A41H used on equipments or pipes of petroleum、air、water and other media that work temperature ≤300℃. A41Y-P/R used on equipments or pipes of corrosive media , that work temperature≤200℃, as the protection device of over pressure. When the internal pressure of equipments and pipes exceed allowed valve, valve automatically open, and exhaust completely; when pressure reduce to rated valve, valve automatically close, ensure safety working of equipments and pipes. Connection flange standard according to JB/T……94/ series