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

Abstract

A steam cooling system ( ) and associated methods are provided which have a first high pressure (HP) steam turbine ( ) having a straight through configuration, a second intermediate pressure (IP) steam turbine ( ) having a straight through configuration positioned adjacent the first HP steam turbine ( ), and a balance piston ( ) positioned adjacent the inlet ( ) of the second IP steam turbine ( ) and between the second IP steam turbine ( ) and the first HP steam turbine ( ). A steam cooling conduit ( ) is preferably positioned to have an inlet adjacent the first HP steam turbine ( ) and an outlet adjacent the balance piston ( ) for providing a steam cooling path therebetween. The system ( ) also has a controller ( ) positioned to control cooling steam pressure, a cooling steam control valve ( ) connected to the conduit ( ) and the controller ( ), a first pressure sensor ( ) in communication with the controller ( ) and positioned adjacent the inlet ( ) of the IP turbine ( ) and downstream from the balance piston ( ) for sensing inlet pressure to the second IP 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 maintain the cooling steam conduit pressure at a predetermined level greater than the inlet pressure of the second IP turbine ( ).