Flange duckbill check valve widely used in the demanding applications of many industries, are precision-molded, one-piece elastomeric valves that provide reliable backflow prevention at low pressure differentials. Duck bill valve allow free flow with positive differential pressure. With negative differential pressure, backflow is checked. Pressure drop across the valve is a feature unique to Rubber Duckbill check valve. They can be designed to operate in a few millimeters (inches) of water to several hundred kPa (psi), depending on valve size, geometry and compound characteristics. Duckbill Check Valves are also designed to start functioning at specific opening and closing pressure ranges, depending on your specifications. Flange Connected Duckbill Check Valve(2"-96") Supply range is from 50mm to 2400mm the Material can be Stainless Steel/Cast Iron/Forged Steel Rubber can be NR/NBR/EPDM/NEOPRENE for your option Cost-effective and Maintenance Free Backflow Prevention Automatically Most Professional Mamufacturer From China.  Features: Easy installation with ring flange, drilling can be DIN/JIS/EN/ANSI, etc. Reliable backflow prevention Lower head loss than conventional check valves 100% elastomeric construction eliminates maintenance Will not corrode, warp or freeze open or shut 1”-2” Cracking Pressure, Low Head loss Custom built for each application based on pressure and flow conditions Reliable and cost-effective alternative to flap-gate and other conventional check valves Maintenance-free operation with no mechanical components that can corrode or seize Will open with as little as 1" W.C. Quiet operation (non-slamming) Excellent corrosion and abrasion resistance Versatile construction for a wide range of applications Manufactured with an integral reinforced rubber flange provided with metal retaining rings for easy bolting directly to the pipe flange, tank wall or head wall Flanges drilled per standard ANSI B16.1/150 lb. pattern; other drilling patterns are available upon request Retaining ring available in galvanized, 304 stainless steel and 316 stainless steel We love hearing from our customers and value your feedback.Here are ways to contact us, 24 hours a day, 7 days a week.Email: Sales@flexible-joints.com, web: www.flexible-joints.com