The Durst division of Regal Beloit Corporation has shipped its second model TG 80/125 turbine turning gear as part of the ongoing expansion of the Kori nuclear power plant in Gori, South Korea. The TG 80/125 will be installed at the Shin-Kori 2 nuclear reactor, the second unit in a four-reactor construction project launched in 2006. Durst shipped the first TG 80/125 in May 2011, for installation at the Shin-Kori 1 reactor. The Kori nuclear power plant is owned and operated by KEPCO. The Nuclear Power Plants Business Group of Doosan Heavy Industries and Construction, Korea's only major nuclear equipment supplier, is collaborating with General Electric on the multi-reactor project.

Designed to fit between the General Electric steam turbine and the Doosan steam generator, the TG 80/125 is used to start up turbines to achieve the required speed. The turning gear is engaged when there is no steam to the turbine. It rotates the turbine at 3.5 rpm, ensuring even heating to prevent uneven expansion. Once the required speed is reached, the turning gear is disengaged and steam is admitted to the turbine - a process that takes approximately 20 seconds.

Durst manufactures 14 model sizes in its turning gear line, from 2 hp up to 100 hp. At nearly 9 tons, the TG 80/125 measures 7 feet long x 6 feet high x 5 feet wide, making it the largest turning gear in the world. The 80/125 designation refers to the turning gear's capacity, indicating a range of 80,000 to 125,000 pounds of breakaway tooth load at the clash pinion interface with the turbine rotor gear.

When the turbine is shut down for maintenance, the TG 80/125 is engaged at 3.5 rpm with the turbine gear. The turning gear rotates the turbine at 3.5 rpm for up to two weeks as the turbine cools down to room temperature. This evens out the temperature distribution around the turbine and prevents warping of the turbine blades and damage to the Babbitt bearings.

Durst recently incorporated design refinements into the TG 80/125, including a new mounting configuration for the torque motor. The new-generation TG 80/125 is driven by a 75 hp main motor and a 1.5 hp torque motor from Marathon Electric, a Regal Beloit company.

Previously, the torque motor was mounted to the main housing. It utilized chains and sprockets to take up all the backlash within the gear meshes. The new design has the torque motor mounted piggyback in relationship to the main motor. The torque motor takes up the gear mesh backlash, and then the main motor takes over the load.