GB/T 16507.3-2022Water-tube boilers - Part 3: Structure design (English PDF)

1 Scope

GB/T 16507.3-2022 is the Chinese national standard on water-tube boilers - part 3: structure design, in the field of energy and heat transfer engineering. The /T suffix marks it as a recommended standard: it is not compulsory by itself, but it becomes binding as soon as a contract, a tender or a customer specification calls it up - which in practice is how most foreign buyers meet it. It was issued on 9 March 2022 by the State Administration for Market Regulation; Standardization Administration of China, and has been in force since 1 October 2022. Classification: ICS 27.060.30, CCS J98. This page is published from the official record of the standard held by the Chinese standards administration: the identification, the dates, the classification and the issuing body are taken from there. The clause text, the tables and the numeric limits are in the document itself, which is delivered complete in English translation.

This document specifies the requirements for the structure design of water-tube boiler drum, start-up (steam water) separator, water storage tank, header, desuperheater, piping, water-cooling wall, superheater, reheater, coal economizer, pipe joint, suspender, opening, door hole, rigid beam, steel structures, escalator and platform. This document is applicable to the structural design of water-tube boilers defined in GB/T 16507.1.

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 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 2900.48, Electrotechnical terminology of boilers

GB 4053 (all parts), Safety requirements for fixed steel ladders and platform

GB/T 16507.1, Water-tube boilers - Part 1: General requirements

GB/T 16507.2, Water-tube boilers - Part 2: Materials

GB/T 16507.4, Water-tube boilers - Part 4: Strength calculation of pressure parts

GB/T 22395, Specification for design of boiler steel structures

JB/T 6734, Calculation method of strength of boiler fillet welding seam

JB/T 6735, Calculation method of strength of boiler hanger rod

3 Terms and definitions

The following terms and definitions defined in GB/T 2900.48 and GB/T 16507.1 apply to this document.

4 Basic requirements

4.1 The basic principles of boiler design shall comply with the provisions of GB/T 16507.1.

4.2 During the design, the calculation loads to be considered and the load calculations to be performed shall be determined according to the provisions of this document and the special requirements of GB/T 16507.1 and GB/T 16507.4.

4.3 The design shall ensure that the wall temperature of the element does not exceed the allowable temperature of the material used. In addition, 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 must also be considered. The selection of materials shall meet the requirements of GB/T 16507.2.

4.4 During the design, the minimum required thickness of the pressure elements shall be determined according to the relevant strength calculation formula or stress analysis calculation formula and regulations in GB/T 16507.4. For non-pressure element bearing loads, their calculation dimensions shall be determined in accordance with relevant regulations.

4.5 The design shall ensure that the evaporation heating surface, superheater, reheater and coal economizer system work reliably under the expected operating conditions. Ensure stable hydrodynamic properties. Prevent heat transfer from deteriorating.

4.6 The structure of the furnace, cladding wall and tail flue shall have sufficient bearing capacity. Prevent permanent deformation and furnace wall collapse. There shall be good sealing.

4.7 The expansion coefficient of the flat steel in the membrane wall structure shall be similar to that of the pipe. The determination of the width of the flat steel shall ensure that the allowable temperature of the material is not exceeded during the operation of the boiler. The weld structure shall ensure the effective cooling of the flat steel.

4.8 The load-bearing structure shall have sufficient strength, rigidity, stability and corrosion resistance when bearing the design load.

4.9 The furnace wall shall have good heat insulation and sealing.

4.10 The design of each component shall ensure that it can expand freely according to the design predetermined direction during operation. The expansion center determined in the design of the suspended boiler proper shall be fixed. An expansion guiding device shall be provided to ensure that the furnace body expands in a predetermined direction. For boilers with a rated pressure of not less than

9.8 MPa, when the equipment and fixed structure cannot withstand instantaneous loads such as safety valve discharge reaction force and earthquake force, damping devices shall be installed at appropriate under various startup modes.

4.20 When the DC power station boiler adopts an external start-up (steam-water) separator to start the system, the working pressure of the isolation valve shall be determined according to the design pressure under the maximum continuous load. The strength of the start-up (steam-water) separator is designed and calculated according to the design parameters of the boiler's minimum DC load. When the built-in start-up (steam-water) separator is used to start the system, the strength of each component shall be calculated according to the design parameters of the maximum continuous load of the boiler.

4.21 For control circulation boilers, low circulation ratio boilers and supercritical pressure composite circulation boilers, the layout of the boiler water circulation pump (starting circulation pump) and its inlet pipes shall prevent vaporization of the working medium in the pipe and at the pump inlet.

4.22 The pipe clamps, hangers, and clamping pipes on the heating surface shall be set reasonably and reliably. Prevent overheating, burning, straining and causing pipes to collide and rub against each other.

5 Solder connection requirements

5.1 The strength calculation of boiler fillet welds shall comply with the provisions of JB/T 6734.

5.2 The main welds of pressure elements and their adjacent areas shall avoid welding accessories as much as possible. If it is unavoidable, the weld of welding accessories may pass through the main weld but shall not terminate in the main weld and its adjacent area.

5.3 The distance (L) between the centerlines of the butt welds on the pipes on the heating surface of the boiler (except dissimilar steel joints) and the straight sections of the pipes shall meet the following requirements:

a) The outer diameter is less than 159mm, L>=2 times the outer diameter;

b) The outer diameter is not less than 159mm, L>=300mm. When the boiler structure is difficult to meet the above requirements, the heat-affected zones of the butt welds shall not overlap, and L>=50mm.

5.4 The butt welds of pipes on the heating surface (except for coiled pipes and formed pipe fittings) shall be located on the straight section of the pipe. The distance from the center line of the butt weld of the pipe on the heating surface to the outer wall of the drum and header, the starting point of the pipe bending, and the edge of the pipe support is at least 50mm. For boilers with a rated working pressure of not less than 3.8MPa, the distance shall be at least 70mm (except for dissimilar steel joints limited by the structure).

5.5 The longitudinal and circumferential butt welds of the drum, start-up (steam-water) separator, water storage tank, header, pipe and pipe, and the splicing weld of the head shall adopt a full penetration structure.

5.6 The longitudinal welds of two adjacent drum sections on the drum (except for those with unequal wall thickness), and the splicing welds of the head and the longitudinal welds of adjacent drum sections shall not be connected to each other. The distance between the centerlines of the welds (external arc length) shall be at least 3 times the thickness of the thicker steel plate, and not less than 100mm.

5.7 For a boiler drum formed by pressing and welding two steel plates with unequal wall thickness, the longitudinal joints of two adjacent drum sections are allowed to be connected. However, the intersection of welds shall be qualified by radiographic inspection.

5.8 Generally, the centerlines of the steel plates on both sides of the longitudinal and circumferential seams of the drum shall be aligned. When the thickness of the steel plates on both sides of the ring seam of the drum is not equal, the edge of one side is also allowed to be aligned. When two elements or steel plates with different nominal thicknesses are butted, if the difference in nominal edge thickness of any of the two sides exceeds the edge deviation value specified in 5.9, the edge of the thick plate shall be cut to be flush with the edge of the thin plate. The chamfered surface shall be smooth. The slope is not greater than 1:3. If necessary, the width of the weld can be calculated within the slope, as shown in Figure 1.

6.3.1 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, maintenance, operation monitoring and cleaning.

6.3.2 The connection between manhole ring and head hole ring of pressure elements of the boiler and drum body and head shall adopt full penetration structure.

6.3.3 The manhole cover, head hole cover and hand hole cover on the pressure elements of the boiler with a rated pressure not less than 3.8MPa shall adopt an internally closed structure or a welded structure. The manhole cover, head hole cover and hand hole cover on the pressure elements of the boiler with rated pressure less than 3.8MPa can adopt flange connection structure.

6.3.4 For boilers with a drum inner diameter not less than 800mm, manholes shall be provided on the drum body or head. When personnel cannot enter the boiler due to structural restrictions, only the head hole may be opened. For boilers with an inner diameter of the drum less than 800mm, at least one head hole shall be provided on the drum body or head.

6 Opening...

7 Drum

7.1 The nominal thickness of the drum body shall not be less than 6mm. When the heating surface tube and the drum are connected by expansion joints, the nominal thickness of the drum body shall not be less than 12mm. The net distance between the holes of expansion joints shall not be less than 19mm.

7.2 When the heating surface tube and the drum are connected by expansion joints, the wall thickness of the tube shall not be greater than 5mm; the outer diameter of the tube shall not be greater than 89mm.

7.3 The length of the shortest drum section on the drum body shall not be less than 300mm.

7.4 The head is made of a whole piece of steel plate as much as possible. When splicing is necessary, two steel plates are allowed to be spliced together. The distance from the splicing weld to the centerline of the head is not greater than 30% of the nominal inner diameter of the head. It shall not pass through the pulling-edge manhole. Splicing welds shall also not be arranged on the arc of the edge of the manhole.

7.5 The center distance between the drum suspender and the circumferential weld of the drum shall not be less than 200mm. The longitudinal cylinder welds within 180° of the lower part of the drum body at the suspender position shall be ground flat.

7.6 For steam boilers with a rated steam pressure greater than 0.8MPa, any connecting pipes (such as water supply pipes, dosing pipes) that can cause local thermal fatigue of header of the water-cooled wall shall be provided with a regular sewage discharge device.

9.3 Corresponding hand holes or inspection holes shall be installed on the header according to the needs of manufacturing and maintenance.

9.4 Reliable anti-wear and heat insulation measures shall be taken for headers washed by flue gas.

9.5 When the two pipe fittings are butt-connected, corresponding measures shall be taken to ensure the conditions for non-destructive testing of the weld.

10 Desuperheater

10.1 For steam boilers with a rated pressure greater than 0.8MPa, the desuperheater water pipe of the spray desuperheater shall be equipped with a sleeve at the place where it passes through the desuperheater cylinder.

10.2 The space between the cylinder and the inner liner of the water spray desuperheater and between the water spray pipe and the pipe seat shall be able to expand freely. There shall be no resonance.

10.3 The length of the inner liner of the spray desuperheater shall meet the requirements of water vaporization. When the inner liner adopts a spliced structure, the spliced welds shall adopt a full penetration structure.

10.4 The structure and arrangement of spray desuperheater shall be easy to repair. An inspection hole with an inner diameter of not less than 80mm shall be provided. Inspection holes shall be located to facilitate endoscopic inspection of inner liners as well as sprinkler pipes.

10.5 The structure of the cooling water pipe of the surface desuperheater shall be able to prevent thermal fatigue cracks of the cooling water pipe.

10.6 When the two table-top desuperheaters are arranged symmetrically from left to right, the arrangement of the cooling water inlet and outlet pipes shall be able to prevent steam lock and pulsation in the desuperheater.

11 Furnace (water-cooling wall)

11.1 The water-cooling wall shall adopt membrane tube panel structure. Ensure the tightness of the furnace.

11.2 Furnace water-cooling wall shall ensure sufficient mass flow rate in its tube, so as to maintain the hydrodynamic stability of the water-cooling wall and the heat transfer protection plates, so as to prevent the tubes from being blown.

12.6 The highest point of the superheater and reheater shall be provided with a pipe seat and valve for discharging air.

12.7 A drain valve shall be installed at the lowest header (or pipeline) of the superheater system and reheater system.

12.8 Superheater and reheater tube bundles shall take measures such as positioning or fixing devices to prevent shaking and abnormal vibration during operation. No rubbing occurs.

12.9 Sufficient space for inspection and cleaning shall be left between the superheaters at all levels and the heating surface tube groups of the reheaters.

13 Coal economizer

13.1 The design of the economizer shall fully consider the protection measures of ash particle wear. When necessary, a baffle plate shall be installed between the economizer tube bundle and the surrounding walls to prevent flue gas from drifting. A reliable anti- wear device shall also be provided on the tube bundle.

13.2 Within the effective range of the soot blower, the economizer and its suspension pipes shall be equipped with anti-wear guards, so as to prevent blowing damage to the pipes.

13.3 The economizer shall be self-draining. The lowest header (or piping) shall be equipped with a drain connection seat with corresponding valves.

13.4 At the highest point of the economizer, a connection seat and a valve for discharging air shall be provided.

13.5 Between the heating surface tube groups such as the economizer arranged in the flue at the rear of the boiler, there shall be a space of sufficient height to facilitate access for maintenance and cleaning.

13.6 For drum boilers, in order to ensure the cooling of the economizer during the start and stop process, recirculation pipes shall be installed, or other protective measures shall be taken.

14 Hanging-supporting devices

14.1 The hanging-supporting device shall have sufficient strength. The strength of each stressed member shall be calculated according to the load and displacement under various operating conditions. Stiffness and stability calculations shall also be performed if necessary.

14.2 The setting of the hanging-supporting device shall meet the overall layout of the boiler and the layout requirements of the supported pressure parts.

14.3 The hanging-supporting device shall be simple and reasonable in structure and easy to install. A mature, reliable and economical structural type shall be selected.

14.4 The thread diameter of the ordinary suspender on the top of the suspending boiler shall not be less than M16.

14.5 The structural type and calculation of the suspender device are in accordance with the provisions of JB/T 6735.

15 Rigid beam

15.1 Rigid beams are used to withstand boiler furnace pressure and transmit horizontal forces. Rigid beams generally do not bear external loads. If subjected to external loads, corresponding measures shall be taken to make the rigid beam system and pipes meet the strength and stiffness requirements.

15.2 The layout of the rigid beam system shall be based on a stress analysis of the tubes and rigid beams. Protect pipes and rigid beams from vibration. The rigid beam itself shall have sufficient strength, rigidity and stability under the design pressure of the furnace.

15.3 The reaction force at the end of the rigid beam shall be clearly transmitted. All stress components meet the strength and rigidity requirements.

15.4 Rigid beams generally use I-shaped cross-sections. Truss structures can also be used.

15.5 There shall be effective heat insulation measures between the rigid beam and the furnace wall, so as to prevent large thermal deviations between the inside and outside of the main beam of the rigid beam.

15.6 Rigid beams shall be provided with necessary drainage holes to prevent water accumulation.

16 Boiler steel structure and escalator as well as platform

16.1 The design of the boiler steel structure shall comply with the provisions of GB/T 22395.

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