What percentage of pressure indicates when a safety valve will lift completely?

A safety valve is designed to lift and relieve pressure from a boiler when the pressure reaches a certain level above the set operating pressure. The correct response indicates that the safety valve will lift completely at 3% overpressure. This standard is crucial for ensuring that boilers function safely and efficiently, providing an essential margin for pressure relief.

When the pressure in the boiler rises to 103% of the maximum allowable working pressure (MAWP), the safety mechanism within the valve is activated fully to prevent any risk of overpressure that could lead to hazardous conditions. A complete lift ensures that the valve remains effective in its primary function: to release excess steam or water vapor and prevent structural failure or explosions.

Understanding this operational threshold is critical for boiler operators, as it directly influences safety protocols and the overall operation of steam systems. Proper maintenance and testing of safety valves at this percentage ensure they are functioning correctly and will provide proper relief at the necessary moment.