haoyunzz9
2009- 9- 8, 05:24 AM
The wafer style butterfly lined valve (http://www.corrosion-resistant-valves.com/corrosion-resistant-pipe-fitting.html) is designed to maintain a seal against bi-directional pressure differential to prevent backflow in systems designed for unidirectional flow. It accomplishes this by using a tightly fitting seal, i.e., gasket, o-ring, precision machined, and a flat valve face on the upstream and downstream sides of the valve.