Power Generation — Boiler Series 3 

Part 3 of 4: Cooling Water In-Leakage to Condensate

Challenge: Identify Condensate Contamination Warning Signals

Condensate purity is essential to total boiler water treatment performance. Analysis of key condensate parameters helps identify and determine the nature of contaminant sources such as steam contamination, corrosion byproducts and in-leakage.

Unfortunately, cooling water in-leakage from the turbine condenser is a common source of condensate return contamination. Dissolved gases and lubricating oils enter through return pumps and pick up dissolved ions and suspended metal particles as corrosion by-products. To prevent these contaminants from entering the boiler, plants often use condensate polishers.

While condenser in-leakage can be detected with conductivity analysis, sodium analysis provides a better method due to its lower detection limit and rapid indication of problems. Sodium analyzers also may be used to monitor mixed-bed condensate polishers for exhaustion.

The most common contaminant in condensate return usually consists of iron or iron oxides. These potentially cause a number of boiler problems including under deposit corrosion, overheating, and blown tubes. Monitoring for excessive hardness, conductivity, and turbidity gives warnings of in-leakage through heat exchangers and condensers. Excessive sodium, phosphate or silica in condensate may indicate carryover problems or condenser leakage. Silica analyzers also indicate the efficiency and regeneration point of condensate polishing systems.