Describe the role of an economizer in a boiler system.

An economizer plays a crucial role in increasing the overall efficiency of a boiler system by preheating the incoming feedwater. By utilizing waste heat from the flue gases before they exit the boiler, the economizer raises the temperature of the feedwater, which reduces the energy needed to bring the water up to a boil. This process not only minimizes fuel consumption but also enhances the boiler's thermal efficiency. By taking advantage of the heat that would otherwise be lost, the economizer contributes to more sustainable operation.

In the context of other choices, measuring pressure and adjusting temperature are functions related to gauges and control systems, not directly tied to the economizer's function. A safety relief mechanism serves a different purpose, focusing on protecting the system from overpressure scenarios rather than improving efficiency through heat recovery. Thus, the economizer's role in preheating feedwater distinguishes it as an essential component for optimizing boiler performance.