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Scale in Cooling Towers & Chillers: Types, Impacts, and Comprehensive Solutions

In cooling systems, scale is an invisible mineral that silently reduces efficiency, increases operating costs, and shortens equipment life. Understanding its types, causes, and solutions is a key step in protecting your investment.

What is Scale and How is it Formed?

Scale is a hard, dense layer formed from minerals dissolved in water that settle on metal surfaces (pipes, heat exchangers, fill) when water is heated or evaporated. The evaporation process in cooling towers concentrates these minerals beyond their saturation point, causing them to settle.

Main Causes of Scale Formation:

  1. High Mineral Content Make-up Water: Hard (high hardness) make-up water sources are the main cause.

  2. Excessively High Concentration Cycles: Prolonged water circulation without sufficient blowdown concentrates minerals.

  3. Uncontrolled Water pH: Excessively high (alkaline) pH promotes the precipitation of minerals such as calcium carbonate.

  4. High Operating Temperature: Heating accelerates chemical reactions and evaporation, which triggers precipitation.

Types of Scale, Problems, and Consequences

1. Calcium Carbonate (Lime) Scale - The Heat Inhibitor

  • Cause: Reaction between Calcium (Ca²⁺) ions, Bicarbonate (HCO₃⁻) ions, and heat.

  • Characteristics: White, grey, or yellowish in colour; very hard and chalky.

  • Problems & Consequences:

    • Decreased Heat Transfer Efficiency: Scale acts as an insulator. A scale thickness of just 1 mm can reduce heat transfer efficiency by up to 10% and significantly increase energy consumption.

    • Blockage: Narrows the flow of water in pipes and nozzles.

    • Under Deposit Corrosion: Becomes a hiding place and breeding ground for bacteria that accelerate corrosion underneath.

2. Silica Scale - Very Hard and Difficult to Clean

  • Cause: Silica (SiO₂) deposition that exceeds its solubility.

  • Characteristics: Very hard, like glass, and very difficult to remove mechanically or chemically.

  • Problems & Consequences:

    • High Resistance: Conventional chemical cleaning methods are often ineffective.

    • Surface Damage: Forced cleaning can scratch and damage metal surfaces.

    • Serious Problem in Chillers: Very dangerous for shell-and-tube heat exchangers.

3. Iron Scale - The Colour Giver

  • Cause: Oxidation and deposition of Iron (Fe) ions from corrosive water or from corrosion of the system components themselves.

  • Characteristics: Reddish brown or black in colour.

  • Problems & Consequences:

    • Promotes Corrosion: Iron deposits can form galvanic corrosion cells.

    • Contaminates Softener Resin: Causes fouling in ion exchange softener systems.

4. Other Scale:

  • Calcium Sulphate (Gypsum): Harder and more difficult to remove than calcium carbonate. Forms when sulphuric acid is overused for pH control.

  • Calcium Phosphate: Often forms due to the use of phosphate-based corrosion inhibitors in water with high hardness.

Comprehensive Scale Prevention and Treatment Solutions by PT. Jaya Sakti Internusa

Prevention is always better and cheaper than cure. JSI offers comprehensive solutions:

  1. Free Water Analysis & Assessment

  2. Our team will take water samples and analyse them in the lab to identify potential scale-forming substances (hardness, silica, iron, etc.).

  3. Customised Water Treatment Programme

    • Scale Inhibitor: A special chemical that works by distorting the crystal structure of minerals, preventing them from settling and keeping them dissolved in water.

    • Automatic pH Controller: Maintains the pH of the water at an optimal level (usually 7.5 - 8.5) to prevent calcium carbonate precipitation.

    • Blowdown Control: Helps automatically regulate the concentration cycle to prevent excessive mineral concentration.

  4. Supporting Equipment

    • Water Softener: Exchanges ions that cause hardness (Ca²⁺ and Mg²⁺) with Sodium ions (Na⁺), producing ‘soft’ and scale-free make-up water.

    • Side Stream Filter: Filters out fine particles that cause sludge before they become a problem.

  5. Chemical Cleaning Services

  6. For systems that are already encrusted with scale, BHL's team of experts provides safe and measured acid cleaning services to dissolve scale without damaging the base metal of your equipment.

Don't let scale reduce your efficiency.

Untreated scale is a silent waste of energy and money. Consult your water treatment issues with JSI experts. We provide the right solutions, not just sell chemicals.