Rotor assembly and refit method

Abstract

A method of coupling at least two sections of a rotor designed to carry the rotating parts of a turbine for the generation of electrical power for a public grid and a modified rotor is described with a coupling of increased diameter exceeding the nominal diameter of the rotor, with the step of removing mass from an volume lying exclusively within the interior of the sections when coupled such that the lateral critical speed of the coupling is moved away from the normal operating speed of the rotor

1 . A method for shifting a critical vibrational mode of a rotor further away from the normal operating speed of the rotor comprising:
 providing the rotor with a coupling that couples contact faces of two rotor sections; and   removing mass from a volume lying exclusively within the interior of the rotor sections when coupled.   
     
     
         2 . The method of  claim 1  wherein the removing mass comprises removing mass from a contact face of the coupling thereby creating a cavity at a coupling end of at least one rotor section. 
     
     
         3 . A rotor for carrying the rotating parts of a turbine for the generation of electrical power for a public grid with the rotor comprising at least two rotor sections coupled with a coupling of diameter exceeding the nominal diameter of the rotor sections, wherein at least one of the rotor sections includes one or more cavities at the end of the at least one rotor section and in the vicinity of the coupling such that the boundaries of the one or more cavities are all interior surfaces when the rotor sections are coupled. 
     
     
         4 . The rotor of  claim 3  wherein the one or more cavities at the end of at least one rotor sections and in the vicinity of the coupling extend from the wall of the rotor into a part of the coupling exceeding the nominal diameter of the rotor sections or are placed in a volume extending from the wall of the rotor sections into a part of the coupling exceeding the nominal diameter of the rotor sections. 
     
     
         5 . The rotor of  claim 3  wherein the at least one of the rotor sections carries the rotating parts of a low pressure steam turbine, such as the rotating blades or airfoils and their respective platforms.