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 H G , 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 À 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 Lðy 1=3 À 1Þð9-12Þ where y ¼ 2ð sa þ pÞ 2 sa À p ð9-12aÞ h ¼ d ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 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 1:78Wh G = sa d 3 1=2 ð9-14Þ where W ¼ total bolt load, kN (lbf ) h G 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 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ZCp= sa p ð9-15Þ Particular Formula 9.8 CHAPTER NINE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 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 À2:4d=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 6Wh G = sa Ld 2 1=2 ð9-16Þ h ¼ p t ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ½ p= sa c 5 p ð9-17Þ where p t 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.) c 5 ¼ a factor depending on the plate thickness and type of stay (Refer to Table 8-15 for values of c 5 .) For sa refer to Tables 8-8, 8-23, and 8-11 p ¼ h 2 sa c 5 p 2 i ð9-18Þ Refer to Chapter 8 P ¼ 27000 hðD À d i Þ 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 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 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 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 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 d i ¼ inside diameter of tube, in P ¼ maximum allowable working pressure, psi P ¼ 186 hðD À d i Þ wD SI ð9-19bÞ where p in MPa; h, D, d i , and w in m D va ¼ð2d i D þ d 2 i Þ 1=2 ð9-20Þ where d i 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 à 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 à area of cross section. Source: IS 2002-1, 1962. DESIGN OF POWER BOILERS 9.11 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF POWER BOILERS 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 4 1 2 diameters in length or height where the length does not exceed 120 times the thick- ness of the plate The maximum allowable working pressure for fur- naces not more than 4 1 2 diameter 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 3 1 2 times the flue diameter in length, and subjected to external pres- sure only p ¼ 0:36ð18:75T À 1:03LÞ D SI ð9-21aÞ where p in MPa; T, D, and L in m p ¼ 51:5ð18:75T À 1:03LÞ D USCS ð9-21bÞ where p in psi D ¼ outside diameter of furnace, in L ¼ total length of furnace between centers of head rivet seams, in T ¼ thickness of furnace walls, sixteenth of an inch p ¼ 29:3T 2 LD SI ð9-22aÞ where p in MPa; T, L, and D in m p ¼ 4250T 2 LD USCS ð9-22bÞ where p in psi; T, L, and D in in p ¼ 56h d SI ð9-23aÞ where p in Pa; h and d in m p ¼ 8100h d USCS ð9-23bÞ where p in psi; h and d in in d ¼ external diameter of flue, in p ¼ 6:7h À 0:4l d SI ð9-24aÞ where p in Pa; h, l, and d in m p ¼ 966h À 53l d USCS ð9-24bÞ Particular Formula 9.12 CHAPTER NINE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF POWER BOILERS 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) l > 600 mm (24 in) and <3 1 2 d p ¼ 68948h 3 D 3 SI ð9-25aÞ 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 p ¼ 10 7 h 3 D 3 USCS ð9-25bÞ where p in psi; h and D in in p ¼ 119h D À 1:9 SI ð9-26aÞ where p in MPa; h and D in m p ¼ 17300h D À 275 USCS ð9-26bÞ where p in psi; h and D in in j< pD 138h SI ð9-27aÞ where p in MPa; D and h in m j< pD 20000h USCS ð9-27bÞ where p in psi; D and h in in Particular Formula DESIGN OF POWER BOILERS 9.13 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF POWER BOILERS 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 16 in) in thickness (Adamson-type rings) (c) Corrugated rings (d) Plain circular flues riveted together in sections p ¼ 6:7h À 0:4l d SI ð9-28aÞ where p in Pa; h and d in m p ¼ 1080h À 59l d USCS ð9-28bÞ where p in psi h ¼ thickness of wall, 1.5 mm (0.06 in) not to be less than 8 mm ( 5 16 in) l ¼ length of flue section, not to be less than 450 mm (18 in) p ¼ 0:4ð300h À 1:03LÞ D SI ð9-29aÞ where p in MPa; h, L, and D in m p ¼ 57:6ð300h À 1:03LÞ D USCS ð9-29bÞ where p in psi; h, L, and D in in p ¼ 68:5 h d SI ð9-30aÞ where p in Pa; h and d in m p ¼ 10000 h d USCS ð9-30bÞ where p in psi; h and d in in h ¼ thickness of tube wall, mm (in), not to be less than 11 mm (0.44 in) p ¼ 6:7d À 0:4l d SI ð9-31aÞ where p in Pa; d and l in m p ¼ 966h À 53l D USCS ð9-31bÞ where p in psi; l and d in in Particular Formula 9.14 CHAPTER NINE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF POWER BOILERS 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 (P a ) The required moment of inertia (I s ) 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 the ratios L=D o and D o =t. Following the procedure explained in Chap. 8, deter- mine B by using Fig. 9-1. Compute the allowable working pressure P a by the help of Eq. (9-32) P a ¼ B ðD o =tÞ ð9-32Þ where D o ¼ outside diameter of furnace or flue, in Compare P a with P.IfP a is less than P select greater value of t (or h) or smaller value of L so that P a is equal to or greater than P, psi I s ¼ LD 2 o t þ A s L A 14 ð9-33Þ where I s ¼ required moment of inertia of stiffening ring about its neutral axis parallel to the axis of the furnace, in 4 A s ¼ area of cross section of the stiffening ring, in 2 A ¼ factor obtained from Fig. 9-1 Assume the values of D o , L, and t (or h) of furnace. Select a rectangular member to be used for stiffening ring and find its area A s and its moment of inertia I. Then find the value of B from Eq. (9-34) B ¼ PD o t þ A s =L ð9-34Þ where P, D o , t, A s ,andL are as defined under Eq. (9-33) After computing B from Eq. (9-34), determine the value of factor A by the help of Fig. 9-1 and B.If the required I s is greater than the moment of inertia I, for the section selected above, select a new section with a larger moment of inertia and determine a new value of I s . If the required I s is smaller than the moment of inertia I selected as above, then that section should be satisfactory. Particular Formula DESIGN OF POWER BOILERS 9.15 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF POWER BOILERS 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 6.894757MPa). (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 9.16 CHAPTER NINE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF POWER BOILERS 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 P ¼ tC 6 D ð9-35Þ where t ¼ thickness, in, not less than 7.8 mm ( 5 16 in) for Leeds, Morison, Fox and Brown, and not less than 11 mm ( 7 16 in) for Purves and other furnaces corrugated by sections not over 450 mm (18 in) long. D ¼ mean diameter, in Values of C 6 are taken from Table 9-10 P ¼ 11000t R À P s sin USCS ð9-36aÞ where t ¼ thickness of wrapper sheet, in R ¼ radius of wrapper sheet, in ¼ minimum efficiency of wrapper sheet through joints or stay holes Particular Formula TABLE 9-10 Values of C 6 for use in Eq. (9–35) C 6 1. For Leeds furnaces, when corrugations are not more than 200 mm (8 in) from center and not less than 56.25 mm (2.25 in) deep 17,300 2. For Morison furnaces, when corrugations are not more than 200 mm (8 in) from center to center and the radius of the outer corrugation is not more than one-half of the suspension curve 15,600 3. For Fox furnaces, when corrugations are not more than 200 mm (8 in) from center to center and not less than 37.5 mm (1.5 in) deep 14,000 4. For Purves furnaces, when rib projections are not more than 225 mm (9 in) from center to center and not less than 34.375 mm (1.375in) deep 14,000 5. For Brown furnaces, when corrugations are not more than 225 mm (9 in) from center to center and not less than 40.625 mm (1.625in) deep 14,000 6. For furnaces corrugated by sections not more than 450 mm (18 in) from center to center and not less than 37.5 mm (1.5 in) deep, measured from the least inside greatest outside diameter of the corrugations and having the ends fitted into the other and substantially riveted together, provided the plain parts at the ends do not exceed 300 mm (12 in) in length Source: ASME Power Boiler Code, Section I, 1983. DESIGN OF POWER BOILERS 9.17 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF POWER BOILERS [...]... 4.88 4.88 4.88 4.88 102 102 102 102 3.66 3.66 4.28 4.28 4.88 5. 18 5. 50 5. 18 5. 50 5. 18 5. 18 4.28 4 .58 4 .58 5. 50 5. 50 6.10 5. 50 6.10 5. 50 5. 50 4.88 4.88 5. 5 6.10 6.10 6.10 6.10 Dry-back scotch boilers Diameter of shell, m Diameter of tubes, mm Inside diameter of furnace, mm Length of grate, m 920 920 970 1 150 1270 970 1 150 1270 1.22 1 .53 1.93 2.03 2.21 1.93 2.03 2.21 970 1040 1140 970 1040 1140 Length... 41,868.0 12 ,50 0–1 2000 13,000 14 ,50 0 12 ,50 0 9 ,50 0 19,000 9 .5 9 9 .5 10 9 6 14 .5 TABLE 9- 15 Average rates of combustion [kg/m2 (lb/ft2 ) of grate surface per hour] draft 12 .55 mm (1 in) water column 2 Fuel used Stationary grate Anthracite Semibituminous Bituminous Lignite 44–68 .5 (9.14) 98 (20) 68 .5 (14) 58 .5 (12) TABLE 9-16 Minimum kilograms (pounds) of steam per h per ft2 of surface Firetube boilers Particulars... Elongation percentage min on gauge length Tensile strength Grade MPa kpsi pffiffiffiffiffi 5. 65 aà a 1 2 3 4 5 362.8–441.3 411.9–490.3 431 .5 52 9.6 460.9 55 9.0 490.3 58 8.4 52 .6–64.0 59 .7–71.1 62.6–76.8 66.8–81.0 71.1– 85. 3 26 25 23 22 21 200 mm Bond test diameter of former 25 23 21 20 19 2t 2t 3t 3t 31 t 2 a Area of cross section Source: IS 350 3, 1966 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)... 0.087–0.10 0.0 75 0.087 0.0 65 0.07 45 0. 056 –0.0 650 0.020–0.0 25 0.011–0.013 0.100–0.1 25 0.0149–0.0186 0.0084–0.0093 0.07 45 0.093 0.037–0. 050 0 0.0279–0.0372 TABLE 9-21 Heating boiler efficiency Firing method Hand-Fired Coal Lignite Subbituminous Bituminous Low-volatile bituminous Anthracite Coke Stoker Conversion Bituminous Anthracite Burner Conversion Natural gas Oil Designed for Burner Stoker 45 kg > 45 kg Gas... Conversion Natural gas Oil Designed for Burner Stoker 45 kg > 45 kg Gas Oil Cast-iron boilers Steel boilers Package units Efficiency, % 49 44–63 50 – 65 44–61 60– 75 75 76 55 –69 63 69–76 51 ; 65; 70 60– 75 65 70 70–80 70–80 68 70 75 REFERENCES 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... 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 Minimum thickness 6 .5 8.0 9 .5 11.0 12 .5 14 .5 Shell and dome plate diameter 910 >910–1370 >1370–1830 >1830 Tube sheet diameter 10 65 >10 65 1370 >1370–1830 >1830 Heating boilers Shell or other plate diameter 10 65 >10 65 153 0 > 153 0–1980... 1220 1370, 152 0 1680, 1830, 1980, 2130 75 100 1 25 Vertical firetube boilers Boiler diameters mm Distance between gauge cocks, mm 910–1220 1 250 –1680 1700–2410 2460–3100 100 1 25 150 1 75 Dry-back Scotch boilers Locomotive-type boilers Low water level 89 mm 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 1 25 mm above the... 3.20 3.36 3.97 4 .58 4 .58 1.22 1.27 1.38 1 .53 1 .53 1.68 1.83 50 62 3.96 4.27 4 .57 4.88 0.76 0.92 1.07 1.22 1.38 1 .53 1.68 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website DESIGN OF POWER BOILERS 9.24 CHAPTER NINE Particular Formula... IT 01 0:3 þ 0:008 D IT 0 0 :5 þ 0:012 D IT 1 0:8 þ 0:020 D or 45H8 À g7 or 45 H8 g7 ð11-34Þ where D is expressed in mm ð11- 35 TABLE 11-1 Relative magnitudes of standard tolerances for grades 5 to 16 in terms of standard tolerance unit ‘‘i ’’ [Eq (11-34)] Grade IT 5 IT 6 IT 7 IT 8 IT 9 IT 10 IT 11 IT 12 IT 13 IT 14 IT 15 IT 16 Values 7i 10 i 16 i 25 i 40 i 64 i 100 i 160 i 250 i 400 i 640 i 1000 i Source:... ð9-42hÞ P ¼ 51 5 à DS ð9-42iÞ H ¼ 50 G ð9-43aÞ S ¼ 11:2  10À3 ð0:424Þà p ð9-43bÞ H ¼ 0:92 ð10Þà P ð9-43cÞ P ¼ 51 ð4:37Þà G 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 ð9-42gÞ G P ¼ 18:3  10À3 ð20Þà or ¼ 51 5 P G Watertube boiler design ð9-42f . (7.8 75) 1.38 200 112 .50 0 (4 .50 ) 131. 25 (5. 25) 153 .1 25 (6.1 25) 1 75. 000 (7.000) 193. 750 (7. 750 ) 212 .50 0 (8 .50 ) 1 .55 2 25 106. 25 (4. 25) 121.8 75 (4.8 75) 146.8 75 (5. 8 75) 162 .50 0 (6 .50 ) 181. 250 (7. 25) . 1 15. 6 25 (4.6 25) 137 .50 0 (5. 50) 162 .50 0 (6 .50 ) 190.6 25 (7.6 25) 0.96 140 112 .50 0 (4 .50 ) 134.3 75 (5. 3 75) 156 . 250 (6. 25) 184.3 75 (7.3 75) 209.3 75 (8.3 75) 1.03 150 106. 250 (4. 25) 128.1 25 (5. 1 25) 150 .000. (7 .50 0) 209.3 75 (8.3 75) 1.24 180 118. 750 (4. 75) 137 .50 0 (5. 50) 162 .50 0 (6 .50 ) 184.3 75 (7.3 75) 203.1 25 (8.1 25) 1.31 190 1 15. 6 25 (4.6 25) 134.3 75 (5. 3 75) 159 .3 75 (6.3 75) 178.1 25 (7.1 25) 196.8 75 (7.8 75) 1.38