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Standard ID | GB/T 16508.3-2022 (GB/T16508.3-2022) | Description (Translated English) | Shell boilers - Part 3: Design and strength calculation | Sector / Industry | National Standard (Recommended) | Classification of Chinese Standard | J98 | Classification of International Standard | 27.060.30 | Word Count Estimation | 75,785 | Date of Issue | 2022-07-11 | Date of Implementation | 2023-02-01 | Older Standard (superseded by this standard) | GB/T 16508.3-2013 | Drafting Organization | Shanghai Industrial Boiler Research Institute Co., Ltd., Shanghai Special Equipment Supervision and Inspection Technology Research Institute, Shandong Huayuan Boiler Co., Ltd., China Special Equipment Inspection and Research Institute, National Industrial Boiler Quality Supervision and Inspection Center (Guangdong), Shanghai Power Generation Equipment Complete Design and Research Institute Co., Ltd., Taishan Group Co., Ltd., Jiangsu Taihu Boiler Co., Ltd., Jiangsu Shuangliang Boiler Co., Ltd., Suzhou Hailu Heavy Industry Co., Ltd., Wuxi Taihu Boiler Co., Ltd., Miura Industry (China) Co., Ltd., Shaanxi Construction Engineering Jinniu Group Co., Ltd. | Administrative Organization | National Technical Committee for Standardization of Boilers and Pressure Vessels (SAC/TC 262) | Proposing organization | National Technical Committee for Standardization of Boilers and Pressure Vessels (SAC/TC 262) | Issuing agency(ies) | State Administration for Market Regulation, National Standardization Administration | Standard ID | GB/T 16508.3-2013 (GB/T16508.3-2013) | Description (Translated English) | Shell boilers. Part 3: Design and strength calculation | Sector / Industry | National Standard (Recommended) | Classification of Chinese Standard | J98 | Classification of International Standard | 27.060.30 | Word Count Estimation | 76,753 | Older Standard (superseded by this standard) | GB/T 16508-1996 | Quoted Standard | GB/T 1576; GB/T 2900.48; GB/T 9252; GB/T 12145; GB 13271; GB/T 16508.1-2013; GB/T 16508.2; GB/T 16508.4; NB/T 47013; JB/T 4730; TSG G0001; TSG G0002 | Drafting Organization | Shanghai IndustrialBoiler Research Institute | Administrative Organization | National Standardization Technical Committee of Boiler and Pressure Vessel | Regulation (derived from) | National Standards Bulletin 2013 No. 27 | Proposing organization | National Boiler and Pressure Vessel Standardization Technical Committee (SAC/TC 262) | Issuing agency(ies) | General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People's Republic of China | Summary | This standard specifies the basic shell boiler pressure components of the design and construction requirements and gives the cast iron boiler (Appendix A), a rectangular box set (Appendix B) and plumbing tube sheet (Appendix C) of the basic design require |
GB/T 16508.3-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 27.060.30
CCS J 98
Replacing GB/T 16508.3-2013
Shell boilers - Part 3: Design and strength calculation
ISSUED ON: JULY 11, 2022
IMPLEMENTED ON: FEBRUARY 01, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 6
1 Scope ... 8
2 Normative references ... 8
3 Terms, definitions and symbols ... 9
4 Symbols ... 10
5 Design requirements ... 11
6 Cylindrical element subject to internal pressure ... 22
7 Cylindrical flues, cupolas, smoke tubes and other elements subjected to external
pressures ... 38
8 Convex head, flue roof, hemispherical flue and convex tube plate ... 54
9 Reinforced flat plates and tube plates with braces ... 63
10 Braces and reinforcements ... 75
11 Flat end covers and cover plates ... 85
12 Foot ring ... 91
13 Hole reinforcement ... 92
14 Welded tees ... 105
Annex A (normative) Test and finite element analysis verification method for
determining the maximum allowable working pressure of elements ... 110
Annex B (normative) Design calculation for water tube plate ... 117
Bibliography ... 120
Shell boilers - Part 3: Design and strength calculation
1 Scope
This document specifies the design requirements and strength calculation methods for
pressure elements of shell boilers. It also specifies the test and finite element analysis
verification methods for determining the maximum allowable working pressure of
elements.
This document is applicable to the design of pressure elements of shell boilers defined
in GB/T 16508.1 [including cylindrical elements bearing internal (external) pressure,
heads, tube plates, end covers, foot rings, etc.] and braces.
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 referenced document (including any amendments) applies.
GB/T 150.3, Pressure vessels - Part 3: Design
GB/T 985.1, Recommended joint preparation for gas welding, manual metal arc
welding, gas-shield arc welding and beam welding
GB/T 985.2, Recommended joint preparation for submerged arc welding
GB/T 1576, Water quality for industrial boilers
GB/T 2900.48, Electrotechnical terminology of boilers
GB/T 9252, Method for pressure cycling test of gas cylinders
GB/T 12145, Quality criterion of water and steam for power plant and steam-
generating equipment
GB/T 16507.3, Water-tube boilers - Part 3: Structure design
GB/T 16508.1, Shell boilers - Part 1: General requirements
GB/T 16508.2, Shell boilers - Part 2: Materials
GB/T 16508.4, Shell boilers - Part 4: Fabrication, inspection and acceptance
JB/T 6734, Calculation method of strength of boiler fillet welding seam
be considered:
1) Internal or external pressure of water or steam;
2) Liquid column static pressure;
3) Working fluid flow resistance;
4) Set pressure of safety valve;
5) The following loads shall also be considered when necessary:
• Self-weight load of pressure element and built-in self-weight load;
• Gravity load of attached equipment;
• Wind, snow loads and seismic loads;
• Other forces of connecting piping (thrust and moment of the piping, etc.);
• Forces caused by temperature gradients and differences in thermal expansion;
• Impact loads when the pressure fluctuates sharply;
• Forces during transport and lifting.
b) The following loads shall be considered when designing load-bearing non-
pressure elements:
1) Permanent loads, including supporting gravity, thermal expansion thrust;
2) Transient loads, including safety valve exhaust reaction force and other short-
term forces.
5.1.3 The design shall ensure that the wall temperature of the element does not exceed
the allowable temperature of the material used. Consider factors such as the temperature
difference between the inner and outer walls of the tube on the heating surface and the
inner wall's resistance to steam oxidation.
5.1.4 The design of the boiler structure shall be convenient for installation, operation,
maintenance and cleaning inside and outside.
5.1.5 The design shall be in accordance with the relevant strength calculation formula
or stress analysis calculation formula and regulations in this document. Determine the
minimum required thickness of the pressure element.
5.1.6 Special-shaped compression elements or structures that cannot be calculated
according to the provisions of Chapters 6 to 14 and Annex B within the scope of this
document can be according to the test and finite element analysis verification methods
specified in Annex A. Determine the maximum allowable working pressure of the
element.
5.1.7 The strength calculation of boiler fillet welds shall comply with the provisions of
JB/T 6734.
5.2 Structural requirements
5.2.1 General requirements
5.2.1.1 The main pressure elements of the shell boiler include boiler shell, header,
piping, centralized descending tube, flue, backfire chamber, tube plate (head), flue roof
and foot ring, etc.
5.2.1.2 Pressure elements shall have sufficient strength. The form of the structure of the
pressure elements, the layout of the openings and welds shall avoid or reduce the
combined stress and stress concentration as far as possible.
5.2.2 Wall thickness and length of boiler shell and flue
5.2.2.1 When the inner diameter of the boiler shell is greater than 1000 mm, the wall
thickness of the boiler shell cylinder shall not be less than 6 mm. When the inner
diameter of the boiler shell is not greater than 1000 mm, the wall thickness of the boiler
shell cylinder shall not be less than 4 mm.
5.2.2.2 The wall thickness of the boiler shell cylinder and tube plate connected by
expansion joints shall not be less than 12 mm. Tubes with an outer diameter greater
than 89 mm shall not be connected by expansion joints.
5.2.2.3 The inner diameter of the flue shall not exceed 1800 mm. The flue wall thickness
meets the following requirements:
a) When the flue inner diameter is less than or equal to 1800 mm and greater than
400 mm, its wall thickness shall not be less than 8 mm and not greater than 22
mm.
b) When the flue inner diameter is less than or equal to 400 mm, the wall thickness
shall not be less than 6 mm.
5.2.2.4 For the backfire chamber of a horizontal internal combustion boiler, the wall
thickness of the cylinder shall be not less than 10 mm and not more than 35 mm.
5.2.2.5 The calculated length of the horizontal flat flue shall not exceed 2000 mm. When
the two ends of the flue are connected to the flange of the tube plate, the calculated
length of the straight flue can be enlarged to 3000 mm.
5.2.3 Safe water level
5.2.3.1 The minimum and maximum safe water levels of boilers shall be indicated on
the boiler drawings.
5.2.3.2 The minimum safe water level of the boiler during normal operation shall be
100 mm higher than the highest fire line. For a horizontal shell boiler with an inner
diameter of the shell not greater than 1500 mm, the minimum safe water level shall be
75 mm higher than the highest fire line.
5.2.3.3 When the water supply to the boiler is stopped, it will continue to run under the
rated load of the boiler. The time for the boiler water level to drop from the lowest safe
water level to the highest fire line (safe precipitation time) shall not be less than 7 min.
For gas (liquid) boilers, it shall not be less than 5 min.
5.2.4 Welding structure
5.2.4.1 The main welds of the main pressure elements of the boiler (including the
longitudinal and circumferential welds of the boiler shell, flue, backfire chamber,
header, etc. and the spliced welds of the head, tube plate, flue roof and foot ring, etc.)
shall adopt full penetration structure. The braces shall not be spliced.
5.2.4.2 For horizontal internal combustion shell boilers with boiler rated pressure not
greater than 2.5 MPa, waste heat boilers including shell boiler elements and through-
flow boilers, except for the joints directly washed by flue gas, if the following
requirements are met, the tube plate, the flue and the boiler shell can be connected by
T-shaped joints. However, overlapping connections shall not be used.
a) Adopt full penetration joint type (see Figure 1). The groove is machined.
b) The connection between the tube plate and the cylinder adopts a plug-in structure
(except for the through-flow boiler).
c) The required thickness of the weld at the connection part of the T-joint shall not
be less than the wall thickness of the tube plate (cover plate). The parts that can
be sealed and welded on the back of the weld seam shall be sealed and welded.
Argon arc welding or other gas-shielded welding shall be used for backing the
parts that cannot be sealed and welded. Guarantee penetration.
d) The welding seam of the T-joint connection part shall be ultrasonically tested
according to the requirements of NB/T 47013.3.
5.2.6.1 The requirements for expansion tube holes are as follows.
a) The net distance between the expansion tube holes shall not be less than 19 mm,
and not less than 6 times the wall thickness of the tube.
b) The distance between the center of the expansion tube hole and the edge of the
weld seam and the starting point of the flange of the tube plate shall not be less
than 0.8d and shall not be less than 0.5d + 12 mm.
c) The expansion tube holes shall not be arranged on the longitudinal weld of the
boiler shell. Also try to avoid the arrangement on the circumferential weld seam.
If the structural design cannot avoid being located in the circumferential weld
seam, the weld seams within 60 mm (if the tube hole diameter is greater than 60
mm, take the hole diameter value) around the tube hole are qualified by
radiographic or ultrasonic testing. There is no slag inclusion defect in the weld
seam on the edge of the tube hole. At the same time, after grinding the inner and
outer surfaces of the weld seam at the tube hole and heat-treating the entire
pressure element, the expansion tube hole can be arranged on the circumferential
weld.
5.2.6.2 Welded tube holes shall meet the following requirements:
a) The tube holes of the centralized descending tube shall not be arranged on the
weld and its heat-affected zone.
b) Other welded tube holes shall not be arranged on the weld seam and its heat-
affected zone.
c) When the structural design cannot be avoided, the weld seams within 60 mm
around the tube hole (if the diameter of the tube hole is greater than 60 mm, take
the value of the hole diameter) shall pass the radiographic or ultrasonic inspection.
There is no slag inclusion defect in the weld seam on the edge of the tube hole. If
the tube joints undergo heat treatment after welding (except for hot water boilers
with a rated outlet water temperature of less than 120°C) to relieve stress, welded
tube holes can be arranged on the weld seam and its heat-affected zone.
5.2.6.3 The clear distance between the edges of welded seams of adjacent welded tube
holes shall not be less than 6 mm. If heat treatment or local heat treatment is done after
welding (except for hot water boilers with rated outlet water temperature less than
120°C), it is not subject to this restriction.
5.2.6.4 The number and position of manholes, head holes, hand holes, cleaning holes,
inspection holes and observation holes opened on boiler pressure elements shall meet
the needs of installation, inspection, maintenance, operation monitoring and cleaning
(clearing). For boilers with smoke tubes in the shell, the arrangement of manholes and
head holes shall consider the maintenance requirements of the upper and lower parts of
the shell. Specific requirements are as follows:
a) For boiler shells with an inner diameter greater than 1000 mm, at least one
manhole shall be opened on the cylinder or head (tube plate). When personnel
cannot enter the boiler due to structural restrictions, only the head hole may be
opened.
b) For boiler shells with an inner diameter of 800 mm ~ 1000 mm, at least one head
hole shall be opened on the cylinder or head (tube plate).
c) At least 3 hand holes shall be provided in the lower part of vertical shell boilers
(except electric heating boilers).
5.3 Corrosion allowance thickness
The corrosion allowance thickness shall be determined according to the following
requirements:
a) For elements with δ >20 mm, take C1≥0 mm;
b) For elements with δ≤20 mm, take C1≥0.5 mm;
c) In the case that severe corrosion may occur, the corrosion allowance thickness
shall be increased accordingly.
5.4 Weld joint coefficient
5.4.1 The quality of weld joints shall comply with the relevant provisions of GB/T
16508.4.
5.4.2 The weld joint coefficient (φw) shall be determined according to the weld type of
the butt joint and the proportion of non-destructive testing.
5.4.3 Double-welded butt joints and full-penetration butt joints equivalent to double-
sided welding are determined as follows:
a) 100% non-destructive testing, φw=1.00;
b) Partial non-destructive testing, φw=0.90.
5.4.4 Single-sided welded butt joints are determined as follows:
a) 100% non-destructive testing, φw=0.90;
b) Partial non-destructive testing, φw=0.80.
5.5 Allowable stress
5.5.1 According to the structural characteristics and working conditions of the elements,
the allowable stress ([σ]) of the material is calculated according to the formula (1)
during the design calculation.
sided fillet welded tube joint (or hole ring), the size of the elliptical hole in the direction
of the corresponding pitch, in millimeters (mm);
NOTE: Plug-in double-sided fillet welding is limited to boilers with pr ≤ 2.5 MPa and non-heated
tube joints (or hole rings).
de - The equivalent diameter of the hole, in millimeters (mm);
dm - The average value of the diameters of two adjacent holes, in millimeters (mm);
do - The outer diameter of the tube, in millimeters (mm);
[d] - The maximum allowable diameter of unreinforced holes, in millimeters (mm);
K - The conversion factor of inclined hole bridge;
K1 - The factor of bent tube shape;
m - The absolute value of the percentage of the lower deviation of the tube thickness
(when it is a negative value) and the nominal thickness of the tube, expressed as a
percentage (%);
n - The ratio of the distance b between the two holes in the direction of the axis of the
cylinder to the arc length α between the two holes in the direction of the circumference
of the cylinder's average diameter;
n1 - The ratio of the radius R of the centerline of the bent tube to the outer diameter of
the tube;
[p]w - The maximum allowable working pressure calculated by bent tube check, in
megapascals (MPa);
R - The radius of the centerline of the bent tube or the radius of the centerline of the arc
header, in millimeters (mm);
s0 - The minimum pitch between two adjacent holes that does not consider the influence
between holes, in millimeters (mm);
s - The pitch between two adjacent holes in the longitudinal direction (axial direction),
or the inner wall spacing of the fire box tube plate, in millimeters (mm);
s' - The pitch of two adjacent holes in the horizontal (circumferential) direction, in
millimeters (mm);
s'' - The pitch of two adjacent holes obliquely, in millimeters (mm);
α' - The angle that the axis of the hole deviates from the radial direction of the cylinder,
in degrees (°);
steel of the cylinder, the d in the calculation of the weakening coefficient shall be taken
as the sum of the inner diameter of the connecting tube (or hole ring) and 2δ1[1-
([σ]1/[σ])] (δ1 is the nominal thickness of the reinforced tube joint or the reinforced ring).
6.6.4 When the pitch of two adjacent holes is less than the s0 value determined
according to the formula (23), and the diameter of the two holes is not greater than the
maximum allowable diameter ([d]) of the unreinforced hole determined according to
13.3.6, the weakening coefficient of the hole bridge shall be calculated according to the
provisions of 6.6.6.
If one of two adjacent holes is larger than the maximum permissible diameter ([d]) of
an unreinforced hole determined in accordance with 13.3.6, under the condition of
meeting the requirements of 13.7.2, the large hole shall be reinforced as a single hole
according to the provisions of 13.3.7~13.3.9. After reinforcement, treat as non-hole.
If two adjacent holes need to be reinforced, the pitch shall not be less than 1.5 times
their average diameter. After reinforcement, treat as non-hole.
When reinforcement is required for both adjacent holes, the reinforcement calculation
shall meet the following requirements in addition to the requirements in 13.3.7~13.3.9:
a) The height of the thickened tube joint is 2.5 times the thickness.
b) The weld leg size of the thickened tube joint is equal to the thickness of the
thickened tube joint.
c) If the pitch of the two holes is less than the sum of the diameters of the two holes,
causing their effective reinforcement ranges to overlap, the reinforcement shall
be carried out in such a way that the total reinforcement area of the two holes is
not less than the sum of the individual reinforcement areas required by each hole.
The area of reinforcement in overlapping parts shall not be counted repeatedly.
6.6.5 For the coal feeding holes and slag outlet holes on the vertical boiler shell, the
holes shall be reinforced according to the provisions of 13.3.7~13.3.9. After
reinforcement, treat as non-hole. The minimum required thickness of coal feeding hole
circle and slag discharge hole circle shall be determined according to 13.4.4.
6.6.6 The hole-bridge weakening coefficients of two adjacent holes are calculated
according to the following method.
a) The hole bridge weakening coefficient of two longitudinally adjacent holes of
equal diameter (see Figure 2) is calculated according to formula (24):
Figure 8 -- Connection between the boiler shell cylinder and the flanged flat tube
plate or convex head
7 Cylindrical flues, cupolas, smoke tubes and other elements
subjected to external pressures
7.1 Overview
This chapter specifies the design calculation methods and structural requirements for
the following cylindrical elements subjected to external pressure:
a) Flue, cupola and smoke tube of vertical shell boilers with rated working pressure
not greater than 2.5 MPa;
b) Flue and backfire chamber of horizontal shell boiler with rated working pressure
not greater than 3.8 MPa;
c) Smoke tubes of horizontal shell boilers with rated working pressure less than 5.3
MPa.
7.2 Symbols
This chapter uses the following symbols:
a - The distance between the neutral axis X-X and the axis X0-X0 passing through the
center of the circle, in millimeters (mm);
Di - The inner diameter of the flue, in millimeters (mm);
Dm - The average diameter of the flue, the average diameter of the straight part of the
corrugated flue, in millimeters (mm);
Do - The outer diameter of the flue, in millimeters (mm);
Et - The elastic modulus at the calculating temperature, in megapascals (MPa);
hJ - The height of the reinforcing ring, in millimeters (mm);
ho - The outer height of the flue roof, in millimeters (mm);
I1 - The moment of inertia of the corrugated section to its own neutral axis, in the fourth
power millimeter (mm4);
I2 - The moment of inertia of the reinforcing ring on its own neutral axis, in the fourth
power millimeter (mm4);
I3 - The moment of inertia of the expansion ring to its own neutral axis, in fourth power
millimeter (mm4);
I', I″, I‴ - The required moment of inertia, in the fourth power millimeter (mm4);
l - The length of the straight section of the edge element, in millimeters (mm);
L - The calculating length of the flue, in millimeters (mm);
n1 - The strength safety factor;
n2 - The stability safety factor;
Ro - The outer radius of the corrugation of the corrugated flue, in millimeters (mm);
R - The center radius of the corrugation of the corrugated flue, in millimeters (mm);
r - The inner radius of the corrugation of the corrugated flue, in millimeters (mm);
s - The corrugation pitch of the corrugated flue, in millimeters (mm);
u - The percentage of roundness of horizontal flat flue;
W - The corrugation depth of the corrugated flue, in millimeters (mm);
X - The added value of calculated length of the flat flue;
α' - The included angle, semi-included angle, in degrees (°);
δ - The nominal thickness of the pressure element, in millimeters (mm);
δc - The calculated thickness of the pressure element, in millimeters (mm);
δJ - The thickness of the reinforcing ring, in millimeters (mm);
δmin - the minimum required thickness of the pressure element, in millimeters (mm);
δs - The design thickness of pressure element, in millimeters (mm);
δe - The effective thickness of the pressure element, in millimeters (mm);
φmin - The minimum weakening coefficient.
7.3 Cylindrical flue
7.3.1 Flat flue
7.3.1.1 The design thickness of the horizontal flat flue is calculated according to
formula (46) and formula (48), whichever is larger.
......
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 meth......
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