Which factor is essential to check during MFP pre-start procedures?

During the pre-start procedures for a Main Feedwater Pump (MFP), one of the most critical factors to check is the seal water lineup. The seal water system is vital for maintaining the integrity of the pump's mechanical seals, which prevent leaks and protect the pump from damage. Proper seal water lineup ensures that there is an adequate supply of water to cool and lubricate the seals, thereby preventing overheating and wear. If the seal water system is not correctly aligned or functioning, it could lead to seal failure, which may result in pump damage and operational issues.

Although other factors like environmental temperature, load demand, and electrical supply voltage are important in general operations, they do not have the direct and immediate implication for the safe and effective startup of the pump as the seal water lineup does. Ensuring that the mechanical seals operate properly by verifying the seal water lineup is essential for the successful and safe operation of the MFP.