A boiler cleaning and maintenance program is a good investment for any facility. Equipment such as boilers should never be neglected or pushed to the bottom of the to-do list. Boilers are one of the most complex — and potentially dangerous — systems within a facility or plant. Yet, with routine maintenance, boilers can stay healthy and operate efficiently for decades.
Boilers serve a specific purpose: to provide heated water or steam using the least amount of energy, for the lowest cost, with little to no downtime. Without regular service, boiler performance diminishes, efficiency falls and breakdowns become frequent.
Regarding boiler maintenance, boiler tubes are the most significant components — and the focus for cleaning tasks. All boilers have two sides that need to be cleaned. The first side is the fireside. It contains the combustion of gas, oil or other fuel, and that combustion can leave behind soot. The second side is the waterside. On the waterside, the water comes into contact with the tubes and absorbs the heat of combustion before being pumped through the pipes to provide heat or process steam. On the waterside, the tubes are subject to scale formation and other hard mineral deposits.
The most common reason for the loss of efficiency in boiler operations is buildup: the accumulation of soot on the fireside and limescale on the waterside of heat exchanger surfaces. Soot that adheres to the tubes is a byproduct of the combustion process. Limescale can occur on any equipment that uses water for heating and cooling.
Either can act as an insulation barrier on the heat transfer surfaces, reducing efficiency. Unfortunately, it does not take much buildup to start impacting the bottom line, and buildup can occur in as little as a few weeks. Once scale or soot forms on the boiler surfaces, the heat transfer is affected. The facility can begin to see a loss in efficiency and a rise in fuel costs.
An example related to managing scale deposits can help illustrate the potential effects of this buildup. Supposed a facility spends about $3.6 million per year in total fuel costs. The facility fails to properly clean the boiler tubes, resulting in an accumulation of 0.03125" of limescale on the waterside surfaces of the tubes. According to the U.S. Department of Energy, this limescale will increase energy costs by around 2 percent, resulting in an additional $72,000 in fuel costs throughout the year. Through proper cleaning and maintenance, this unnecessary increase in expenses could have been avoided.
Ignoring the presence of scale will only worsen the impact because the scale will be harder to clean, increasing efficiency loss. A boiler operating at proper efficiency can avoid costing a facility thousands of dollars extra on monthly utility bills.
Efficiency is not the only thing impacted by scale. When scale deposits are ignored and allowed to increase, it can cause under-deposit corrosion, which eats into the base of the metal. As time goes on, such corrosion can result in tube or equipment failures and even reduce the life of the equipment.
What to Know About Boiler Cleaning
The type of fuel burned affects the severity of firetube corrosion and fouling.
- Natural gas, propane and petroleum fuels such as gasoline or No. 2 diesel fuel produce lighter fouling that can be removed by brushes without the need for heavy scrapers.
- Boilers burning wood, medical or municipal waste, and petroleum fuels like No. 6 fuel oil have thicker fouling. The thick fouling requires a more powerful cleaning system with brushes and scraping tools.
As the benefits of boiler cleaning are now clear, here are six tips for boiler cleaning and maintenance:
- Stick to an inspection and maintenance schedule.
- Understand the chemical and mechanical cleaning options.
- Know your scale.
- Equip yourself effectively.
- Maintain daily logs.
- Perform visual inspections.
Schedule Inspections and Maintenance. Typically, it is recommended that a qualified staff member or a third party inspect and clean the boiler at least once a year. This interval may vary depending on specific operating conditions, water quality, hours of usage, and seasonality. If you notice a decrease in equipment performance or an increase in energy costs, you can conduct inspections and cleanings more frequently.
For seasonal units, boiler manufacturers recommend cleaning before and after the heating season. Whether you create a maintenance plan internally or work with an outside partner, having a schedule in place can help keep you on track.
Understand Chemical and Mechanical Cleaning Options. Many operators will notice a significant reduction in operating costs by removing the contaminants on both the waterside (scale formation) and the fireside (soot formation) of boilers. The method needed for cleaning differs depending on the thickness and type of deposits present. Typically, soot is removed effectively with a mechanical solution that includes a vacuum option. Limescale on the waterside is removed best through chemical cleaning methods. Chemical scale removal involves acid descalers to dissolve the minerals through a chemical reaction between the scale (primarily calcium carbonate) and the acidic liquid.
Know Your Scale. Not all scale is the same. While calcium carbonate is the most common type of scale, other elements such as iron oxide, silica and phosphates can develop. Understanding which type of scale is present in your equipment will help determine the proper solution.
Equip Yourself Effectively. Every facility and situation is different, so it is essential to make sure you have the tools to effectively and safely perform boiler cleaning. For soot removal, there are a variety of mechanical cleaning systems, brushes and scrapers. Nylon brushes are best for light deposits. Steel spring brushes and brass brushes provide extra strength for removing soot deposits in firetube boilers. Scraper tools offer more power for those jobs that require more than a brush.
For limescale removal, having a specialized pump and chemical system typically yields better results.
Maintain Daily Logs. By keeping a daily log, it will be easier to identify any significant changes or red flags. Monitoring data such as the type and amount of fuel used, flue gas temperature, makeup water volume, steam pressure, temperature and volume is recommended. If you notice reduced flow rates, increased energy consumption or a reduction in heat transfer, that is an indication that the equipment may not be operating correctly or at optimum performance.
Perform Visual Inspections. Looking at the boiler tubes and conducting a visual inspection to check for soot and limescale accumulation can be done on a more frequent basis to help ensure the boiler tubes are free of buildup. After maintenance, a video scope also can be used to determine whether all of the deposits were removed during the cleaning process.
In conclusion, boiler-cleaning technology has come a long way. While it used to be a time-consuming process of using long rods and brushes, newer equipment and systems have made it easier and faster. All facility maintenance personnel should be aware of the maintenance and cleaning schedule as well as how to use the cleaning system and tools to clean and sanitize equipment properly.
Maintenance and cleaning may not feel like a priority, but taking the time to regularly check your equipment and commit to preventive maintenance can help save on expenses and unexpected downtime throughout the year. The cost of descaling and tube cleaning is small when you consider the price and inconvenience of a major boiler repair.
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