Class 5 Boiler Practice Exam

According to ASME sec IV part HG400, the safety valve size for a 15lb steam heating boiler must not exceed what size?

1. 2 NPS

2. 4 NPS

3. 4 1/2 NPS

4. 6 NPS

The correct answer is: 4 1/2 NPS

In accordance with ASME Section IV, Part HG-400, the maximum size of the safety valve for a steam heating boiler operating at a pressure of 15 psi is specifically regulated to ensure the safe operation of the system. The criteria set forth by the ASME provides clear guidelines for determining the appropriate safety valve size. The selected answer, indicating that the safety valve size must not exceed 4½ NPS (Nominal Pipe Size), aligns with the requirements established based on the boiler's pressure and capacity. Safety valves play a critical role in protecting the boiler from overpressure scenarios; hence, selecting an appropriately sized safety valve is essential for ensuring that it can discharge sufficient steam to prevent a dangerous buildup of pressure. Understanding the significance of safety valve sizing helps maintain product integrity and operator safety. Valves that are too large or too small can lead to inefficiencies and potentially catastrophic failures. In this case, while larger size options may seem appealing for safety, they exceed the parameters set by ASME for a boiler with a maximum operating pressure of 15 psi and, therefore, would not be compliant with safety regulations.