Old Hickory Turbine Generator Rehabilitation

The Nashville District U.S. Army Corps of Engineers (USACE) competitively awarded a firm fixed-price construction contract to rehabilitate turbine generator units at Old Hickory Power Plant, Hendersonville, TN. Summary of work for the Old Hickory Turbine Generator Rehab Project: The overall goal of this project is to increase generator maximum output to 45 MW. This will be accomplished by rewinding units 1, 2, and 3 and replacing turbines runner for the same units. Unit 4's generator was rewound in 2021, but the turbine runner was not replaced. All the mechanical system to support this new load will have to be assessed and refurbished. While the units are down for rehabilitation there will be some efforts to upgrade or replace systems associated with the turbine generators. General Project: The term of the project is estimated at two (2) years of model testing, design, and fabrication for the first unit. Followed by an additional eighteen (18) months of installation per base unit. Electrical Work: The primary electrical scope of work is to accomplish the rewind and restack of the generator stators on Units 1, 2, and 3 to 45,000 kVA, with a 0.9 power factor at 13.8 kV. The electrical work includes, but is not limited to replacing the stator winding, replacing core laminations, reinsulating rotor poles, and model verification. Other major electrical scope items for Units 1, 2 and 3 include but are not limited to the installation of a machine condition monitoring system, refurbishment of rotor field poles and field leads, replacement of cable, wiring, relays, and RTDs, and furnishing and installing new high resistance grounding systems. The scope of work for each unit will culminate with testing and commissioning. Turbine Work: The primary mechanical scope of work is the replacement of the Kaplan turbine runners of Units 1, 2, and 3 to an increased rated output of 61,600 hp at 54 feet of net head, along with replacement of the wicket gates. Turbine runner and wicket gate replacement for Unit 4 will be at the option of the Government. The existing turbine runners are 264-in diameter, 5-bladed Kaplan runners rated at 35,000 hp at a net head of 45 feet. Other turbine work will be focused around stay ring, bottom ring, headcovers, turbine shaft, bearings, operating ring, servomotors, and facing plates. A special item in this contract will be producing a display from the existing runner. Old Hickory's powerhouse has experienced historical movement that has rendered the stator core eccentric to the discharge ring by as much as one-quarter inch on some units. Refurbishment of the discharge rings by machining and weld overlay is a feature of work that shall accomplish cavitation repair and the re-establishment of concentric unit alignment. Mechanical Work: During the rehab all the mechanical support systems will be inspected, refurbished, or upgraded. This will include but not limited to brake ring, brake cylinders, thrust bearing coolers, float switches, digital relays, turbine guide bearing lubrication system, high pressure lift system addition, vacuum breakers, and wicket gate lubrication system, and rotating exciter will be removed. The contractor will be required to provide all plant, labor and materials to construct these features.