| 摘要 |
A dual check valve backflow prevention apparatus of lightweight, compact construction which provides low flow losses and which maintains a small positive pressure differential under static flow conditions via use of a magnetic valve closure mechanism. The apparatus comprises a main valve housing which contains two check valve assemblies. Each check valve assembly has a clapper valve which uses a low friction magnetic pull closure force and drip tight seals in the forward flow direction for maintaining a small positive pressure differential under static conditions. The magnetic bias for the closure force is preferably located in the center of the flow stream. An additional closure force may be provided by a spring or gravity assistance.
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