7.2.1 Fluorescein method
The steam side of the condenser is flooded to above the tubenest with a 10 mg/kg solution of the sodium salt of fluorescein. A search is carried out in the waterbox using ultra-violet light to detect traces of fluorescein. The tube which is leaking is therefore identified.
There are, however, disadvantages of this method:
- It is restricted to underslung condensers off-load.
- The reverse action of water pressure on the tubes compared with normal operation is known to close up the leak in some cases.
- The water pressure is low at the top of the condenser and small leaks may escape detection.
- Residual fluorescein can affect feedwater and boiler water analysis, and impair judgement as to whether repair of the leak was successful.
- This method requires an operator to carry it out.