Runner seals for hydraulic turbines

A water turbine comprising:

• a vertically disposed runner composed of vertically spaced crown and band elements connected together by a plurality of runner vanes, said runner having a radially disposed intake and a vertically disposed discharge opening;
• an annular stationary discharge ring disposed adjacent to and beneath said band element and defining an opening therethrough coaxial with said runner discharge opening;
• a stationary head cover disposed adjacent to and above said crown element;
• a draft tube connected to said discharge ring and defining a water passageway coaxial with said discharge ring opening and vertically spaced from the end of said runner defining said discharge opening;
• an annular substantially axially directed first sealing surface formed on the radially inner facing surface of the lower end of said band element;
• a throat ring releaseably connected to the lower end of said discharge ring providing a radially inner facing surface mating with said draft tube and said runner discharge opening to form a surface continuation of said water passageway;
• and an annular substantially axially outer facing surface of said throat ring cooperating with said first sealing surface to form therebetween a restricted water passage, all radially outer facing surfaces of said runner being spaced from any surface of said stationary structure a distance greater than the distance between the surfaces forming said restricted water passage.