Method of Increasing Service Interval Periods in a Steam Turbine
AssigneeSiemens Power Generation, Inc.
InventorsJames C. Bellows, Sudhir Rajagopalan, James W. Dorow
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Abstract
A method of increasing service interval periods in a steam turbine by neutralizing sodium hydroxide in contaminated steam in a high temperature and a high pressure portion of a steam turbine by placing a protective covering over at least a portion of each of the bolts of a nozzle block assembly. The protective covering neutralizes contaminants in contaminated steam to reduce stress cracking of the bolts during steam turbine operation, and thus extend the useful life of the bolts and reduce the need for service work to repair or replace damaged bolts.
Claims20
A method of increasing service interval periods in a steam turbine, upon sodium hydroxide contaminated water being injected into the steam cycle thereby producing steam contaminated with sodium hydroxide, by reducing an amount of sodium hydroxide in the steam in a relatively high temperature and relatively high pressure portion of said steam turbine by modifying a nozzle block assembly mounted to a stationary portion in said steam turbine, wherein said nozzle block assembly comprises a nozzle block comprising flow passages for guiding a flow of the steam from a nozzle chamber to a first row of rotating steam turbine blades, said nozzle block having a plurality of counterbored holes disposed therein;
- a plurality of bolts passing through said counterbored holes to fasten said nozzle block to said stationary portion of said steam turbine, and each of said bolts comprising a head portion, a threaded portion, and a shank portion between said head portion and said threaded portion, said method comprising:
- applying a protective aluminum covering over at least one thread of said threaded portion of at least one of said bolts proximate said shank portion, said protective aluminum covering configured for converting at least a portion of the sodium hydroxide into an aluminum compound effective to neutralize the portion of the sodium hydroxide in the steam at said portion of said nozzle block assembly adjacent said bolts so as to reduce stress corrosion cracking of said bolts during steam turbine operation over a substantial number of hours of operation of said steam turbine, and for limiting production of said aluminum compound effective to reduce deposition of said aluminum compound on portions of said steam turbine downstream of said nozzle block assembly.
A method of increasing service interval periods in a steam turbine, upon alkali metal hydroxide contaminated water being injected into the steam cycle thereby producing steam contaminated with at least one alkali metal hydroxide, by reducing an amount of the alkali metal hydroxide in the steam in a relatively high temperature and relatively high pressure portion of said steam turbine and converting at least one alkali metal hydroxide in contaminated steam into a non-corrosive compound by modifying a nozzle block assembly mounted to a stationary portion in said steam turbine, wherein said nozzle block assembly comprises a nozzle block comprising flow passages for guiding a flow of the steam from a nozzle chamber to a first row of rotating steam turbine blades;
- said nozzle block having a plurality of holes disposed therein;
- a plurality of bolts passing through said holes to fasten said nozzle block to said stationary portion of said steam turbine;
- and each of said bolts comprising at least a head portion and a threaded portion;
- said method comprising:
- disposing a protective getter proximate at least one of said bolts, said getter configured for converting at least a portion of the at least one alkali metal hydroxide into an aluminum compound effective to neutralize at least a portion of the at least one alkali metal hydroxide in the steam at said portion of said nozzle block assembly adjacent said bolts so as to reduce stress corrosion cracking of said bolts during steam turbine operation over a substantial number of hours of operation of said steam turbine.
A steam turbine nozzle block assembly comprising:
- a nozzle block comprising a plurality of vanes defining flow passages for guiding steam from a nozzle chamber passage to a first row of rotating steam turbine blades;
- and a plurality of holes;
- a plurality of bolts for passing through said holes to fasten said nozzle block to a stationary portion of a steam turbine;
- each of said bolts comprising a head portion, a threaded portion, and a shank portion between said head portion and said threaded portion;
- and
- a protective getter disposed proximate at least one of said bolts, said protective getter configured for converting a portion of alkali metal hydroxide contaminants present in the steam into an aluminum compound effective to neutralize the portion of the alkali metal hydroxide contaminants at said bolts so as to reduce stress corrosion cracking of said bolts during steam turbine operation over a substantial number of hours.
Dependencies are inferred from the claim text.