BSEE
Here, Glen Peters, Technical Support Manager at Viega discusses the importance of ensuring building service systems are not only installed and commissioned correctly but also maintained appropriately to prevent contaminaon, corrosion and replacement of pipework.
maintenance. While the system may be designed, installed and commissioned correctly, if it is not maintained and monitored on a regular basis it can leave the system vulnerable to contamination and corrosion. One of the most common issues that engineers may encounter is incorrectly specified pipework with low pressures. This is often the result of the pipe being oversized as the supply pressure cannot be sufficiently maintained within the larger pipe. One possible source of drinking water contamination is backflow of fluids drawn into drinking-water systems from other pipework or outlets. This can occur as a result of high pressure within equipment attached to the pipework or inadequate pressure in the system as a whole. A low flow rate can also be caused by pipework that is too small and restricts the amount of water that can be supplied. Therefore, when installing new or replacement pipework, ensuring optimum system pressure and flow velocity will prevent stagnation and
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contamination of the system later on. Stagnant water in the system provides an ideal environment for bacteria and is one of the most common causes of contamination because it provides an environment in which bacteria such as Legionella Pneumophila can grow. Considerate system designs can help ensure that the layout does not allow water to stagnate and that the pipe is sized correctly to help maintain pressure
hen working with heating systems, hot and cold water, and potable water pipework, issues
can arise due to poor
MAINTENANCE & REFURBISHMENT Ensuring the correct solution
and flow. However, the usage patterns of the building must also be considered, as interruptions to the norm will also cause stagnation. For example, certain types of buildings, such as those on school, college or university campuses, will be used with high frequency during term time but will often be left unattended for weeks at a time during holidays. Similarly, second homes, seasonal hotels and office buildings may have rooms, areas or even floors that are left unoccupied for extended periods. To prevent stagnation and the build-up of bacteria during this time, a plan should be in place to flush the system. Automatic and manually activated flushing systems are available that simplify the process in buildings that will regularly be unoccupied. Alternatively, pipework can be manually flushed by opening each outlet to refresh the water. Another element to consider regarding bacterial contamination is temperature. It is important that the temperature of water in the pipework is not allowed to rise or fall excessively, as this can also promote the growth of bacteria. Legionella bacteria breed most effectively between 25°C and 45°C and although hot water may be heated and stored above the recommended 50°C, the temperature at the outlets on the highest floor or furthest sections of the building could be lower. Similarly, as cold-water travels through the pipework there is a possibility that the temperature will rise, particularly when the route is next to sources of heat. Therefore, ensuring the correct level of insulation is installed and maintained is vital – not only to maximise energy efficiency but to protect the quality of the water. Insulation that has not been fitted during the installation can be retrofitted as part of system maintenance to help maintain water quality.
When adding new equipment to the system, engineers should keep in mind that bacteria can be introduced early in the supply chain – including during the manufacturing process. Any water left in the product after wet leakage tests in the factory will encourage the growth of micro- organisms during storage.
Water pipework is also vulnerable to corrosion, which is often due to the level of dissolved oxygen present in most systems. While it is possible to deoxygenate water, for most applications this is a very expensive and impractical solution. However, there are steps that can be taken to extend the lifespan of the pipework. For example, on large projects, where it’s possible for there to be a long period of time between the installation of the pipework and the building being used, it is preferable to perform dry leakage testing with dry clean air or inert gas rather than water. Once the system is filled it is recommended that draining the system is avoided wherever possible as this inevitably exposes the pipework to much higher levels of oxygen. As soon as oxygen comes into contact with water on the surface of base metals, corrosion is likely to occur. If it becomes necessary to drain the system, the work should be planned to limit the amount of time it is left before being refilled.
Where remedial work and repairs have to be made, press connection technology has a number of benefits. Press connection technology is significantly faster than traditional methods, as the connectors can be pressed in a matter of seconds and are permanently secure. What’s more, because there are no hot works, it is much safer – removing the risk of fire and the need for fire prevention measures.
Finally, it is highly recommended to establish a regular chemical maintenance schedule to ensure the systems continue to function as intended. Heating systems should be dosed with a with a high-quality chemical inhibitor that prevents the accumulation of sludge and protects the metal in the system from corrosion and possible limescale build up. The concentration of these chemicals in the water can deplete over time so this must be checked as part of the maintenance cycle. Ensuring the levels of inhibitor in the system will not only protect the pipework from corrosion and to maintain operating efficiency, but will also protect the boilers, pumps and other equipment from the damaging effects of sludge. The installation and maintenance of pipework for large buildings plays a key role in the longevity of the system. By securing a regular maintenance schedule, engineers will reduce the need for expensive and time-consuming remedial work later on and will also ensure that the system will perform to the highest possible standard.
To find out more about Viega’s range of precision engineered press connection systems for heating, water and gas applications visit the website.
www.viega.co.uk
14 BUILDING SERVICES & ENVIRONMENTAL ENGINEER DECEMBER 2020
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