Minnesota Boiler License Practice Exam

What is the minimum relieving capacity of a smaller valve when mounted singly with a larger valve?

1. 20%

2. 35%

3. 50%

4. 70%

The correct answer is: 50%

The minimum relieving capacity of a smaller valve when mounted singly with a larger valve is determined by the need to ensure that the system can manage overpressure conditions effectively. In the context of boiler systems, this capacity is crucial for maintaining safety and preventing potential explosions. The answer of 50% reflects the requirement that the smaller valve needs to be capable of relieving at least half the pressure that may be generated by the system in cases of malfunction or failure. This standard helps to ensure that there is sufficient capacity for the combined valves to manage overpressure situations. A smaller valve’s capability must be sized appropriately relative to any larger valve to ensure that when both are utilized, the system has adequate relief capacity if one fails or if a fault condition arises. Designing the system so that the smaller valve has a relieving capacity of at least 50% of the total requires careful calculation of potential pressure buildups within the system, ensuring safety margins are maintained. In this scenario, the other options, such as 20%, 35%, and 70%, do not align with standard practices for providing adequate safety through pressure relief. They may not meet the necessary criteria for effective system protection combined with the larger valve's operation and could jeopardize safe operation under numerous conditions.