How to prevent corrosion of the main unit and its accessories after the turbine is shut down
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Dear colleagues in the hydropower industry, I would like to ask how corrosion protection is carried out for the main unit and its accessories after the turbine is shut down.
If it is left unused for an extended period without maintenance, with the water inside drained, it is advisable to purge it; then close the upstream and downstream valves or use blind flanges for isolation, and finally fill it with nitrogen for protection. (1–2 kilograms of charge is sufficient; be sure to check the pressure regularly.)
Generally, what is the specific duration in days? And how is corrosion prevention achieved for other components such as bearings, control and safety systems, as well as coolers like condensers?
It’s fine to shut down for three to five days under normal circumstances; if it exceeds a week, it’s best to provide nitrogen protection. Bearings and adjustment systems normally operate using oil, so there is no need for special protection. But if conditions permit, the lubricating oil bearings of the oil pump can be activated; there’s no need to worry about the security system. If you are a turbine-driven centrifuge, starting the oil pump requires the compressor to supply seal air. Therefore, the lubrication system generally does not require protection. The gas-sealed condensation system can also be protected by filling it with nitrogen, just like a steam turbine
If the turbine stops operating, the oil system can no longer function; then how can other components such as bearings, control systems, and safety systems be protected from corrosion?
The oil system usually does not require attention; the bearings and control systems operate properly under lubrication. Even if the oil stops flowing, there will still be oil remaining in the bearing grooves, and a oil film will be present in the oil system. So there’s no need to consider it.