CMRP Lubrication Management 2 — Questions and Answers
Question 1: An ISO cleanliness code reported as 16/14/11 for a hydraulic fluid describes:
- Lubricant viscosity at 40°C, 100°C, and flash point respectively
- Water, fuel, and acid contamination levels
- Particle count ranges per milliliter at 4, 6, and 14 micron size thresholds (Correct answer)
- Percentage of additive depletion at three service intervals
Correct answer: Particle count ranges per milliliter at 4, 6, and 14 micron size thresholds
The ISO 4406 cleanliness code uses three scale numbers representing particle counts per milliliter at ≥4 µm, ≥6 µm, and ≥14 µm, quantifying solid contamination level.
Question 2: The primary benefit of an oil analysis program in a reliability-centered maintenance strategy is to:
- Determine the exact color grade of the lubricant in service
- Schedule all oil changes on a fixed 3-month calendar interval
- Monitor lubricant condition and wear metal trends to enable condition-based maintenance (Correct answer)
- Replace lubricants annually regardless of equipment condition
Correct answer: Monitor lubricant condition and wear metal trends to enable condition-based maintenance
Oil analysis acts as a 'blood test' for machinery, detecting degradation and wear metal trends that allow maintenance to be triggered by actual condition rather than arbitrary schedules.
Question 3: Which lubricant additive category forms a protective film on metal surfaces to prevent rust and corrosion from water and acidic contaminants?
- Viscosity index improvers
- Rust and corrosion inhibitors (Correct answer)
- Anti-wear (AW) additives
- Pour point depressants
Correct answer: Rust and corrosion inhibitors
Rust and corrosion inhibitors adsorb onto metal surfaces to create a barrier that prevents oxidation and chemical attack from water, acids, and other corrosive agents.
Question 4: Over-greasing a rolling element bearing most commonly leads to:
- Insufficient lubrication film between rolling elements
- Excessive heat generation from grease churning and bearing failure (Correct answer)
- Improved sealing against external contamination
- Accelerated additive depletion without heat increase
Correct answer: Excessive heat generation from grease churning and bearing failure
Excess grease fills the bearing cavity, forcing rolling elements to churn through grease rather than run freely, generating heat that causes premature bearing failure.
Question 5: Kinematic viscosity of a lubricating oil, measured in centistokes (cSt), represents:
- The oil's resistance to oxidation at elevated temperature
- The oil's resistance to flow under gravity at a specified temperature (Correct answer)
- The concentration of anti-wear additives in parts per million
- The flash point temperature divided by the oil's density
Correct answer: The oil's resistance to flow under gravity at a specified temperature
Kinematic viscosity (cSt) is the ratio of dynamic viscosity to fluid density and describes how readily the oil flows under gravitational force at a given temperature.
Question 6: Oil mist lubrication is the preferred delivery method for high-speed, lightly loaded rolling element bearings primarily because it:
- Provides the thickest possible lubricant film at all loads
- Delivers minimal oil quantity, reducing churning losses and heat generation (Correct answer)
- Allows grease to be applied without stopping the equipment
- Eliminates the need for lubricant filtration systems
Correct answer: Delivers minimal oil quantity, reducing churning losses and heat generation
Oil mist delivers a controlled aerosol of fine oil droplets that satisfies lubrication requirements of high-speed bearings while minimizing energy losses and heat from excess lubricant churning.
Question 7: A steadily increasing Total Acid Number (TAN) trend in sequential oil samples most likely indicates:
- Improved base oil refining and additive performance
- Decreasing water content as condensation evaporates
- Ongoing oil oxidation and progressive additive depletion (Correct answer)
- Higher base oil viscosity from thermal polymerization only
Correct answer: Ongoing oil oxidation and progressive additive depletion
Rising TAN reflects accumulation of acidic oxidation by-products and exhaustion of alkaline additives, signaling that the lubricant is approaching end of service life.
CMRP Lubrication Management 2
An ISO cleanliness code reported as 16/14/11 for a hydraulic fluid describes: