What is the primary purpose of a vent on the open feedwater heater?

The primary purpose of a vent on the open feedwater heater is to remove oxygen and non-condensable gases. When steam is used to heat water in the feedwater heater, it is crucial to eliminate any dissolved gases, especially oxygen, as they can lead to corrosion in the boiler system. The vent allows these gases to escape, ensuring that the feedwater is of high quality and free from contaminants that could potentially damage the boiler components or reduce its efficiency.

Addressing the other options: Improving steam efficiency relates more to optimizing the thermodynamic processes rather than the direct function of the vent. Increasing water temperature is a result of the heating process but does not directly involve the venting function. Maintaining boiler pressure is essential for effective operation but is not the primary role of the vent on the open feedwater heater; rather, it is managed through other aspects of the boiler system.