Question 18 DDE04 - Designated Duty Engineer - 1000-4000 HP

The Correct Answer is C **Why Option C is Correct:** The problem states that the desired oil injection rate is 3 drops per cranking minute, but the observed rate is only 1 drop per minute. This indicates that the current flow rate of lubricant is insufficient. The in-line lubricator uses a metering needle valve to control the amount of oil dispensed into the airstream. To increase the flow rate (the number of drops per minute), the metering needle valve must be adjusted to allow a larger opening, thereby permitting more oil to exit the reservoir and enter the air line. Therefore, the valve should be further opened. **Why the Other Options are Incorrect:** * **A) The in-line lubricator oil injection metering needle valve should be further closed.** Closing the metering needle valve would restrict the oil flow even further, decreasing the injection rate below the current 1 drop per minute, which is the opposite of the desired outcome (3 drops per minute). * **B) The oil in the in-line lubricator should be replaced with oil of lower viscosity than specified.** The problem explicitly states that the "oil viscosity is correct." Changing the oil to a lower viscosity (thinner) oil might potentially increase the flow rate, but it would violate the manufacturer's specifications, potentially leading to inadequate lubrication film strength or other operational issues, especially since the pressure and temperature conditions are assumed normal. The first and proper step is always mechanical adjustment if the specified parameters (pressure and viscosity) are already met. * **D) The starting air pressure supplied to the air-starting motors should be increased.** While some lubricators are pressure-differential activated, the problem states that the "start air pressure is within the normal range." Increasing the pressure above the normal operating range (250 psig) is unnecessary, potentially dangerous for the air motor components, and is not the primary mechanism for adjusting the oil drip rate in most standard in-line lubricators; the needle valve is.