Question 2 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is C **Why Option C ("Lithium-based grease") is correct:** Lithium-based grease (often referred to as lithium soap grease or lithium complex grease) is the most commonly used type of grease worldwide, and this prevalence extends significantly to the maritime industry. It is highly favored aboard ships because it offers an excellent balance of properties crucial for shipboard machinery, including: 1. **High-Temperature Stability:** It performs well in engine rooms and hot operating environments. 2. **Excellent Water Resistance:** This is critical in the marine environment where equipment is constantly exposed to moisture, spray, and potential seawater contamination. 3. **Good Mechanical Stability:** It resists softening or thinning under shear stress. 4. **Versatility:** It is suitable for a wide range of applications, including bearings, stern tube seals, deck machinery, winches, and general lubrication points, allowing ships to standardize on a single, multipurpose grease. **Why the other options are incorrect:** * **A) Lime-based grease (or Sodium/Lime):** While historically used (especially lime/calcium greases), general lime-based greases are typically poor performers when exposed directly to water, making them unsuitable for many shipboard applications. * **B) Calcium-based grease:** Standard calcium (soap) greases have good water resistance, but they generally have lower maximum operating temperatures compared to lithium complex greases. While some advanced calcium sulfonate greases are excellent for marine use, the most *commonly* used general-purpose grease remains lithium-based. * **D) Aluminum-based grease:** Aluminum complex greases offer excellent water resistance and adhesiveness, making them suitable for some specific marine applications (like open gear or cable lubrication). However, they are typically more expensive and not used as the standard, multipurpose grease in the volume that lithium-based grease is utilized aboard a typical vessel.