... gate valves are available in temperature classes L, P, R, S, T, and U specified in API 6A ... FF, product specification levels (PSL) from 1 through 3 and performance requirement (PR) 1.Features:Simple structure ... gate valves are available in temperature classes L, P, R, S, T, and U specified in API ... FF, product specification levels (PSL) from 1 through 3 and performance requirement (PR) 1.The rising stem ...