It is essential that a good water treatment regime is employed (BSRIA Guidelines), particularly on closed circuit systems, to ensure effective management of that system (BSRIA BG50:2013).
The water in such systems if left untreated can cause a number of problems leading to increased risks to safety and health, reduced efficiency and the lifespan (sustainability) of the system itself.
Unwanted growth of harmful bacteria and biofilm, the accumulation of scale (hardness salts), metallic corrosion and the build-up of suspended solids can all contribute to failures of the system of some form.
The correct treatment of such system water is therefore vital if these issues are to be effectively managed.
Open and closed recirculating systems can be either heating (LTHW, MTHW & HTHW) or cooling (chilled water and condensed water). They typically rely on water or water based solutions as their heat transfer fluid.
Water is used due to its high specific heat capacity which makes it highly efficient to transport energy as either LTHW or CHW. However, problems can arise because the metals used in most systems are readily corroded in the presence of water and oxygen.
If the system is new it should be chemically cleaned prior to the start of the corrosion treatment program. Chemical cleaning removes oil, mill scale, dirt welding fluxes and other contaminants that can interfere with the performance of treatment chemicals. Chemical cleaning is also recommended for older systems that suffer from corrosion.
In water systems there are two basic ways to prevent corrosion of unprotected metal surfaces:
Inhibitors often work by reacting with or forming a layer of film onto the metallic surface, protecting it from corrosion. There are many forms of inhibitors which are classified according to their various properties and functionality such as; cathodic, precipitation, organic or volatile corrosion inhibitors (VCIs or VPIs).
In a multi-metal system the corrosion inhibitor selected should contain a blend of inhibitors that will offer protection for each metal. In addition to the primary corrosion inhibitors additional agents are also required to buffer and control the PH levels.
In general the selection of one treatment method over another is normally determined by the incoming water quality.
Overall it is hugely important to demonstrate that a heating or chilled water system has been adequately cleaned and the quality of its water is under control. The following should be referenced:
Primary Water Group Ltd are a Pegler Yorkshire approved water treatment service provider. By using Primary Water Group Ltd our customers can have peace of mind when treating and commissioning of water systems.
The service provides the long term system protection by ensuring all technical requirements are addressed and considered before the system is cleaned. Pegler Yorkshire will provide schedules and specifications that cover the scope of works and advise the best solution to deliver a complete and safe system.
Additional information available from BSRIA: www.bsria.co.uk/news/article/water-treatment-for-closed-heating-and-cooling-systems/