If a boiler designed for 125 psi is now operating at 15 psi, what must be done regarding the safety valve?

When a boiler designed for a higher pressure, such as 125 psi, is operating at significantly lower pressure, like 15 psi, the existing safety valve may not operate correctly if it is designed for the higher pressure. It's important for a safety valve to have a set pressure that corresponds to the operating range of the boiler to ensure proper safety and function.

Installing a safety valve with a larger disk and a lower pressure rating is necessary because the valve needs to open at the lower pressure to protect the system effectively during overpressure situations. A safety valve set for the higher pressure may not open at 15 psi, which could lead to dangerous situations if there were to be an increase in pressure.

Therefore, this option ensures that the safety valve will function properly within the operating parameters of the boiler, keeping the system safe and compliant with safety regulations.