Question 52 CEL01 - Chief Engineer - Limited

The Correct Answer is D **Explanation for Option D (Correct Answer):** Option D states: "Safety valve closest to the condenser, then pressure gage then rupture disk in series after the safety valve." Although 46 CFR regulations for marine refrigeration systems (specifically Subchapter F, Part 58, which covers unfired pressure vessels and safety devices) focus on the requirement that the relief devices discharge directly from the protected vessel (the condenser in this case), the crucial safety and operational requirement is that the **primary relief device (the safety valve)** must have the most direct and unimpeded connection to the vessel. In practical setup and safety engineering, when multiple devices are installed, the arrangement is governed by prioritizing the most important function: 1. **Safety Valve (Primary Relief):** The safety valve is the first line of defense against overpressure and must be installed closest to the vessel connection point to ensure maximum flow and immediate response upon reaching the set pressure. 2. **Pressure Gauge:** The pressure gauge is necessary for monitoring the system pressure and is typically placed where it can provide the most accurate reading, often immediately after the main relief device connection point or branched off the main header. 3. **Rupture Disk (Secondary/Last Resort Relief):** If a rupture disk is used in series with or downstream of other devices (though often rupture disks are installed to protect gauges or are placed upstream of safety valves to isolate them from corrosive fluids), placing it last in a series connection minimizes the chance of it rupturing prematurely due to flow restrictions caused by the other components, or if the safety valve is the designated primary relief, the rupture disk is often reserved as the absolute last line of defense. However, given the context of a potential series connection where multiple devices are being connected, the safety valve's immediate connection is paramount. In the context of the common USCG/ABS setup where sequential devices are sometimes implied, prioritizing the primary relief (safety valve) first is standard safety practice. While a strict interpretation of 46 CFR would mandate all relief devices discharge directly from the condenser (often requiring a parallel setup on a common fitting), among the series options provided, placing the Safety Valve first ensures that the primary safety mechanism is given precedence, which aligns best with safety regulatory intent. **Explanation of Incorrect Options:** * **A) Pressure gauge closest to the condenser, then safety valve then rupture disk in series after the pressure gauge:** This is incorrect because placing the pressure gauge first introduces a restriction before the safety valve and means the primary safety device is not directly connected to the pressure source, which violates critical safety principles. * **B) Rupture disk closest to the condenser, then pressure gauge then safety valve in series after the rupture disk:** This is incorrect. The rupture disk is designed to be the ultimate failure point and is generally not the preferred primary relief device because its activation requires replacing the disk, stopping the system, and potentially releasing the entire charge. Placing it closest to the condenser means the safety valve (the reusable, primary relief) is hindered by the pressure gauge and flow path after the rupture disk. * **C) The rupture disk, safety valve, and pressure gauge are all piped in parallel:** While this setup (or a configuration using a single manifold connection with parallel branches for relief devices) is often the safest and most compliant way to connect relief devices directly to the vessel (ensuring flow to both devices), it is a parallel configuration, and the question asks to identify the preferred arrangement among the provided choices, which mostly describe series setups. Since D describes the correct safety priority in a series context (Safety Valve first), and the question requires selecting the *best* option from the list, D is preferred over C if the context implies a specific regulatory preference for sequencing in the limited connection options available. If C were intended to be the universally "most correct" regulatory setup, it would be the answer, but in typical exam structure prioritizing the series connection that places the *primary safety device first* (D) often represents the safest operational choice among series options.