Question 17 3AE02 - Third Assistant Engineer (Alt)

The Correct Answer is B. **Explanation of why Option B is correct:** A conventional mooring winch is designed not only to heave and pay out the mooring line but also to maintain the necessary tension. The most crucial safety feature when the line is secured is the brake system. The brake must have a high capacity to hold the required working tension and resist sudden increases in load caused by ship movement (wave action, wind gusts, currents). However, if the tension reaches a level that approaches the Minimum Breaking Load (MBL) of the mooring line, the brake is deliberately designed to slip. This controlled slippage, known as the "rendering point" or "holding power," ensures that the tension does not exceed a dangerous threshold (typically set by regulations, often around 60% to 80% of the MBL, though the winch *brake capacity* is usually higher than the required holding power) which would snap the line. If the line snaps, it creates a highly dangerous situation (snapback) and requires immediate replacement. By allowing the brake to render (slip), the line is protected, the dynamic forces are absorbed, and the line tension is momentarily relieved. **Explanation of why the other options are incorrect:** * **A) A high-capacity brake is required to hold a load equal to the breaking strength of the mooring line. For reasons of safety, no slippage of the brake is permitted.** This is incorrect. While the brake capacity is high, if the tension reaches the breaking strength of the line, the line will fail, creating a safety hazard. Safety demands that the brake slips *before* the line breaks. * **C) A high-capacity brake is required to hold a load exceeding the breaking strength of the mooring line. For reasons of safety, no slippage of the brake is permitted.** This is fundamentally incorrect and dangerous. If the brake held a load exceeding the line's breaking strength without slipping, the mooring line would certainly fail before the brake, which defeats the purpose of protecting the line and personnel. * **D) A low-capacity brake is required to hold a load far below the breaking strength of the mooring line, but it is required to slip at a lower tension to avoid mooring line breakage.** This is incorrect regarding capacity. A mooring winch needs a **high-capacity** brake to handle the substantial dynamic loads and working tensions required to secure a large vessel, often resisting forces well into the tens of tonnes. A low-capacity brake would be inadequate for the working environment.