Shaft rubbing creates frictional heat which then causes bowed rotors. STAR’s Retractable Packing is designed to have greater radial clearance at start-up, prior to going through the first critical. As the steam flow increases in the turbine, the steam pressure behind the packing ring overcomes the spring and friction forces, causing the packing ring to close to the desired radial clearance, while avoiding any contact between the rotor and packing teeth. 

Retractable Steam Turbine Ring

Retractable Turbine Packing Ring