Tech Note July 1996
Technical Notes from Dr. Mel Giberson, P.E. – TRI President
The 750 MW Westinghouse Turbine-Generator Improved
by TRI Manufactured Products and Services consisted of an HP, IP and two LP turbines, a generator and an exiciter.1 All of the original turbine bearings were the OEM’s standard 4-pad design.
- The entire machine had to be aligned to bearing No.1. This bearing had no provision for making bearing alignment moves.
- Overall HP rotor vibration.
- The original design did not provide an easy method of flushing the lube oil supply and drain pipes.
- No provision was made for blocking the lube oil flow to specific bearings for maintenance.
- Only one vertical vibration proximity sensor for each bearing. It was located in the pedestal oil seal where seal tooth scratches on the shaft would negatively affect the indicated vibration, providing uncertain balance data.
- Two TRI Align-A-Pad bearings replaced the original No.1 and No.2 bearings in the HP turbine. Now the No.1 bearing can be aligned independently. Alignment moves can now be made with high reliability and maintain almost 100% contact to the pedestal bore without hand-working the alignment pads.
- Using proprietary software, TRI tilting pad bearings were designed to minimize rotor vibratory amplitudes. TRI’s bearing design has more tilting pads than the original bearing, and these TRI pads self-align to the shaft under all conditions; even at operating speed. Therefore, no twist and tilt checks are necessary during installation.
- The thin sheet metal pedestal cover was modified in the TRI shop to provide for rigid external mounting of the “dual vibration probes”. These probes read journal motion relative to the bearing and bearing (not pedestal cover) seismic motion. The vibration since start-up has been approximately 1 mil throughout the load range.
- TRI manufactured “flush cock valves” for 3″, 4″ and 5″ pipe sizes. These valves control the lube oil supply. Each plug has three clearly marked positions: Run, Flush and Block. It is not possible to change the valve position while the lube oil is on.
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