Question 36 OSE01 - Chief Engineer - OSV

The Correct Answer is B. **Explanation for Option B (Correct):** The auxiliary boiler described is a coil-type, water-tube, forced-circulation boiler (often referred to generically as a "flash boiler" or similar high-capacity, compact design, like Clayton or Aalborg OC designs). 1. **Inspection Difficulty:** These boilers use a long, continuous helical or spiral coil of tubing to contain the water. Due to the small diameter, extreme length, numerous bends, and the general construction of the coil stack, it is virtually impossible to gain visual or physical access to the internal (water) surfaces of the tubes for inspection. Therefore, coil water-sides are **very difficult to inspect**. 2. **Cleaning Method:** If scale (calcium or magnesium deposits) forms on the internal surfaces, conventional mechanical cleaning methods are impractical. A water jet or wire brush cannot navigate the tight bends and long length of the coiled tubing effectively. Therefore, the only practical, efficient, and complete method for removing scale from the complex internal geometry of the coil is **chemical cleaning** using an appropriate descaling acid solution (often inhibited hydrochloric acid or similar proprietary mixtures) circulated through the system. **Explanation for Incorrect Options:** * **A) Coil water-sides are very difficult to inspect AND mechanical cleaning with water jet or wire brush is a practical and efficient method of scale removal.** * This is incorrect because mechanical cleaning (water jet or wire brush) is not a practical or efficient method for cleaning the internally scaled, complex geometry of a boiler coil. * **C) Coil water-sides are relatively easy to inspect AND mechanical cleaning with water jet or wire brush is a practical and efficient method of scale removal.** * This is incorrect on both counts. Coil water-sides are extremely difficult to inspect, and mechanical cleaning is ineffective. * **D) Coil water-sides are relatively easy to inspect AND chemical cleaning with a suitable acid is the only practical and efficient method of scale removal.** * This is incorrect because the coil water-sides are definitively **not** easy to inspect due to their design.