Data centres use vast quantities of water as part of their function, and the quality of this water is very important. In the absence of quality control, water will corrode, scale and foster microbial development. To run at full efficiency data centre operators need to ensure that the water they use is within their quality parameters and that the plumbing is free of biofilm and corrosion. Proper water treatment systems are critical for data centres.
Here we look one of the biggest culprits that can negatively impact your data centre.
What is limescale?
Limescale is caused by a build-up of calcium and magnesium minerals in water. This ‘hard’ water is formed when rainwater filters through rocks like chalk and limestone, picking up minerals along the way. Hard water is the root cause of limescale and unfortunately 60% of the UK is supplied by hard water.
When it undergoes an energy change, which could mean inducing heat, pressure changes or changing state, the chemical equilibrium in the water shifts causing soluble calcium bicarbonate to become insoluble calcium carbonate (CaCO3) which is effectively precipitated out of the water binding to surfaces in a whiteish chalk-like substance called calcite.
How does limescale impact a data centre?
- Scale in pipes – Scale formation in pipes decrease bore diameter and create rough pipe inner surfaces. Both issues result in increased energy required by the circulation/booster pump; more energy (pressure) is needed to push water through tighter orifices and overcome increased frictional losses. In cases of spraying water onto a heat exchange surface to drive sensible heat rejection (generally known as adiabatic coolers), the spray nozzles, if blocked due to scale will reduce the efficiency of the heat exchange process.
- Scale in heat exchangers – Heat exchangers have conduits of many very narrow channels in which cooled water passes through, balancing the temperature of each medium on either side of the heat exchange surface. In a data centre application, this means rejecting heat from the data suites to maintain a desired temperature in the server racks. These narrow channels within the heat exchanger, if fouled with scale, will cause sections of the heat exchange surface to not be available to reject heat. In addition, scale acts as an insulator, it is estimated that every 1mm of scale decreases the ability to transfer heat by 7-10%. In a data centre where a significant percentage of the site’s total energy use is used to cool the servers, increases of just a few percent in energy consumption can translate to a huge hike in operational financial expenditure.
- Micro-organisms – Bacteria found within water circuits, especially those used in heat exchange applications such as cooling towers and adiabatic coolers, thrive due to the warmer temperatures at which these ‘open water circuits’ operate at. Heat exchange open water circuits generate sprays and are therefore deemed as a high risk for the transference of legionella pneumophila, which is responsible for most cases of legionnaires disease.
Mitigation of this biological load is achieved by introducing either biocides, utilising ultraviolet light or including other technologies designed to kill, deactivate or reduce micro-organisms. Scale deposits can be a dangerous breeding ground for bacteria. They provide nutrients which help them grow and offer a rough, uneven surface for the bacteria to attach to and form biofilms which, after a short period of time, are difficult to remove. Biofilms allow the bacteria to multiply, increasing the risk of transference of the bacteria to different areas of the circuit which can lead to microbial induced corrosion (MIC) and in worse case scenarios be carried on escaped water vapour for miles.
- Reverse Osmosis – Scale formation on membrane surfaces reduce the ability of the water to transition to the permeate side of the membrane. This decreases the permeate flow rate, increasing the volume of water sent to drain as concentrate and the energy required to maintain the desired output flow rate.
How Purite water solutions can help prevent these issues in your data centre
By replacing the calcium and magnesium ions with sodium using an Ion Exchange Process prevents scale forming minerals being released into the process water circuit. This ‘water softening’ is a globally accepted process for preventing water system issues and allows the data centre to maintain energy efficiency at day 1 design characteristics.
Purite’s range of Ion exchange water softeners can tackle flow rates from a few litres per hour to 100’s m3/h using configurations of either simplex, duplex, triplex or even quadruplex vessels to offer dependability and resilience for mission critical water systems.
With options of stand-alone or skid mounted prefabricated ‘plug and play’ solutions backed up with CAD models, Purite provides the contractor and end user with simple and hassle-free integration of key plant reducing stress on delivery programs.
Apart from the inherent positives of maintaining a limescale free water circuit, our water softeners use water meters for measuring the volume throughput. The water softener counts the capacity which is calculated during start-up based on the hardness level of the feed water. It then initiates regenerations as required therefore minimising the water used ensuring efficient water consumption and contributing to the decarbonisation effort data centres are facing.
Find out more about our technologies and technical solutions for data centres.
