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, a South African manufacturer of boilers and supplier of water treatment components, a total water treatment programme should pursue the following goals:
- Maintenance of free caustic corrosion potential
- Minimise caustic deposit formation due to scale and suspended solids by chelation and sludge conditioners, so that blowdown will remove potential problems
- Eliminate oxygen content through de-aeration or other mechanical means
- Prevent carryover and foaming
- Promote the effective use of fuels
He adds that a complete 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 says. “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.
“If one considers that the annual cost of water treatment chemicals and services on industrial boilers, 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 tons of steam a day would require (under normal conditions) 1.3 tons of coal per day. Over a period of a month, the normal requirement would be 28 tons of coal. Due to the scale build-up the operation now requires an extra 2.8 tons of coal for the same boiler performance. At average cost of R1 100 / ton 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 Maasdorp. “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 the 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,” says Maasdorp. “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 sue 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,” concludes Maasdorp.
- For more information, visit www.allmech.co.za.
