CLS Lubricant Selection & Management 3 — Questions and Answers
Question 1: A worm gear drive requires a lubricant to handle sliding contact between steel and bronze components. Which additive type should be avoided?
- Friction modifiers
- Anti-wear additives
- Sulfur-based EP additives (Correct answer)
- Viscosity index improvers
Correct answer: Sulfur-based EP additives
Sulfur-based EP additives corrode bronze and other yellow metals, making them unsuitable for worm gear drives with bronze components.
Question 2: The Viscosity Index (VI) of a lubricant measures its:
- Resistance to oxidation across temperatures
- Rate of viscosity change with temperature (Correct answer)
- Viscosity at the pour point
- Maximum usable operating temperature
Correct answer: Rate of viscosity change with temperature
Viscosity Index quantifies how much a lubricant's viscosity changes with temperature; a higher VI means less viscosity change.
Question 3: Which synthetic base oil type offers the best performance for very wide operating temperature ranges, from -60°F to +400°F?
- Polyalphaolefin (PAO)
- Polyalkylene glycol (PAG)
- Alkylated naphthalene (AN)
- Silicone fluid (Correct answer)
Correct answer: Silicone fluid
Silicone fluids maintain usable viscosity across extremely wide temperature ranges, from very low to very high temperatures, surpassing PAOs.
Question 4: A technician notices a gear oil has turned milky white in color. This most likely indicates:
- Oxidation degradation
- Water contamination (Correct answer)
- Metal particle contamination
- Additive depletion
Correct answer: Water contamination
A milky or cloudy white appearance in gear oil is a classic sign of water emulsification or contamination.
Question 5: When lubricating an open gear drive exposed to washout and contamination, which lubricant form is most appropriate?
- Thin fluid oil ISO VG 68
- Asphaltic (bituminous) open gear compound (Correct answer)
- Synthetic PAO ISO VG 150
- Light grease NLGI 00
Correct answer: Asphaltic (bituminous) open gear compound
Asphaltic open gear compounds provide extreme adhesiveness and high film thickness to cling to teeth and resist wash-off under harsh exposure.
Question 6: Which AGMA lubricant number corresponds approximately to an ISO VG 460 industrial gear oil?
- AGMA 4
- AGMA 7
- AGMA 8 (Correct answer)
- AGMA 9
Correct answer: AGMA 8
AGMA 8 corresponds to an approximate ISO VG 460 viscosity range for industrial gear lubricants.
Question 7: A plant has multiple hydraulic systems requiring different viscosity oils. What is the primary risk of using a higher-than-specified viscosity hydraulic oil?
- Increased pump cavitation and reduced efficiency (Correct answer)
- Oil film too thin causing wear
- Seals swelling and leaking
- Increased flash point risk
Correct answer: Increased pump cavitation and reduced efficiency
Oil that is too viscous increases resistance to flow, which can cause pump cavitation, reduced efficiency, and poor response in cold start conditions.
CLS Lubricant Selection & Management 3
A worm gear drive requires a lubricant to handle sliding contact between steel and bronze components.
Which additive type should be avoided?