Question 35 OSE01 - Chief Engineer - OSV

The Correct Answer is D **Why Option D ("Use of an air lance") is correct:** The use of an air lance (often referred to as 'soot blowing' or 'lancing') is the standard, most practical, and most efficient method for removing dry, loose soot and ash deposits from the fire-sides of boiler tubes, particularly in operating or shut-down auxiliary boilers on vessels. The soot is dislodged by the force of compressed air (or sometimes steam) directed through a tube or lance that is inserted between the boiler tubes or access ports. This method is dry, relatively quick, requires minimal setup, and avoids creating sludge or thermal stress associated with wet methods. **Why the other options are incorrect:** A) **Use of a high-pressure water jet:** While effective for hard scaling, using a high-pressure water jet (water washing) to remove soot is generally inefficient and creates significant issues. It turns the soot into corrosive, difficult-to-handle sludge, and critically, it introduces large amounts of moisture into the refractory, insulation, and inaccessible areas of the boiler, leading to potential corrosion (especially if sulfur compounds are present) and damage unless extreme drying measures are taken immediately afterward. B) **Use of a suitable acid:** Chemical cleaning (acid cleaning) is reserved for removing hard scale (calcium/silicate deposits) from the **water-side** of the boiler, not the routine removal of soot and ash from the **fire-side**. Using acid on the fire-side would be highly hazardous, difficult to apply evenly, impractical on a routine basis, and would likely damage the tube material and refractory. C) **Use of a power-driven wire brush:** While small areas of superheater elements or localized deposits might be handled with a brush, using a power-driven wire brush is impractical and inefficient for cleaning the extensive, tightly packed tube banks of a natural-circulation water-tube boiler. It is slow, physically demanding, and cannot access the inner rows of tubes effectively, making it non-compliant with the requirement for a "most practical and efficient way."