At what percentage of nominal working pressure should the relief valve be set?

The proper setting for a relief valve is typically at 175% of the nominal working pressure. This setting ensures that the system is protected from excessive pressure that could lead to damaging leaks, explosions, or failures. By setting the relief valve higher than the nominal working pressure, it allows the system to operate safely under normal conditions while providing a safeguard if pressure unexpectedly increases beyond the normal operating range. The relief valve will open and release pressure if it reaches this higher threshold, preventing potential damage to the system components.

The other percentages listed do not align with standard practice for relief valve settings, as they either risk failure to protect the system at lower operating pressures or may cause unnecessary frequent activation of the relief valve. Thus, the 175% setting strikes a balance between allowing normal function and ensuring safety in case of pressure spikes.