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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
7/24/2019 ASME Section III NP Extract
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
7/24/2019 ASME Section III NP Extract
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
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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
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//
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
7/24/2019 ASME Section III NP Extract
6/6
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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
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