Patent ID: 7954323

Claim:
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 sacrificial component comprising 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 sacrificial component is a metallic aluminum component and is positioned in a gap between an outer surface of said bolt and a surface of at least one of said nozzle block and said stationary portion of said steam turbine to both prevent passage of said steam through said gap and to convert 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.