GB/T 16508.4-2022Shell boilers—Part 4: Fabrication, inspection and acceptance (English PDF)

3.1 Cold forming

Plastic deformation processing that is performed below the recrystallization temperature of the workpiece metal.

3.2 Hot forming

Plastic deformation processing that is performed above the recrystallization temperature of the workpiece metal.

3.3 Tube forming

Processing process of tube bending, upsetting, necking, flaring, etc.

5.1 General

5.1.1 Boiler manufacturers shall formulate guidance documents for the use of material marks for pressure elements and main load-bearing members, welder marks in the fabrication process, non-destructive testing marks, product part identification numbers, and inspection status marks.

5.2 Marking method

5.2.1 Marking shall adopt the following methods or a combination of the following methods.

5.2.2 Steel stamps shall not be used in the following situations.

5.2.3 When the method of 5.2.1~5.2.2 cannot be used for marking, the positioning map can be used instead of marking.

7.1 General requirements

7.1.1 When cold forming is used, the cold brittleness of the steel used shall be considered.

7.1.2 When hot forming is used, the temper brittle temperature zone of the steel shall be avoided.

7.2 Corrugated forming of boiler shell and cylindrical shell section, tube plate (head), U-shaped foot ring and flue 7.2.1 The continuous forming process shall be adopted for hot forming or cold forming of circular tube plates, heads, U-shaped foot rings and furnace corrugations.

7.2.2 Tube plates, heads and U-shaped foot rings shall be pressed and formed from a single piece of steel plate.

7.2.3 The appearance quality after forming shall meet the following requirements.

7.2.4 The actual thickness of the pressure element after forming shall not be less than the minimum required thickness required by the design. Special parts are according to the following requirements.

7.2.5 The deviation of the inner diameter of the circular tube plate, the head and the outer ring of the U-shaped bottom ring shall meet the requirements of Table 1.

7.2.10 The inner diameter (di) deviation of the flue hole of the circular tube plate (see

Figure 2a), Figure 2c) and Figure 2d), and the inner diameter (di) deviation of the inner ring of the U-shaped bottom ring (see Figure 3) shall not exceed the ones specified in

7.3 Tube forming, threaded pipe thread pressing and pipe end necking

7.3.1 Tube forming shall comply with the provisions of GB/T 16507.5.

7.3.2 After the tube is rolled and threaded, there shall be no defects such as cracks and wrinkles on the surface. The shape deviation, size deviation and surface roughness of the threaded smoke tube shall meet the requirements of the design documents.

8.1 Boiler shell, flue, header

8.1.1 The cylindrical shell section butt joints of the shell, flue, the butt joint of the cylinder body and the tube plate (head), and the butt joint of the header meet the following requirements.

8.1.2 The straightness of the boiler shell and flue per meter length shall not be greater than 1.5 mm. The full-length straightness shall comply with the relevant provisions of

GB/T 16507.5.The total length deviation of the boiler shell is. The length deviation and full-length straightness of the header shall comply with the relevant provisions of GB/T 16507.5.

8.2 Serpentine tubes, membrane wall tube panels, wing (fin) tubes, etc.

8.2.1 The fabrication of serpentine tubes and membrane wall tube panels shall be carried out in accordance with the relevant requirements of GB/T 16507.5.

8.2.2 The fabrication of high-frequency resistance welding spiral wing (fin) tubes shall be carried out in accordance with the relevant requirements of NB/T 47030.

8.3 Braces

8.3.1 Braces (including straight tie rods, diagonal tie rods, stay tubes, stay plates) shall not be spliced.

8.3.2 The dimensional deviation of the braces shall meet the requirements of the design documents.

8.6 Steel structure

The fabrication and inspection of boiler steel structure shall meet the requirements of NB/T 47043.

8.7 Assembly of pressure elements

8.7.1 The assembly of tube joints on the boiler shell and header shall meet the following requirements.

8.8.5 Individual protrusions with a height exceeding 1 mm on the surface of the pressure element shall be ground.

8.8.6 The cracks and gaps caused by the quality of the steel plate not meeting the requirements and over-burning shall not be repaired by welding.

8.8.7 Surface grinding and welding repair shall meet the following requirements.

9.1 General requirements

9.1.1 The calculated temperature at the expansion joint shall not exceed 400°C.

9.2 Expansion joint tube hole

9.2.1 The expansion joint tube holes shall not be opened on the spliced weld of the tube plate or the longitudinal weld of the boiler shell (drum). When the expansion joint tube hole must be opened on the circumferential weld, it shall be handled according to 11.4.6 b).

9.3 Expansion joint tubes

9.3.1 There shall be no defects such as heavy skin, cracks, longitudinal grooves, and pressure deviation on the surface of the expansion joint tube. The depth of defects such as transverse grooves and pits at the expansion joint shall not be greater than 10% of the nominal wall thickness of the tube.

9.3.2 The material of the expansion joint tube shall be selected with a hardness lower than that of the boiler shell (drum).

9.4 Selection of tube expander

9.4.1 The initial minimum diameter of the tube expander shall be less than the minimum internal diameter of the tube. Make sure that the tube expander fits smoothly into the tube hole.

9.5.2 The ambient temperature during expansion shall be higher than 0°C.

9.5.3 A test expansion shall be carried out before formal expansion, so as to determine a reasonable expansion rate.

9.6 Calculation methods for tube expansion rate

9.6.1 Inner diameter control method

When inner diameter control is used, the tube expansion rate shall generally be controlled within the range of 1%~2.1%. The tube expansion rate can be calculated according to the formula (1).

9.8 Sticking expansion requirements

9.8.1 The expansion rate for sticking expansion shall be controlled at 0.1%~0.5% (inner diameter control method). The maximum shall not be greater than 0.7%.