Question 157Steam Plants - QMED

The correct answer is B. The turning gear is used to prevent turbine rotor distortion while warming-through or while cooling, since distortion is an issue when warming-through or cooling. This is because the rapid expansion and contraction of the turbine rotor during the warming-through and cooling processes can lead to distortion of the rotor if it is not properly supported. The turning gear slowly rotates the turbine, gearing, and shaft to evenly distribute the thermal stresses and prevent uneven expansion or contraction that could damage the turbine. Using the turning gear during both warming-through and cooling is necessary to protect the turbine from rotor distortion. The other options are incorrect because they do not fully capture the purpose and use of the turning gear to prevent turbine rotor distortion during both the warming-through and cooling processes.