... ) Nominal Diameter DN: 50-700mm(2-28") CST42Y Automatic Re-Circulating Control Valve (reflux valve) is installed at the outlet of centrifugal pump to ... mediums recycle in pumps under load motion, ensure the minimum flow for pumps safety operation and maintain their stable operation. It ... nickel, zirconium, Hastelloy, Monel, 316,310,304,WC6 and etc. Automatic Recirculation Control Valve (Return Valve)