Minnesota Boiler License Practice Exam 2025 - Free Boiler License Practice Questions and Study Guide

The question regarding the maximum psi allowed before the safety valves open pertains to the functioning and regulation of boiler safety systems. Safety valves are designed to relieve pressure when it reaches a predetermined limit to prevent over-pressurization, which could lead to equipment failure or explosions.

When safety valves are set at a certain pressure—12 psi in this case—they typically begin to open at that set point. The maximum allowable pressure before the safety valves will open is typically the set pressure itself. This means that as soon as the pressure reaches 12 psi, the valves will start to open to relieve any excess pressure and maintain safe operation.

If a pressure of 13 psi were allowed before the valves opened, this would indicate a failure in the safety system, as the purpose of the safety valve is to activate precisely at the set point (12 psi in this case) to avoid reaching potentially dangerous pressures.

Thus, the correct understanding of how safety valves operate dictates that the maximum allowable pressure before the valves would open is at or just below the set pressure, which means that pressures above the set limit (such as 13 psi) are unsafe. In this context, the maximum permitted pressure before the safety valve activation aligns with the set limit, reinforcing the significance of