What pressure must each feedwater source be capable of supplying to the boiler?

For a feedwater source to effectively supply water to a boiler, it must maintain a pressure that exceeds the pressure thresholds set by the safety valves. The rationale behind this requirement is to ensure safe and reliable operation of the boiler system.

When the feedwater source delivers pressure that is at least 3% higher than the highest set safety valve pressure, it guarantees that water flows into the boiler under sufficient pressure to counter any potential back pressure that could occur when the boiler is operating. This is essential for maintaining proper water levels and preventing issues such as overheating or maintain steam quality.

If the feedwater were to be supplied at a lower pressure, especially below the safety valve pressure, it could lead to operational failures or unsafe conditions, as the boiler may not receive adequate water to maintain steam production.

The other options do not offer the same level of assurance for safe operation. For instance, simply matching the safety valve pressure may not account for fluctuations and pressure drops that can occur during operation. Similarly, a pressure 2% higher than the lowest safety valve does not provide the necessary margin above the highest valve setting, compromising safety. Lastly, equal to the maximum boiler capacity does not consider the operational dynamics and pressure relationships within the system.

Thus, ensuring that