the responsibility of the Certiflcate Holder to

state

these conditions

in

the

Design

Report

(NB-3550).

22

Special

feahrres such

as

wear

surfaces or

seating surfaces may demand

special

alloys or

proprietary

lreaments.

The

absence

ofsuch

materials from Section II, Par"t

D,

Subpart

1,

Tables

2A

and

2B

shall notbe

construed

to

prohibit

their

use and

such nraterials do not

require approval under

Appendix IV

[NB-z121),

23 r\

listecl

pressrlre

rated

valve is one listed in the tables of ASIvIE 815.34.

A

nonlisted

pressrrre

rated

valve

is

one

whose

Design

Pressure

and

Temperarure do not

specifically appear in

those tables

[NB-3543J.

24

For

all

listed

pressure

ralings

except

Class 150,

the Pressure Rafing Class

lndex

is

the same

as

the

pressure

rating

ciass

designation. For

Class

150 use 115

for

the

Pressure

Rating

Class

lndex.

25

Adjacent

poirrfs

are defined as

points

which

are

spaced

less

than

the distance

ZJF|

from

each

other, where R and t

are

the

mean radius and thickness, respectively, of

the

vessel,

nozzle,

flange,

or other

component in

which

the

points

are

iocated,

26

For

piping

products,

such as tees

and branch connections,

the

second

term of

eqs. NB-3652[9), NB-3553.1(a)tf0),

and

NB-3653.2(aJ(11),

namely

that

containing

&16 is

ro

be

calculated

as

referred

to in

NB-3583.1(d).

27

Socket welds

shall

not be

used

where

the

existence of crevices

could accelerate corrosion.

28

The flexibility of a curved

pipe

or

welding elbow

is

reduced

by

end

effects,

provided

either

by

the

adjacent

stralght

pipe

or by the

proximity

of other relatively

stiff

members

which

inhibit

ovalizalion of the cross section. in certain

cases,

these end effects

may aiso

reduce

the stress.

29 c

equals

nominal wall

thickness,

30

Welds

that

are

exposed to corrosive

acbion

should

have a

resistance

to

corrosion

that

is

not

substarrtialty less than

that

oF the cladding. Thc use of

filler

metal

that

will

deposit

weld

metal

which

is

similar

to

the composition

of

the

cladding

material

is

reconrmended.

lf weld

metal

ol

different composition

is

used, it

should

have

properties

compatible

lvith

the

applicahon.

31 An

interntediate

postweld

heat

treatntenr

lor

this

purpose

is

defined

as

a

poslweld

heat

lreatment

performed

on a

weld

wilhin

a temperature

range not lower

than the rninimum

holding temperature

range

to whrch the weld

shall

be

subjected

during the

final

postweld

heat rreatment.

32

A

radioglaphic examination

[NB-5111(a)]

is

required; a

preservice

exarnination

[NB-5111[b]]

may

ornray

not be

required

lor

compliance

to the Design

Specification

INCA-3252(c)).

33 SNT-TC-IA is a Recommended Practice

for

Nondestructive

Testing Personnel

Quaiificarion

and

Certification

pttbiished

by the American Sociely

for

Nondestructive'l'esting,

1711 Arlingate

Lane, P.0.

Box

28518, Columbus, 0H

+3228-051-8.

34 Personnel qualified

by examination

and

certifled

to the

previous

editions

of SNT-TC-1A

are

considered to

be

qualified

to

the editiotr

referenced

in Tabie

NCA-7100-2

when

the

recertificatiorr

is based

on continuing satisfactory

performance.

Ail

reexanrinations

and

new exanrinations

shall be

in accordance with

the

edition

referenced

in

Tabie

N

CA-7 100-2.

35

Employer

as

used in

this Articie

shall include:

N Certificdte Holders;

Qualiry

System Certificate Holdersj Ivlaterial

Organizalions

who hre

qualified

in

accordance

with NCi\-3842; and

organizations

rvbo provide

subcontracted

nondestructive

exanrirration services

to

organizalions

described

above.

274

D-1


5/6

6,'f

NL-ss

//

ASII{E

2011a

SECTI0N

tll,

DwIS|ON 1

.NC

Adjacent

points are

defined

as

points

that

are

spaced

less

than

lhe

distance

z.fRT

fronr each other, where R and t are

the mean

radius

and thickness,

respectively,

of

the vessel,

nozzle,

flange,

or dther

part

in which the

points

are located.

The head

design

curves

have been

developed

considering

membrane

stress

requirements,

plastic

collapse,

ryclic

load

conditions,

and the

effects of

maximum

allowable

toierances

in accordance lvith

NC-4222,

See A-4000 of Appendix

A

lor

the

design

formulas

for the curyes

ol Fig,

NC-3224.6-1'

Heads

having

D/2h

= 2 have

equivalent

torisphericai properties

of

a

torisphere

of

L/D

=

0,90

and

rlD

=

0.17,

The

minimum

thickness

for

ali

pipe

materials

is

the

nominal

thict


6/6

,g

i)

7

f1

4

d

?.

D

t:

)

n

Q

p"-L.

"*

N

i:

--3:,,

I

ASIIIE 2011a

SECTION

IIl, DIVISION

1

.

ND

18

Side

plates

of

a flat

sided

vessel are defined as

any

olthe

flat

plates

forming

an

integral

part

of

the

pressure

retaining

enclosure.

19

Written for fittings with internal

threads

but

also

applicabie

to

externally

threaded and

socket

or bun

welded

fittings.

20

tD

is defined

in

XI-3130.

21 All

dimensions

given,

for

size of vessel

on which inspection

openings

are

required,

are

nominal,

22

ltis

recognized

that

other

acceptable

procedures

may

existthar

also conslilute

adequate design methods,

and

it is

nol

--r._th?

intention

to rule

out

these a-lternafive

methods

provided

they can

be

shown to

have been

satisfactory by

a*ual

sqvrce

expenence,

23

ICAUTION:

pertain

types

of double

seated

valves

have the

capability

of trapping

liquid in the hody

or

bonnet

carrity

in

the

closed

position.

If

such

a cavity accumulates

liquid and is

in

the

closed

position

at

a

time when

adjacenl system

piping

is

increasing

in tempera$re,

a

substantial and

uncontrolled

increase in

pressure

in

the

body

or bonnet cavity

may

result. Where such a

condltion

is

possible,

it is the responsibility

of the Owner

or his designee

to

provide,

or

require to be

provided,

protection

against

harmful

overpressure

in

such valves.

24

The

minimum thicknesses of straight

pipe

shown in

Table ND-3642.1(cJ-1

should be sufficient to allow

the

pipe

to

meet the minlmum wall thickness

requirements

of

ND-3641

after

having

been bent

on the radii

shown.

25 Expansion

Joint

Manufacturers Association,

25

North

Broadway,

Tarrytown,

NY 10591.

25

See

Appendix

II, II-1520G),

27

The

pressure

term

in

eqs.

ND-3652[8), ND-3653.1(aJ(9ai, ND-3653.1[bJ(9bJ

and

ND-3553,2(c)[11)

may

not apply

tor bellows and expansion

joints,

28 Design Pressure nray

be used

lf

the

Design

Specification

states

that

peak pressure

and

earthquake

need

not

be taken

as acting

concurrently,

29

Socket

welded

joints

should

not

be used

where the

existence

of

crevices

qould

result in accelerated corosion.

30

Fillet and

partial

penerration

welds should not be

used

where

severe

yibration

is expected.

31 These

rules do not limit

storage fanks

from

being

installed below

grade

or

below

ground,

provided

the

tanks

are

not

subject to external

pressure

resulting

from earth or fill,

32 The limitalion of the

Design

Pressure to atmospheric

is

nol

intended

to

preclude

the use

of these

tanks

at vapor

pressure

slightly

above

or

below atmospheric

within

the

range

normally

required

to

operate

vent

valves.

If

these

pressures

or

vacuums

exceed

12

ozf

in.z,

especially

in

combination

with

large

diameter

lank, the lorces

involved

may

require special consideration

in

the

desigrr.

33

Any

specified corrosion allowance

for the

shell

plates

shall

be

added to

the calculated

thickness.

34

The nominal

thickness

of shell

plates

refers to

the

tank shell as

constructed.

The

thicknesses

specified

are based

on

erection requirements.

35 API

Standard 2000,

L96B Edition, Venting

Atmospheric and

Low Pressure

Storage

Tanks, American

Perroleum

lnstitute, 1220 L

Street,

NW, Washington,

DC

20005-4070.

35

The

decrease

in

yteld

stress at

Design

Temperature

shall

be

taken

into

accounL

37

The formulas appiying to self-supporting

roofs

provide

for

a

unifornr

live

load of 25

lb/ftz

(1.2

kPaJ.

3Mhenever

a

tank is to

be operated

with

liquid

levels that

at no

time

reach the

top

of

the rool

but

is

to

be

filled to

the

very top

of the

roof

during

the

hydrostatic

test,

it shall

be designed

for both

of

these

maximum

liquid

level

conditions,

using

in

each

case

the density

of

the liquid employed.

If

a

tank is

not

designed

to be nlied to the very top of

the

roof,

overfili

protection

is required,

A

suitable

mat'gin

shali

be

allowed between

the

pressure

pormally

existing

in the

gas

or

vapor

space and

the

pressure

at

which the

reliefvalves

are sel, so

as

to

allow for

the

increases

in

pressure

caused by

variations in

the

temperature

or

gravily

of

the

liquid contents

of

the tank

arrd

other

factors

affecting

the pressule

in

the

gas

or vapor

space,

J :

plfi"lyi:uy'llill

b='.q91 :l E1.tBt :y re, :9.-ys:te-tielr{-ygry.e='--?le-:s

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39

40

L/b

D-)3

Documents

ASME Section III NP Extract