What is one of the requirements for the sources of feedwater for certain boilers?

One of the requirements for the sources of feedwater for certain boilers is that one must be a pump or injector. This is important because boilers require a consistent and reliable supply of feedwater to maintain safe operating pressures and to ensure efficient steam generation.

In systems where feedwater is critical for operation, having a pump or injector serves as a mechanical means to deliver water into the boiler. This allows for precise control over the feedwater flow and pressure, which is vital for the operational stability of the boiler. While other options might imply alternative methods or configurations, the requirement for at least one source to be a pump or injector ensures that the boiler can function effectively under varying operational conditions, thereby enhancing reliability and safety.

Therefore, it is essential for compliance with safety regulations and best practices in boiler operation that one of the feedwater sources involves a mechanical feeding method like a pump or injector.