Massachusetts 2nd Class Fireman's Practice Exam

How do the settings of safety valves on superheaters compare to those on drum safety valves?

1. Set the same

2. Set lower

3. Set higher

4. Do not exist

The correct answer is: Set lower

The settings of safety valves on superheaters are typically set lower than those on drum safety valves due to the different operating conditions and pressure scenarios they encounter. Superheaters are designed to increase the temperature of steam, thereby increasing thermal efficiency; however, they need extra protection against excessive pressure that could cause equipment failure or serious safety hazards. Since superheaters operate at higher temperatures but often face fluctuating pressure levels, the safety valve must be calibrated to relieve pressure at a lower threshold. This proactive approach helps prevent potential damage to components in a superheater system, which can be more sensitive compared to the drum, where safety valves are generally set to higher levels to manage a larger volume of water and steam under more stable pressure conditions. The distinct roles and operational parameters of superheaters and drums in a steam system necessitate these differences in safety valve settings to ensure safety and efficiency.