Question 691Steam Plants - Assistant Engineer

The correct answer is B) viscosity. When the temperature of the main turbine lubricating oil is lowered, the viscosity (thickness) of the oil will increase. This is because the lower temperature causes the oil molecules to move more slowly, resulting in higher resistance to flow, or higher viscosity. The increase in viscosity is a key factor in proper lubrication and protection of the turbine's moving parts. The other answer choices are incorrect because lowering the temperature would not directly affect the pour point (A), flash point (C), or concentration of contaminants (D) in the lubricating oil. Those properties are influenced by other factors, such as the oil's composition and the presence of impurities.