1 Scope
This document specifies the design requirements and strength calculation methods for pressurized components of boiler shells, and specifies the test and finite element analysis verification methods for determining the maximum allowable working pressure of the components.
This document applies to the design of pressurized components [including cylindrical components subjected to internal (external) pressure, heads, tube plates, end caps, lower foot rings, etc.] and pulling braces of boiler shells as defined in GB/T 16508.1.
2 Normative references
The contents of the following documents constitute the essential provisions of this document through the normative references in the text. Among them, note the date of the reference document, only the date of the corresponding version applicable to this document; do not note the date of the reference document, its latest version (including all the revision of the list) applicable to this document.
GB/T 150.3 Pressure vessels Part 3: Design
GB/T 985.1 Recommended bevels for gas welding, electrode arc welding, gas shielded welding and high energy beam welding
GB/T 985.2 Recommended bevels for submerged arc welding
GB/T 1576 Water quality in industrial boilers
GB/T 2900.48 Electrical terminology boiler
GB/T 9252 Pressure cycle test method for gas cylinders
GB/T 12145 Thermal power generating sets and steam power equipment water vapor quality
GB/T 16507.3 Water tube boiler part 3; structural design
GB/T 16508.1 Pot and shell boilers Part 1: General provisions
GB/T 16508.2 Boilers in pot shells Part 1:Materials
GB/T 16508.4 Boilers in pot shells Part 4:Manufacture, inspection and acceptance
JB/T 6734 Calculation method for strength of boiler fillet welds
NB/T47013.3 Nondestructive testing of pressure-bearing equipment Part 3; Ultrasonic testing
3 Terms and definitions
The terms defined in GB/T 2900.48 and GB/T 16508.1 and the following terms and definitions apply to this document.
3.1
calculating temperature
Under normal operating conditions, the set metal temperature of a pressurized component or a non-pressurized component under load (the arithmetic mean of the internal and external wall temperature). Note: Usually also referred to as the calculated wall temperature.
3.2
Working pressureworking pressure
In the normal design operating conditions, the highest pressure under pressure components.
3.3
Calculating pressurecalculating pressure
In the calculation of temperature, used to determine the pressure of the calculated thickness of the pressurised element.
3.4
Calculated thickness required thickness
The thickness of the pressurised element as determined by the theoretical calculation formula. Note, if necessary, the calculated thickness takes into account the thickness required for other loads.
3.5
design thickness The sum of the calculated thickness and the additional thickness.
3.6
Corrosion allowance thickness
The additional thickness required for the design life of the component to take into account corrosion thinning.
3.7
Lower tolerance of thickness
The absolute value of the negative value of the allowable lower tolerance of thickness specified in the material standard. Note, no negative values are taken as 0.
3.8
process additional thickness
The maximum reduction in material thickness allowed by the manufacturing process of the component in the stamping, coiling or bending process.
3.9
minimum required thickness
The minimum required thickness of a component to carry the calculated pressure, calculated temperature and other loads, and to take into account corrosion thinning factors.
3.10
Nominal thickness
The design thickness rounded upwards to the thickness of the standard steel specification. Note, i.e. the thickness indicated on the drawing.
3.11
Effective thicknesseffective thickness
Nominal thickness minus the corrosion margin, steel thickness under the deviation and process additional thickness after the thickness.
3.12
The highest fire line
The highest point on the water side of the boiler evaporating heated surface which is scoured by flame or high temperature flue gas.
3.13
breathing spacecomponent space
In order to prevent excessive temperature stress, the boiler tube plate on the wall temperature of different adjacent components of the minimum distance between.
3.14
Hydrostatic test pressure
In the hydrostatic test, according to the provisions of the boiler as a whole or pressurized components (components) imposed by the pressure.
4 Symbols
The following symbols apply to this document.
5 Design requirements
5.1 Basic requirements
5.1.1 The boiler design should use advanced technology so that the product meets the requirements of safety. Reliable and efficient, economic and environmental protection requirements, according to the GB/T 16508.1
Relevant provisions for design.
5.1.2 The design shall determine the calculated loads to be considered and the load calculations to be made in accordance with the following requirements.
a) The design of pressurised components should take into account the loads caused by the following conditions:
1) The internal or external pressure of water or steam;
2) the static pressure of the liquid column:
3) work resistance to flow:
4) Safety valve setting pressure;
5) If necessary, the following loads should be taken into account:
● Self-weight load of the pressurized components and the inner assembly;
● gravity loads on ancillary equipment;
wind, snow and earthquake loads;
other forces acting on the connected pipes (pipe thrusts, moments, etc.);
Forces caused by temperature gradients and differences in thermal expansion;
Shock loads due to rapid pressure fluctuations;
● Forces during transport and lifting.
5.2 Structural requirements
5.2.1 General requirements
5.2.1.1 The main pressurised components of a boiler shell include the shell, the collector box, the pipes, the centralised drop tubes, the furnace chamber. Return combustion chamber as well as tube plate (head), top and bottom foot ring of the furnace bile, etc.
5.2.1.2 The pressurised elements should be of sufficient strength. The form of the structure of the pressurised element, the arrangement of the openings and welds should avoid or reduce compound stresses and stress concentrations as far as possible.
5.2.2 Wall thickness and length of pot shell and furnace chamber
5.2.2.1 When the inner diameter of the shell is greater than 1 000 mm, the wall thickness of the shell shall be not less than 6 mm; when the inner diameter of the shell is not greater than 1 000 mm, the wall thickness of the shell shall be not less than 4 mm.
5.2.2.2 Expanded connection of the pot shell, tube plate, the wall thickness should be not less than 12 mm; tubes with an outside diameter of more than 89 mm should not be connected by expansion.
5.2.2.3 The inner diameter of the furnace chamber shall not exceed 1 800 mm, and the wall thickness of the chamber shall be in accordance with the following provisions:
a) the inner diameter of the furnace bile is less than or equal to 1 800 mm and more than 400 mm, its taking the thickness of the jig should not be less than 8 mm, and not more than
22 mm;
b) When the inner diameter of the furnace chamber is less than or equal to 400 mm. The wall thickness should be not less than 6 mm.
5.2.2.4
Horizontal internal combustion boiler combustion chamber, the wall thickness of the simplified part should be not less than 10 mm, and not more than 35 mm.
5.2.2.5 The calculated length of the horizontal straight furnace bile should not exceed 2000 mm, when the ends of the furnace bile are connected with the tube plate wrenching edge, the calculated length of the straight furnace bile can be enlarged to 3000 mm.
5.2.3 Safe water level
5.2.3.1 The minimum and maximum safe water level of the boiler shall be indicated on the boiler drawing.
5.2.3.2 The minimum safe water level for a boiler in normal operation shall be 100 mm above the maximum fire boundary and 75 mm above the maximum fire boundary for horizontal shell boilers with an inner diameter of the shell not greater than 1500 mm.
5.2.3.3 If the boiler stops feeding water and continues to operate under rated load, the boiler water level should drop from the minimum safe water level to the maximum fire time (safe water drop time) not less than 7 min, for gas (liquid) boilers should not be less than 5 min.
5.2.4 Welded construction
5.2.4.1 Boiler main pressure components of the main welding seam (including the shell, furnace bile, combustion chamber, the longitudinal and circumferential weld box, as well as the head, tube plate, furnace bile top and foot ring, etc. splice welding seam) should be fully welded through type structure; pulling the brace should not be spliced.
6 Cylindrical components under internal pressure
6.1 Overview
This chapter specifies the cylindrical components subjected to internal pressure, including the simplified. Collector, internal pressure pipe. The design calculation method and structural requirements of components such as large cross-pipe.
6.2 Symbols
7 The round simple furnace bile, cupola, flue pipe and other elements subject to external pressure
7.1 Overview
This chapter specifies the design calculation methods and structural requirements for the following round, simple elements subjected to external pressure:
a) The furnace liner, cupola and flue pipe of vertical pot and shell boilers with a rated working pressure of not more than 2.5 MPa;
b) the furnace chamber of horizontal boilers with a rated working pressure of not more than 3.8 MPa. Combustion chamber;
c) the flue tube of a horizontal boiler with a rated working pressure of less than 5.3 MPa.
7.2 Symbols
8 Convex heads, bile tops, hemispherical bile and convex tube plates
8.1 Overview
This chapter specifies the convex head (including ellipsoidal, hemispherical, butterfly, etc.) which is subject to internal or external pressure. butterfly, etc.), bile tops, convex tube plates (including ellipsoidal. Arch-shaped, etc.) and other components of the design calculation methods and structural requirements.
8.2 Symbols
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Design requirements
6 Cylindrical components under internal pressure
7 The round simple furnace bile, cupola, flue pipe and other elements subject to external pressure
8 Convex heads, bile tops, hemispherical bile and convex tube plates
