SYSTEM FOR CONTROLLING THRUST IN STEAM TURBINE

PROBLEM TO BE SOLVED: To provide a system for maintaining a thrust level of a steam turbine within an acceptable range of values.SOLUTION: A system 102 controls net thrust of a steam turbine system 90 having a stepped rotating shaft 98. A first leak off line 120 fluidly couples a first stage 122 of a turbine section to a packing 112 upstream of a stepped portion 110 on the rotating shaft 98; a second leak off line 130 fluidly couples a second stage 132 of the turbine section that is subsequent to the first stage 122 to a step area 134 upstream of the stepped portion; and a connection line 140 fluidly couples the first leak off line 120 to the second leak off line. The lines include control valves on which a controller 150 actively controls the net thrust by regulating thrust pressure on the stepped portion by using steam from the first and the second stages of the turbine section. The controller also prevents damage on an active retractable seal 114 by use of the control valves.