Shaft sealing system for steam turbines

In a turbine system including a first turbine section and a downstream section, each of the first turbine section and the downstream section having a respective rotating member including at least one stage mounted on a shaft, and each of the first turbine section and the downstream section further having a stationary member surrounding the respective rotating member and defining a steam flow path, a shaft sealing system, the shaft sealing system comprising:

• at least one seal disposed about each of a first end and a second end of the shaft of the first turbine section and being configured to prevent entry of ambient air into the first turbine section, wherein the at least one seal includes a main seal and a steam seal disposed axially outboard of the main seal, and wherein the at least one seal disposed about each of the first end and the second end of the shaft of the first turbine section comprises a hydrodynamic non-contacting seal comprising a carbon segmented circumferential seal;
• a first buffer seal disposed axially outboard of the at least one seal disposed about the first end of the shaft of the first turbine section;
• a second buffer seal disposed axially outboard of the at least one seal disposed about the second end of the shaft of the first turbine section;
• and a first connection line for conducting steam from the first turbine section to a first stage in the downstream section of the turbine system, the first stage having a lower operating pressure than the first turbine section such that during operation steam is drawn through, the first connection line from a first annulus disposed between the main seal and the steam seal about the first end of the shaft of the first turbine section and from a second annulus disposed between the main seal and the steam seal about the second end of the shaft of the first turbine section to the first stage, wherein the downstream section of the turbine system is a distinct turbine section from the first turbine section, the downstream section of the turbine system being one of:
• a low pressure section of the turbine system, a combined intermediate pressure/low pressure section of the turbine system, or an intermediate pressure section of the turbine system, and the first turbine section being one of:
• a super high pressure section of the turbine system, a high pressure section of the turbine system, or an intermediate pressure section of the turbine system, and wherein the shaft sealing system does not require the use of a condenser other than a main condenser of the turbine system, and wherein an area about each of the first and the second ends of the shaft of the first turbine section inboard of the main seals are at a pressure greater than atmospheric pressure.

A method for, in a turbine system including a first turbine section and a downstream section with each of the first turbine section and the downstream section having a respective rotating member including at least one stage mounted on a rotating shaft and a stationary member surrounding the respective rotating shaft and defining a steam flow path, sealing the shaft of the first turbine section, the method comprising:

• providing at least one seal disposed about each of a first end and a second end of the shaft of the first turbine section, including configuring the at least one seal to prevent entry of ambient aft into the first turbine section, wherein the providing at least one seal includes providing a main seal and providing a steam seal disposed axially outboard of the main seal, and wherein the providing at least one seal further includes providing a hydrodynamic non-contacting seal comprising a carbon segmented circumferential seal;
• and conducting steam from the first turbine section to a first stage in the downstream section of the turbine system via a first connection line, the first stage having a lower operating pressure than the first turbine section, including connecting the first connection line to the first stage such that the first stage acts as a vacuum source, connecting a first annulus disposed between the main seal and the steam seal about the first end of the shaft of the first turbine section and connecting the first connection line to a second annulus disposed between the main seal and the steam seal about the second end of the shaft of the first turbine section, wherein the downstream section of the turbine system is a distinct turbine section from the first turbine section, the downstream section of the turbine system being one of, a low pressure section of the turbine system, a combined intermediate pressure/low pressure section of the turbine system, or an intermediate pressure section of the turbine system, and the first turbine section being one of, a super high pressure section of a turbine system, a high pressure section of the turbine system, or an intermediate pressure section of the turbine system, and wherein the shaft of the first turbine section sealing system does not require the use of a condenser other than a main condenser of the turbine system, and wherein an area about each of the first and the second ends of the shaft of the first turbine section inboard of the main seals in the first turbine section are at a pressure greater than atmospheric pressure.