Water Expert Andy Ball: What is meant by scaling or fouling?

Fouling refers to the accumulation of unwanted material on solid surfaces, most often in an aquatic environment. The fouling material can consists of either living organisms (biofouling) or be a non-living substance (inorganic or organic). Other terms used in the literature to describe fouling include: deposit formation, encrustation, scaling, scale formation, crudding, and deposition. The last four terms are less inclusive than fouling; therefore, they should be used with caution.

Components subject to fouling

The following lists examples of components that may be subject of fouling and the direct effects of fouling:

heat exchanger surfaces – reduces thermal efficiency, increases temperature, creates corrosion, increases use of cooling water

piping, flow channels – reduces flow, increases pressure drop, increases energy expenditure, may create flow oscillations

ship hulls – increases fuel usage, reduces maximum speed

turbines – reduces efficiency, increases probability of failure

solar panels – decreases the electrical power generated

reverse osmosis membranes – reduces efficiency of water purification, increases pressure drop, increases energy expenditure

electrical heating elements – increases temperature of the element, increases corrosion, reduces lifespan

nuclear fuel in pressurized water reactors – axial offset anomaly

injection/spray nozzles (e.g., a nozzle spraying a fuel into a furnace) – incorrect amount injected, malformed jet, component inefficiency, component failure

venturi tubes, orifice plates – inaccurate or incorrect measurement of flow rate

pitot tubes in airplanes – inaccurate or incorrect indication of airplane speed

teeth – promotes tooth disease, decreases aesthetics