High-Pressure Gate Valve Retrofit at a Central Asian Power Plant
Project Overview
The project implemented high-pressure gate valve and control valve retrofits on the main steam and feedwater systems of a Central Asian power plant, replacing aged main steam gate valves and adding feedwater pump minimum-flow control valves.
Challenge
The plant's units have been in service for many years. Main steam gate valves developed internal leakage and sticking after long high-temperature operation, and frequent start-stop and load-following caused thermal fatigue of the sealing faces. The feedwater pump minimum-flow recirculation loop suffered cavitation and noise. The retrofit also had to compress the outage window without affecting the generation plan.
Our Solution
Main steam gate valves were replaced with WC9 (F22) / F91 (C12) high-temperature materials and pressure-seal bonnets, with Trim 5 (Stellite 6 weld overlay) sealing faces resistant to high-temperature erosion. A multi-stage cage-guided control valve was added to the feedwater pump minimum-flow loop to suppress cavitation and noise; check valves were re-selected for closing characteristics to reduce water hammer; construction was cut over in stages under a modular plan, with third-party witnessing for pressure testing.
Results
After the retrofit, internal leakage and sticking in the main steam system were eliminated, and cavitation and noise in the feedwater pump loop were significantly reduced. Sealing faces and actuators performed correctly during unit start-up and shutdown. Outage time stayed within the planned window, and the project produced a reusable technical solution for power plant retrofits.