Refrigeration Plant Operator B Practice Test

To enable an oil to flow at a much lower temperature, which additive should be added?

1. Viscosity index improver

2. Pour point depressants

3. Dispersant

4. Thickening agent

The correct answer is: Pour point depressants

The appropriate additive to facilitate oil flow at lower temperatures is a pour point depressant. These additives work by modifying the wax structure within the oil, which can solidify and restrict flow as temperatures drop. By altering the crystallization process of the wax, pour point depressants lower the temperature at which the oil becomes too viscous to flow smoothly, thereby improving its pumpability in cold conditions. In contrast, viscosity index improvers enhance the oil's viscosity at high temperatures but do not specifically address flow issues at lower temperatures. Dispersants primarily help keep particles suspended within the oil, preventing sludge formation, while thickening agents can actually increase the oil's viscosity, making it less suitable for low-temperature applications. Therefore, pour point depressants are essential for ensuring that oil remains manageable and effective in colder conditions.