Question 30 DDE01 - Designated Duty Engineer - Unlimited HP

The Correct Answer is D ### Explanation for Option D (Correct) The air box drains on two-stroke engines accumulate heavy sludge, which is a mix of carbon deposits, oil, and water. This material often solidifies or becomes extremely sticky, forming a dense mechanical plug, particularly at the drain valve or where the piping elbows. To clear such a mechanical blockage effectively, safely, and thoroughly, physical intervention is necessary. **Mechanically poking through the drain opening with a rod** (or thin wire) breaks up the solidified plug, allowing the accumulated liquids and broken sludge to flow into the drains tank. This is the standard procedure for confirmed mechanical blockages in these lines. ### Explanation of Incorrect Options **A) Blow through the drain openings with compressed air to clear the drains.** While compressed air can clear fluid-based blockages, it is often ineffective against the dense, sticky sludge found in air box drains. Furthermore, using high-pressure air can be dangerous, potentially rupturing the piping or gaskets, or causing the oily sludge to spray out unexpectedly if the blockage suddenly yields. **B) Increase the crankcase pressure to blow the air box drain openings clear.** The crankcase is entirely separate from the air box drains. Increasing crankcase pressure is operationally dangerous (risking oil spray and damage to bearings/seals) and is technically irrelevant to the air box draining system. **C) Increase the air box pressure to blow the air box drain openings clear.** The air box pressure is determined by the engine load and the turbocharger output. While the air box is pressurized, increasing this pressure is only achievable by increasing engine load, which is poor operating practice simply to clear a drain. More importantly, the scavenging air pressure is generally not high enough (or focused enough) to overcome a solidified sludge blockage. If the initial scavenging pressure couldn't push the accumulation out, a slightly higher operational pressure increase will be equally ineffective against the mechanical resistance of the sludge.