What are the main types and causes of weld defects?
Incomplete penetration is often caused by insufficient heat input or improper groove design. Porosity is mostly caused by wet flux or poor protection. Slag inclusions are caused by slag not floating out of the molten pool in time. Cracks may be related to material hardening tendency or residual stress. Undercuts are the result of excessive welding speed or excessive current. The critical control parameters of each defect need to be determined through process tests.
How to determine the pressure of the water pressure test?
The test pressure is generally 1.5 times the design pressure and not less than the minimum value specified in the standard (such as API 5L requires ≥1.25 times). The pressure holding time is not less than 10 seconds, and observe whether there is leakage or pressure drop. High-pressure pipelines need to be gradually increased in sections to avoid instantaneous shock. The test water needs to be filtered, and the chloride ion content is ≤50ppm. The pressure curve will be recorded and included in the quality file.
Comparison of the advantages and disadvantages of ultrasonic testing and radiographic testing?
Ultrasonic wave (UT) is sensitive to area defects (such as cracks), can be imaged in real time and has no radiation risk. Radiography (RT) is easier to detect volume defects (pores), and the results are intuitive and can be archived. UT detection is faster and suitable for online applications, but it requires high operator skills. RT equipment is expensive and requires protective measures, and is suitable for spot checking key welds. Modern production lines often use a combination of the two.
What are the latest revisions to the API 5L standard?
The 47th edition adds toughness requirements for steel grades above X70 and refines the HIC (hydrogen-induced cracking) test method. Added technical terms for pipelines based on strain design. Revised the dimensional tolerance range of PSL2 products. Strengthened the requirements for digital work orders and traceability systems. Added an appendix to the special material specifications for CO₂ transmission pipelines.
How to establish a full-process quality traceability system?
Give each steel pipe a unique code and associate it with data such as the batch number of the steel coil and welding parameters. Use the MES system to record the inspection results of each process, including dimensions, mechanical properties, etc. Set up QR code scanning points at key workstations to update production status in real time. The quality data is stored in the cloud, and the storage period is not less than the design life of the pipeline. If a problem occurs, it can be traced back to the raw material supplier through the system.
