Question 59 OSE01 - Chief Engineer - OSV

The Correct Answer is A. Maintaining a tight system and promptly repairing leaks (Option A) is the best line of defense in minimizing cooling system problems, particularly when using questionable make-up water. Closed, recirculating cooling systems rely on maintaining a specific concentration of chemical inhibitors (such as nitrites, molybdates, or organic acid technology) in the coolant mixture (water plus antifreeze/inhibitor). When the system leaks, this chemically treated coolant escapes, and it must be replaced with fresh make-up water, which is often untreated or has questionable mineral content (such as high hardness or chlorides). Every time questionable make-up water is added, it dilutes the effective concentration of the corrosion inhibitors and introduces new dissolved solids, which contribute to scale, corrosion, and deposits. By maintaining a tight system and minimizing the need for make-up water, you preserve the integrity and effectiveness of the existing, chemically-treated coolant, thereby stabilizing the cooling system chemistry and significantly reducing the risk of corrosion and scaling. Here is why the other options are incorrect: B) **Increasing the frequency of draining, flushing, and re-filling the system:** While necessary for major maintenance, increasing the frequency of this process is counterproductive as a preventative measure. Every time the system is drained and refilled, it wastes expensive chemical inhibitors and requires the introduction of large quantities of new, potentially questionable make-up water. This dramatically increases the operational cost and the frequency of system upsets associated with introducing poor-quality water. C) **Maintaining cooling water temperatures at lower-than-normal values:** Operating an engine at below optimal temperatures can increase fuel consumption, lead to incomplete combustion, and cause 'cold corrosion' (sulfuric acid condensation). While it slightly slows chemical reaction rates, it does not address the core problem of poor water quality, nor does it prevent scale formation which is related more to concentration than temperature (within the normal operating range). D) **Maintaining cooling water temperatures at higher-than-normal values:** High temperatures significantly accelerate corrosion rates and increase the tendency for dissolved solids (especially calcium and magnesium hardness salts) to precipitate out of solution, leading to rapid scale formation and overheating. This practice would exacerbate, not minimize, cooling system problems.