Cooling tower scale forms when dissolved species exceed their solubility and precipitate on surfaces. Heat-transfer areas are especially vulnerable because temperature and local concentration can differ from bulk water conditions.
Common drivers
- High cycles of concentration: evaporation concentrates hardness, alkalinity, silica and other ions.
- High pH: can increase calcium carbonate scaling tendency.
- High surface temperature: changes solubility and promotes deposition on heat exchangers.
- Loss of inhibitor feed: pump failure, empty chemical tank or blocked injection line can remove protection quickly.
- Poor blowdown control: conductivity rises beyond the intended limit.
- Suspended solids: can act as nucleation sites and form mixed deposits.
Identify the deposit before changing the program
Not every white or hard deposit is calcium carbonate. Silica, calcium sulfate, iron corrosion products and process contamination can look similar. Deposit analysis can prevent the wrong corrective action.
Check the water balance
Compare current make-up chemistry, circulating chemistry, COC and blowdown rate with the original design basis. A change in water source or seasonal quality can make an old treatment target unsuitable.
Review chemical delivery
Confirm dosing pump output, calibration, tank level, suction condition and injection point. A controller may show “on” while the pump is not actually delivering the expected volume.
Corrective action
The response may include reducing cycles temporarily, restoring chemical feed, improving filtration or cleaning deposits using an approved procedure. Avoid aggressive cleaning without understanding metallurgy and deposit chemistry.
A good troubleshooting sequence is: identify the deposit → verify water chemistry → verify mechanical control → verify chemical feed → correct root cause.