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Click here to download the complete technical paper in pdf format.

Abstract:

During 1982 a west coast utility unit was experiencing frequent condenser tube leaks in the inlet end of the seawater cooled condenser employing copper alloy tubes. These leaks were identified to be the result of inlet end erosion/corrosion. Based on measurements of statistically significant tube samples, high numbers of tube failures were projected for the near future. Three alternatives were evaluated to remedy the problem:

• Retube the condenser
• Install inlet end protective shields
• Epoxy coat the inlet end of the tubes

All tube samples pulled prior to 1982 had shown little or no erosion/corrosion in areas other than the inlet end after more than 14 years service. The same was also noted in other units at the station for up to 20 years service. Since the causes of the difficulties were isolated to a specific section of the condenser. It was expected that the inlet shield would be quite effective in eliminating the inlet end erosion problem without causing any harmful side effects on the tubes or tube sheet with properly maintained cathodic protection and ID tube cleanliness program.

Recently a tube specimen was removed during the 2004 maintenance outage to determine root cause failure of a leaky tube that was plugged prior to the outage. The leak was determined to be the result of through wall damage from steam impingement that had occurred near the exit end of the condenser tube. Inspection of the tube section that contained the sleeve insert confirmed that the inserts were performing as intended in 1982 projection in providing inlet end protection of the condenser tubes to allow for long-term restoration of the condenser tubes.

Click here to download the complete technical paper in pdf format.

Source: CTI Industries