COMMON mistakes and oversights that can cause system failures in boilers or water-cooling plants can be averted by putting in place a proper water treatment and regular maintenance plan.
Lionel Maasdorp, MD of Allmech, a leading South African manufacturer of boilers and supplier of water treatment components, says one of the most prevalent issues the company comes across is skimping on water pre-treatment or on ongoing maintenance. “Unfortunately, we often have cases where costs or downtime could have been reduced had a proper water treatment plan been implemented from the start,” he says.
Maasdorp explains that effective water treatment requires treatment both before and after introduction of water into the boiler or cooling tower. “The selection of pre-treatment option will depend on the quality of the source water, the chemical characteristics of the water, the quantity of make-up feed water required, plant operating practices, and so on,” he says. “Many companies skip water treatment, including pre-treatment, because they’re looking to minimise costs, but this might actually increase costs in the long run as it can affect the boiler or water-cooling tower’s efficiency (driving up energy usage and thereby costs) and ultimately significantly shorten its lifespan.”
The problems that water treatment aims to address
Anelia Hough, water treatment consultant at Allmech, explains that there are four common problems that can occur in boilers and cooling towers that affect how effect the system is: corrosion, fouling, biological contamination, and scaling.
“A total water treatment programme should address any impurities in the source water (pre-treatment), the water treatment itself (filtration and / or chemical treatment) and ongoing testing and maintenance,” she says. “Raw water sources are likely to contain amounts of suspended and dissolved impurities, depending on the source (whether it’s municipal, borehole, river or dam water), and the geographical area, among other things.”
In boiler operations, poor water quality results in poor quality steam, which is why pretreatment of feedwater is critical. The aim of this step is to remove impurities to control deposition, carryover, and corrosion in the boiler system, which affect the boiler’s effectiveness and, in the long run, can cause costly down time and unscheduled repairs.
In cooling towers, the treatment focus is on the water-replacing bleed, and evaporated and leaked water from the cooling tower. “If makeup water is not treated in cooling towers, we almost always see scale and corrosion taking place, which can drastically decrease the efficiency of the system,” says Hough.
Microbiological fouling is another concern. This is when organisms settle on the surface of the cooling tower. They secrete a polysaccharide layer for protection, which then collects silt from the water, thus growing thicker and further reducing heat transfer.
The next stage in the “water treatment life cycle” is what’s known as “after-treatment”. This involves adding chemicals to the water to ensure it is fit for a specific purpose. For example, Allmech offers a range of SANS 1827 food-grade chemicals for boilers, which are safe for food, beverage, pharmaceutical and agricultural uses. For cooling towers, the company supplies chemicals that act as scale and corrosion inhibitors (for open and closed systems), along with micro biocides, dispersants and cleaning agents.
A final important step
Beyond setting up the correct treatment systems and procedures, Maasdorp says that one of the most effective ways to ensure boiler or cooling tower health is to schedule regular maintenance checks.
“A comprehensive preventive maintenance programme not only keeps your boiler or cooling tower up and running reliably, but also ensures you get the maximum life span from your system,” he says. “It’s also a priority in ensuring the safety of your people” he concludes.
For more information, visit the Allmech website: www.allmech.co.za
