External midspan packing steam supply

Abstract

An external supply pipe is disclosed, for supplying steam to a mid-span packing disposed about a shaft coupling a high pressure (HP) and an intermediate pressure (IP) section of an opposed flow steam turbine. The external supply pipe is disposed on an exterior of the steam turbine casing, which allows for direct measurement of steam flow to the mid-span packing.

What is claimed is: 
     
         1 . An opposed flow steam turbine comprising:
 a high pressure (HP) section and an intermediate pressure (IP) section connected by a shaft;   a mid-span packing disposed about the shaft between the HP section and the IP section;   a casing disposed about the steam turbine, substantially enclosing the HP section, the IP section, the shaft, and the mid-span packing; and   a supply pipe for supplying steam to the mid-span packing, wherein the supply pipe is disposed substantially on an exterior of the casing.   
     
     
         2 . The opposed flow steam turbine of  claim 1 , wherein the supply pipe is connected at an upsteam end to a throttle steam line. 
     
     
         3 . The opposed flow steam turbine of  claim 1 , wherein the supply pipe further comprises a control valve for setting a desired flow rate for steam delivered through the supply pipe. 
     
     
         4 . The opposed flow steam turbine of  claim 1 , wherein the supply pipe further comprises a thermowell for measuring a temperature on an interior of the supply pipe. 
     
     
         5 . The opposed flow steam turbine of  claim 1 , wherein the supply pipe further comprises a flanged orifice, the flanged orifice further including at least one pressure tap on a flange thereof. 
     
     
         6 . The opposed flow steam turbine of  claim 1 , wherein the mid-span packing limits a steam flow to the HP section, and provides cooling to the IP section. 
     
     
         7 . The opposed flow steam turbine of  claim 1 , wherein the supply pipe delivers a known quantity of steam to the mid-span packing. 
     
     
         8 . An external supply pipe for supplying steam to a mid-span packing of an opposed flow steam turbine having a casing, wherein the supply pipe is disposed substantially on an exterior of the casing. 
     
     
         9 . The external supply pipe of  claim 8 , wherein the supply pipe further comprises a control valve for setting a desired flow rate for steam delivered through the supply pipe. 
     
     
         10 . The external supply pipe of  claim 8 , wherein the supply pipe further comprises a thermowell for measuring a temperature on an interior of the supply pipe. 
     
     
         11 . The external supply pipe of  claim 8 , wherein the supply pipe further comprises a flanged orifice, the flanged orifice further including at least one pressure tap on a flange thereof. 
     
     
         12 . The external supply pipe of  claim 8 , wherein the supply pipe delivers a known quantity of steam to the mid-span packing. 
     
     
         13 . A method of controlling a steam flow entering an intermediate pressure (IP) section of an opposed flow configuration steam turbine, the method comprising:
 providing a supply pipe coupled at an upstream end to a throttle steam line, and at a downstream end to a mid-span packing, the mid-span packing being disposed about a shaft coupling a high pressure (HP) section and the IP section; and   supplying through the supply line a known quantity of steam,   wherein the supply pipe is disposed substantially on an exterior of a casing enclosing the steam turbine, and   wherein the mid-span packing provides cooling to the IP section, and the HP section is substantially sealed.   
     
     
         14 . The method of  claim 13 , wherein the leakage flow from the HP section to the IP section is nominal. 
     
     
         15 . The method of  claim 14 , wherein the steam flow into the IP section is substantially supplied by the supply pipe. 
     
     
         16 . The method of  claim 13 , wherein the known quantity of steam supplied through the supply line flows from the mid-span packing into the HP section and the IP section depending on a pressure in each of the HP section and the IP section. 
     
     
         17 . The method of  claim 13 , further comprising setting a desired flow rate for steam delivered through the supply pipe with a control valve. 
     
     
         18 . The method of  claim 13 , further comprising providing a thermowell for measuring a temperature on an interior of the supply pipe. 
     
     
         19 . The method of  claim 13 , further comprising providing a flanged orifice on the supply line, the flanged orifice further including at least one pressure tap on a flange thereof. 
     
     
         20 . The method of  claim 13 , further comprising:
 using the known quantity of steam supplied to the mid-span packing to determine at least one of:   an HP section power output, an IP section power output, an IP steam path efficiency, an LP section power output, or an LP efficiency.