How Dosing Ratios Affect the Cost of Chemical Use Over Time

Operational managers want to get the best value possible from their maintenance supplies. When it comes to steam boiler chemicals and other water treatment solutions, it might seem like the best value is based on the price per kilogram or litre of a can of chemicals. However, this is not always accurate because how long chemical supplies last, and their ultimate cost, also depends on the recommended dosing ratio.

Anelia Hough, water treatment consultant at Allmech, leading South African manufacturer of boilers and supplier of water treatment components, says it’s a mistake to only focus on the immediate price per can of chemicals and to not consider the cost of the chemicals over time. “The cost of chemicals for a boiler over time depends on several factors, such as the type of boiler, the type of chemicals used, the frequency of use, and the amount of chemicals used (dosing rate per kilogram of steam),” she says.

Chemicals used for steam boilers include oxygen scavengers, phosphates, polymers and alkalinity builders/pH boosters. The cost of these chemicals varies depending on the quality, the type of chemical and the amount used. Effective chemical water treatment should prevent scale and corrosion in the feedwater, and steam condensation in the system and boiler.

The correct dosing ratio is important for several reasons. First, it ensures that the chemicals are being used effectively and efficiently. Using too little of a chemical can result in poor water quality and increased maintenance costs. In the same way, using too much of a chemical can result in over-treatment and increased operating costs.

Second, dosing ratios have a direct impact on the monthly running cost of a boiler. A chemical may be more expensive per can, but if it has a lower dosing ratio than an equivalent-sized can that requires more of the chemical per litre to work effectively, the more expensive can is actually the cheaper option once the running costs are factored in.

Label guidanceChemicals legally have to include their dosing information on their packaging, and using this information correctly is a key part of managing the overall cost of a particular chemical.

In an economic climate where everyone is having to carefully balance costs, it may not necessarily pay in the long term to buy what seems to be a lower priced can of chemicals – especially when the dosing rate is factored in.

Looking at the bigger picture“It is important to note that the cost of chemicals is just one aspect to consider when assessing the costs of boiler maintenance. Other factors include enhanced operational performance, lower total operating costs, reducing the risk for downtime/technical issues, labour costs, equipment costs, downtime cost and energy costs,” adds Hough.

Allmech recently helped a holiday resort that was struggling to get the right pH levels in the boilers heating its pool water and that had installed a demineralisation plant that it ultimately did not need.

“The customer operates two different size boilers for its operations. An 8-ton steam boiler for summer and a 10-ton steam boiler for winter. In essence, hot water is supplied to two sections of the holiday resort via heat exchangers – the open big pools and the indoor hot pools – that need a constant temperature of between 26 and 28°C,” says Hough.

After assessing the setup, it was clear that the incorrect chemical water treatment was being used for the boilers. By solving the treatment issue, it became clear that the expensive-to-operate demineralisation plant was no longer necessary. In fact, the plant had been hindering the system by reducing the pH levels to concerningly low levels. Eliminating the need for the demineralisation plant and getting the right quality chemicals at the correct dosing rate for the boilers’ maintenance saved the resort around R90 000 and over 171 000 litres of water each month.