1. What is the key international standard for SSAW pipes in oil & gas?
API 5L / ISO 3183 / GB/T 9711 is the primary standard governing line pipe for pipeline transportation systems. It covers various quality levels and supplementary requirements for different service conditions-4.
2. What are the different quality levels in API 5L/GB/T 9711?
The standard specifies two main quality levels: PSL 1 (standard requirements) and PSL 2 (more stringent, with enhanced toughness and testing). It also includes supplementary annexes for even higher requirements, like Annex G for resistance to ductile fracture propagation (similar to a PSL 3) and Annex H for sour service-4.
3. What special requirements apply to SSAW pipes for "Sour Service"?
For acidic environments containing H₂S, Annex H of GB/T 9711 imposes strict controls, including low sulfur content (max 0.002%), inclusion shape control (e.g., calcium treatment), mandatory HIC (Hydrogen Induced Cracking) and SSC (Sulfide Stress Cracking) tests, and hardness limits-4.
4. What is the "Manganese-Carbon (Mn/C) ratio" concept in pipeline steel?
This is a key metallurgical concept where API 5L allows a trade-off: for every 0.01% reduction in Carbon content below the maximum limit, the Manganese content can be increased by 0.05%. This enables the development of higher strength with better weldability-4.
5. Why is the internal weld bead profile important for SSAW pipes?
The spiral internal weld bead can create significant flow resistance for pumped media. A smooth, controlled bead profile is crucial for pipelines with internal coatings to reduce friction, as a prominent bead can disrupt the coating and increase power consumption and operating costs
