What is Calcium Scale or Limescale?
Limescale (or Calcium Scale) is a hard, off-white chalky substance often found on the metallic parts of water-operated machinery. It is particularly common in machinery and equipment that involves heating elements (such as boilers) or heat transfer elements (such as heat exchangers).
Limescale is also found in metal pipes, pumps, filters and other water equipment to varying degrees, depending on water quality.
The build up of this scale, over time, can severely interfere with efficiency and reliability of machinery, pipework and processes leading to decreased efficiency and costly failures.
Where does Limescale come from?
Limescale deposits (often referred to simply as “scale”) are caused by small amounts of naturally occurring minerals, which are present in most tap water supplies. Under certain conditions these minerals form deposits of Calcium Carbonate, Magnesium Hydroxide and Calcium Sulphate on metal surfaces, particularly when heat is applied.
Water containing higher concentrations of these minerals is known as “hard water” and it is the main factor in determining how much scale is produced.
Hard Water in Australia
Hard water in Australia varies greatly from region to region. Measured in parts-per-million the Australian Water Association has detected ranges of 10ppm to 148ppm across the capital cities.
- Melbourne: 10-26ppm
- Canberra: 40ppm
- Darwin: 31ppm
- Hobart: 5.8-34.4ppm
- Brisbane: 100ppm
- Perth: 29-226ppm
- Adelaide: 134-148ppm
Water hardness can easily be measured with equipment ranging from inexpensive test strips to more expensive digital equipment.
Commercial Impacts of Limescale
Limescale build-up inside machinery and water equipment slowly but surely interferes with proper performance. Because performance degradation can occur slowly these changes often go unnoticed leading to long term losses of efficiency that persist for long periods.
Limescale build-up on heat transfer surfaces acts as an insulator, reducing the effectiveness of heat transfer. In heating applications this can result in increased energy usage and load on heating elements. In cooling operations equipment may experience increased thermal stress due to ineffective cooling, leading to reduced efficiency and increased failure rates.
Pipes and pumps affected by limescale experience decreased throughput as the scale build up narrows critical apertures. Over time limescale can restrict even large diameter pipes to a mere trickle and, in some cases, completely block flow.