Machine Design Databook Episode 1 part 9 ppt

The thickness of a blank unstayed full-hemispherical

head with the pressure on the concave side

The formula for the minimum thickness of head when

the required thickness of the head given by Eqs. (9-9)

and (9-10) exceeds 35 percent of the inside radius

UNSTAYED FLAT HEADS AND COVERS

The minimum required thickness of flat unstayed

circular heads, covers and blind flanges as per

ASME Power Boiler Code

The minimum required thickness of flat unstayed

circular heads, covers or blind flange which is

attached by bolts causing edge moment Fig. 8-9( j)

as per ASME Power Boiler Code

For details of bolt load HG, bolt moments, gasket

materials, and effect of gasket width on it

The minimum required thickness of unstayed heads,

covers, or blind flanges of square, rectangular, ellipti￾cal, oblong segmental, or otherwise noncircular as per

ASME Power Boiler Code

For values y, C, and
sa refer to Tables 7-1, 7-3, and 7-6.

h ¼ pL

1:6
sa ð9-11aÞ

h ¼ pL

ð2
sa
0:2pÞ ð9-11bÞ

Equation (9-11b) may be used for heads exceeding

12.5 mm (0.5 in) in thickness that are to be used with

shells or headers designed under Eqs. (9-9) and (9-10)

and that are integrally formed on seamless drums or

are attached by fusion welding and do not require

staying.

h ¼ Lðy1=3
1Þ ð9-12Þ

where

y ¼ 2ð
sa þ pÞ

2
sa
p ð9-12aÞ

h ¼ d ffiffiffiffiffiffiffiffiffiffiffiffiffiffi

Cp=
sa p ð9-13Þ

where

C ¼ a factor depending on the method of attachment

of head on the shell, pipe or header (refer to

Table 8-6 for C)

d ¼ diameter or short span, measured as shown in

Fig. 8-9

h ¼ d½Cp=
sa þ 1:78WhG=
sad3



1=2 ð9-14Þ

where

W ¼ total bolt load, kN (lbf )

hG ¼ gasket moment arm, Fig. 8-13 and Table 8-22.

Refer to Tables 8-20 and 8-22 and Fig. 8-13

t or h ¼ d ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

ZCp=
sa p ð9-15Þ

Particular Formula

9.8 CHAPTER NINE

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DESIGN OF POWER BOILERS

The minimum required thickness of unstayed non￾circular heads, covers, or blind flanges which are

attached by bolts causing edge moment Fig. 8-9 as

per ASME Power Boiler Code

The required thickness of stayed flat plates (Figs. 8-10

and 8-11) as per ASME Power Boiler Code

The maximum allowable working pressure for stayed

flat plates as per ASME Power Boiler Code

For all allowable stresses in stay and stay bolts

Also for detail design of different types of heads,

covers, openings and reinforcements, ligaments, and

bolted flanged connection

COMBUSTION CHAMBER AND

FURNACES

Combustion chamber tube sheet

The maximum allowable working pressure on tube

sheet of a combustion chamber where the crown

sheet is suspended from the shell of the boiler as per

ASME Power Boiler Code

where

Z ¼ 3:4
2:4d=a ð9-15aÞ

a ¼ long span of noncircular heads or covers measured

perpendicular to short span, m (in)

Z need not be greater than 2.5

Equation (9-15) does not apply to noncircular heads,

covers, or blind flanges attached by bolts causing bolt

edge moment

h ¼ d½ZCp=
sa þ 6WhG=
saLd2



1=2 ð9-16Þ

h ¼ pt

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

½ p=
sac5 p ð9-17Þ

where

pt ¼ maximum pitch, m (in), measured between

straight lines passing through the centers of the

stay bolts in the different rows

(Refer to Table 9-7 for pitches of stay bolts.)

c5 ¼ a factor depending on the plate thickness and

type of stay (Refer to Table 8-15 for values of

c5.)

For
sa refer to Tables 8-8, 8-23, and 8-11

p ¼ h2

sac5

p2

i

ð9-18Þ

Refer to Chapter 8

P ¼ 27000 hðD
diÞ

wD

USCS ð9-19aÞ

where

h ¼ thickness of tube, in

w ¼ distance from the tube sheet to opposite com￾bustion chamber sheet, in

Particular Formula

DESIGN OF POWER BOILERS 9.9

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DESIGN OF POWER BOILERS

TABLE 9-7

Maximum allowable pitch for screwed staybolts, ends riveted over

Pressure Thickness of plate, mm (in)

7.8125 (0.3125) 9.375 (0.375) 10.9375 (0.4375) 12.500 (0.50) 14.0625 (0.5625) 15.6250 (0.625) 17.1875 (0.6875)

MPa psi Maximum pitch of staybolts, mm (in)

0.67 100 131.25 (5.25) 159.375 (6.375) 184.375 (7.375)

0.76 110 125.000 (5.000) 150.000 (6.000) 175.000 (7.000) 209.375 (8.375)

0.83 120 118.750 (4.75) 143.750 (5.75) 168.750 (6.75) 200.000 (8.000)

0.86 125 118.750 (4.75) 140.625 (5.625) 165.625 (6.625) 193.750 (7.75)

0.90 130 115.625 (4.625) 137.500 (5.50) 162.500 (6.50) 190.625 (7.625)

0.96 140 112.500 (4.50) 134.375 (5.375) 156.250 (6.25) 184.375 (7.375) 209.375 (8.375)

1.03 150 106.250 (4.25) 128.125 (5.125) 150.000 (6.000) 178.125 (7.125) 200.00 (8.000)

1.10 160 103.125 (4.125) 125.000 (5.000) 146.875 (5.875) 171.875 (6.875) 193.750 (7.75)

1.17 170 100.000 (4.000) 121.875 (4.875) 140.625 (5.625) 168.150 (6.75) 187.500 (7.500) 209.375 (8.375)

1.24 180 118.750 (4.75) 137.500 (5.50) 162.500 (6.50) 184.375 (7.375) 203.125 (8.125)

1.31 190 115.625 (4.625) 134.375 (5.375) 159.375 (6.375) 178.125 (7.125) 196.875 (7.875)

1.38 200 112.500 (4.50) 131.25 (5.25) 153.125 (6.125) 175.000 (7.000) 193.750 (7.750) 212.500 (8.50)

1.55 225 106.25 (4.25) 121.875 (4.875) 146.875 (5.875) 162.500 (6.50) 181.250 (7.25) 200.000 (8.00)

1.72 250 100.000 (4.000) 115.625 (4.625) 137.50 (5.50) 156.250 (6.25) 171.875 (6.875) 175.625 (7.625)

2.07 300 106.250 (4.25) 125.000 (5.000) 140.625 (5.625) 156.250 (6.25) 175.00 (7.000)

Source: ASME Power Boiler Code, Section I, 1983.

9.10

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DESIGN OF POWER BOILERS

The vertical distance between the center lines of tubes

in adjacent rows where tubes are staggered

For minimum thickness of shell plates, dome plates,

and tube plates and tube sheet for firetube boiler

For mechanical properties of steel plates of boiler

D ¼ least horizontal distance between tube centers on

a horizontal row, in

di ¼ inside diameter of tube, in

P ¼ maximum allowable working pressure, psi

P ¼ 186 hðD
diÞ

wD

SI ð9-19bÞ

where p in MPa; h, D, di, and w in m

Dva ¼ ð2diD þ d2

i Þ

1=2 ð9-20Þ

where di and D have the same meaning as given

under Eq. (9-19)

Refer to Table 9-8

Refer to Table 9-9

Particular Formula

TABLE 9-8

Minimum thickness of shell plates, dome plates, and tube sheet for firetube boiler

Diameter of Minithickness

Shell and dome plates Tube sheet Shell and dome plates Tube sheet

m in m in mm in mm in

0.9 36 1.05 42 6.25 0.25 9.375 0.375

>0.9–1.35 >36–54 >1.05–1.35 >42–54 7.81 0.3125 10.94 0.4375

>1.35—1.8 >54–72 >1.35–1.8 >54–72 9.375 0.375 12.5 0.500

>1.8 >72 >1.8 >72 12.5 0.50 14.06 0.5625

Source: ASME Power Boiler Code, Section I, 1983.

TABLE 9-9

Mechanical properties of steel plates for boilers

Tensile strength Yield stress, percent Elongation percent

min of tensile gauge length,

Grade MPa kpsi strength 5.65 ffiffiffiffiffi

a p a

1 333.4–411.9 48.4–59.7 55 26

2A 362.8–480.5 52.6–69.7 50 25

2B 509.9–608.0 74.0–88.2 50 20

a a area of cross section.

Source: IS 2002-1, 1962.

DESIGN OF POWER BOILERS 9.11

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DESIGN OF POWER BOILERS