Method of modifying integral steam chest steam turbines

Abstract

A method of eliminating cracking between a steam turbine casing and a welded integral steam chest includes removing the integral steam chest from the steam turbine casing and replacing it with a separate and spaced apart steam chest having a plurality of steam exit ports. Steam inlet diffusers located in the turbine casing and normally connected to steam passageways in the integral steam chest are each connected to a corresponding steam exit port in the spaced apart steam chest. The connection between the spaced steam chest and the turbine casing is made by a plurality of relatively flexible steam pipes. Preferably, the integral steam chest is removed by cutting away the welded junction between the turbine and steam chest at a level corresponding to a radially outer end of the inlet diffusers in the turbine casing. The diffusers are each re-bored to a uniform diameter suitable for insertion of the flexible steam pipes. Each steam pipe is then welded to a corresponding diffuser. The separate spaced apart steam chest may be held in its spaced apart relation to the turbine casing by a relatively thin wall support member welded to the turbine casing. Steam control valves are preferably incorporated in each of the steam exit ports of the spaced apart steam chest and coupled to control means for controlling the admission of steam into the turbine casing.