This standard specifies the requirements on the manufacturing and acceptance of boiler structure.
This standard is applicable to the steel structure of stationary boiler and the welded steel structures such as platform and stairs. The steel structures include: Upright post, plate beam, beam, frame and truss.
2 Normative References
GB 700 "Carbon Structural Steels"
GB 1591 "High Strength Low Alloy Structural Steels"
GB 4159 "Metallic materials-Low-temperature Charpy Impact Test"
GB 6654 "Thick Carbon Steel and Low-alloy Steel Plates for Pressure Vessels"
JB 3375 "Receiving Acceptance of Raw Materials for Boiler"
JB/T 1614 "Boiler Pressure Parts--Mechanical Test for Welded Joints"
JB/T 2636 "Boiler Pressure Parts—Metallographic Examination and Fracture Test of Weld Joints"
JB/T 1615 "Specification for Painting and Packing of Boilers"
JB 1152 "Boiler and Steel Pressure Vessels--Ultrasonic Flaw Detection of Butt Welds"
JB 3965 "Magnetic Particle Inspection of Steel Pressure Vessels"
3 Technical Requirements
3.1 Materials
3.1.1 The materials for steel structures shall be adopted according to those specified in the related technical documents. The steel products and welding materials for manufacturing the steel structures shall be in accordance with the requirements of design pattern and the related technical documents, the material substitution shall be examined and approved according to the established procedures.
3.1.2 Both the steel products and the welding materials for manufacturing the steel structures must be with the material quality certificate and be inspected by the inspection department according to those specified in JB 3375 and this standard, the one that is not inspected or is rejected in the inspection is disallowed to be put into production.
3.1.3 The mechanical performances and chemical compositions of the steel products shall be in accordance with the following requirements:
a. The common carbon structural steel shall be in accordance with those specified in GB 704 and shall be supplemented to assure the yield strength point, cold test and carbon content meet those specified in this standard.
b. The low alloy structural steel shall be in accordance with those specified in GB 1591.
c. The carbon steel and common low alloy steel for pressure vessels shall be in accordance with GB 6654.
3.1.4 The low alloy structural steel used for manufacturing the upright post, main beam and the secondary beam connected with the main beam as well as the carbon steel and common low alloy steel plate for pressure vessels shall be supplemented to assure the impact ductility at normal temperature be no less than 27J (2.8kgf?m) when the plate thickness is no less than 36mm; as for the members with the calculated temperature at or below -20℃ and the other members requiring low-temperature impact test according to the design requirement, clause on the test temperature of impact ductility and the acceptance criterion shall be added in the procurement contract according to the design requirement.
3.2 Splicing
3.2.1 When splicing the steel plate or formed steel, the splicing work shall be in accordance with the design pattern and those specified in this standard. When splicing the steel products for the plate beam with the manufacturing height no less than 2m, the steel products shall be spliced according to the splicing diagram countersigned by the departments concerned.
3.2.2 After laying off the steel products, their cur edges shall be free from such macroscopic imperfection as demixing or slag inclusion.
3.2.3 When splicing the carbon steel plates in thickness no less than 36 mm for the plate beam with manufacturing height no less than 2 m or splicing the low-alloy steel plates in thickness no less than 32mm, ultrasonic flaw detection shall be conducted onto the steel plates within the area away from the weld center by two times of the plate thickness added by 30 mm at both sides of the butt weld, or the magnetic particle inspection may also be conducted onto the shaped groove face, no defects that may influence the quality can exist.
3.2.4 When splicing the angle steel, channel steel or I-section steel, the welds covered by the reinforced plate shall be adopted with Y-groove single-surface welding, the rest spliced welds shall be adopted with the V-groove double-surface welding. The leg dimension K (Figure 1) of the fillet weld on the reinforced plate shall comply with the requirements of the manufacturing plant.
