Details of GB/T 9711-2023 Steel Pipe for Pipeline Transportation Systems in the Petroleum and Natural Gas Industry

GB/T 9711-2023, "Steel Pipe for Pipeline Transportation Systems in the Petroleum and Natural Gas Industry," is a key technical standard for my country's petroleum and natural gas steel pipelines. As the replacement for GB/T 9711-2017, it will be officially released and implemented in 2023. This standard update marks my country's continued progress in energy transportation equipment technology and is of great significance for ensuring national energy security and improving pipeline construction quality.

First, Background and Significance of the Standard Revision

With the advancement of major pipeline projects such as the "West-East Gas Pipeline" in my country, high-pressure, large-diameter, and high-grade pipelines have become a development trend. The original 2017 version of the standard exhibited limitations in addressing new requirements such as X80 and above steel grade pipelines, service in low-temperature environments, and strain design. This revision incorporates international developments related to API SPEC 5L 46th Edition (2022) and incorporates the past five years of domestic pipeline construction experience, particularly the accumulated experience in pipeline technology for special environments such as high-altitude cold regions and seismic zones. Upon implementation, this standard will unify the technical requirements for domestic steel pipe manufacturing, testing, and acceptance, providing technical support for the "One Nationwide Network" oil and gas pipeline layout.

Second, Major Technical Changes

1. Upgraded Material Requirements: A new PSL2+ quality grade has been added, with stricter toughness specifications for X80 and above steel pipes: the Charpy impact energy at -30°C has been increased from ≥40J to ≥60J; a shear area percentage requirement for the DWTT (Drop Weight Tear Test) has been introduced, stipulating a minimum of 85% at the minimum design temperature. For sour environments, the HIC (hydrogen-induced cracking) and SSC (sulfide stress corrosion) test methods have been refined, with NACE TM0284-2016 and NACE TM0177-2016 being designated as the benchmark testing standards.

2. Optimized Dimension and Tolerance System: The outer diameter range for steel pipes has been expanded to 60 inches (1524mm), and the upper wall thickness limit has been increased to 40mm. For large-diameter steel pipes with a diameter ≥ 1219mm, the ovality tolerance has been tightened from 0.5%D to 0.3%D. The "medium diameter measurement method" has been introduced to replace traditional outside diameter measurement, making it more adaptable to modern pipemaking processes. New requirements for thermomechanically rolled (TMCP) steel pipe deformation heat treatment control have been added, stipulating that the final rolling temperature fluctuation must not exceed ±15°C.

3. Updates to non-destructive testing technology: Automatic ultrasonic testing (AUT) has been upgraded from an optional requirement to a mandatory requirement for PSL2 steel pipes, with detection sensitivity increased to a Ø2mm flat-bottom hole equivalent. Two new technical standards, phased array ultrasonic testing (PAUT) and electromagnetic ultrasonic testing (EMAT), have been added, increasing the defect detection rate to 99.5%. 100% digital radiography (DR) testing of butt weld areas has been specifically mandated, with an image resolution of at least 200μm.

4. Enhanced environmental adaptability: A new -45°C low-temperature impact test procedure has been added, specifying a holding time of at least 10 minutes. For areas prone to geological disasters, strain capacity design indicators have been introduced: compressive strain ≥ 0.5% and tensile strain ≥ 2%. Adhesion testing of the three-layer PE anti-corrosion coating in a carbon dioxide corrosive environment has been added, with the cross-cut test requirement reaching Level 1.

Third, Innovations in the Quality Control System

The standard establishes a full lifecycle quality traceability mechanism, requiring manufacturers to use an MES (Manufacturing Execution System) to record all process parameters from steelmaking to pipe production, with data retention for at least 30 years. The "digital twin" concept has been introduced, requiring each steel pipe to be accompanied by a QR code containing information such as material certificates and test reports. A new "blind sample test" has been added to the factory acceptance process, where a third party randomly inserts simulated defects into test specimens to verify the reliability of the inspection system. 1. International Benchmarking and Difference Analysis: Compared to API SPEC 5L, my country's standard distinguishes itself in three key areas: First, it surpasses API's DWTT performance requirements. API allows a minimum shear area of 70% for individual specimens, while GB/T 9711-2023 requires an average of ≥85% for each group of specimens. Second, it incorporates a reliability-based design factor, reducing the traditional safety factor of 0.72 to a range of 0.6-0.8. Third, it employs a unique "dual certification" model, which not only complies with API monogram requirements but also requires approval from the National Pipeline Network Corporation's QHSE system audit.

2. Engineering Application Impact: This standard has been pioneered in natural gas pipeline projects, with X80 steel-grade 1422mm Φ steel pipe achieving an average Charpy impact energy of 210 J at -40°C, a 40% improvement over the previous generation. During the construction of the Sichuan-Eastern Gas Transmission Line 2, large-deformation-resistant steel pipe produced according to the new standard successfully crossed the Longmenshan Fault Zone, achieving an axial strain capacity of 2.3%. The implementation of the new standard is expected to reduce pipeline lifecycle costs by 12% and drop the accident rate to 0.3 accidents per thousand kilometers per year.

3. Future Technology Outlook: With emerging demands for hydrogen pipelines and CCUS (carbon capture and storage), the standards committee has initiated preliminary research. The next step will be to incorporate hydrogen embrittlement sensitivity assessment methods (such as TDS permeation testing) and develop a material index system for steel pipes suitable for 30% hydrogen mixed transmission environments. Regarding smart pipelines, technical specifications for steel pipes with integrated fiber optic sensors are being developed to enable online monitoring of multiple parameters: stress, corrosion, and leakage.

The implementation of this standard requires collaboration across the industry chain: steel companies need to upgrade their LF refining and calcium treatment processes; pipe mills need to equip themselves with intelligent inspection equipment such as laser profilometers; and engineering units should establish a BIM-based digital acceptance system. The National Pipeline Network Corporation has also issued the "Uniform Regulations for Steel Pipe Technical Specifications," establishing a three-tiered technical management system consisting of standards, specifications, and detailed rules, providing a comprehensive technical support framework for the high-quality development of my country's oil and gas pipeline network.