Question 300Steam Plants - 1st Asst/Chief

The correct answer is B) never exceed 170°F. The maximum lube oil temperature leaving a large, main propulsion steam turbine bearing should never exceed 170°F. This is a general industry standard and recommended practice to ensure proper lubrication and prevent damage to the turbine bearing. Exceeding this temperature limit could lead to accelerated wear, increased viscosity, and potential failure of the lubrication system. The other options are incorrect because: A) there is no universal limit of 70°F above the inlet temperature, C) 130°F is too low and may not provide adequate lubrication, and D) the lube oil outlet temperature from the centrifugal purifier is not the limiting factor for the turbine bearing temperature.