ASME Section VIII div 2 2010. ASME Boiler and Pressure Vessel Code. Alternative Rules

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2010 SECTION VIII, DIVISION 2

4-145

i) STEP 9 – Calculate the quantity

using the following equation:

⎛⎞

−+

⎜⎟

⎝⎠

(4.6.15)

j) STEP 10 – Calculate the stresses at the shell-to-flat head junction and opening-to-flat-head junction

using Table 4.6.2.

k) STEP 11 – Check the flange stress acceptance criteria in Table 4.6.3. If the stress criteria are satisfied,

then the design is complete. If the stress criteria are not satisfied, then re-proportion the flat head and/or

opening dimensions and go to STEP 3.

4.6.5 Nomenclature

A shell outside diameter.

inside diameter of the shell.

inside diameter of the opening.

factor depending upon the method of attachment of head, shell dimensions, and other items

as described in Table 4.6.1. It should be noted that the value of

C for a welded cover

includes a factor of 0.667 that effectively increases the allowable stress for such

constructions to 1.5S.

D is the long span of noncircular heads or covers measured perpendicular to short span.

d diameter, or short span, measured as indicated in figure shown in Table 4.6.1.

E joint factor.

e flange stress factor.

hub stress correction factor for the nozzle opening-to-flat head junction.

hub stress correction factor the shell-to-flat head junction

E weld joint factor (see paragraph 4.2).

F flange stress factor for the nozzle opening-to-flat head junction.

F flange stress factor for the shell-to-flat head junction

g hub thickness at the large end of the shell-to-flat head junction.

g hub thickness at the small end of the nozzle opening-to-flat head junction.

g hub thickness at the small end of the shell-to-flat head junction.

g hub thickness at the large end of the nozzle opening-to-flat head junction.

g hub thickness at the large end of the shell-to-flat head junction.

h gasket moment arm (see Table 4.16.6).

h hub length at the large end of the nozzle opening-to-flat head junction.

h hub length at the large end of the shell-to-flat head junction.

L perimeter of a noncircular bolted head measured along the centers of the bolt holes, or the

flange stress factor, as applicable.

operating moment.

moment acting at the shell-to-flat head junction.

2010 SECTION VIII, DIVISION 2

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m thickness ratio

tt.

P internal design pressure.

inside corner radius on a head formed by flanging or forging.

S allowable stress from Annex 3.A for the head evaluated at the design temperature.

S allowable stress from Annex 3.A for the head evaluated at the gasket seating condition.

T flange stress factor.

t minimum required thickness of the flat head or cover.

required thickness of the flat head or cover for the gasket seating condition.

t required thickness of the flat head or cover for the design operating condition.

t nominal thickness of the flange on a forged head at the large end.

t nominal thickness of the flat head or cover.

t required thickness of a seamless shell.

t nominal thickness of the shell.

t throat dimension of the closure weld

U flange stress factor.

V flange stress factor for the nozzle opening-to-flat head junction.

V flange stress factor for the shell-to-flat head junction

W operating bolt load at the design operating condition.

W gasket seating bolt load at the design gasket seating condition.

Y length of the flange of a flanged head, measured from the tangent line of knuckle, or the

flange stress factor, as applicable.

factor for noncircular heads and covers that depends on the ratio of short span to long span,

or the flange stress factor, as applicable.

integral flat head stress parameter.

()

slope of head with central opening or nozzle times the modulus of elasticity, disregarding the

interaction of the integral shell at the outside diameter of the head.

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2010 SECTION VIII, DIVISION 2

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4.6.6 Tables

Table 4.6.1 – C Parameter for Flat Head Designs

Detail Requirements Figure

•

0.17C = for flanged circular and noncircular heads

forged integral with or butt welded to the vessel with

an inside corner radius not less than three times the

required head thickness, with no special requirement

with regard to length of flange.

•

0.10C = for circular heads, when the flange length

for heads of the above design is not less than:

1.1 0.8

Ydt

⎛⎞

⎜⎟

=−

⎜⎟

⎝⎠

•

0.10C = for circular heads, when the flange length

Y less than the requirements in the above equation

but the shell thickness is not less than:

1.12 1.1

ttYdt=− for a length of at least

dt . When 0.10C = is used, the taper shall be

at least 1:3.

•

3rt=

minimum shall be used

Taper

Center Of Weld

Tangent Line

•

0.17C = for forged circular and noncircular heads

integral with or butt welded to the vessel, where the

flange thickness is not less than two times the shell

thickness, the corner radius on the inside is not less

than three times the flange thickness.

•

rt= minimum shall be used

•

[

]

max 0.33 , 0.20Cm= for forged circular and

noncircular heads integral with or butt welded to the

vessel, where the flange thickness is not less than

the shell thickness, the corner radius on the inside is

not less than the following:

10 (0.375 .)

38 (1.5 .)

rmm in

or t mm in

≤

(

)

min 0.25 , 19 0.75 .

38 (1.5 .)

rtmmin

for t mm in

⎡⎤

⎣⎦

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Table 4.6.1 – C Parameter for Flat Head Designs

Detail Requirements Figure

•

0.13C =

for integral flat circular heads when:

- the dimension

d does not exceed 610 mm (24 in.)

- the ratio of thickness of the head to the dimension

d is not less than 0.05 or greater than 0.25

- the head thickness

t is not less than the shell

thickness

- the inside corner radius is not less than

0.25t

- the construction is obtained by special techniques

of upsetting and spinning the end of the shell, such

as employed in closing header ends.

•

3rt=

minimum shall be used

0.33C = for circular plates welded to the end of the

shell when

t is at least 1.25

t and the weld details

conform to the requirements of paragraph 4.2.

See paragraph 4.2 for

detail of weld joint,

not less than 1.25 t

[

]

max 0.33 , 0.20Cm=

for circular plates if an inside

fillet weld with minimum throat thickness of

0.7

t is used

and the details of the outside weld conform to the

requirements of paragraph 4.2.

See paragraph 4.2 for

details of weld joint

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Table 4.6.1 – C Parameter for Flat Head Designs

Detail Requirements Figure

•

0.3C =

for circular and noncircular heads and

covers bolted to the vessel as indicated in the

figures.

• When the cover plate is grooved for a peripheral

gasket, the net cover plate thickness under the

groove or between the groove and the outer edge of

the cover plate shall be not less than the following

thickness.

For circular heads and covers:

1.9

For noncircular heads and covers:

SLd

0.25C = for circular covers bolted with a full-face

gasket to shells and flanges.

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Table 4.6.1 – C Parameter for Flat Head Designs

Detail Requirements Figure

0.3C =

for a circular plate inserted into the end of a

vessel and held in place by a positive mechanical locking

arrangement when all possible means of failure (either by

shear, tension, compression, or radial deformation,

including flaring, resulting from pressure and differential

thermal expansion) are resisted with a design factor of at

least four. Seal welding may be used, if desired.

Retaining Ring

Threaded Ring

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Table 4.6.2 – Junction Stress Equations for an Integral Flat Head With Opening

Head/Shell Junction Stresses Opening/Head Junction Stresses

()

1.1

sss

fX E Bg

⎛⎞

⎜⎟

⎝⎠

1.91 1

0.64

sss

BBgt

⎛⎞

⎜⎟

⎝⎠

()

0.57 1

0.64

sss

XE t

BBt

ZF M

BBgt

⎛⎞

⎜⎟

⎝⎠

=− +

1HO H

SXS

1RO R

SXS

0.64

TO T

sss

ZFM

SXS

BBgt

where

Lg B

(

)

1.33 1

te M

Lt B

SZS

=−

−

Note:

0.0

= for the case of an opening

without a nozzle

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Table 4.6.3 – Stress Acceptance Criteria for an Integral Flat Head With Opening

Head/Shell Junction Stresses Opening/Head Junction Stresses

1.5

Sho

SS≤

RS ho

SS≤

TS ho

SS≤

()

HS RS

≤

()

HS TS

≤

1.5

Oho

≤

RO ho

≤

TO ho

≤

(

)

HO RO

≤

(

)

HO TO

≤

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2010 SECTION VIII, DIVISION 2

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4.6.7 Figures

For Nozzle

h (Shell)

(Shell)

(Nozzle)

This Half Depicts

Opening Without Nozzle

Without Nozzle

(Nozzle)

This Half Depicts

Opening With Nozzle

h (Nozzle)

Juncture May Or

May Not Have Taper

Figure 4.6.1 – Integral Flat head With a Large Central Opening

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4.7 Design Rules for Spherically Dished Bolted Covers

4.7.1 Scope

4.7.1.1 Design rules for four configurations of circular spherically dished heads with bolting flanges are

provided in paragraph 4.7. The four head types are shown in Figures 4.7.1, 4.7.2, 4.7.3, and 4.7.4. The

design rules cover both internal and external pressure, pressure that is concave and convex to the spherical

head, respectively. The maximum value of the pressure differential shall be used in all of the equations.

4.7.1.2 For head types with a bolted flange connection where the gasket is located inside the bolt circle,

calculations shall be made for two design conditions, gasket seating and operating conditions. Details

regarding computation of design bolt loads and flange moments for these two conditions are provided in

paragraph 4.16. If a flange moment is computed as a negative number, the absolute value of this moment

shall be used in all of the equations.

4.7.1.3 Calculations shall be performed using dimensions in the corroded condition and the uncorroded

condition, and the more severe case shall control.

4.7.2 Type A Head Thickness Requirements

4.7.2.1 The thickness of the head and skirt for a Type A Head Configuration (see Figure 4.7.1) shall be

determined in accordance with the rules in paragraph 4.3 for internal pressure (pressure on the concave

side), and paragraph 4.4 for external pressure (for pressure on the convex side). The skirt thickness shall be

determined using the appropriate formula for cylindrical shells. The head radius,

L , and knuckle radius, r ,

shall comply with the limitations given in these paragraphs.

4.7.2.2 The flange thickness of the head for a Type A Head Configuration shall be determined in

accordance with the rules of paragraph 4.16. When a slip-on flange conforming to the standards listed in

Table 1.1 is used, design calculations per paragraph 4.16 need not be done provided the design pressure-

temperature is within the pressure-temperature rating permitted in the flange standard.

4.7.2.3 Detail (a) in Figure 4.7.1 is permitted if both of the following requirements are satisfied.

a) The material of construction satisfies the following equation.

0.625

≤ (4.7.1)

b) The component is not in cyclic service, i.e. a fatigue analysis is not required in accordance with

paragraph 4.1.1.4.

4.7.3 Type B Head Thickness Requirements

4.7.3.1 The thickness of the head for a Type B Head Configuration (see Figure 4.7.2) shall be

determined by the following equations.

a) Internal pressure (pressure on the concave side)

(4.7.2)

b) External pressure (pressure on the convex side) – the head thickness shall be determined in accordance

with the rules in paragraph 4.4.

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