Hydraulic piston with embedded linear variable differential transducer for precision position sensing

A tie bolt stretch system comprising:

• a rotor assembly including a compressor section coupled with a turbine section by a curvic coupling;
• the compressor section including at least one of a powerhead compressor and a load compressor;
• a tie bolt in operative communication with the rotor assembly, the tie bolt joining the compressor section to the turbine section;
• a stretch tool in operative communication with the tie bolt;
• the stretch tool comprising:
• a hydraulic piston in operative communication with the tie bolt, the hydraulic piston including a shaft with a predetermined dimension;
• a sensor in operative communication with the stretch tool, the sensor configured to indicate a dimensional change of the predetermined dimension;
• and
• a controller in operative communication with the sensor and a servo valve;
• the servo valve is fluidly coupled with a hydraulic pump;
• the hydraulic pump fluidly coupled with the hydraulic piston;
• wherein the controller is configured to operate the hydraulic piston responsive to a signal from the sensor to attain a predetermined preload stretch on the tie bolt, curvic coupling, compressor section and turbine section.

A process for stretching a tie bolt with a tie bolt stretch system comprising:

• forming a rotor assembly coupling a compressor section with a turbine section through a curvic coupling;
• coupling a tie bolt in operative communication with the rotor assembly;
• joining the compressor section to the turbine section with the tie bolt;
• coupling a stretch tool in operative communication with the tie bolt;
• the stretch tool comprising:
• a hydraulic piston in operative communication with the tie bolt, the hydraulic piston including a shaft with a predetermined dimension;
• a sensor in operative communication with the stretch tool, the sensor configured to indicate a dimensional change of the predetermined dimension;
• and
• a controller in operative communication with the sensor and a servo valve;
• the servo valve is fluidly coupled with a hydraulic pump;
• the hydraulic pump fluidly coupled with the hydraulic piston;
• wherein the controller is configured to operate the hydraulic piston responsive to a signal from the sensor to attain a predetermined preload stretch on the tie bolt, curvic coupling, compressor section and turbine section.