Abstract: Method and apparatus to limit and control rotational loss heating such as occurs in a large steam turbine in the bypass mode of operation under no-load and low-load operating conditions. According to the invention, a portion of the high pressure bypass steam is admitted to the lower pressure sections of the turbine to provide motive fluid for driving the turbine while, simultaneously, a second portion of the high-pressure bypass steam is admitted to the high-pressure section of the turbine in a reverse-flow direction to pass backwards therethrough and limit the rotational loss heating. The two flows may be proportioned to control rotational loss heating in both the high-pressure and lower pressure sections of the turbine. A reverse-flow valve and a ventilator valve are provided for routing the reverse-flow of steam.