Question 30 3AE01 - Third Assistant Engineer

The Correct Answer is D. **Why Option D is Correct:** Option D, "Bleed off all hydraulic pressure from the system," is the absolutely essential safety step before servicing or repairing any high-pressure hydraulic starting system. Hydraulic systems, especially those designed to start large diesel engines, store significant energy under high pressure (often several thousand PSI). If the system is opened while pressurized, this stored energy can violently release oil, hoses, or components, causing severe injury or death. Bleeding the pressure ensures the system is de-energized, making it safe to open connections and replace parts. **Why the Other Options are Incorrect:** * **A) Place all control levers in the "HOLD" position:** While a good operational practice, placing levers in "HOLD" (or neutral) does not guarantee that residual pressure, accumulator pressure, or trapped pressure is released from the lines that will be opened for servicing. The system must be physically de-pressurized. * **B) Ensure that the hydraulic fluid reservoir is full:** The fluid level is a maintenance check, not a critical pre-service safety procedure. The state of the fluid level has no bearing on the immediate danger posed by stored pressure when opening the system. * **C) Block all hydraulic hoses using high-pressure covers:** High-pressure covers are typically used to protect connectors or ends of hoses when they are disconnected, preventing contamination. They are protective covers, not pressure-releasing devices. They offer no protection against the danger of stored pressure when the system is first opened.