What is the lifting pressure tolerance for safety valves installed on 1200 psig boilers?

The lifting pressure tolerance for safety valves installed on 1200 psig boilers is plus or minus 10 psig. This tolerance is critical to ensure the safety and proper functioning of the boiler system. Safety valves are designed to release pressure when it exceeds a certain threshold, which prevents potential overpressure situations that could lead to catastrophic failures or explosions.

The specification of a tolerance of plus or minus 10 psig means that the actual lifting pressure of the safety valve can be slightly above or below the setting, within that range, while still conforming to safety standards. This ensures that the valves will operate effectively even with slight variations caused by manufacturing tolerances or environmental conditions.

A narrower tolerance, such as plus or minus 5 psig, might not accommodate the acceptable variations in pressure readings or potential wear and tear of the valve components over time. Similarly, broader tolerances of plus or minus 15 psig or plus or minus 20 psig would increase the risk of the safety valve failing to operate at the correct pressure, leading to safety hazards. Thus, the selection of plus or minus 10 psig as the tolerance strikes a balance between operational safety and realistic mechanical variations.