Abstract: Aiming at the structural particularities and safety risk characteristics of crude oil storage tanks, combined with relevant design specifications, an engineering application design of the critical-state carbon dioxide (CO2) protection system for crude oil storage tanks was carried out. According to the engineered pipe network and the structure of primary and secondary sealing rings of the storage tank determined by the application design, a test platform was designed and built to conduct a feasibility test of the protection system. The results show that the peak inlet pressure of the nozzle at the end of the pipe—the most unfavorable point in the designed critical-state CO2 pipeline—reaches 2.481 MPa, and the discharge pressure is maintained above 1.5 MPa for more than 300 seconds. The minimum ambient temperature at the sealing ring can reach -57.7 ℃, and the maximum CO2 volume fraction is 36%. The test verifies the practical feasibility of the critical-state CO2 pipe network for crude oil storage tanks, and demonstrates that critical-state CO2 has excellent cooling and inerting effects on oil tank fires, which provides a strong basis for the application of critical-state CO2 in the field of oil tank fire prevention and control.

Key words: critical-state carbon dioxide, crude oil storage tank, sealing ring fire, cooling, inerting