If no mechanical feed is attached to a boiler, what is the safety valve set pressure?

The safety valve set pressure is crucial for ensuring the safe operation of a boiler, particularly in the absence of a mechanical feedwater supply. In the context of boilers, the set pressure is the point at which the safety valve opens to release steam and prevent overpressure situations that could lead to catastrophic failures.

When no mechanical feed is present, there is a specific percentage of the boiler's maximum allowable working pressure that dictates the setting for the safety valve. This percentage is determined by safety engineering standards to ensure that the boiler can vent excess steam safely without risking pressure buildup.

In this case, setting the safety valve at 6% above the maximum allowable working pressure is recognized as a common standard, which ensures an adequate margin for safety and also allows for operational flexibility. Choosing this percentage allows the boiler to operate effectively under varying load conditions while ensuring safety.

This percentage provides a balance between efficiency and safety, which is why it is the correct choice in this situation.