Steam turbine overload valve and related method

Abstract

A steam turbine operating system includes at least a high pressure turbine section and a low pressure section; one or more control valves arranged to admit steam from a boiler to the high pressure turbine section; a condenser arranged to receive steam exhausted from the low pressure section and to convert the steam to a liquid; a top heater arranged to receive liquid from the condenser and to heat the liquid via heat exchange with steam from the high pressure section, and to return the heated liquid to the boiler; and an overload bypass valve arranged to supply steam bypassed around the one or more control valves directly to the top heater.

1 . A steam turbine operating system comprising at least a high pressure turbine section and a low pressure section; one or more control valves arranged to admit steam from a boiler to the high pressure turbine section; a condenser arranged to receive steam exhausted from the low pressure section and to convert the steam to a liquid; a top heater arranged to receive liquid from the condenser and to heat said liquid via heat exchange with steam from the high pressure section, and to return the heated liquid to the boiler; and an overload bypass valve arranged to supply steam bypassed around said one or more control valves directly to said top heater. 
   
   
       2 . The operating system of  claim 1  wherein bypass steam from the overload valve and steam from the high pressure turbine section are drained from said top heater. 
   
   
       3 . The operating system of  claim 1  wherein said overload bypass valve is moveable between open and closed positions. 
   
   
       4 . The operating system of  claim 3  wherein said overload bypass valve is moveable incrementally in a throttling manner. 
   
   
       5 . The operating system of  claim 3  wherein said bypass overload valve is moveable manually at the discretion of operating personnel. 
   
   
       6 . The combination of  claim 3  wherein said bypass overload valve is moveable automatically in response to a signal indicative of turbine load. 
   
   
       7 . A method of operating a steam turbine delivering power to a connected load and adapted to receive steam from a steam generating source, the turbine having one or more control valves for controlling the admission of steam to higher pressure stages of the turbine; a condenser  134  arranged to receive steam exhausted from said turbine and convert the steam to a liquid; and a bypass overload valve connected to receive steam from the steam source, the method comprising the steps of:
 (a) maintaining said bypass overload valve closed while controllably positioning said control valves to admit steam to the turbine to sustain a preselected power load;   (b) at least partially opening said bypass overload valve; and   (c) returning steam passing through said bypass overload valve to said top heater.   
   
   
       8 . The method of  claim 7  wherein said bypass overload valve is manually caused to be opened and closed at an operator's discretion. 
   
   
       9 . The method of  claim 7  wherein said bypass overload valve is automatically caused to be opened and closed in response to a signal indicative of turbine load.