Cleaning generator cooling systems

copper oxidation phenomenon

If the optimal chemical parameters of the stator winding cooling water are not met, the oxygen in the water reacts with the copper. The optimal operating parameters for copper cooling systems are dissolved oxygen contents below 50 ppb or above 2 ppm. In these ranges, the transition of copper ions into solution occurs slowly and poses no hazards. On the other hand, in the 200-500 ppb range, corrosion processes proceed relatively quickly and amplify the risk of sediment deposition.

A similar problem of unwanted oxidation can occur during generator shutdown when improperly protected channels are exposed to atmospheric oxygen.

clogging of cooling channels

The hollow ducts inside the rod are very narrow, usually 1 mm high and 5 mm wide. Two types of oxides-copper and copper-are formed in equilibrium in oxidation processes, mainly depending on the oxygen concentration present. These oxides dissolve, migrate and re-deposit (preferably in a demineralizer), regardless of which oxide is formed. Over time and depending on the chemistry of the water, the oxides can begin to clog the copper hollow tubes in the generator.

As a direct consequence of the reduction in coolant flow, the operating temperature of the winding bars will increase, and the generator’s output will need to be reduced. In extreme cases, an emergency shutdown of the generator will be necessary to remove the cause of excessive heating of the generator stator winding.

generator cooling system cleaning technology

With our advanced cleaning method, we can non-destructively remove copper oxides from the system and restore full cooling performance of the cooling water system.

Cleaning with complexing compounds removes copper oxides without damaging system materials. The method includes dedicated monitoring of process parameters, tailored addition of chelating agent and oxidant, and proprietary auxiliary agents. The proposed technology can be used as part of a planned generator outage. Preventive maintenance cleaning can save the plant from a possible forced shutdown.

cleaning of generator cooling systems – benefits of the service

• The technology used and the concentration of chemicals are safe for winding copper.
• Little interference with the demineralized water system during the flushing process.
• The entire process is performed in accordance with safety standards, with constant supervision by experienced personnel.
• Flushing effects (i.e., decrease in winding temperature, improvement of medium flow through the winding) visible immediately after the process is completed.
• Reduction in operating costs and risk of failure.

It is good practice to observe the condition of the cooling water system by monitoring key parameters such as winding temperature, cooling water differential pressure, and O2 content of the generator stator winding cooling water. It is also recommended to include winding flushing during scheduled maintenance/repairs.