Pipe System Flushing
As a pre-commissioning activity, hydronic pipework flushing can be defined as the act of pumping water, in sufficient quantity and velocity, through a given section of pipe or piping.
These HVAC piping systems include chilled water piping, condenser water piping, high temperature hot water (HTHW) piping, and primary / secondary heating water piping, etc.
The treatment of water in modern closed heating and cooling systems is essential for the avoidance of microbiological fouling (bio-fouling), corrosion and scale. These problems can result in energy wastage, poor system performance, and the need for early replacement of plant and components. The consequences of inappropriate or non-existent water treatment can sometimes be disastrous.
System contaminants such as mill scale, jointing compound and building debris will inevitably be found in newly-fabricated heating and cooling pipework systems. If allowed to remain in the system in sufficient quality, these contaminants will make the system prone to blockage at strainers, control valves and small bore heat exchangers. They may also initiate further corrosion and encourage the growth of micro-organisms.
The process starts with terminal units and plant items isolated, by filling a section of pipe or piping at required test pressure with biocide dosed water, such that the flow of water through the system will forcibly remove any loose rust, mill scale or construction debris from the system.
Pre-commission cleaning is achieved through a process of flushing and chemical cleaning (where required) followed by the addition of biocides and inhibitors. Since it is not possible to directly examine all the internal surfaces of the system, the success of pre-commission cleaning is inferred from water samples that are analysed for a range of parameters including, but not limited to, suspended solids, iron and bacteria.
All completed test reports will be submitted to the contractor or client who in turn will submit to the design engineer. Defects or potential issues will be raised throughout the process and then again highlighted within the reporting structure.
