DL5190.8-2012电力建设施工技术规范第8部分:加工配制(英文版)
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2.4 Welding

2.4.1 The steels,welding materials,welding methods and post-weld heat treatment adopted for the first time shall be carried out with welding procedure qualification and shall be approved according to"The Code of Welding Procedure Qualification"(DL/T 868).

2.4.2 The welding groove type and dimension shall meet the design requirements.When there is no requirement for design,they shall be implemented according to the requirements of"Recommended Joint Preparation for Gas Welding,Manual Metal Arc Welding,Gas-shield Arc Welding and Beam Welding"(GB/T 985.1)and"Recommended Joint Preparation for Submerged Arc Welding"(GB/T 985.2).

2.4.3 The weld joint grade of the steel structure shall meet the design requirements,when there is no requirement for design,the grading shall be carried out according to the load property,loading condition,working condition and importance of its located position:

1 Grade 1 weld joint:the butt weld joint that bears tension and shear force and is designed according to equal strength,the composite weld joint of butt joint and angle joint.

2 Grade 2 weld joint:the butt weld joint that bears pressure and is designed according to equal strength,the composite weld joint of butt joint and angle joint.

3 Grade 3 weld joint:other weld joints except for Grade 1 and 2 ones.

2.4.4 The classification of weld joints of air & flue gas ducts/raw coal & pulverized coal piping and steam/water pipelines shall be implemented according to the requirements of"The Code of Welding for Power Plant"(DL/T 869).

2.4.5 Welding shall be conducted provided that effective protection measures are taken,if one of the following conditions exists:

1 The relative humidity is larger than 90%.

2 The surface of the weldment is humid or covered with ice and snow.

3 The wind speed during manual arc welding and submerged-arc welding exceeds 8m/s.

4 The wind speed during argon arc welding and CO2 gas shielded welding exceeds 2m/s.

5 The ambient temperature of carbon structural steels is less than-10℃;the ambient temperature of low-alloy structural steels is less than 0℃.

2.4.6 The weld preheating and post-weld heat treatment shall be implemented according to the requirements of"The Code of Welding for Power Plant"(DL/T 869)and"The Code for the Welding Heat Treatment for Power Plant"(DL/T 819).

2.4.7 The weld joint surface shall be free from such defects as cracks,weld overlap,undercut,porosity,slag inclusion,arc crater,electric arc scratch,incompletely filled groove or root shrinkage.

2.4.8 The weld joints of the steel structure shall be inspected according to the following requirements:

1 As for carbon structural steels,when the weld joint is cooled to the ambient temperature,the nondestructive testing shall be carried out for the weld joint that easily generates delayed cracks after 24h passed from the completion of the welding.

2 As for Grade 1 and 2 weld joints which the full penetration is required in the design,the ultrasonic testing shall be adopted to detect the internal defects;if the ultrasonic testing fails to make a judgment on defects,then the radiographic testing shall be adopted.

3 The non-destructive testing shall meet the requirements of"Method for Manual Ultrasonic Testing and Classification of Testing Results for Ferritic Steel Welds"(GB 11345)or"Methods for Radiographic Inspection and Classification of Radiographs for Fusion Welded Butt Joints in Steel"(GB/T 3323).The quality grade shall be in accordance with those specified in Table 2.4.8.

Table 2.4.8 Table of weld joint quality grade

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Note:As for the nondestructive testing on weld joints,the percentage shall be calculated according to the number of the weld joint of the same type and the same welding condition,the testing length shall not be less than 200mm and the weld joint shall be not less than one.

2.4.9 The internal inspection on weld joints of steam/water pipelines shall be implemented according to the requirements of"The Code of Welding for Power Plant"(DL/T 869).

2.4.10 As for the unqualified weld joint,it may be repaired by replacing the unqualified part.Generally,such repairing at the same position shall not be carried out for three times at maximum,while that of the heat resistant steel shall not be carried out for two times at maximum.The quality analysis shall be carried out before repairing,and the process measures for repairing shall be implemented only after the examination and approval of the technical director of welding.

2.4.11 The repaired weld joint shall be inspected according to the previous method.