Boiler Steels

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

подпись: boiler materials 171For 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

подпись: tubePipe

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

подпись: boilers for power and processIn 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

подпись: 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

подпись: 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

подпись: 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

подпись: boiler materials

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