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General Technical Requirements for the Manufacturing of Boiler Steel Structures with Welded Joints and High-Strength Bolt Connections 1 Subject Matter and Scope of Application This standard applies to the manufacturing and inspection of boiler steel structures with welded joints and high-strength bolt connections; such steel structures include columns, plate girders, beams, frames, and trusses. Ordinary welded steel components (such as guards, guards for smoke and air ducts, anti-vibration devices, etc.) shall still be manufactured and inspected in accordance with the provisions of JB/T1620-93. In the areas on rigid beams where high-strength bolts are used for connections, the friction surfaces need not be treated; however, the tolerances regarding hole spacing and position shall comply with the provisions of this standard, while the rest shall be manufactured and inspected in accordance with JB/T1620-93. This standard must be used in conjunction with the technical specifications JB/T1620-93. 2 Reference standards: JB/T1620 – Technical requirements for the manufacture of steel structures for boilers; GB700 – Carbon structural steel; GB1591 – Low-alloy structural steel; GB4159 – Method for metal low-temperature Charpy impact testing; GB6654 – Thick steel plates made of carbon and low-alloy steels for pressure vessels; JB1152 – Ultrasonic testing of butt welds in boilers and steel pressure vessels; JB/T1614 – Test methods for the mechanical properties of welded joints in boiler pressure components; JB/T2636 – Metallographic and fracture inspection methods for welded joints in boiler pressure components; JB3965 – Magnetic particle testing for steel pressure vessels. 3 Technical requirements: 3.1 Materials: 3.1.1 Material quality certificates must be available for the steel used in manufacturing steel structures, as well as for the welding materials. These materials must be inspected by a testing department in accordance with the regulations specified in JB3375-91 “Inspection of raw materials for boilers”. Materials that have not been inspected or that fail the inspection shall not be used in production. Steel plates used in structures where the height of the column cross-section is H≥250 mm (referring mainly to the upper and lower connecting plates, excluding plates such as reinforcement plates or partitions on the columns themselves) also need to be inspected in accordance with the provisions of JB3375. 3.1.2 The materials used for manufacturing steel structures shall meet the requirements of the design drawings and relevant technical documents; the substitution of materials shall be carried out in accordance with the provisions of Q/GS-03-1.6-94 (Procedures for Substitution of Product Materials). 3.1.3 Ordinary carbon steel Q235 and low-alloy steel 16Mn shall comply with the provisions of GB700 and GB1591; SM400B and SM490B steel plates shall comply with JIS G3106 and the provisions of the order contract. 3.1.4 To prevent mixing of materials, marking is required; material marking and transplantation shall be carried out in accordance with the provisions in G1611 and G9004. For imported materials, their respective steel grades shall be marked. 3.1.5 For low-alloy structural steel used in manufacturing columns, main girders, and secondary girders connected to the main girders, as well as carbon steel and low-alloy steel plates for pressure vessels, it is required that when the plate thickness is 36 mm or more, an additional requirement is that the impact energy at room temperature be not less than 27 J. If no specified value for the base material is given, it shall be not less than 27 J (with a specimen cross-sectional size of 10×10 mm). 3.2 Welding and Surface Quality 3.2.1 After flame cutting of steel plates and sections, the quality of the cut surface shall comply with the specifications in ZBJ59002.3-88; the quality grade of the cut surface is Grade II, Class 3. The dimensional tolerances of the workpieces shall meet Class B accuracy requirements, and the surfaces must be polished smooth after gas cutting. 3.2.2 When the plate thickness is 32 mm or greater, the surface of the groove prepared by gas cutting must be polished smoothly, and a magnetic particle inspection must be carried out; if the groove is prepared by mechanical methods, a magnetic particle inspection is not required. 3.2.3 For H-shaped steel that needs to be welded together by our factory due to unsuccessful procurement from external sources or other reasons, the allowable deviations in its cross-sectional dimensions and the technical requirements shall comply with the provisions of YB3301-92. 3.2.4 The base plates of columns or secondary columns shall, in principle, not be joined together. 3.2.5 The tolerance α for the lock groove size is +1–3 mm ； t is +1.5-1mm ； For R of ±4mm, the lock seam cut must be smooth; the dimensional tolerance of the lock seam is shown in Figure 1. file:///D:/WG_dictionary/WG0xxx/dwg/0118-1.wmf CAD details 3.2.6 For steel sections cut mechanically, the inclination at their ends shall not exceed 0.5 mm, and burrs must be removed; for parts that have had their edges planed, the straightness of those planed edges shall be P≤2 mm (see Figure 2). file:///D:/WG_dictionary/WG0xxx/dwg/0118-2.wmf CAD details 3.2.7 The degree of bending (deflection) of the sheet metal shall be carried out in accordance with the tolerance values in Table 1. Table 1: Thickness tolerances for mm steel plates. Remarks: δ≤8: 0.01B; here, “B” represents the minimum specified dimension of the supporting surface. 8＜δ≤15: 0.008B. δ＞15: 0.006B. Note: The value of B is determined by the inspection department; generally, a value of 1m is recommended for B. 3.2.8 The requirements for staggering of lap welds shall be in accordance with the provisions in JB/T1620. 3.2.9 The groove form and dimensions for the free butt welds of steel plates may refer to the provisions in GB985–986-88 (see Standard No. 95009). 3.2.10 The splicing of rolled or welded H-shaped steel can follow the regulations for splicing I-beams. 3.3 Welding 3.3.1 Before welding, the grooves and areas to be welded must be cleaned of slag, oil, rust, paint, and other substances that could affect welding quality; after welding, surface defects such as weld beads, flux residue, and spatter must also be removed. 3.3.2 When welding seams on plate girders with H ≥ 1.4 m, if manual welding is used, alkaline electrodes must be employed; for submerged arc welding, alkaline fluxes are permitted. 3.3.3 For components subjected to tack welding, the length of the weld seam must be at least 50 mm. For areas where tack welding is performed on steels such as 16Mn and SM490B, surface crack inspection (using the naked eye or a magnifying glass) is required prior to the final welding, in order to prevent crack formation. 3.3.4 The assembly and welding of welded parts shall be carried out in accordance with the process specifications; no metal strips, electrodes, or similar materials shall be inserted into the gaps around the welds. 3.3.5 When welding on plate girders with a height H ≥ 1.4 m, the welder must have passed the examinations specified in the \"Rules for Welder Certification for Boilers and Pressure Vessels\" before being allowed to carry out such work; other components should be welded by trained and skilled welders. Welds on large plate girders that have undergone non-destructive testing must bear the welder’s mark. (Note: Definition of a skilled welder: can be a qualified welder or an experienced welder without a qualification certificate). 3.3.6 For welded components, a 40 mm long weld plate shall be left at both the beginning and end of the weld; it shall be cut off, polished, and any burrs removed. 3.3.7 Weldments temporarily welded on steel structures as required by the manufacturing process shall be removed ultimately only by grinding with a grinder or cutting with air plasma; thereafter, the area shall be ground smooth and surface cracks shall be inspected (using dye penetrant testing or magnetic particle testing). 3.3.8 The weld height shall strictly comply with the specifications in the design drawings; the weld surface shall be uniformly scale-like, and must be free from any defects such as cracks, inclusions, lack of fusion, numerous pores, cratering, and burn-through. 3.3.9 When there are both welding and bolted connections at the component joints, welding should be carried out first, followed by bolting. 3.3.10 At connection joints, such as those at the top and bottom plates of columns, the pre-welded mating surfaces must make good contact to ensure that the final cross-section as well as the top and bottom plates are flat, with the component’s centerline being perpendicular to them. Each layer of column joint plate shall be planed, with the flatness of the planed end face not exceeding 0.3 mm; the tilt tolerance of the planed end face shall not be greater than B/750 (where B is the width), and shall not exceed 1 mm at most. 3.3.11 Areas where the tack welds have not been properly welded or have cracked must not be used for further work; they must first be cleaned thoroughly or ground away using a grinding wheel. 3.3.12 When the cross joint is a butt weld (with bevels), 100% ultrasonic testing shall be carried out. When the cross joints are corner welds, for the “+” shaped joints in the columns, ultrasonic testing is carried out only on the area where they meet the main frame beams; that is, 250 mm above and below the beam height is subject to ultrasonic testing, while the remaining areas are inspected at 25% intensity. If quality is stable, the inspection length can be reduced to 10%. 3.4 High-strength bolt connections 3.4.1 The diameter (dn) of the holes in components connected by high-strength bolts, as well as the corresponding tolerances, are shown in Table 2. Table 2: Thread specifications; d: Diameter; dn: Hole diameter; Roundness (difference between maximum and minimum diameters): M22 – 24+0.52, 0 ≤1.5; M24 – 26+0.84, 0; M30 – 32+0.84, 0. The surface roughness of the hole walls is 12.5. 3.4.2 High-strength bolt holes should preferably not be located on the weld seams; the distance between the centerline of the weld seam and the edge of the high-strength bolt hole should be ≥100 mm, as shown in Figure 3. If it cannot be avoided, it should be handled only after approval by the designer in advance. file:///D:/WG_dictionary/WG0xxx/dwg/0118-3.wmf CAD details 3.4.3 For holes that cannot pass the gauge inspection, it is necessary to obtain approval from the design and process departments before drilling them larger or performing welding repairs; rewelding should be carried out using welding rods with the same performance grade as the base material. It is strictly prohibited to use steel blocks to fill such holes, and records must be kept for all holes that have been treated in this manner. 3.4.4 The assembly penetration rate measured using a plug gauge with a diameter of less than 0.5 mm shall be not less than 85%, and the assembly penetration rate measured using a plug gauge with a diameter of less than 1 mm shall be not less than 100%. 3.4.5 The perpendicularity tolerance △C between the wall of the bolt hole and the surface of the component shall be ≤0.03δ, with a maximum value not exceeding 1 mm (Figure 4); after the hole diameter is machined, there should be no debris such as burrs, chips, or splashes around it. The surface at the joint should be smooth, clean, and oil-free. file:///D:/WG_dictionary/WG0xxx/dwg/0118-4-5.wmf CAD details 3.4.6 When two or more plates are connected to each other, they must remain concentric; the coaxiality tolerance △C for the connection holes of any two plates should be less than or equal to 1 mm (Figure 5). 3.4.7 Allowable deviation of hole spacing (Figure 6). file:///D:/WG_dictionary/WG0xxx/dwg/0118-6.wmf CAD details a. The allowable deviation for the spacing t1 between adjacent holes within the same group is ±0.7mm. b. The allowable deviation for the distance t2 between any two holes within the same group is ±1mm. c. The allowable deviation of the distance t3 between the diagonals of the hole group within the same set is ±1.5 mm. d. The allowable deviation for the end hole spacing t4 between adjacent groups is ±1.2 mm. e. The allowable deviation of the distance L1 between any set of holes and the reference line is ±1.2 mm. f. The absolute value of the difference between the diagonal distances of adjacent holes, a-b, should be less than or equal to 2 mm. 3.4.8 The diameter tolerance for the foot bolt holes is ±3 mm, and the deviation of the center line of the hole from the center line of the column foot base plate shall not exceed 2 mm. 3.5 Treatment of the friction surfaces of components 3.5.1 The friction surfaces in the area of high-strength bolt connections must be treated by shot blasting or sandblasting (acid cleaning is generally not recommended). The friction coefficient of the treated surface must be greater than or equal to 0.45. 3.5.2 Burrs, residues, curling, and cutting burrs on the friction surface must be completely removed. The treated friction surface should have protective measures in place to prevent it from becoming contaminated with dirt and oil. 3.5.3 It is strictly prohibited to make any marks on the friction surface, and painting is not allowed within a radius of 60 mm around the edge of the bolt at the outermost part of the hole group. 3.5.4 For specimens used to determine the friction coefficient, they should be made of the same material as the steel structure they represent, with the same treatment method for the friction surfaces. They should also be manufactured in the same batch, using high-strength bolts of the same performance grade and diameter. Inspection is carried out in batches based on the tonnage of the steel structure (taking individual projects as a unit); generally, a batch consists of around 1500 to 2000 tons (if the tonnage is less than 2000 tons, it is still considered one batch). Each batch is divided into three groups of specimens for testing, and the testing methods and requirements are specified in G/Z45-95. 3.6 Heat Treatment 3.6.1 If preheating is required before welding the components, it shall be determined based on the material properties, plate thickness, and welding process. 3.6.2 The heat treatment range and requirements shall be in accordance with the provisions of JB/T1620-93; heat treatment shall be carried out after the welds have passed inspection. 3.6.3 During local heat treatment of the weld, the area 100 mm on each side of the weld is heated. 3.6.4 Treatment of basic welding electrodes: Pre-bake at 300–350°C for 2 hours, remove them from the oven at 100–120°C, and place the electrodes in a box kept at 120°C. 3.6.5 After welding the joints of plate girders and column flange plates and undergoing heat treatment, it is strictly prohibited to initiate an arc at any location to avoid the occurrence of magnetoelectric effects; if such effects do occur, the surface must be polished before undergoing magnetic particle inspection. 3.6.6 When overall heat treatment is required for the tensile member, it shall be indicated on the drawing. 3.7 Manufacturing and assembly tolerances 3.7.1 The joints between rolled steel sections, or between welded plate girders and rolled steel sections, are cut in accordance with G1310-76. The joint seams between rolled steel sections and welded plate girders, or between welded plate girders themselves, are cut in accordance with the design drawings. The seams must be smooth and accurate; any residual burrs are not allowed. The length tolerance for the components forming these seams should be negative (see Figure 7). file:///D:/WG_dictionary/WG0xxx/dwg/0118-7.wmf CAD Details 3.7.2 For beams connected by end plates or angle steel, the flatness of the end plates or angle steel shall be ≤0.5 mm, and their perpendicularity shall be one thousandth of the beam’s height. 3.7.3 When end plates are used for connecting the beam ends, the method for machining the surface of these end plates is determined by the manufacturing process, provided that the flatness is ≤0.5 mm. 3.7.4 The local planarity of the web of the plate beam shall be such that △ is ≤ 2 mm at the joint areas, and ≤ 3 mm in the remaining areas (see Figure 8). file:///D:/WG_dictionary/WG0xxx/dwg/0118-8-9.wmf CAD details: 3.7.5 The deviation of the column centerline at the upper and lower ends of the column shall be △α≤2mm, as shown in Figure 9. 3.7.6 Deviation △H of the cross-sectional height H of beams or columns: When H ≤ 2 m, the deviation △H is ±2 mm. When H > 2m, the deviation △H is ±4mm. The △H for the joint area is ±2.5 mm. The deviation △B of the beam support cross-sectional width B is ±2mm. The deviation △B of the beam support section’s width B is ±3 mm, as shown in Figure 10. file:///D:/WG_dictionary/WG0xxx/dwg/0118-10.wmf CAD Details 3.7.7 The inclination value △e of the composite slab beam deck and the bending tolerance △e ； (See Figure 11) The perforated area has △e ≤ 1.5 mm ； The pore-free area has △e≤3mm. file:///D:/WG_dictionary/WG0xxx/dwg/0118-11.wmf CAD Details 3.7.8 Torsion value for combined beams and columns: the hole area △c ≤ 5 mm (check the relative displacement △c of the end plates) (see Figure 12-a). The out-of-straightness of beams and columns shall be ≤5mm (including in the longitudinal and transverse directions). The offset and tilt offset △e at the center of the web of composite beams and columns is ≤2 mm (see Figure 12-b). file:///D:/WG_dictionary/WG0xxx/dwg/0118-12.wmf CAD details 3.7.9: The tolerance for deformation and unevenness after welding the column base plate is △e≤2mm (see Figure 13-a); the elevation of the center of the base plate above the column axis is △c≤2mm (see Figure 13-b). file:///D:/WG_dictionary/WG0xxx/dwg/0118-13.wmf CAD details 3.7.10 The large slabs are not allowed to bend downward; the upward camber Δc shall be ≤ 7 mm (see Figure 14). file:///D:/WG_dictionary/WG0xxx/dwg/0118-14.wmf CAD Detail 3.7.11: In the top plate, the error in the upper and lower connections welded to the web is +20 (see Figure 15). file:///D:/WG_dictionary/WG0xxx/dwg/0118-15.wmf CAD Detail 3.7.12: The deviation of the length L from the zero elevation line to the planed end of the column is 0–1 mm; the deviation of the distance H between the zero elevation and the plane of the column’s bottom plate is 0–2 mm (see Figure 16). The perpendicularity △C between the bottom plate and the column axis is ≤2 mm. file:///D:/WG_dictionary/WG0xxx/dwg/0118-16.wmf CAD Details 3.7.13 All connections in the direction of the flanges and webs (including those between steel members, between steel members and steel plates, and between plates) should be perpendicular to one another, with the tolerance for this perpendicularity being less than or equal to 1 mm (see Figure 17). file:///D:/WG_dictionary/WG0xxx/dwg/0118-17.wmf CAD Details 3.7.14: The length tolerances for columns, beams, and diagonal braces are specified in Table 3 (see Figure 18). file:///D:/WG_dictionary/WG0xxx/dwg/0118-18.wmf CAD details: Table 3 – Nominal dimensions in mm. L: L≤6m, 6m＜L≤12m, 12m＜L≤25m. For columns: ±1.0, ±1.5, ±3; for beams: 0-2, 0-3, 0-4. For diagonal braces: ±2, ±4, ±5. Note: In the case of a negative tolerance for beams, it is possible to use shims of corresponding thickness, with the thickness of such shims not exceeding 4mm. 3.7.15 The offset ΔC between the center line of the hole group in the column itself and the center line of the column shall be ≤ 1 mm. The distance t between the column butt weld and the edge line of the hole pattern on the column body shall be ≥ 200 mm. (See Figure 19) file:///D:/WG_dictionary/WG0xxx/dwg/0118-19.wmf CAD Detail 3.7.16: The deviation of the center line of a component from the center line of the adjacent row of holes shall comply with the provisions in Figure 20. file:///D:/WG_dictionary/WG0xxx/dwg/0118-20.wmf CAD Detail 3.7.17: Specification for the deviation △L1 of the distance L1 between the supports at both ends of the slab-beam and the reference line (see Figure 21); it is +20 when there are holes, and +5–2 when there are no holes. The verticality tolerance ΔC of the transverse reinforcement plates or partitions between beams and columns shall not exceed 2 mm. Deviation △L2 of distance L2 between the intermediate reinforcement plate or partition and the beam/column reference ； It is +2 mm for the perforated areas and ±4 mm for the non-perforated areas (see Figure 21). file:///D:/WG_dictionary/WG0xxx/dwg/0118-21.wmf CAD Details 3.7.18: The deviations of the lengths L1 and L2 of the angle steel beams with bolts welded at both ends are ±0.6 (see Figure 22). file:///D:/WG_dictionary/WG0xxx/dwg/0118-22.wmf CAD Details 3.7.19 Tolerance Elements: a) Tolerance elements for columns are shown in Figure 1; b) Tolerance elements for beams are shown in Figure 2; c) Tolerances for beam-column weld joints are shown in Figure 3; d) Tolerances for vertical and horizontal support joints are shown in Figure 4. 4 Trial Assembly: 4.1 After the fabrication of the components in each floor, they should be assembled flatly, with no less than two rows per floor. The flat assembly should include both planar and three-dimensional aspects. For outsourced or distributed products, the scope of trial installation should be specified in the contract or agreement signed with the other party. 4.2 The friction surface clearance before tightening shall be less than or equal to 1 mm (Figure 23). file:///D:/WG_dictionary/WG0xxx/dwg/0118-23.wmf CAD Details 4.3: The percentage of holes for node assembly shall comply with the provisions of section 3.4.4. During trial installation, bolts of the same diameter should be used, with a quantity equal to 30% of those required per node, and at least 2 bolts in total. 4.4 After the components are properly positioned during the trial installation, rivets should be added, with a quantity of no less than 10% of the number of holes. 4.5 The main allowable tolerances for planar fit are shown in Table 4. Table 4: Fit items for planes – Allowable tolerances. Center distance between struts or chords in a plane: ±2; Diagonal of a plane: ±3; Deflection of diagonal supports within a plane: ±3. 4.6 If the test is unsuccessful, the fitting area should be expanded. Components that fail the test must be revised until they meet the requirements before being released for shipment. Records should be kept of the components that have been revised. If qualified components can ensure the quality of trial assembly under reliable and stable manufacturing conditions, and are approved by the inspection department in advance, trial assembly can be appropriately reduced or eliminated. 5 Inspection and Acceptance 5.1 After the steel structure is fabricated, in addition to the inspections and acceptances specified in this standard, the following inspections and acceptances shall also be carried out. 5.2 The raw materials used in manufacturing steel structures must be inspected in accordance with relevant material standards and the various requirements of this standard. 5.3 Check the dimensional tolerances of the finished products; the joining of steel materials and the surface quality of welds shall meet the requirements of this standard. 5.4 For any type of component, 100% ultrasonic inspection shall be carried out on the butt welds made from ordinary carbon steel with a plate thickness of δ≥36 mm, or low-alloy steel with a plate thickness of δ≥32 mm, after welding. 5.5 When the height H of the plate girder is ≥ 1.4 m, if the thickness of the girder web is one of the following values, one of the transverse welds on the web shall be randomly selected (with a total length equal to the width of the web) for 100% ultrasonic testing; the location of the inspection shall be determined by the inspection authority. a) Ordinary carbon steel with δ<36mm. b) Low-alloy steel with δ<32mm. 5.6 When the height H of the plate girder is ≥ 1.4 mm, and if the thickness of the girder’s web is one of the values specified below, 100% ultrasonic testing shall be carried out on all \"T\" joints in the web, with the inspection area covering 200 mm above, below, to the left, and to the right of each \"T\" joint. a) Ordinary carbon steel with δ<36mm. b) Low-alloy steel with δ<32mm. 5.7 Non-destructive testing shall be carried out on the four fillet welds that connect the deck plate to the web of large slab girders; if the applicable requirements are met as specified in clause 5.2.1 of JB/T1620-93, then the non-destructive testing shall comply with the provisions of clause 5.2.2. 5.8 For the brackets of each beam, one bracket is sampled every 3; 100% ultrasonic testing (magnetic particle testing may also be used) is conducted on the weld at the outer side of one of the sampled brackets that connects to the beam corner. 5.9 For low-alloy steel welds with a plate thickness δ > 32 mm, magnetic particle testing must be carried out on the root of the weld as well as within a range of 200–250 mm around the arc initiation and extinction points. 5.10 Magnetic particle testing shall be performed on the fillet welds of low-alloy steel with a plate thickness δ > 32 mm (whichever plate has a thickness greater than 32 mm). The inspection length for each fillet weld shall be not less than 25%; the inspection area is determined by the inspection department, but provided that the stability of the weld quality can be ensured, the inspection length may be 10%. Fillet welds that have passed ultrasonic testing can be exempted from magnetic particle testing. 5.11 For low-alloy steel components with a plate thickness δ ≤ 32 mm, when using submerged arc automatic welding, magnetic particle testing must be carried out at the beginning and end of the weld seam as well as within a range of 200–250 mm from the starting point of welding. 5.12 For ultrasonic testing of butt welds, compliance with Grade I as specified in JB1152 \"Ultrasonic Testing of Butt Welds in Boilers and Steel Pressure Vessels\" is required to be considered acceptable. For magnetic particle testing of fillet welds, the standards set out in JB3965 \"Magnetic Particle Testing of Steel Pressure Vessels\" apply, with the acceptance criteria being: a) No cracks or pores are allowed ； b) The defect display does not exceed Grade II as specified in this standard. The requirements and acceptance criteria for ultrasonic testing of corner welds on large plate girders are in accordance with G0803 \"Technical Requirements for Ultrasonic Testing of Corner Welds on Boiler Large Plate Girders\". 5.13 In the steel frame roof deck layer, some beams are welded with shear plates; 1 out of every 3 such beams is inspected randomly. The \"\"-shaped fillet welds on the inspected shear plates are subject to 100% ultrasonic testing (magnetic particle testing can also be used), and the welds at the corners must be continuous. 5.14 Product specimens 5.14.1 For plate girders that are required to undergo non-destructive testing in accordance with clause 5.2.1 of JB/T1620, mechanical property tests and metallographic inspections shall also be carried out on the butt welds on them. 5.14.2 For butt welds that require mechanical property testing and metallographic inspection, one welding joint test plate (hereinafter referred to as the test plate) shall be fabricated during the welding of such components, one for each boiler or each batch (of components made from the same material using the same welding procedure). The thickness of the test plate shall be the maximum thickness among the weldments in each boiler or batch. 5.14.3 One weld test plate shall be fabricated for the butt joints of every 3 layers of steel frames (using the same material and the same welding procedure). The thickness of the test plate should be the maximum thickness among the weldments in that layer. For main girders with H ≥ 2m, take the largest girder and use one test plate. 5.14.4 The inspection items, quantity, test plate methods, and acceptance criteria for weld test plates shall be in accordance with the provisions of Table 5. Table 5 Test items, Number of specimens (pieces), Test methods and acceptance criteria: Tensile test – 2, JB/T1614-94; Cold bending test – 2, JB/T1614-94; Metallographic test – 1, JB/T2636-94; Normal temperature impact test – 3, JB/T1614-94; Low temperature impact test – 3, GB4159-84; Same as the base material per clause 3.1.4 of JB/T1620. Note: 1) The low temperature impact test is carried out only when specified in the drawing or technical documents ； 2) Two cold bending tests shall be conducted (one for the face side and one for the back side). If either the face-side or back-side test fails, only the failing test will be repeated. 5.14.5 Requirements for specimens regarding the friction coefficient; the inspection methods are specified in Article 3.5.4. 5.14.6 For welds specified in clauses 5.4 to 5.8 that have been inspected by non-destructive testing and are found to be defective, and for which a 100% inspection of the weld length has not been carried out, all welds of the same type must be inspected thoroughly. Defective welds must be repaired, and the repaired areas must undergo 100% non-destructive testing to ensure quality; generally, repairs to a weld at the same location should not be performed more than three times. 5.14.7 High-elevation bolt connections are all purchased components; their technical requirements, testing methods, inspection rules, markings, and packaging must comply with the relevant standards. 5.14.8 The inspection department shall inspect the material and manufacturing quality in accordance with the drawings and the provisions of this standard; once all inspections are successful, a pass mark shall be issued, and the results of the key inspection items shall be recorded in the boiler quality certificate. Note: The items required by JB/T56142-94 are included as the main items in the quality assurance document. 6 Painting, Packaging, and Shipping 6.1 Before painting the steel structure, its surface must be thoroughly cleaned of oxide scale, weld slag, and spatter; painting should only be carried out after the surface reaches a metallic appearance. 6.2 Painting is not allowed within 60 mm around the edges of the outermost bolt holes; protective measures must be taken for the friction surfaces at the time of shipment. 6.3 The top surface at the end of the column may not be painted. 6.4 Each part and component must be marked with a part number, drawing number, serial number, weight, and a mark indicating the direction of the column. 6.5 The product packaging must be secure, and it should be further reinforced when loaded onto the vehicle to prevent damage during transportation. 6.6 All components and parts of the steel structure shall be subject to inspection and acceptance before they can be painted, packaged, and shipped; the painting and packaging shall be carried out in accordance with the requirements of G0501-92 \"Technical Specifications for Painting and Packaging of Boilers\". 6.7 Examples of component markings are shown in Figure 5. Figure 1: Columns file:///D:/WG_dictionary/WG0xxx/dwg/0118f1.wmf Figure 2: Beams file:///D:/WG_dictionary/WG0xxx/dwg/0118f2.wmf Figure 3: Beam-column weld joints file:///D:/WG_dictionary/WG0xxx/dwg/0118f3.wmf Figure 4: Vertical and horizontal support joints file:///D:/WG_dictionary/WG0xxx/dwg/0118f4.wmf Figure 5: Component markings and assembly markings file:///D:/WG_dictionary/WG0xxx/dwg/0118f5.wmf Figure 6: file:///D:/WG_dictionary/WG0xxx/dwg/0118f6.wmf