If no Condensate Pumps are running, what system supplies seal water to the MFP?

The correct answer is the Demin Water System, which serves an essential role in supplying seal water to the Main Feedwater Pump (MFP) when condensate pumps are not operational. In many steam systems, maintaining the proper sealing and lubrication within pumps is critical to ensure efficiency and prevent wear. The demineralized water system is designed to provide highly purified water, free from minerals and contaminants that could harm sensitive equipment.

Using demineralized water as seal water is advantageous because it helps prevent the buildup of scale and corrosion within the pump and associated piping. In the absence of condensate pumps, relying on the demin water system guarantees that the seal water remains clean and effective under various operating conditions.

Other systems such as the cooling water system, backup water supply, or condensate return line may not provide the same level of purity or pressure required for effective seal water operation in the MFP, making the demineralized water system the most suitable choice in this scenario.