Deluge valve with valve seat drain

A valve for sealing and selectively opening a flow path from a water-filled inlet to a dry outlet, the valve comprising:

• (a) a valve body having a valve opening surrounded by a first annular valve seat region, and having a second annular valve seat region surrounding said first annular valve seat region, said valve body including at least one drainage channel in fluid connection with a space between said first and second annular valve seat regions, said drainage channel providing a fluid drainage path to outside said valve body;
• (b) a plug displaceable between an open state and a closed state for closing said valve opening, said plug having a first annular seal deployed for sealing against said first annular valve seat region and a second annular seal deployed for sealing against said second annular valve seat region, said plug being integrated with a flexible diaphragm;
• and
• (c) a cover cooperating with said diaphragm to define a control chamber between said diaphragm and said cover,
• wherein said plug includes a peripheral section of elastomeric material forming a bridge between an upper peripheral portion of said plug and said second annular seal such that a pressure difference between said control chamber and said drainage channel effects a shear deformation of said peripheral section, thereby varying a closing force of said second annular seal against said second annular valve seat region,
• and wherein said second annular seal and said peripheral section of said plug are configured such that, during displacement of said plug from said open state towards said closed state, said second annular seal closes against said second annular valve seat region prior to contact between said first annular seal and said first annular valve seat region, said second annular seal being elastically deformed so as to be pressed into contact with said second annular valve seat region when said plug reaches said closed state.