For many power plants, makeup water comes from a fresh water surface supply such as a lake or river, and more often than not, the levels of hardness ions (calcium and magnesium) and bicarbonate ions are very high.  Unlike familiar compounds like table salt or sugar, calcium carbonate becomes less soluble in water as the temperature rises.  So, as the cooling water warms, plating of calcium carbonate scale on to tube surfaces becomes a distinct possibility.  This was just the case for a large, Midwest nuclear power plant this summer, as calcium scale began to coat their 40,000+ stainless steel condenser tubes.  The plant became aware of the problem as unit efficiency began to plummet.

The plant attempted to remove the scale by various means including chemical treatment and mechanical cleaners, but was unable to effectively remove the scale that ranged in thickness from .012" to .035".  After contacting Conco for assistance, an action plan was developed to utilize Cal-Buster™ technology developed by Conco to remove the scale.   The Cal-Buster is a patented two-staged cleaner featuring carbide cutting wheels designed to fracture the crystalline eggshell-like surface of calcium carbonate scale.  Cal-Busters are custom built to match the tube dimensions and the thickness of scale found inside the tube.  Depending on scale thickness, one or more passes of various sizes of Cal-Buster may be required.  In this case, the job required two initial passes for the majority of the condenser's tubes with Cal-Busters sized .935" and .942", with additional passes for tubes along the tubesheet periphery, where thicker scale was seen using cleaners sized .925" and .915".  After cleaning operations ceased, 12 tons of scale had been removed from the water box and the condenser was returned to service.  It's estimated that a larger amount of scale had actually been removed, but much of the fractured scale had washed down the outlet drain during cleaning operations.

If your condenser is experiencing an issue with calcium scale or any efficiency robbing deposit, call Conco today for a no-nonsense solution!  1-800-345-3476 or info@concosystems.com