Recently, the project "Development of Automatic Welding Technology for Longitudinal Seams of SINOPEC LNG Storage Tanks", led by No.4 Construction Company and jointly undertaken by SINOPEC Natural Gas Branch and SINOPEC Engineering Incorporation (SEI), has been successfully promoted and applied to the 220,000-cubic-meter LNG storage tank of the Tianjin LNG (Phase II) Project. This marks the first adoption of automatic welding technology for longitudinal seams of large LNG storage tanks within SINOPEC. The technology replaces the traditional manual welding method for LNG storage tanks and realizes full mechanized welding for the inner tank walls of LNG storage tanks.
As the main developer of the research project, No.4 Construction Company attaches great importance to the development work. Led by the company's Technical Department, a research team consisting of the Modern Welding Research Institute, Storage and Transportation Engineering Company, and Tianjin LNG (Phase II) Project of the company has been set up to carry out joint research.
On May 18, 2021, the Engineering Department of the Group Corporation organized and held a feasibility analysis seminar on the automatic welding process for longitudinal seams of large LNG storage tanks. The Natural Gas Branch, SEI, the General Station of Quality Supervision, China No.4 Construction Company and other participants attended the discussion and research, reviewed the development plan for the technical feasibility of automatic welding for longitudinal seams of LNG storage tanks compiled by China No.4 Construction Company, and completed the application for project initiation of the development work.
On November 2, 2021, the Engineering Department of the Group Corporation invited industry experts to conduct an expert review on the development plan for the automatic welding process for longitudinal seams of 9Ni steel proposed by China No.4 Construction Company.
On March 18, 2022, the Engineering Department of the Group Corporation organized and held a phased evaluation meeting for the technical development project "Development of Automatic Welding Technology for Longitudinal Seams of SINOPEC LNG Storage Tanks". Participants in the evaluation included the Science and Technology Department, Materials and Equipment Department of the Group Corporation, Natural Gas Branch, General Station of Quality Supervision, Fourth Construction Company, SEI, Guangzhou Engineering Company and other entities, as well as specially invited experts. All attendees unanimously agreed that the automatic welding technology for inner tank longitudinal seams of LNG storage tanks developed in this research project boasts excellent welding performance and favorable surface finish, and is eligible for trial application in engineering projects such as Tianjin LNG (Phase II).
The research team conducted in-depth studies on equipment selection, welding traveling systems, equipment frame dimensions, welding power sources, wire feeders, shielding gas, groove types and other aspects, and carried out numerous trials and improvements of process parameters as well as optimizations of welding machines. The Welding Research Institute completed preliminary process development, fabricated 120 test plates and produced 330 test specimens for performance tests.
On April 13, 2022, the research team completed equipment commissioning for the Tianjin LNG (Phase II) Project and took the lead in applying the longitudinal seam automatic welding technology to the No. 6 storage tank. By analyzing and evaluating the application results of four on-site welding seams, the team verified the superior performance of the longitudinal seam automatic welding process technology and successfully realized the on-site application of this technology at the construction site.
On February 13, 2023, the first automatic vertical seam welding for LNG low-temperature storage tanks of Sinopec was initiated on Tank No.9 of the Tianjin LNG (Phase II) Project. As of March 15, 52 vertical seams of Tank No.9 had been fully welded with a one-time welding qualification rate of 99.98%. The design documents specify Grade II as the acceptable qualification level for weld radiographic films, yet all weld films achieved the Grade I standard. The welds feature excellent surface formation, superior exterior appearance and uniform welding ripples, earning unanimous praise from all parties on site.
Developing the automatic welding process technology for longitudinal seams of LNG storage tanks to realize welding automation can not only ease the current shortage of welders, reduce the labor intensity of construction workers, greatly improve the welding efficiency of tank longitudinal seams, shorten the construction period for tank wall plate installation, cut enterprises' construction costs and enhance their market competitiveness, but also maintain the leading position of the enterprise's LNG storage tank welding technology in the industry.
The high-efficiency hot wire TIG welding is adopted to avoid severe pollution such as smoke and noise generated by carbon arc gouging back chipping or grinding in traditional manual welding processes, thus creating a green and environmentally friendly construction environment free of smoke, dust and noise.
The company adheres to management innovation and technological innovation, commits itself to the transformation of innovative achievements, accelerates technological progress and application, and gives full play to the supporting and guaranteeing role of its research teams in on-site project guidance and technical breakthroughs. It will maintain and expand the company's leading professional advantages, and provide strong support for building a world-leading technology-oriented engineering construction enterprise.
