With the gradual development of domestic Type III hydrogen cylinders towards large volume gas cylinders for heavy-duty vehicles, storage and transportation gas cylinders for long tube trailers, and gas cylinders for hydrogen refueling stations, Tianjin Runde Zhongtian Steel Pipe Co., Ltd. is committed to applying the original hot expansion and cold drawing process route for producing cold drawn seamless steel pipes for gas cylinders to the development of large-diameter aluminum alloy seamless pipes. By using the small caliber thick walled hot extruded 6061 aluminum alloy seamless pipe produced by Shandong Yankuang Light Alloy Co., Ltd. through expansion and extraction process, we have successfully developed large-diameter aluminum alloy seamless pipes with different inner diameters, optimal cold spinning efficiency, and highest material utilization rate, with an average wall thickness of 15.5mm, for manufacturing 260L, 390L, and 450L Type III 35Mpa vehicle hydrogen cylinders.
 
In line with the product development concept of applying one generation, researching and developing one generation, and reserving one generation, the company has successfully developed large-diameter aluminum alloy seamless pipes with different inner diameter sizes and an average wall thickness of 12mm. The successful development of such products will enable manufacturers of Type III 35Mpa vehicle mounted hydrogen cylinders to eliminate the processes of cold spinning, cutting, internal and external grinding, and ultrasonic cleaning in the production process, and directly enter the hot spinning and closing process, thereby further improving the manufacturing efficiency of Type III 35Mpa vehicle mounted hydrogen cylinders and greatly reducing environmental costs and potential quality risks such as hydraulic oil, grinding dust, and cleaning agents in the above processes. In addition, by increasing the thickness of the inner liner to improve fatigue resistance while reducing the use of carbon fiber, the goal of continuously reducing the manufacturing cost of Type III 35Mpa vehicle mounted hydrogen cylinders can be achieved.
 
The company has also successfully developed large-diameter aluminum alloy seamless pipes with an outer diameter of 509mm, a wall thickness of 14mm, a length of 3000mm, and 6000mm for use in the production of Type III 52Mpa hydrogen storage and transportation cylinders for long tube trailers by CSSC Shuangrui (Luoyang) Special Equipment Co., Ltd. The application of such cylinders will significantly reduce the transportation cost to less than 15 yuan/kg, thereby enabling the production of 5 yuan/kg green hydrogen from photovoltaic and wind power generation to be smoothly transported to different usage scenarios with price advantages over oil and electricity. This will completely solve the problem of high hydrogen transportation costs hindering the development of hydrogen and open up the situation of comprehensive application of hydrogen. At the same time, the direct filling of Type III 52Mpa storage and transportation hydrogen cylinders into Type III 35Mpa vehicle mounted hydrogen cylinders has been achieved, reducing the investment in hydrogen refueling stations and completely solving the problem of difficult refueling for people's livelihoods. The company has conducted comprehensive technical exchanges and maintained close communication with domestic manufacturers of long tube trailer gas cylinders, such as Shijiazhuang Anruike Gas Machinery Co., Ltd., Sinoma Technology (Suzhou) Co., Ltd., and Haiying Aerospace Materials Research Institute (Suzhou) Co., Ltd.