Practice Test Geeks(CLS) Certified Lubrication Specialist Practice Test
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Lubrication Fundamentals & Applications Flashcards

7 cards from real CLS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Lubrication Fundamentals & Applications flashcards as text

  1. What is the significance of the 'film thickness ratio' (lambda, λ) in lubrication?

    Answer: It compares the minimum film thickness to the composite surface roughness

    Lambda ratio (λ = minimum film thickness / composite RMS surface roughness) determines the lubrication regime: λ>3 is full-film, 1–3 is mixed, and <1 is boundary.

  2. Which type of wear is caused by the formation and collapse of vapor bubbles in a lubricant?

    Answer: Cavitation erosion

    Cavitation erosion occurs when vapor bubbles form due to local pressure drops and then implode near metal surfaces, generating intense shock waves that pit the surface.

  3. What is the 'pour point' of a lubricant?

    Answer: The lowest temperature at which a lubricant will flow under gravity

    Pour point is the lowest temperature at which a lubricant will still flow, typically 3°C above the temperature at which flow ceases.

  4. In elastohydrodynamic lubrication (EHL), what happens to the lubricant's viscosity under very high contact pressures?

    Answer: Viscosity increases dramatically, allowing it to support high loads

    In EHL contacts, pressures can reach several GPa, causing the lubricant's viscosity to increase by orders of magnitude (piezo-viscous effect), enabling it to support high loads.

  5. What does the term 'oil bleed' refer to in the context of grease?

    Answer: Separation of base oil from the thickener during storage or use

    Oil bleed (or oil separation) is the release of base oil from the thickener matrix; controlled bleed is necessary for grease to lubricate, but excessive bleed indicates an unstable product.

  6. Which additive type is specifically designed to prevent rust on ferrous metal surfaces in contact with water?

    Answer: Rust inhibitor

    Rust inhibitors (e.g., sulfonates, carboxylates) adsorb onto ferrous surfaces to displace water and form a protective barrier against rust formation.

  7. What is the role of a demulsifier additive in a lubricating oil?

    Answer: To promote rapid separation of water from the oil

    Demulsifiers reduce interfacial tension between oil and water, encouraging water droplets to coalesce and settle out so they can be drained, protecting equipment.