Lubrication Systems and Practices Flashcards
6 cards from real Millwright Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Lubrication Systems and Practices flashcards as text
What does the viscosity grade of a lubricating oil describe?
Answer: The oil's resistance to flow at a given temperature
Viscosity is a measure of an oil's resistance to flow; higher viscosity oils flow more slowly and are used in higher-load, lower-speed applications.
Which type of grease is most commonly used in electric motor bearings operating at high temperatures?
Answer: Lithium complex grease
Lithium complex grease has excellent high-temperature stability (dropping point above 260°C/500°F) and is the most widely specified grease for motor bearings.
Over-greasing a rolling element bearing is dangerous because it can cause:
Answer: Excessive heat from churning and possible seal damage
Excess grease causes the rolling elements to churn through the grease, generating heat, which can degrade the lubricant and damage seals.
What is the primary function of a splash lubrication system in a gearbox?
Answer: To use the rotation of gears to splash oil onto mating surfaces
Splash lubrication relies on the lower gears dipping into an oil sump and throwing oil onto gear teeth and bearing surfaces through rotation.
What does a milky or cloudy appearance in gearbox oil indicate?
Answer: Water contamination (emulsification)
Milky or cloudy oil indicates water has mixed with the oil and formed an emulsion, which severely reduces the oil's lubricating ability.
An NLGI grade 2 grease is considered:
Answer: Medium consistency — the most common general-purpose grease grade
NLGI Grade 2 is a medium-consistency grease (similar to peanut butter) and is the most widely used grade for general industrial bearing applications.