Question 48

The Correct Answer is A. **Explanation for Option A (suction side of pump):** The primary function of a cargo pump relief valve is to protect the pump and associated piping from over-pressurization, which typically occurs if the pump is running against a closed discharge valve (or if a blockage occurs downstream). When the relief valve opens, it needs a safe and effective place to send the pressurized fluid. Piping the relief valve output back to the **suction side of the pump** achieves two critical goals: 1. **Pressure Relief:** It immediately relieves the excessive pressure in the discharge line. 2. **Containment and Recirculation:** It keeps the cargo (often hazardous or valuable) contained within the system. The fluid is simply recirculated through the pump until the discharge path is cleared or the pump is stopped. **Explanation for Incorrect Options:** **B) atmosphere through pump vent:** Piping a relief valve to the atmosphere is generally unacceptable for cargo systems, especially those carrying flammable, toxic, or polluting liquids (like oil or chemicals). This would release hazardous vapors or liquid spills directly onto the deck, creating a safety and environmental hazard. Vents are usually for small amounts of vapor/air, not for the full flow capacity of a relief valve. **C) crossover line:** While the crossover line connects different parts of the cargo system, it is typically a high-pressure line itself (potentially pressurized by other pumps). Sending the relieved fluid here might not offer sufficient pressure relief if the entire manifold/crossover system is already under pressure, defeating the purpose of the valve. The most reliable low-pressure point for a pump relief valve is its own suction intake. **D) cargo pump pressure gauge:** A pressure gauge is an instrument used for measurement, not a component capable of handling or directing fluid flow. Piping a relief valve (which can flow a significant volume of liquid) to a delicate gauge fitting is impossible and nonsensical in an engineering context.