A48Y type spring fully open safety valve is suitable for equipment and pipelines with steam, air and other media working temperature ≤ 350 ℃. A44Y type spring fully open safety valve is suitable for equipment and pipelines with working temperature ≤ 300 ℃ for media such as air and petroleum, as an overpressure protection device. The product connection flange standard PN<6.4mpa produced by Shanghai First Ring Road is in accordance with JB T-94 series 1.2 standard. Pn ≥ 6.4mpa according to jb/and t-94 series 2 standards 6.4mpa press jb>