Boiler steels are of high-quality characterized by low carbon and high weldability, high consistency, definite high-temperature properties, and a long history of satisfactory usage. They are manufactured and tested to the specified codes.

All the boiler steels should be procured only from code-approved manufacturers, and code recognition comes only after stringent and periodic verification regarding compli­ance to the set standards for manufacturing processes, stage inspections, and documenta­tion. The machines, the work procedures, the inspection stages, and even workmen such as welders must be qualified individually. Thus, all the pressure part (PP) materials in a boiler must come from fully recognized sources and meet minimum set patterns conform­ing to a defined quality.

All boiler PP materials are invariably provided with material test certificates (TCs) in which the material source and all appropriate tests at various manufacturing stages of steel, as outlined in the code are detailed. Usually, the TCs, so prepared by the steel maker, are further certified by an independent third-party agency to confirm the reliability of the reports supplied by the manufacturer.

All steels used in making various parts of a boiler and all stage inspections are recorded as specified by the code, in the designated formats to finally create a manufacturing TC. The manufacturing and material TCs together capture the entire history of a PP.

All this effort is taken because the PPs made from various steels have to withstand a lot of pressure safely at high temperatures, without any leakage or rupture. The manu­facturing and material certificates of all boiler parts are compiled as the PP documen­tation of the boiler. It is then submitted to the code-approved authorities or insurance companies for the mandatory registration of the boiler, prior to commercial operation. A comprehensive documentation for each and every PP is created this way so that the history of a failed part may be traced should any failure occur during the boiler operation.

Today we have almost taken for granted the safety of PPs in boilers, operating even at highest pressures and temperatures. This safety may be attributed to the stringent quality measures evolved at all stages of manufacture of raw steels and components, together with the meticulous documentation at every stage.

Steel Forms Required for Various Pressure Parts Type of Pressure Part Raw Steel Required Drums and reheater header Plates Coils for superheater, reheater, economizer Tubes Boiler bank Tubes Membrane, division wall panels Tubes and strip All headers and large-bore downcomers Large bore pipe All integral piping Small bore pipes/tubes All nozzles including on headers and drums Forgings

Various PP assemblies and the raw steels required are given in Table 5.2. Thus, the PP material requirements are as follows:

1. Plates

2. Tubes

3. Pipes

4. Forgings

5. Castings (occasionally)

The mean metal temperature range of 450-480°C is the rough dividing line for carbon steels (CS) and alloy steels (AS).

Boilers require a variety of steels, starting from low-strength low-carbon steels to high — strength high-alloy steels and even stainless steel (ss) for various parts. However, with the success of 9Cr-1Mo-V steels, the use of ss has considerably reduced. The limiting tempera­ture and the strength required are the main factors that decide the appropriate metallurgy. The pattern of a steady progression from carbon to ss is as follows.

Carbon steels	Low carbon
	High carbon
Alloy steels	C-Mn/C-Mo steels
	1 1/4% Cr-1/2 Mo steels
	2 1/4% Cr-1% Mo
	9Cr-1Mo-V
Stainless steels

The boiler design codes specify which steels are required.

Boiler Quality (BQ) Plates

Boiler quality plates are required to withstand high pressure and temperature: high pres­sure in drums, high temperature in RH outlet headers, and both high pressure and tem­perature in superheater (SH) headers made from plates. The most important requirements of BQ plates are as follows:

• Consistency and uniformity of properties across the length, width, and thickness of the plate

• High purity of steel

• No inclusions or air pockets

These requirements make BQ plates not easy to roll by all mills, particularly in higher thicknesses. Boiler quality plates are characterized by the following:

• Low carbon content for good weldability

• High tensile strength to limit drum thicknesses

• Fully killed (deoxidized)

• High thicknesses

There are three categories of plates available with progressively increasing tensile strength:

1. Carbon steel (low, medium, and high carbon)

2. Low-alloy steel

3. High-alloy steel

Plate selection. The metal temperature and the strength required are the prime considerations.

• In the American boiler-making practice, CS is favored, even with increasing carbon (—0.35%), resulting in thicker drums, as opposed to the European practice of adopt­ing low-carbon low-alloy plates (—0.25%) of higher strength, which yield thinner drums that are more conducive to faster boiler dynamics.

• High-carbon steel plates of both SA 515 and SA 516 are extensively used in the industry. For lower thicknesses up to 40 mm, coarse-grained steel of SA 515 of suitable grade is used, whereas for thicknesses up to 100 mm, fine-grained steel of SA 516 is generally preferred.

• For even higher-pressure applications, SA 299 in CS and SA 302 in AS are popular to contain the thickness.

• High-alloy steels are of European origin and are generally not found in American standards. With higher alloy content and higher tensile and, more importantly, higher yielding strengths, these high-alloy steels reduce the plate thicknesses dramatically. Table 5.3 lists various American and European plate materials in common use.

Plates are generally procured in normalized condition except in the case of plates used for making dish ends when they are obtained in annealed condition. It is always prudent to subject the plates to magnetic particle and ultrasonic testing thoroughly on arrival in the workshop to eliminate any possibility of inclusions and imperfections. There have been cases when inclusions have been detected at the final stage after the drum has been almost completed, upsetting the entire project schedule because drums have long manu­facturing cycles. While ordering drum plates, extra material is to be included as specified by the codes for test coupons required for testing purposes.

Boiler Tubes

As indicated in Equation 1.15, the thickness of a PP is directly proportional to the inside pressure and diameter. In case of drums, the diameter is large, but as the temperature is low, the higher stress values of the plate manage to contain the thickness. For tubes, the case is reversed with metals experiencing the highest temperatures in SH and RH and, consequently, having the lowest stress values. The range of tube materials required in a boiler is therefore far higher than the range for plate materials.

BQ Plates—American Specifications and Equivalents

	American Plate Specifications (SA)
Plate Specifications	Nominal Composition	C%	Tensile (kpsi)	Yield (kpsi)	Tensile (MPa)	Yield (MPa)	Maximum (°C)	British Equivalent (BS 1501)	German Equivalent (DIN 17155)
1. Carbon steels
285 Gr C	C	0.22	55	29	380	200	482	161^30	C	H-U	C-Mn
515 Gr 70	C	0.35	70	38	480	265	538	224-490	C-Mn	17Mn4	C-Mn
516 Gr 70	C	0.35	70	38	480	265	538	224-490	C-Mn	17Mn4	C-Mn
299	C	0.30	75	40	515	275	538	224-490	C-Mn	19 Mn6	C-Mn
2. Low-alloy steels
302 Gr B	Lf/o Mn-1/2 Mo	0.25	80	50	550	350	538	—		15 Mo3	C-l/2 Mo
3. Medium-alloy steels
38711 cl 11	L-J-% Cr-1/2 Mo	0.17	75	45	515	315	566	Gr 620B	1-} % Cr-1/2 Mo	13Cr044	L-J-% Cr-1/2 Mo
38722 cl 2	2~% Cr-1% Mo	0.17	75	45	515	315	577	Gr 622B	2~% Cr-1% Mo	10Cr-Mo9 10 2 % Cr-1% Mo
4. High-alloy steels
NA NA		0.17 0.19	80 87	56 61	551 600	386 420	500 500	Gr 271 (DUCOL)	Ni-Cu-Mo-V	15NiCu- MoNb5 (WB36)

Notes: Brief details of popular drum plates to American standards are provided here and are compared with the other popular equivalent British and German plates.

Boiler Materials 171

For accurate and current details, the readers must refer to the latest specifications.

Tensile strength reduces as the plate thickness increases. Tensility given here refers to higher thicknesses. Tensile and yield strength values given are the minimum values. Figures in MPa are rounded off.

The equivalent plate indicated is not an identical material. It is the closest by tensile strength but differs in almost all other major parameters.

Plates of high-alloy steels are popular in Europe. The values given in the table against this item are not for American plates but of Ducol and WB36, respectively. NA, not available.

Differences between Tubes and Pipes

Tube

Pipe

Both heat transfer and conveyance

Material amenable for closer bending, as C is lower

Welding is easier due to lower C

Sizes up to 125 mm OD and hence smaller tubes

Designated by outside diameter

Closer tolerance on thickness

Only conveyance and not heat transfer Material suitable only for limited bending

Sizes up to 1000 mm and beyond, and hence larger pipes Designated by nominal bore (NB) upto 12 in. (304.8 mm) Larger tolerances

Pipes also experience the same tough conditions as tubes. Because they are outside the gas pass, the temperatures experienced are a little lower.

Tubes versus Pipes

Tubes and pipes are not identical. The most important difference is that pipes do not trans­fer heat. Further differences are mentioned in Table 5.4. Tubes and pipes are manufactured to different specifications and are not interchangeable even in the narrow overlapping range up to 125 mm.

Seamless and Electric Resistance-Welded (ERW) Tubes

Boiler tubes are manufactured by two processes, and are classified as follows:

1. Seamless tubes—produced by piercing a red-hot billet with a plunger

2. Electric resistance-welded tubes produced by folding and welding steel strip, called skelp

Both types of tubes are extensively used in boiler making, although certain reserva­tions for ERW tubes are entertained even today based on the ability of the weld seam to withstand the temperatures and tube expansion forces after initial failures a few decades ago when ERW tubes were first introduced. In terms of weldability, bending, and physical and chemical properties, the seamless and the ERW tubes are nearly the same. In fact the ERW tubes are superior and preferred for lower thicknesses, as they are made from plate materials, which render the

• Inside tube surface smooth resulting in lower inside-pressure drop

• Bore concentric to OD, unlike in seamless tubes, and thus better suited for tube expansion

• Lower costs

ERW tubes are well accepted in CS execution. However, ERW tube thickness is limited to ~6 mm for welding and folding considerations of the skelp. Although ERW tubes are made of low-alloy steels and covered in SA 250, their usage is still low.

ERW tubes are used for medium-pressure CS applications in the industrial boilers, whereas the seamless tubes are used for utility boilers and the high-temperature AS tubes for industrial boilers. The European market has an overwhelming preference for seamless tubes.

Hot-Finished and Cold-Drawn Seamless Tubes (HFS and CDS)

As the tubes come out of the tube mill, they are hot finished and their tolerance levels are high. For furnace, boiler bank (BB), and economizer (ECON) sections, the slightly higher pressure drop in HFS tubes makes no significant difference. Even in SHs of smaller boilers, the higher pressure drop is of no consequence. Cold-drawn seamless tubes have closer tolerance, and for SH and RH duties in large boilers, tolerance makes a large difference. CDS tubes are produced from HFS tubes by reheating them to the appropriate temperature and rerolling to a closer finish. Naturally, this additional work makes the CDS tubes more expensive. Unless the duty demands, the CDS tubes are not used in boiler making. The hardness of CDS tubes is also higher on account of work hardening.

Tubes and Comparison

Carbon, alloy, and occasionally ss tubes are employed in boiler making as shown in Table 5.5. Tubes to American specifications are listed along with the BS and DIN equiva­lents, which are the other popular globally accepted specifications.

Tubes are rolled in sizes from 12.7 to 127 mm (0.5-5 in.) OD, and almost all sizes from 31.8 mm OD onward are used in boilers. Tubes are always designated by their outside diameters.

Selection of Tube Materials

Temperature limits, based on accelerated oxidation, determine the basic applicability of any material. Thereafter, the strength of the material at the operating temperature gov­erns the selection. As shown in Figure 1.7, the permissible stresses, particularly at the low temperatures, do not vary much (<250° C approx.); but at the elevated temperature, they deteriorate sharply beyond 450°C. Each incremental improvement in metallurgy is costlier by 20-40%. The increase in allowable stress level should be more than this incremental cost to justify the superior material and cut down the thickness and the overall cost. Often it does. That is how more expensive materials such as T22 and T91 are used for relatively lower temperatures. A good boiler design has the following features:

• Maximum use is made of low-carbon steels due to their ease of manufacture and repair.

• The thicknesses are kept to a minimum by using superior metals to lower the thermal inertia.

• The use of ss is minimized due to the expense, much higher elongation, suscepti­bility to stress corrosion, and possible problems arising from welding dissimilar metals.

For very high temperature service, TP 321 has been in use for several years. Improved stress values in the code have made 304H and 347H more popular. TP 316H is required only for very high steam temperatures of ~600°C.

Table 5.6 lists various commonly used carbon, alloy, and ss tubes and pipes as per differ­ent codes with their areas of application in different parts of the boiler.

Boiler Quality Tubes to American Specifications and Their BS and DIN Equivalents

		American Tube Specifications (SA)					British Equivalent (BS 3059)	German Equivalent (DIN 17175) for Seamless
	Nominal Specification	Temperature Limit (°C)	Tensile (kpsi)	Yield (kpsi)	Tensile (MPa)	Yield (MPa)	Use
1. Carbon steel
Low tensile
178 A (ERW)	C(<0.18)	510	47	26	324	179	1,2,3	ERW 320	St 37.8 (DIN 17177)
192	C(<0.18)	510	47	26	324	179	1,2,3	SI 360	St 35.8
Medium tensile
210 A-l	C(<0.2 7)	510	60	37	414	255	1,2,3	SI 440	St 45.8
High tensile
210 C	C(<0.35)	510	70	40		276	2,3
178 C (ERW)	C(<0.35)	510	60	37	414	255	2,3	ERW 440	St 42.8 (DIN 17177)
178 D (ERW)		510	70	40		276	1,2,3
2. Low-alky steel
209 T1	C-i Mo	524	55	30	379	207	1,2,3	SI 243	15M03
209 T 1A	C—j Mo	524	60	32	414		2,3
213 T2	YCr-y Mo	552	60	30	414	207	1,3
213 T 11	L{% Cr-^-Mo	566	60	30	414	207	3	620-460	13CrMo44
213 T 22	2j% Cr-1% Mo	602	60	30	414	207	3	622-490	10CrMo9 10
3. High-alloy steel
213 T 9 1	9Cr-lMo-V	649	85	60	586	414	3	622 Gr 91	X 10 Cr MoV Nb 9-1
4. Stainless steel
213 TP-304 H	18Cr-8Ni	760	75	30	517	207	3	CFS 304 S 51	X2 Cr Ni $19-11
213 TP-321 H	18Cr-10Ni-Ti	760	75	30	517	207	3	CFS 321 S 51	X6 Cr Ni Ti $18-10
213 TP-347 H	18Cr-10Ni-Cb	760	75	30	517	207	3	CFS 347 S 51	X5 Cr Ni Nb $18-10
213 TP-316 H	16Cr-12Ni-2Mo	760	75	30	517	207	3	CFS 316 S 51	X5 Cr Ni Mo $17-1-22
213 TP-310 H	25Cr-20Ni	816	75	30	517	207	3	CFS 310 S 51

Notes: Safe maximum outside tube wall metal temperatures given here are on the basis of oxidation resistance. Design codes decide the permissible temperature limits. For CS usage beyond 454°C when permitted by the code, special inspection is required for 100% weld efficiency.

Boilers for Power and Process

In the column pertaining to use, 1 refers to furnace walls exposed to high heat, 2 refers to ECON and other enclosures not exposed to high heat, and 3 refers to SH and RH.

$ refers to DIN 17456, which is the specification for ss tubes. The equivalents are for basic steels without suffix H. Steels with suffix H are modified to suit high- temperature duties of SH and RH by increasing the carbon content by 0.02%.

Thickness as per SA standards is usually the minimum thickness with no negative tolerance, whereas with BS and DIN, it is the nominal thickness with appropriate negative tolerance.

Common Steel Tubes and Pipes with Their Areas of Application in Boilers Standards Applications Steel American British German Economizer Evaporator SH RH MS Hot RH Feed Grade Content ASME SA BS DIN 17175 Tube Tube Tube Tube Pipe Pipe Pipe Carbon 0.15-0.25°C 192 3059-320,360 St 35.8, St 45.8 X X Steel 210 A1 Tubes 53 Gr A, B 3601-320,360,410 St 35.8, St 45.8 X X Pipes 106 Gr A, B 3602-320,360,410 Mo steel 0.3-0.5Mo Tl, PI 3059-243 15Mo3,15Mo5 X X X X X Cr-Mo-V ■|Cr-|Mo 3604-660 14MoV63 X X Steel Cr-Mo ■|Cr-|Mo T2,P2 X X X X X Steel LCr-i-Mo T12, P12 X X X X L±Cr-2Mo Til, PU 3059-620 3604-620/440,460 13CrMo44 X X X X 2-jCr-lMo T22, P22 3059-622 3604-622 10CrMo9 10 X X X X 9Cr-lMo T91, P91 3059-629 3604-629 X12CrMo91 X X X X Ferritic SS 12Cr-lMo 0.3 V 3059-762 X20CrMoV121 X X X Austenitic 18Cr-8Ni TP304,304H 3059-304S18 X5CrNil89 X X SS 3065-304S59 X12CrNil88 18Cr-8Ni-Ti TP321H 3059-321S18 3065-321S59 X10CrNiTil89 X X 18Cr-8Ni-Nb TP347H 3059-347S18 3065-347S59 X10CrNiNbl89 X X 18Cr-8Ni-2fMo TP316H 3059-316S18 3065-316S59 X5CrMol810 X5CrNiMol812 X X

Boiler Materials

Oi

Tubes are received in strapped bundles. The individual tubes are stenciled with the speci­fication and are color coded for proper identification. It is not advisable to punch the tubes lest their outer layer should be destroyed, making them susceptible to creep damage. The material codes for tubes and pipes contain both mandatory and optional requirements, covering various testing and supply aspects, which should be mutually agreed upon at the time of order placement for ensuring smooth supply per requirements.

If there are sufficient numbers, tubes can be ordered in any exact length, which saves time and cost in resizing. Tubes for BB can be additionally ordered with ends annealed to ease the tube expansion.

Hydraulic testing (HT) of individual tubes before dispatch from the tube mill is an ideal QA measure, but it costs more time and money. Nondestructive tests such as full-fledged online eddy current testing, which runs along with the tube rolling, are good substitutes for HT besides being cheaper and faster.

Table 5.7 lists the commonly used tubes with their diameters and thicknesses and pro­vides the tube weight in kilograms per meter.

Tube thickness is normally expressed in wire gauge. There are two popular designa­tions, namely, standard wire gauge (SWG) as per British practice and Birmingham wire gauge (BWG) as per American practice. They are similar as can be seen in the comparison in Table 5.8. Note that the thicknesses are in steps of —10%.

Tube Sizes and Weights in kg/m Length TABLE 5.7 Tube OD British Standard Wire Gauge (SWG) 1 2 3 4 5 6 7 8 9 10 11 12 In. Mm 7.620 7.010 6.401 5.893 5.385 4.877 4.470 4.064 3.658 3.251 2.946 2.642 3/4 19.05 2.149 2.080 1.998 1.912 1.814 1.706 1.607 1.502 1.338 1.266 1.171 1.069 1 25.40 3.343 3.179 2.998 2.834 2.657 2.467 2.306 2.139 1.962 1.775 1.630 1.483 1 1 31.75 4.534 4.278 4.002 3.855 3.635 3.232 3.008 2.775 2.532 2.286 2.093 1.896 1 1 38.10 5.728 5.374 5.003 4.682 4.344 3.996 3.710 3.412 3.107 2.795 2.556 2.310 I! 44.45 6.923 6.473 6.007 5.604 5.187 4.761 4.410 4.048 3.681 3.304 3.015 2.723 2 50.80 8.117 7.572 7.008 6.526 6.030 5.525 5.108 4.685 4.252 3.812 3.478 3.136 2 1 57.15 9.308 8.668 8.012 7.451 6.873 6.286 5.807 5.322 4.826 4.321 3.940 3.550 2 -3- ^ 8 60.33 10.138 9.219 8.514 7.910 7.297 6.670 6.158 5.640 5.111 4.577 4.170 3.757 2 1 63.50 10.502 9.767 9.016 8.373 7.720 7.050 6.509 5.958 5.397 4.832 4.340 3.967 2 -43- 69.85 11.697 10.631 10.168 9.295 8.590 7.815 7.208 6.595 5.971 5.341 4.862 4.380 2 -7­8 73.03 12.293 11.414 10.518 9.758 8.983 8.196 7.559 6.913 6.257 5.594 5.092 4.587 3 76.20 12.891 11.962 11.021 10.220 9.406 8.579 7.910 7.231 6.546 5.850 5.325 4.793 3 -1­3 4 82.55 14.082 13.061 12.021 11.142 10.250 9.344 8.609 7.868 7.116 6.358 5.784 5.207 3 -1­3 2 88.90 15.276 14.160 13.026 12.64 11.093 10.105 9.308 8.504 7.690 6.867 6.247 5.620 4 101.60 17.665 16.356 15.030 13.911 12.779 11.634 10.709 9.777 8.835 7.887 7.169 6.447 4 1 107.95 18.856 17.455 16.030 14.833 13.622 12.399 11.411 10.414 9.409 8.396 7.631 6.860 4 1 114.30 20.050 18.550 17.035 15.755 14.466 13.163 12.110 11.050 9.980 8.905 8.090 7.174 5 127.00 22.439 20.749 19.039 17.602 16.152 14.689 13.511 12.320 11.126 9.925 9.016 8.104 5 1 133.35 23.630 21.844 20.044 18.524 16.995 15.453 14.210 12.960 11.700 10.433 9.475 8.517 5 1 139.70 24.824 22.944 21.044 19.450 17.839 16.218 14.912 13.596 12.274 10.942 9.938 8.930 5 — 5 16 141.28 25.125 23.219 21.297 19.679 18.052 16.408 15.086 13.757 12.418 11.070 10.052 9.036 6 152.40 27.12 25.139 23.049 21.293 19.525 17.743 16.310 14.870 13.419 11.959 10.860 9.758

Common Sheet and Tube Thicknesses Gauge No. British Standard Wire Gauge (SWG) Birmingham Wire Gauge (BWG) Mm In. Mm In. 000 9.449 0.372 10.794 0.425 00 8.839 0.348 9.651 0.380 0 8.230 0.324 8.633 0.340 1 7.620 0.300 7.620 0.300 2 7.010 0.276 7.213 0.284 3 6.401 0.252 6.579 0.259 4 5.893 0.232 6.045 0.238 5 5.385 0.212 5.558 0.220 6 4.877 0.192 5.156 0.203 7 4.470 0.176 4.571 0.180 8 4.064 0.160 4.191 0.165 9 3.658 0.144 3.759 0.148 10 3.251 0.128 3.403 0.134 11 2.946 0.116 3.047 0.120 12 2.642 0.104 2.768 0.109 13 2.337 0.092 2.412 0.095 14 2.032 0.080 2.108 0.083 15 1.829 0.072 1.828 0.072 16 1.626 0.064 1.650 0.065 17 1.422 0.056 1.472 0.058 18 1.219 0.048 1.245 0.049 19 1.016 0.040 1.067 0.042 20 0.9144 0.036 0.8890 0.035 21 0.8128 0.320 0.8128 0.032 22 0.7112 0.028 0.7112 0.028 23 0.6096 0.024 0.6096 0.025 24 0.5588 0.022 0.5588 0.022 25 0.5080 0.020 0.508 0.020

Pipes

Pipes are designated by nominal bore (NB) for sizes up to 304.8 mm (12 in.) and by OD beyond that size. In boilers, pipe materials are used in the following three areas:

1. Headers and downcomers placed inside or outside the gas stream

2. Integral piping, namely, drain, vent, blowdown, soot blower (SB), attemperator, and interconnecting piping

3. Piping for feed water (FW), main steam, and reheated steam

Only seamless piping is used because of both high pressure and high temperature. Pres­sure pipes used in oil and gas industry, such as line pipes or submerged arc welded (SAW) pipes, are not employed in boilers. Table 5.9 lists the popularly used BQ pipes to American specifications and their equivalents in BSand DIN.

In a boiler, most pipe required is for headers. In industrial boilers of up to 400 tph, the headers fall broadly in the range of 168-760 mm OD with thicknesses from 16-80 mm. Thick headers, like thick drums, are to be avoided because they hinder quick start and shutdown of the boiler. Headers placed in the gas passes are cooled by the water inside.

TABLE 5.9 Boiler Quality Pipes to American Specifications and Their Equivalent BS and DIN Standards American Specifications (SA) British Equivalent (BS) German Equivalent (DIN 17175) Nominal Specifications Temperature Tensile Limit (°C) (kpsi) Yield (kpsi) Tensile (MPa) Yield (MPa) Use 1. Carbon steel Medium Tensile 106 Gr B C(<0.30)a 510 60 35 414 241 1, 2, 3 3602 CFS 460 St 45.8 High tensile 106 Gr (°C) C(<0.35)a 510 70 40 482 276 1, 2, 3 2. Low-alloy steel 335 P1 C-2 Mo 468 55 30 379 207 2, 3 S1 243 15 M03 335 P12 C-2 Mo 566 60 30 414 207 1 335 P11 1__% Cr — Mo 566 60 30 414 207 1, 2, 3 3604 CFS 620 13CrMo44 335 P22 2__% Cr-1% Mo 593 60 30 414 207 1, 2, 3 3604 CFS 622 10CrMo9 10 3. High-alloy steel 335 P91 9Cr-1Mo-V 649 85 60 586 414 1, 2, 3 3604-2 Gr 91 X10CrMoV Nb9-1

Note: In the column pertaining to use, 1 refers to furnace walls exposed to high heat, 2 refers to ECON and other enclosures not exposed to high heat, and 3 refers to SH and RH. a Limited to a temperature of 427°C (800°F) and for pipes outside of boiler setting for fear of graphitization by steam.

In utility boilers, the RH headers are thicknesses rolled from plates, as the diameters go beyond the usual pipe rolling range. Table 5.10 lists the pipes by NB and thicknesses (mm) and unit weights (kg/m) as per ANSI.

Pressure Castings and Forgings

For pressure holding, forgings are better suited than castings due to their dense structures that make them lighter. Castings are good for making intricate shapes and thick walls. They are also cheaper to produce because they need no dies, and hence are popular in valve making. Boiler parts of similar to valves can be made of pressure castings. In normal boilers, there are nearly no pressure castings. Table 5.11 lists the castings and forgings to American specifications with their BS and DIN equivalents. In a boiler, forgings are used for making various pressure components such as

1. Nozzles for drum, header, and pipes

2. End closures for headers

3. Pipe fittings such as elbows, bends tees, reducers, expanders

4. Pipe and header attachments such as weldolets, pads, thermowells

5. Special forgings such as tube joints

Because of larger sizes and superior metallurgy, the drum, main steam, and RH header nozzles, together with pipe bends in SH and RH areas, constitute more than 70% of the total value, although they form only —10% of the total forgings by numbers. Table 5.11 lists the popular pressure castings and forgings to American specifications along with their British and German equivalents.

TABLE 5.10 Pipe Schedules, Thicknesses (mm), and Weights (kg/m) as per ANSI Nominal Pipe Size (in.) OD (mm) 5S 10S 10 20 30 STD 40S 1/8 10.30 — 1.42 — — — 1.73 1.73 0.28 0.37 0.36 1/4 13.70 — 1.65 — — — 2.24 2.24 0.51 0.63 0.64 3/8 17.10 — 1.65 — — — 2.31 2.31 0.64 0.84 0.84 1/2 21.30 1.65 2.11 — — — 2.77 2.77 0.82 1.01 1.27 1.30 3/4 26.70 1.65 2.11 — — — 2.87 2.87 1.04 1.31 1.69 1.71 1 33.40 1.65 2.77 — — — 3.38 3.38 1.33 2.13 2.50 2.55 42.20 1.65 2.77 — — — 3.56 3.56 1.68 2.76 3.39 3.46 48.30 1.65 2.77 — — — 3.68 3.68 1.95 3.17 4.05 4.13 2 60.30 1.65 2.77 — — — 3.91 3.91 2.44 4.01 5.44 5.54 2- 2 73.00 2.11 3.05 — — — 5.16 5.16 3.77 5.36 8.63 8.81 3 88.90 2.11 3.05 — — — 5.49 5.49 4.60 6.59 11.29 11.52 3- 2 101.60 2.11 3.05 — — — 5.74 5.74 5.29 7.55 13.57 13.84 4 114.30 2.11 3.05 — — — 6.02 6.02 5.96 8.52 16.07 16.40 5 141.30 2.77 3.40 — — — 6.55 6.55 9.67 11.82 21.77 22.20 6 168.30 2.77 3.40 — — — 7.11 7.11 11.55 14.13 28.26 28.83 8 219.10 2.77 3.76 — 6.35 7.04 8.18 8.18 15.09 20.37 33.31 36.81 42.55 43.39 10 273.10 3.40 4.19 — 6.35 7.80 9.271 9.27 23.09 28.34 41.77 51.03 60.3 61.52

40	60	Xs	80S	80	100	120	140	160	Xxs
1.73	—	2.41	2.41	2.41	—	—	—	—	—
0.37		0.47	0.48	0.47
2.24	—	3.02	3.02	3.02	—	—	—	—	—
0.63		0.80	0.82	0.80
2.31	—	3.20	3.20	3.20	—	—	—	—	—
0.84		1.10	1.12	1.10
In	—	3.73	3.73	3.73	—	—	—	4.78	7.47
1.27		1.62	1.65	1.62				1.95	2.55
2.87	—	3.91	3.91	3.91	—	—		5.56	7.82
1.69		2.20	2.24	2.20				2.90	3.64
3.38	—	4.55	4.55	4.55	—	—	—	6.35	9.09
2.50		3.24	3.29	3.24				4.24	5.45
3.56	—	4.85	4.85	4.85	—	—	—	6.35	9.70
3.39		4.47	4.56	4.47				5.61	7.77
3.66	—	5.08	5.08	5.08	—	—	—	7.14	10.15
4.05		5.41	5.51	5.41				7.25	9.56
3.91	—	5.54	5.54	5.54	—	—	—	8.74	11.07
5.44		7.48	7.63	7.48				11.11	13.44
5.16	—	7.01	7.01	7.01	—	—	—	9.53	14.02
8.63		11.41	19.64	11.41				14.92	20.39
5.49	—	7.62	7.62	7.62	—	—	—	11.13	15.24
11.29		15.27	15.59	15.27				21.35	27.68
5.74	—	8.08	8.08	8.08	—	—	—	—	—
13.57		18.63	19.01	18.63
6.02	—	8.56	8.56	8.56	—	11.13	—	13.49	17.12
16.07		22.32	22.77	22.32		28.32		33.54	41.03
6.55	—	9.53	9.53	9.53	—	12.70	—	15.88	19.05
21.77		30.97	31.59	30.97		40.28		49.11	57.43
7.11	—	10.97	10.97	10.97	—	14.27	—	18.20	21.95
28.26		42.56	43.42	42.56		54.20		67.56	79.22
8.18	10.31	12.70	12.70	12.70	15.09	18.26	20.62	23.01	22.23
42.55	53.08	64.64	65.95	64.64	75.92	90.44	100.92	111.27	107.92
9.27	12.70	12.70	12.70	15.09	18.26	21.44	25.40	28.58	25.40
60.31	81.55	81.55	83.19	96.01	114.75	133.06	155.15	112.33	155.15

Boiler Materials

(continued) ‘■Ј>

Nominal Pipe Size (in.)	OD (mm)	5S	10S	10	20	30	STD	40S	40	60	XS	80S	80	100	120	140	160	Xxs
12	323.90	3.96 31.89	4.57 36.73	—	6.35 49.73	8.38 65.20	9.53 73.88	9.52 75.32	10.31 79.73	14.27 108.96	12.70 97.46	12.70 99.43	17.48 132.08	21.44 159.91	25.40 186.97	28.58 208.14	33.32 238.76	25.40 186.97
14	355.60	3.96 35.06	4.78 42.14	6.35 54.69	7.92 67.90	9.53 81.33	9.53 81.33	—	11.13 94.55	15.09 126.71	12.70 107.39	35.71 281.70	19.05 158.10	23.83 194.96	27.79 244.65	31.75 253.56	35.71 281.70	—
16	406.40	4.19 42.41	4.78 48.26	6.35 62.64	7.92 77.83	9.53 93.27	9.53 93.27	—	12.70 123.30	16.66 160.12	12.70 123.30	40.49 365.35	21.44 203.53	26.19 245.56	30.96 286.64	36.53 333.19	40.49 365.37	—
18	457.00	4.19 47.77	4.78 54.36	6.35 70.57	7.92 87.71	11.13 122.38	9.53 105.16	—	14.27 155.80	19.05 205.74	12.70 139.15	45.24 459.37	23.88 254.55	29.36 309.62	34.93 365.56	39.67 408.26	45.24 459.37	—
20	508.00	4.78 60.46	5.51 70.00	6.35 78.55	9.53 117.15	12.70 155.12	9.53 117.15	—	15.09 183.42	20.62 247.83	12.70 155.12	50.01 564.81	26.19 311.17	32.54 381.53	38.10 411.49	44.45 508.11	56.01 564.81	—
22	559.00	4.78 66.57	5.54 70.06	6.35 86.54	9.53 129.13	12.70 171.09	9.53 129.13	—	—	22.23 294.25	12.70 171.09	53.98 672.26	28.58 373.83	34.93 451.42	41.28 527.02	47.63 600.63	53.98 672.26	—
24	610.00	5.54 84.16	6.35 96.37	6.35 94.53	9.53 141.12	14.27 209.64	9.53 141.12	—	17.48 255.41	24.61 355.26	12.70 187.06	59.54 808.22	30.96 422.08	38.89 547.71	46.02 640.03	52.37 720.15	59.54 808.22	—
26	660.00	—	—	7.92 127.36	12.70 202.72	—	9.53 152.87	—	—	—	12.70 202.72	—	—	—	—	—	—	—
28	711.00	—	—	7.92 137.32	12.70 218.69	15.88 271.21	9.53 164.85	—	—	—	12.70 218.69	—	—	—	—	—	—	—
30	762.00	6.35 120.72	7.92 150.36	7.92 147.28	12.70 234.67	15.88 292.18	9.53 176.84	—	—	—	12.70 234.67	—	—	—	—	—	—	—
32	813.00	—	—	7.92 157.24	12.70 250.64	15.88 312.15	9.53 188.82	—	17.48 342.91	—	12.70 250.64	—	—	—	—	—	—	—
34	864.00	—	—	7.92 167.20	12.70 266.61	15.88 332.12	9.53 200.31	—	17.48 364.90	—	12.70 266.61	—	—	—	—	—	—	—
36	914.00	—	—	7.92 176.96	127.0 282.27	15.88 351.70	9.53 212.56	—	19.05 420.42	—	12.70 282.27	—	—	—	—	—	—	—
38	965.00	—	—	—	—	—	9.53 244.54	—	—	—	12.70 298.24	—	—	—	—	—	—	—
40	1016.00	—	—	—	—	—	9.53 236.53	—	—	—	12.70 314.22	—	—	—	—	—	—	—
42	1067.00	—	—	—	—	—	9.53 248.52	—	—	—	12.70 330.19	—	—	—	—	—	—	—
44	1118.00	—	—	—	—	—	9.53 260.50	—	—	—	12.70 346.16	—	—	—	—	—	—	—
46	1168.00	—	—	—	—	—	9.53 272.25	—	—	—	12.70 351.82	—	—	—	—	—	—	—
48	1219.00	—					9.53 284.24				12.70 377.79

Boilers for Power and Process

Pressure Castings and Forgings to American Spйcifications and Their Equivalent BS and DIN Standards American Specifications (SA) British Equivalent (BS) German Equivalent (DIN) Nominal Specification Temperature Limit (°C) Form Tensile (kpsi) Yield (kpsi) Tensile (MPa) Yield (MPa) 1. Carbon steel Med. tensile SA 216-WCA C(<0.25) 510 Casting 60 30 414 207 1504-430 17245-GS C25 High tensile SA 216-WCB C(<0.30) 510 Casting 70 36 482 248 SA 105 C(<0.35) 510 Forging 70 36 482 248 1503 460-224 17243-17Mn4 2. Low-alloy steel SA 182 F12 C—|Mo 468 Forging 70 40 482 276 SA336 F12 C—|Mo 566 Forging 70 40 482 276 SA 182 Fll L% Cr-| Mo 566 Forging 70 40 482 276 1503-620 17243-13CrMo44 SA217WC6 L% Cr-| Mo 593 Casting 70 40 482 276 1504-621 SA 182 F22 2% Cr-1% Mo 602 Forging 75 45 517 310 1503-622 17243-10CrMo910 SA217WC9 2% Cr-1% Mo 602 Casting 70 40 482 276 1504-622 3. High-alloy steel SA 182 F 91 9Cr-lMo-V 649 Forging 85 60 586 414 1503-2Gr 91 4. Stainless steel 182 F304 H 18Cr-8Ni 760 Forging 75 30 517 207 1503-304 182 F 316 H 16Cr-12Ni-2Mo Forging 75 30 517 207 1503-316 351 CH 20 25Cr-12Ni 816 Casting 70 30 482 207

Note: The tensile and yield strengths are the minimums.

Boiler Materials