A42Y type spring fully open safety valve is suitable for equipment and pipelines with working temperatures ≤ 300 ℃ for media such as air, petroleum gas, liquids, etc. A42-P and A42Y-R spring fully open safety valves are suitable for equipment and pipelines with corrosive media operating at temperatures ≤ 200 ℃. The A48Y spring fully open safety valve produced by Shanghai First Ring Road is suitable for use as an overpressure protection device on steam, air and other medium equipment and pipelines with a working temperature of ≤ 350 ℃.