Poor boiler water treatment is the primary cause of poor boiler performance, according to Chris Paterson, managing director of specialist operations and maintenance service provider to the steam and boiler sector, Associated Energy Services (AES). This is Part 2 of a two-part series.
AES operations director Ray Lund notes that the relationship between on-site boiler operators and water treatment companies forms a strong foundation for a watertight boiler water treatment strategy: “We partner with water treatment companies to train boiler operators in the importance – and practice – of testing feedwater daily. If any elements are out of specification, they raise that with the regional AES team, and we escalate this to our water treatment partners.”
At the beginning of the process, solids are removed via different forms of filtration. Plants with very high TDS might require the installation of a reverse osmosis (RO) plant which can be an effective energy-saver, as it requires fewer blow-downs of the boiler to clean it out.
“Typically, with municipal water supply, the TDS is low, so we proceed directly to a softener. However, there are some areas in the country where the water is very hard. We look at various technologies to identify the most cost-effective way in which to manage that over the long term,” says Lund.
PH control is always critical and must remain within the right parameters to facilitate the formation of a protective layer which protects the internal surfaces of the boiler.
Lund adds that oxygenates should also not be overlooked: “It is important to remove as much oxygen as possible before water goes into a boiler to prevent oxygen pitting – especially when boilers have economisers, as there will be oxygen left in the water, causing pitting corrosion and increasing the risk of equipment failures.”
Another consequence of poor water treatment is foaming: this results in liquids – rather than hot gas – being carried from the boiler into the steam piping network and flowing through the system, which can cause a condition known as ‘water hammer’. Pockets of water travel at the same velocity as the heated gas – potentially causing severe damage when reaching a pipe bend.
“This foaming also disrupts the measurement of water levels to the point where – despite indications that these are correct – there may be very little to no water in a boiler, causing it to overheat or even to explode,” he explains.
The last resort: tipping the ‘scales’
According to Lund, when scale has built up to the point where the equipment is at risk and efficiencies are compromised, clients have two options – using an on-line descalant – or a difficult and expensive off-line acid wash, which essentially “pickles the boiler”.
In this instance – in addition to lost production time – as it can take up to four days to acid wash a boiler: the cost of the chemicals, as well as neutralising and disposing of the resulting acid effluent can have a very negative financial impact. Boilers requiring repairs after this acid wash process will further add to the overall cost.
“Years of poor boiler water treatment can really add up, with negative operational and financial consequences. With this in mind – and aligned with our performance guarantee to clients, we do as much as we can to ensure that all AES clients are aware of potential water quality concerns and the related risks, allowing for timeous preventative action to be taken if required,” Paterson concludes.
Source: AES