A comprehensive boiler maintenance programme not only keeps your boiler up and running reliably, but also ensures equipment longevity and improves safety for employees. However, many companies try to save costs on water treatment to reduce operating costs and meet production demands. While this can save money in the short term, it may have the opposite effect in the long run.
According to Lionel Maasdorp, MD at Allmech, leading South African manufacturer of boilers and supplier of water treatment components, a total water treatment programme will generally include monitoring sludge build up, checking pH levels, removing oxygen, treating condensate and maintaining correct alkalinity levels.
“The first aspect of stopping scale formation is to have a good idea of the makeup water that is feeding your system,” he advises. “Pre-softening the water before feeding it to the boiler is generally the first step in eliminating scale formation. Even if you have soft water, you’ll still need chemical scale inhibitors inside the boiler.”
Proper water treatment ensures there’s no efficiency lost and negates tube damage. It requires the right balance of chemical treatment and control.
“Taking the annual cost of water treatment chemicals and services on industrial boilers into account, it’s a small percentage of the cost of the equipment itself,” he says. “It makes sense to rather foot the bill for water treatment than risk lower production or even equipment failure in the long term.
“There are also other hidden costs of skimping on water treatment. For example, as a rule of thumb, one millimetre of scale build-up can increase fuel consumption by 2%. If you have 5mm of scale build-up on the boiler tubes, you might be paying an extra 10% on your monthly fuel bills.”
As an example, a coal-fired boiler producing 10 tonnes of steam a day would require (under normal conditions) 1.3 tonnes of coal per day. Over a period of a month, the normal requirement would be 28 tons of coal. Due to scale build-up, the operation now requires an extra 2.8 tonnes of coal for the same boiler performance. At an average cost of R1100 for a tonne of coal, the company spends an extra R40 000 for the year – just on extra fuel.
“The cost of removing scale from boilers is also high and results in longer inspection times, leading to loss of production,” says Lionel. “Over time, it affects the material integrity of the boiler.
“By maintaining the correct water treatment regime and by adhering to the basic principles of looking after your boiler and water treatment plant, the cost of the water treatment services and chemicals should be covered by your savings on downtime and cleaning the boiler. Of course, the major saving is the longer lifetime for your boiler, as that’s the biggest capital expense.”
Aside from scale, another issue that proper water treatment can mitigate against is boiler corrosion. This is caused by the interaction of water chemistry, the environment of the facility, operation procedures, and materials used in the construction of the system. Dissolved gases in the boiler, such as oxygen, carbon dioxide and ammonia, will aggravate corrosion.
“Oxygen is the most aggressive gas in a boiler,” adds Lionel. “Internal water treatment using chemicals in the feed water and raising the temperature are ways to remove oxygen in the water.”
Water treatment is also vital in ensuring correct pH levels are maintained (to avoid failure of safety equipment due to foaming).
“Improper and non-existent feed water treatment is a major cause of boiler failures, which ultimately results in boiler downtime and costly repairs. The better you maintain your boilers, the less energy they’ll need to operate, resulting in cost savings from lower energy consumption,” Lionel concludes.