What is boiler water carryover and what causes it?

• A. Condensation of steam in the economizer.
• B. Entrained boiler water solids in steam due to high TDS, high pressure/level, or improper water chemistry.
• C. Leakage in feedwater pump seals.
• D. Excessive flue gas temperature.

Answer: (B)

Boiler water carryover is the phenomenon where water droplets from the boiler, along with dissolved solids, are entrained in the steam that leaves the boiler. This happens when the water in the boiler becomes foamy or when liquid water is sheared off by the rising steam, so the steam isn’t clean or dry as it leaves the drum.

The main causes are high total dissolved solids (TDS) in the boiler water, high steam pressure (which increases steam velocity and entrainment), and improper water chemistry that promotes foaming or priming. When TDS is elevated, solids can stabilize foamy, unstable water surfaces; high pressure and level can physically push more water droplets into the steam; and poor chemistry can reduce surface tension control, making carryover more likely. The result is steam that contains moisture and solids, which can deposit in turbines and piping and cause damage.

Condensation of steam in the economizer describes moisture forming from cooling steam, not solids carried with steam, so it isn’t carryover. Leakage in feedwater pump seals involves loss of water rather than carryover into the steam. Excessive flue gas temperature affects heat transfer, not the presence of entrained boiler water solids in the steam.