Standards related to:

GB/T 16508.3-2013**GB/T 16508.3-2013: PDF in English (GBT 16508.3-2013) **

GB/T 16508.3-2013

NATIONAL STANDARD OF THE

PEOPLE’S REPUBLIC OF CHINA

ICS 27.060.30

J 98

Replacing GB/T 16508-1996

Shell Boilers -- Part 3: Design and strength calculation

ISSUED ON: DECEMBER 31, 2013

IMPLEMENTED ON: JULY 1, 2014

Issued by: General Administration of Quality Supervision, Inspection and

Quarantine of the PRC;

Standardization Administration of the PRC.

Table of Contents

Foreword ... 3

1 Scope ... 5

2 Normative References ... 5

3 Terms and Definitions ... 6

4 Symbols and Units ... 6

5 Basic Requirements for Design ... 7

6 Cylindrical Parts Subject to Internal Pressure ... 13

7 Cylindrical Boiler Furnace, Circular Flue, Smoke Tube and Other Part

Subject to External Pressure ... 30

8 Convex Head, Boiler Furnace Top, Hemispherical Boiler Furnace and

Convex Tube Plate ... 46

9 Flat Plates and Tube Plates with Tension Brace (Support and Reinforcement)

... 55

10 Tension Braces and Reinforcing Parts ... 66

11 Flat Cover and Cover Plate ... 76

12 Foot Ring ... 81

13 Opening and Opening Reinforcement ... 84

14 Welded Tee Junction ... 96

15 Verification Method for Determining Maximum Permissible Operating

Pressure of Part ... 101

Appendix A (Informative) Design Calculation of Pressure Part on Cast-iron

Boiler ... 108

Appendix B (Informative) Design Calculation of Rectangular Header ... 110

Appendix C (Informative) Design Calculation of Water Tube Plate ... 116

Shell Boilers -- Part 3: Design and strength calculation

1 Scope

This Part of GB/T 16508 specifies the design and structural requirements for basic

pressure parts of shell boilers, and provides the basic design requirements for cast-

iron boiler (Appendix A), rectangular header (Appendix B) and water tube plate

(Appendix C).

This Part is applicable to the design calculation for cylindrical parts subject to internal

and external pressures, heads, tube plates, tension braces and foot rings as well as

opening and reinforcement.

2 Normative References

The following referenced documents are indispensable for the application of this

document. For dated references, only the edition cited applies. For undated references,

the latest edition of the normative document (including any amendments) applies.

GB/T 1576 Water Quality for Industrial Boilers

GB/T 2900.48 Electrotechnical Terminology of Boilers

GB/T 9252 Method for Cycling Test of Gas Cylinders

GB/T 12145 Quality Criterion of Water and Steam for Generating Unit and

Steam Power Equipment

GB 13271 Emission Standard of Air Pollutants for Boiler

GB/T 16508.1-2013 Shell Boilers - Part 1: General Requirements

GB/T 16508.2 Shell Boilers - Part 2: Material

GB/T 16508.4 Shell Boilers - Part 4: Fabrication, Inspection and

Acceptance

NB/T 47013

(JB/T 4730)

Nondestructive Testing of Pressure Equipment

TSG G0001 Boiler Safety Technical Supervision Administration

Regulation

TSG G0002 Supervision Administration Regulation on Energy

Conservation Technology for Boiler

3 Terms and Definitions

For the purposes of this document, the terms and definitions established in GB/T

16508.1 and GB/T 2900.48 apply.

4 Symbols and Units

Meanings and units of the symbols used in chapters and sections of this Part are as

follows:

Et - the elasticity modulus of material upon temperature calculation, MPa;

p - the calculating pressure, MPa;

[p] - the maximum permissible operating pressure upon verifying calculation, MPa;

pr - the rated pressure of boiler, MPa;

p0 - the operating pressure, MPa;

ts - the saturation temperature of medium corresponding to the calculating pressure

(the rated outlet temperature of hot water boiler), °C;

tc - the calculating temperature, °C;

tmave - the rated average temperature of medium, °C;

Δpa - the design additional pressure (the set pressure of relief valve), MPa;

Δph - the liquid column static pressure borne by pressure part, MPa;

Δpf - the additional pressure of dynamic resistance of medium flow, MPa;

η - the correction coefficient;

shall not exceed 2000mm; where butt connection is adopted for boiler furnace ends

and tube plate flange, the calculating length of the plain boiler furnace may be

increased to 3000mm.

5.1.4 The lowest safe water level of the steam boiler shall be 100mm higher than the

highest fire line; however, for the horizontal shell boiler with the inside diameter not

greater than 1500mm, the lowest safe water level shall be 75mm higher than the

highest fire line. The minimum and maximum safe water level of the boiler shall be

indicated in the drawing.

5.1.5 The structural type of pressure component (part) as well as the arrangement of

openings and welds shall avoid or reduce the combined stress and stress

concentration as possible. The adopted weld type shall comply with the design

document and GB/T 16508.4. The weld subject to non-destructive testing shall be

designed as the type for which the required non-destructive testing may be carried out.

5.1.6 Full-penetration butt joint shall be adopted for main weld of the main pressure

part for the boiler (e.g. longitudinal and circumferential welds of shell, boiler furnace,

reversal chamber and header, as well as butt welds of head, tube plate, boiler furnace

top and foot ring); overlapped structure shall not be adopted for the weld of boiler

pressure part; splicing shall not be adopted for tension brace.

5.1.7 Where the inside diameter of shell is greater than 1000mm, man-hole shall be

arranged on the shell or head (tube plate); where personnel cannot enter into the boiler

due to structural constraint, only inspection hole may be arranged; for the boiler with

smoke tube arranged in shell, the arrangement of man-hole and inspection hole shall

give consideration to the overhaul demand of both upper and lower parts of shell; for

the shell boiler with inside diameter of shell as 800~1000mm, at least one inspection

hole shall be arranged on shell or head (tube plate); the quantity of hand-holes

arranged at the lower part of vertical shell boiler shall meet the requirements of

cleaning and inspection and shall not be less than 3.

5.1.8 For the boiler with furnace, the combustion shall be completed in furnace.

Water entering into the boiler shall not directly scour the boiler furnace. For the boiler

with inside diameter of furnace greater than 1400mm or heat input greater than 12MW,

at least 3 measuring points shall be arranged in boiler for temperature measurement.

5.1.9 The hydraulic test pressure shall meet the requirements of GB/T 16508.1.

5.1.10 Corrosion allowance

The corrosion allowance shall meet the following requirements:

a) For the pressure parts with nominal thickness δ>20mm and all plain

5.4 Discharge requirements

5.4.1 The excess air coefficient at smoke discharge point shall meet the following

requirements:

a) For the combustion boiler in coal combustion chamber and the layered coal-

burning boiler with membrane wall, the excess air coefficient at smoke

discharge point shall not exceed 1.4;

b) For other layered coal-burning boiler, the excess air coefficient at smoke

discharge point shall not exceed 1.65;

c) For the pressure combustion oil-fired (gas-fired) boiler, the excess air coefficient

at smoke discharge point shall not exceed 1.15;

d) For the negative pressure combustion oil-fired (gas-fired) boiler, the excess air

coefficient at smoke discharge point shall not exceed 1.25.

5.4.2 During system design of boiler, the drive motor of matched auxiliary machine

of boiler should be equipped with frequency converter.

5.4.3 The design smoke discharge temperature of boiler shall meet the following

requirements:

a) Not higher than 230°C for steam boiler with rated evaporation less than 1t/h;

b) Not higher than 180°C for hot-water boiler with rated thermal power less than

0.7MW;

c) Not higher than 170°C for steam boiler with rated evaporation greater than or

equal to 1t/h and hot-water boiler with rated thermal power greater than or equal

to 0.7MW.

5.4.4 The boiler shall be equipped with necessary desulfurization and dedusting

equipment and should be equipped with de-nitration equipment; the discharge of boiler

air pollutants shall meet the requirements of GB 13271.

5.5 Permissible stress

5.5.1 The permissible stress [σ]J of common materials in this Part is selected

according to GB/T 16508.2; sometimes structural characteristics and operating

conditions of parts shall also be considered while used for design calculation; multiply

the correction coefficient according to Formula (1):

cylindrical parts subject to internal pressure, including shell, header, internal pressure

tube, large horizontal water tube, etc.

6.2 Symbols and units

a - the arc length between two openings along the mean-diameter peripheral

direction of the shell upon calculating the slant ligament efficiency, mm;

a1 - the technological coefficient of bent tube;

b1 - the thickness reduction ratio of actual manufacturing process of outer thickness

of bent tube;

C - the additional thickness, mm;

C1 - the corrosion allowance of pressure part, mm;

C2 - the manufacturing thickness reduction of pressure part, mm;

C3 - the thickness tolerance of steels for pressure part, mm;

Di - the inside diameter of shell, mm;

Do - the outside diameter of header shell, mm;

d - the pitch length of opening diameter, the dimension of elliptical opening in the

direction of corresponding pitch length, mm;

de - the equivalent diameter of opening, mm;

dm - the mean diameter of two adjacent openings, mm;

do - the outside diameter of tube, mm;

K - the conversion coefficient of slant bridge;

K1 - the shape coefficient of bent tube;

m - the absolute percentage of the lower thickness deviation (negative) to the

nominal thickness of tube, %;

n - the ratio of the distance (b) between two openings along the axial direction of

shell to the arc length (a) between two openings along the mean-diameter

peripheral direction of the shell;

n1 - the ratio of the radius R of bent tube centerline to the outside diameter of tube;

[p]w - the maximum permissible calculating pressure upon verifying calculation of

bent tube, MPa;

R - the radius of bent tube centerline or the arc header centerline, mm;

s0 - the minimum pitch length between two adjacent openings for which the inter-

opening effect may not be considered, mm;

s - the pitch length between two adjacent openings in longitudinal (axial) direction

or the interval between inner walls of firebox tube plate, mm;

s′ - the pitch length between two adjacent openings in the horizontal (circumferential)

direction, mm;

s″ - the pitch length between two adjacent openings in inclined direction, mm;

a - the angle of opening axis deviating from the radial direction of shell, °;

δ - the nominal thickness of pressure part, mm;

δ′ - the thickness deviation of abutting edge, mm;

δc - the required thickness of pressure part, mm;

δmin - the minimum thickness of finished pressure part, mm;

δbc - the theoretical required thickness at the outer side of bent tube made of steel

tube, mm;

δbe - the effective wall thickness at the outer side of bent tube, mm;

δbmin - the minimum thickness at the outer side of finished bent tube, mm;

δe - the effective thickness of pressure part, mm;

φ - the attenuation coefficient of longitudinal bridge;

φ′ - the attenuation coefficient of horizontal bridge;

φ″ - the attenuation coefficient of slant bridge;

φd - the equivalent attenuation coefficient of slant bridge;

φd=1.00) (among which, the minimum value shall prevail). Where the bridge is located

in weld, it shall be treated according to the relevant requirements in 6.9.3.

6.6.2 For weld passing the inspection for technical requirements for fabrication, the

welded joint coefficient φw is selected according to GB/T 16508.1. Where the

circumferential weld is opening-free, the circumferential welded joint coefficient may

not be considered.

6.6.3 Where the pitch length (longitudinal, horizontal or slant) between two adjacent

openings in opening row is not less than the value calculated according to Formula

(23), the attenuation coefficient of bridge may not be calculated.

0 2 ( )m iS d D (23)

Where, dm is determined according to Formula (29).

6.6.4 Where the pitch length between two adjacent openings is less than the s0 value

calculated according to Formula (23), and the diameter of either opening is not greater

than the maximum permissible diameter of the un-reinforced opening determined

according to 13.3.6, the attenuation coefficient of bridge shall be calculated according

to the requirements of 6.6.6~6.6.12.

Where one of the two adjacent openings in opening row is greater than the maximum

permissible diameter of the un-reinforced opening specified in 13.3.6, reinforcement

shall be carried out based on single opening according to the requirements of

13.3.7~13.3.9 under the conditions specified in 13.7.2. Opening-free treatment shall

be carried out after reinforcement.

Where both adjacent openings shall be reinforced, their pitch length shall not be less

than 1.5 times of their mean diameter.

Where both openings shall be reinforced, reinforcement calculation shall not only meet

the requirements of 13.3.7~13.3.9, but also meet the following requirements:

a) The height of thickened tube joint shall be 2.5 times the thickness;

b) The weld leg dimension of thickened tube joint shall be equal to the thickness

of thickened tube joint;

c) Where the pitch length of two openings is less than the diameter sum of two

openings, thus resulting in overlap of their effective reinforcement scope,

reinforcement shall be carried out according to the method that the total

reinforcement area of two openings is not less than the sum of reinforcement

Formula (40):

1 3

1 12 (4 1)

C C

n n

(40)

Where, n1 is the ratio of radius of bent tube centerline to the outside diameter of tube.

6.7.3 Additional thickness of tube subject to internal pressure

6.7.3.1 Upon design calculation, the additional thickness of tube is calculated

according to Formula (38).

For straight water tube, C1 is treated according to the principle in 6.7.1; for heat

exchange tube, C1 and C2 are taken as 0 while C3 is calculated according to Formula

(41):

3 1( )100 c

mC C

(41)

For bent tube made of steel tube, C1 is treated according to the principle in 6.7.1; for

heat exchange tube, C1 is taken as 0 while C2 and C3 are respectively calculated

according to Formulas (42) and (44):

2 1

( )100 bcC C

(42)

Where, the technological coefficient α1 of bent tube is calculated according to Formula

(43):

25 od

(43)

Where the actual fabrication process reduction ratio b1 for the thickness at the outer

side of bent tube is greater than the calculated a1 value, a1 shall be taken as the actual

fabrication process reduction ratio for the thickness at the outer side of bent tube.

3 1 2( )100 bc

mC C C

(44)

6.7.3.2 Upon verifying calculation, the additional thickness C of tube is calculated

according to Formula (38).

For straight tube, C1 is treated according to the principle in 6.7.1; for heat exchange

tube, C1 and C2 are taken as 0 while C3 is calculated according to Formula (39).

6.9.1 For expansion tube orifice, the bridge attenuation coefficient φ, φ′ and φ″ shall

not be less than 0.3; the distance from the expansion tube orifice center to the weld

edge shall not be less than 0.8d, and shall not be less than 0.5d+12mm; the

longitudinal weld shall be free from any expansion tube orifice; the expansion tube

orifice, where necessary at circumferential weld, shall meet the requirements of "Boiler

Safety Technical Supervision Administration Regulation" (TSG G0001).

6.9.2 The thickness of shell of expansion tube shall not be less than 12mm. The clear

distance between expansion tube orifices shall not be less than 19mm. Expansion

connection should not be adopted for the tube with outside diameter greater than

63.5mm.

6.9.3 The welded tube orifice shall be kept away from main weld as possible, and the

clear interval between tube orifice weld edge and adjacent main weld edge less than

10mm shall be avoided. Where it is inevitable, the welded tube orifice shall meet the

following requirements:

a) The main weld within the range of 1.5 times of the tube opening diameter (the

tube opening diameter, where less than 60mm, is 0.5d+60mm) to the tube

orifice center passes the radiographic testing or ultrasonic testing, and the

opening surrounding shall be free from slag inclusion defect;

b) Residual stress of the tube or tube joint after welding is eliminated through heat

treatment or local heat treatment.

In this case, the attenuation coefficient of this position is taken as the product of bridge

attenuation coefficient and welded joint coefficient.

The clear interval of weld edges of adjacent welded tube orifices should not be less

than 6mm, where heat treatment or local heat treatment is carried out after welding,

this limit ceases to be effective.

6.9.4 See Figure 7 for the connection type of flat tube plate or convex head of shell

and flange.

6.9.5 The groove fillet welding, where adopted for shell and flat tube plate, shall meet

the following requirements:

a) The rated pressure of boiler shall not be greater than 2.5MPa;

b) The position with smoke temperature not greater than 600°C (the position free

of smoke erosion and equipped with reliable heat insulation may not limited by

the above-mentioned condition);

I′, I″ and I″′ - the required inertia moment, mm4;

l - the length of straight section of flanged part, mm;

L - the calculating length of boiler furnace, mm;

n1 - the strength security coefficient;

n2 - the stability security coefficient;

Ro - the outside radius of corrugation of corrugated furnace, mm;

R - the medium radius of corrugation of corrugated furnace, mm;

r - the inside radius of corrugation of corrugated furnace, mm;

s - the corrugation pitch length of corrugated furnace, mm;

u - the roundness percentage of horizontal plain boiler furnace;

W - the corrugation depth of corrugated furnace, mm;

X - the increment of calculating length of plain furnace;

α - the distance between neutral axis x-x and circle-center-penetrating axis x0-x0,

mm;

α′ - the half included angle, rad (radian);

δ - the nominal thickness of pressure part, mm;

δc - the theoretical required thickness of pressure part, mm;

δmin - the minimum thickness of finished pressure part, mm;

δs - the design thickness of pressure part, mm;

δe - the effective thickness of pressure part, mm;

φmin - the minimum attenuation coefficient.

7.3 Cylindrical boiler furnace

7.3.1 Plain boiler furnace

C=C1+C2+C3 (73)

Generally, 0.5mm is taken as the additional thickness C1 of corrosion thickness

reduction; if the thickness is larger than 20mm, 0mm may be taken as the corrosion

allowance; if the corrosion thickness reduction exceeds 0.5mm, then the actually

possible value of corrosion thickness reduction is taken. The additional thickness C3,

which considers the lower thickness tolerance (where is negative value) of material, is

determined according to relevant material standards. The additional thickness C2,

which considers the technology thickness reduction, shall be determined according to

specific technology; generally, 0.1δ may be taken as the thickness reduction of

stamping technology.

8.3.11 Where the head inside diameter Di is larger than 1000mm, the nominal

thickness of head shall not be less than 6mm; while if Di is not larger than 1000mm,

then the nominal thickness of head should not be less than 4mm. The nominal

thickness of boiler furnace top and hemispherical boiler furnace shall not be less than

8mm; and the nominal thickness of hemispherical boiler furnace shall not be larger

than 22mm.

8.3.12 Convex head of hot spinning may be calculated according to the requirements

of this chapter; however, technology opening must be made on the head top after

spinning, the minimum opening diameter is not less than 80mm.

8.3.13 The opening on head shall comply with the following requirements:

a) For the boiler furnace opening on the head, the projection distance between

two opening edges shall not be less than the diameter of the smaller opening

(Figure 24), in this case, the reduction of bridge is ignored;

b) The projection distance between the opening edge of boiler furnace and head

edge should not be less than 0.1Di+δ (Figure 24);

c) For the orifice located nearby the man-hole, the distance between the orifice

edge and the starting point of man-hole flange or the weld edge shall be not

less than δ (Figure 25);

d) The flange opening shall not be located on welds (Figure 25).

9 Flat Plates and Tube Plates with Tension Brace (Support

and Reinforcement)

9.1 Scope

This chapter is applicable to the design and calculation methods and structural

requirements for those flat plates and tube plates subject to pressure and provided

with brace tubes (including the flat plates insider and outside the tube bank area of

smoke tube, top plates of firebox, boiler heads with vertical circular flue, tube plates

and cambered plates of Cochran boiler etc.). For the design and calculation methods

of rectangular headers and water tube plates, refer to Appendix B and Appendix C

respectively.

9.2 Symbols and units

α - the major semi-axis of elliptical ring (inside dimension), mm;

b - the minor semi-axis of elliptical ring (inside dimension), mm;

C - the flat plate coefficient including man-hole and head-hole;

De - the equivalent diameter;

Di - the inside diameter of shell, mm;

d - the diameter of opening, mm;

de - the equivalent circle diameter, mm;

dh - the calculating diameter of man-hole or head-hole (sum of α and b), mm;

di - the inside diameter of smoke tube, mm;

E - the maximum dimension of cambered plate from the inner wall of shell to outer

wall of tube plate, mm;

K - the coefficient;

L1 - the distance from the intersection point of tube row center of outermost side of

Cochran boiler and thickness median line of front tube plate to shell centerline, mm;

L2 - the distance from the intersection point of tube row center of outermost side of

Cochran boiler and thickness median line of back tube plate to shell centerline, mm;

r - the inside radius of flange, mm;

s - the inner wall interval of firebox tube plate, mm;

SH - the interval of reinforcing transverse beam on firebox top plate, mm;

S1 - the transverse pitch length of tube opening on firebox tube plate, mm;

S2 - the vertical pitch length of tube plate in Cochran boiler, mm;

Z - the coefficient;

δ - the nominal thickness of pressure part, mm;

δH - the thickness of reinforcing transverse beam on the firebox top plate, mm;

δc - the theoretical required thickness of pressure part, mm;

δe - the effective thickness of pressure part, mm;

φ - the ligament efficiency of the vertical tube row at the outermost side of Cochran

boiler tube plate.

9.3 Flat plates with tension brace and those beyond smoke tube bank area

9.3.1 The thickness of flat plates with tension brace and those beyond smoke tube

bank area is calculated according to Formula (76):

1[ ]e

pKd (76)

9.3.2 Upon verifying calculation, the maximum permissible operating pressure is

calculated according to Formula (77):

21[ ] [ ]

Kd

(77)

9.3.3 The calculating pressure of connected parts is taken as calculating pressure;

the calculating temperature is selected according to Table 4.

9.4.4 The nominal thickness of tube plate shall not be less than 12mm where the

diameter of expansion connection tube is not larger than 51mm; while that shall not be

less than 14mm where the diameter of expansion connection tube is larger than 54mm.

The nominal thickness of tube plate shall not be less than 8mm where welding is

adopted for the connection of tube and tube plate; while that shall not be less than

10mm if the inside diameter of tube plate is larger than 1000mm.

9.4.5 The bridge shall not be less than 0.125d+12.5mm where expansion connection

is adopted for tube and tube plate. The clear distance of adjacent weld edges shall not

be less than 6mm in welding tube plate bridge unless post-weld heat treatment is

carried out.

9.4.6 The distance between tube opening weld edge and flange starting point shall

not be less than 6mm. For expansion connection tube, the distance between the center

of tube opening and the starting point of flange shall not be less than 0.8d and shall

not be less than 0.5d+12mm.

9.4.7 For the tube plates contacting with flue gas which exceeds 600°C, measures

shall be taken to eliminate the interval for welded smoke gas or brace tube, and the

tube ends shall also meet the requirements of 10.5.8.

9.4.8 For firebox tube plates, where the firebox top plate is reinforced with beam

(Figure 33), the compressive strength of horizontal bridge shall also be verified

according to Formulas (80) and (81):

400

186( )i m

psS

S d R

(80)

భ

(81)

Where,

di - the inside diameter of smoke tube, mm;

s - the inner wall interval of firebox tube plate, mm;

S1 - the transverse pitch length of tube opening, mm (see Figure 33).

The larger value calculated according to Formulas (76) and (80) shall be taken as the

thickness of firebox tube plate; the smaller value calculated according to Formulas (77)

and (81) is taken as the maximum permissible operating pressure.

9.5 Firebox top plate with reinforcing transverse beam

9.7.2 If the vertical tube row at the outermost side of Cochran boiler tube plate is

expansion connection tube, then the tube head of every other smoke tube shall be

welded according to the requirements of 10.5.8. It is not required if it is welded tube

opening. The other structural requirements for tube plate shall meet the relevant

requirements of 9.4.3~9.4.7.

9.7.3 The number of gusset plate shall be determined according to the calculated Z

value by Formula (87) if the cambered plate of tube plate is supported by gusset plate

(or other tension brace).

iEpDZ (87)

Where,

E - the maximum dimension of cambered plate from inner wall of shell to outer wall of

tube plate (Figure 35).

For back tube plate (combustor tube plate), the gusset plate at least shall be:

Z>25000 1 piece

Z>35000 2 pieces

Z>42000 3 pieces

For front tube plate (smoke tube plate), the gusset plate at least shall be:

Z>25000 1 piece

Z>47000 2 pieces

9.7.4 The thickness of the shell plate connected with both sides of tube plate shall at

least be 1.5mm larger than the thickness obtained by the Formula of cylindrical shell.

9.8 See Appendix B for the rectangular header

9.9 See Appendix C for the calculation for water tube plate

10 Tension Braces and Reinforcing Parts

10.1 This chapter specifies the design and calculation methods and structural

requirements for the component space between boiler parts, as well as tension braces

(draglink and brace tube, diagonal rod etc.) and reinforcing parts (gusset plate,

reinforcing transverse beam etc.).

10.2 Symbols and units

A - the supporting area of tension brace, mm;

d - the opening diameter, the dimension of elliptical opening at the direction of

corresponding pitch length, mm;

F - the nominal and actually measured sectional area of tension brace, mm2;

Fmin - the minimum required sectional area of tension brace, mm2;

hH - the calculating height of beam, mm;

KH - the coefficient;

Kw - the dimension of weld leg of pull rod, mm;

Lw - the length of weld, mm;

s - the inner wall interval of firebox tube plate, mm;

sH - the interval of reinforcing transverse beam in firebox top plate, mm;

α - the included angle of diagonal bar or gusset plate and flat tube plate, (°);

δ - the nominal thickness of tube plate, mm;

δb - the thickness of gusset plate, mm;

δH - the nominal thickness of reinforcing transverse beam on firebox top plate, mm;

δHmin - the minimum required thickness of reinforcing transverse beam, mm;

δ1 - the thickness of brace tube, mm;

δw - the thickness of weld joint, mm.

10.3 Component space (see Figure 36)

10.3.1 Sufficient component space (the minimum distance between adjacent parts

with different temperature on flat plate) shall be left on flat plat to avoid the occurrence

of overlarge temperature difference stress.

10.3.2 The component spa......

Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.