Machine Design Databook Episode 1 part 9 ppt

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 A

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
sarefer to Tables 7-1, 7-3, and 7-6

p

ð9-13Þwhere

C ¼ a factor depending on the method of attachment

of head on the shell, pipe or header (refer toTable 8-6 for C)

d ¼ diameter or short span, measured as shown inFig 8-9

h ¼ d½Cp=
saþ 1:78WhG=
sad31=2 ð9-14Þwhere

W ¼ total bolt load, kN (lbf )

hG¼ 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 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

ZCp=
sap

ð9-15Þ

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

pt¼ maximum pitch, m (in), measured betweenstraight lines passing through the centers of thestay bolts in the different rows

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

c5¼ a factor depending on the plate thickness andtype of stay (Refer to Table 8-15 for values of

c5.)For
sarefer to Tables 8-8, 8-23, and 8-11

p ¼h

2
sac5

p2 i

ð9-18ÞRefer to Chapter 8

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

di¼ inside diameter of tube, in

P ¼ maximum allowable working pressure, psi

P ¼ 186hðD
diÞ

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

Dva¼ ð2diD þ di2Þ1=2 ð9-20Þwhere diand D have the same meaning as givenunder Eq (9-19)

Mechanical properties of steel plates for boilers

Tensile strength Yield stress, percent Elongation percent

min of tensile gauge length,

Plain circular furnaces

FURNACES 300 mm (12 in) TO 450 mm (18 in)

OUTSIDE DIAMETER, INCLUSIVE

Maximum allowable working pressure for furnaces

not more than 41

2 diameters in length or heightwhere the length does not exceed 120 times the thick-

ness of the plate

The maximum allowable working pressure for

fur-naces not more than 41diameter in length of height

where the length exceeds 120 times the thickness of

the plate

Circular flues

The maximum allowable external pressure for riveted

flues over 150 mm (6 in) and not exceeding 450 mm

(18 in) external diameter, constructed of iron or steel

plate not less than 6 mm (0.25 in) thick and put

together in sections not less than 600 mm (24 in) in

length

The formula for maximum allowable external

pres-sure for riveted, seamless, or lap-welded flues over

450 mm (18 in) and not exceeding 700 mm (28 in)

external diameter, riveted together in sections not

less than 600 mm (24 in) nor more than 31

2times theflue diameter in length, and subjected to external pres-

D ¼ outside diameter of furnace, in

L ¼ total length of furnace between centers of headrivet seams, in

T ¼ thickness of furnace walls, sixteenth of an inch

where p in psi; h and d in in

d ¼ external diameter of flue, in

The maximum allowable working pressure for

seam-less or welded flues over 125 mm (5 in) in diameter

and including 450 mm (18 in)

(a) Where the thickness of the wall is not greater

than 0.023 times the diameter as per ASME

Power Boiler Code

(b) Where the thickness of the wall is greater than

0.023 times the diameter

Equations (9-24) and (9-25) may applied to riveted

flues of the size specified provided the section are

not over 0.91 m (3 ft) in length and the efficiency ()

of the joint

where p in psi and d in in

h ¼ thickness of wall in 1.5 mm (0.06 in)

where p in MPa; h and D in m

p ¼ maximum allowable working pressure

D ¼ outside diameter of flue

h ¼ thickness of wall of flue

THE MAXIMUM ALLOWABLE PRESSURE

FOR SPECIAL FURNACES HAVING

WALLS REINFORCED BY RIBS, RINGS,

AND CORRUGATIONS

(a) Furnaces reinforced by Adamson rings

(b) Another expression for the maximum allowable

working pressure when plain horizontal flues

are made in sections not less than 450 mm

(18 in) in length and not less than 8 mm (5

16in) inthickness (Adamson-type rings)

where p in psi; h and d in in

h ¼ thickness of tube wall, mm (in), not to be lessthan 11 mm (0.44 in)

Ring-reinforced type

The required wall thickness of a ring-reinforced

fur-nace of flue shall not be less than that determined

by the procedure given here

The allowable working pressure (Pa)

The required moment of inertia (Is) of circumferential

stiffening ring

The required moment of inertia of a stiffening ring

shall be determined by the procedure given here

The expression for B

The value of factor A

Assume a value for h (or t) and L Determine theratios L=Doand Do=t

Following the procedure explained in Chap 8, mine B by using Fig 9-1 Compute the allowableworking pressure Paby the help of Eq (9-32)

deter-Pa¼ðDB

where Do¼ outside diameter of furnace or flue, inCompare Pawith P If Pais less than P select greatervalue of t (or h) or smaller value of L so that Paisequal to or greater than P, psi

Is¼

LD2o



t þAsL

A

where

Is¼ required moment of inertia of stiffening ringabout its neutral axis parallel to the axis of thefurnace, in4

As¼ area of cross section of the stiffening ring, in2

A ¼ factor obtained from Fig 9-1Assume the values of Do, L, and t (or h) of furnace.Select a rectangular member to be used for stiffeningring and find its area Asand its moment of inertia I.Then find the value of B from Eq (9-34)

I, for the section selected above, select a new sectionwith a larger moment of inertia and determine anew value of Is If the required Isis smaller than themoment of inertia I selected as above, then thatsection should be satisfactory

FIGURE 9-1 Chart for determining wall thicknesses of ring reinforced furnaces when constructed of carbon steel (specified yield strength, 210 to 262 MPa (30 to 38 kpsi) (1 kpsi ¼ 6.894757 MPa) (Source: ‘‘Rules for Construction of Power Boilers,’’ ASME Boiler and Pressure Vessel Code, Section I, 1983 and ‘‘Rules for Construction of Pressure Vessels,’’ Section VIII, Division 1, ASME Boiler and Pressure Vessel Code, July 1, 1986.)1;2

Corrugated furnaces

The maximum allowable working pressure (P) on

corrugated furnace having plain portion at the ends

not exceeding 225 mm (9 in) in length

Stayed surfaces

The maximum allowable working pressure (P) for a

stayed wrapper sheet of a locomotive-type boiler

16in) for Purves and other furnacescorrugated by sections not over 450 mm (18 in)long

D ¼ mean diameter, inValues of C6are taken from Table 9-10

P ¼ 11000t

R
P

where

t ¼ thickness of wrapper sheet, in

R ¼ radius of wrapper sheet, in

 ¼ minimum efficiency of wrapper sheet throughjoints or stay holes

in length

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

The longitudinal pitch between stay bolts or between

the nearest row of stay bolts and the row of rivets at

the joints between the furnace sheet and the tube

sheet or the furnace sheet and the mud ring

Cross-sectional area of diagonal stay (A)

The total cross-sectional area of stay tubes which

support the tube plates in multitubular boilers

P

s sin  ¼ summated value of transverse spacing(s sin ) for all crown stays considered in onetransverse plane and on one side of the verticalaxis of the boiler

s ¼ transverse spacing of crown stays in the crownsheet, in

 ¼ angle any crown stay makes with the vertical axis

2

USCS ð9-37aÞwhere

t ¼ thickness of furnace sheet, in

R ¼ outside radius of furnace, in

P ¼ maximum allowable working pressure, psi

L ¼



2:535  109

t2PR

2

SI ð9-37bÞwhere P in Pa; t, L, and R in m

A ¼aL

where

a ¼ sectional area of direct stay, m (in)

L ¼ length of diagonal stay, m (in)

l ¼ length of line drawn at right angles to boiler head

or a projection of L on a horizontal surfaceparallel to boiler drum, m (in)

At¼ðA
aÞP

sa

ð9-39Þwhere

A ¼ area of that portion of tuber plate containingthe tubes, m (in)

a ¼ aggregate area of holes in the tube plate, m2(in2)

P ¼ maximum allowable working pressure, Pa(psi)

sa¼ maximum allowable stress value in the tubes,MPa (psi) j>48 MPa (7 kpsi)

sais also taken from Table 8-23The pitch of stay tubes shall conform to Eqs (9-17)and (9-18) and using the values of C7 as given inTable 9-11

The pitch from the stay bolt next to the corner to

the point of tangency to the corner curve for stays

at the upper corners of fire boxes shall be as given

T ¼ thickness of plate in sixteenths of an inch

P ¼ maximum allowable working pressure, psi

C7¼ factor for the thickness of plate and type of stayused

pt¼ 7592

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

C7ðT2=pÞp

angularity of tangent linesðÞ

SI ð9-40bÞwhere ptand T in m, and p in Pa

Refer to Table 9-11

HG

ranges from 35 to 45 in firetube boilers;

37 is a good working value ð9-41aÞS

P¼0:92 to 1:12 m2(10 to 12 ft2) forexternally fired boiler per hp

¼ 0:74 m2(8 ft2) for Scotch boiler per hp ð9-41eÞ

The units in parentheses are in US Customary System units.

TABLE 9-11

Values ofC7for determining pitch of stay tubes

Pitch of stay tubes in the bounding rows

When tubes have nuts not outside of plates

When tubes are fitted with nuts outside of plates Where there are two plain tubes between two stay tubes 120 130

Where there is one plain tube between two stay tubes 140 150

Where every tube in the bounding rows is a stay tube and

each alternate tube has a nut

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

Design of a vertical straight shell multitubular boiler

P

DS

N ¼ 64  10
3to 73 10
3 ð9-41gÞH

WHS

SHSWHS¼1

A ¼ Total area of steam segment

D ¼ Diameter of shell or drum

h ¼ Height of the segment to be occupied by steam

FIGURE 9-2 Disengaging surface in horizontal cylindrical shell (Source: Reproduced from G B Haven and G W Swett, The Design of Steam Boilers and Pressure Vessels, John Wiley and Sons, Inc., 1923.)1

FIGURE 9-3 Areas of circular segments (Reproduced from G B Haven and G W Swett, The Design of Steam Boilers and Pressure Vessels, John Wiley and Sons, Inc., 1923.)1

Watertube boiler design

For mechanical properties of carbon and carbon

manganese steel plates, sections and angles for

marine boilers pressure vessels and welded machinery

and mechanical properties of steel plates for boilers

For properties of boilers

For evaporation of water, average rate of combustion

of fuels, and minimum rate of steam produced

Refer to Table 9-13Refer to Tables 9-14 to 9-16

For permissible strain rates of steam plant equipments

For water level requirements of boilers

For minimum allowable thickness of plates for boilers

For disengaging surface per horsepower

For heating boiler efficiency

Refer to Table 9-17Refer to Table 9-18Refer to Table 9-19Refer to Table 9-20Refer to Table 9-21TABLE 9-14

Evaporation kg (lb) of water per kg (lb) of fuel reduced to standard condition

[from and at 373 K (1008C)]

Approximate Evaporation

per kg (lb) of fuel, Type of fuel kJ/kg Btu/lb kg (lb)

Average rates of combustion [kg/m2(lb/ft2) of grate

surface per hour] draft 12.55 mm (1in) water column

Fuel used Stationary grate

Minimum kilograms (pounds) of steam per h per ft2of surface

Firetube boilers Watertube boilers

Oil-, gas-, or powder-fired 30.9 14 35.3 16

Source: ASME Power Boiler Code Section I, 1983.

TABLE 9-17

Permissible strain rates for steam plant equipment

Strain rate Machine part per hour

Turbine disk (pressed on shaft) 10
9

Bolted flanges, turbine cylinders 10
8

Steam piping, welded joints, and boiler tubes 10
7

Superheated tubes 10
6

TABLE 9-18Water level requirementsa

Horizontal return Vertical firetube tubular boilers boilers Distance Distance Boiler between Boiler between diameters, gauge cocks, diameters gauge cocks,

above surface of tubes for all diameters: distance between gauge cocks may be reduced

to a minimum of 75 mm

Low water level must be 75–125 mm above the water surface of the crown sheet; distance between gauge cocks is usually 75 mm for all diameters

a Low water level 890 mm above surface of tubes.

TABLE 9-19

Minimum allowable thickness of plates for boilers (all dimensions in mm)

Power boilers Heating boilers Shell and dome Tube sheet Shell or other Tube sheet or Minimum thickness plate diameter diameter plate diameter head diameter

9.5 >1370–1830 1065 >1530–1980 >1065–1530 11.0 >1065–1370 >1980 >1530–1980

1 Haven, G B., and G W Swett, The Design of Steam Boilers and Pressure Vessels, John Wiley and Sons, Inc.,New York, 1923

2 ‘‘Rules for Construction of Power Boilers,’’ ASME Boiler and Pressure Vessel Code, Section I, 1983

3 ‘‘Rules for Construction of Pressure Vessels, ’’ ASME Boiler and Pressure Vessel Code, Section VIII, Division I,July 1, 1986

4 Code of Unfired Pressure Vessels, Bureau of Indian Standards, IS 2825, 1969, New Delhi, India

5 Nichols, R W., Pressure Vessel Codes and Standards, Elsevier Applied Science Publishing Ltd., Barking, Essex,England, 1987

6 Lingaiah, K., and B R Narayana Iyengar, Machine Design Data Handbook, Engineering College CooperativeSociety, Bangalore, India, 1962

7 Lingaiah, K., Machine Design Data Handbook, Vol II (SI and Customary Metric Units), Suma Publishers, galore, India, 1986

Ban-8 Lingaiah, K., Machine Design Data Handbook, (SI and U.S Customary Units), McGraw-Hill Publishing pany, New York, 1994

Com-Disengaging surface Type of boiler m2/kW m2/hp

g acceleration due to gravity, m/s2(ft/s2)

ri inside radius, m (in)

ro outside radius, m (in)

h thickness of disk at radius r from the center of rotation, m (in)

h2 thickness of disk at radius r2from the center of rotation, m (in)

uniform tensile stress in case of a disk of uniform strength,

MPa (psi)

 tangential stress, MPa (psi)

r radial stress, MPa (psi)

z axial stress or longitudinal stress, MPa (psi)

 density of material of the disk, kg/m3(lbm/in3)

! angular speed of disk, rad/s

DISK OF UNIFORM STRENGTH

ROTATING AT ! rad=s (Fig 10-1)

The thickness of a disk of uniform strength at radius r

from center of rotation

The general expression for the radial stress of a

rotating disk of uniform thickness