Steam cooling system for balance piston of a steam turbine and associated methods

A steam cooling system comprising:

• a balance piston positioned between a first steam turbine and a second steam turbine and adjacent an inlet of the second steam turbine;
• a common heated steam conduit region positioned between the first steam turbine and the second steam turbine to supply steam substantially simultaneously to the first steam turbine and the second steam turbine;
• a cooling steam conduit having an inlet adjacent the first turbine and an outlet adjacent the balance piston for providing a steam cooling path therebetween;
• a cooling steam controller positioned to control cooling steam pressure within the conduit;
• a cooling steam control valve connected to the cooling steam conduit and the controller;
• a first pressure sensor in communication with the controller and positioned adjacent the inlet of the second steam turbine and downstream from the balance piston for sensing inlet steam pressure to the second steam turbine;
• and
• a second pressure sensor positioned in communication with the controller in the conduit upstream from the first pressure sensor and the balance piston and downstream from the cooling steam control valve for sensing conduit cooling steam pressure so that the cooling steam control valve operationally opens and closes to regulate the cooling steam conduit pressure at a predetermined level greater than the inlet pressure of the second steam turbine.

A steam cooling controlling apparatus for controlling cooling steam pressure during cooling steam flow between at least a pair of steam turbines, the apparatus comprising:

• a cooling steam controller positioned to control cooling steam pressure, the controller being responsive to sensing differences in steam pressures;
• a cooling steam control valve positioned to be connected to conduit in fluid communication with at least a pair of steam turbines and to said controller;
• a first pressure sensor in communication with said controller and positioned adjacent an inlet of at least one of the pair of steam turbines for sensing inlet steam pressure to the at least one of the pair of steam turbines;
• and
• a second pressure sensor positioned in communication with said controller in the conduit upstream from the first pressure sensor and downstream from the cooling steam control valve for sensing conduit cooling steam pressure so that the cooling steam control valve operationally opens and closes to maintain the cooling steam conduit pressure at a predetermined level greater than the inlet pressure of a downstream steam turbine of the at least a pair of steam turbines.

A method of steam cooling a turbine system, the method comprising steps of:

• positioning a balance piston adjacent the inlet of an intermediate pressure (IP) steam turbine and between inlets of both the IP steam turbine and a high pressure (HP) steam turbine;
• providing a steam cooling path between the IP and HP steam turbines and in communication with the balance piston;
• and
• controlling cooling steam pressure during cooling steam flow between the HP turbine and the IP turbine so that the cooling steam conduit pressure is operationally maintained at a predetermined level greater than the inlet pressure of the IP turbine.