Can boiler maintenance impact your bottom line? You bet it can. When a boiler is operating at optimum efficiency, it can help save thousands of dollars on a facility’s energy costs. Sounds great, but how can you make sure that happens?
Energy efficiency in a boiler really centers on keeping the boiler clean and free of scale and soot. The boiler is one of the most complex systems in the facility — and also one of the most dangerous. It is important to incorporate boiler cleaning into the maintenance plan.
Boiler cleaning is not always top of mind and, if everything appears to be working properly, routine maintenance may fall to the wayside. However, putting off a total cleaning until performance starts to suffer means fuel and efficiency losses quickly build. Out of sight should not mean out of mind. Being proactive rather than reactive when it comes to maintenance yields benefits such as reducing downtime costs, saving energy, identifying recurring problems and extending the life of the boiler.
Firetube boiler cleaning systems can be compact, portable and easy to use. With some systems, one operator can thoroughly clean a boiler in less time than is required by other cleaning methods simply by flipping a switch.
Scale and soot buildup causes equipment to run harder to maintain the same output. Once scale forms on boiler surfaces, both fuel and efficiency losses quickly ramp up. According to the Department of Energy, even normal scale (1/32” thickness) produced by low pressure applications leads to a 2 percent fuel loss. In high pressure applications, the resulting iron plus silica deposits can result in fuel losses of up to 7 percent. And, while 2 percent may not sound like much, the Environmental Protection Agency offers a helpful example: A firetube boiler using 450,000 million BTU of fuel (at $8 per million BTU), run 8,000 hours per year, with 1/32” of normal scale, means a yearly operating cost spike of more than $70,000.
Scale develops naturally, and it is inevitable that it is going to end up in the equipment. It does not take much to start impacting the efficiency of the equipment, which in turn adds to operating expenses. The primary concern is the heat transfer surfaces where scale builds up. The scale creates a layer that affects heat transfer and increases power usage, diminishing the effectiveness of the entire system.
As noted by research from North Carolina State University, the reduced heat conductivity of scale leads to big problems. If left untreated, 0.5” thick scale can lead to a 70 percent increase in fuel usage and significantly reduce overall boiler efficiency. In other words, it does not take a lot of scaling to equal big problems and unnecessary expenses.
Reduced heat conductivity of scale leads to big problems: If left untreated, 0.5” thick scale can lead to a 70 percent increase in fuel usage and significantly reduce overall boiler efficiency. Preventive maintenance is the best way to get ahead of scale buildup.
While it may seem easy to push boiler maintenance to the bottom of the to-do list, preventive maintenance is the best way to get ahead of scale buildup. An ideal time to perform the boiler maintenance and cleaning is during the summer months when the boilers are shut down.
There are two types of tubular boilers: firetube and watertube. In the watertube boiler, water is carried in the tubes and heated to the point that it becomes high pressure steam. In the firetube boiler, water surrounds the tubes and hot gases travel through the tubes. Both watertube and firetube boilers use similar methods for cleaning.
Here are a few helpful tips to get started with descaling:
- Incorporate both mechanical and chemical cleaning.
- Conduct visual inspections.
- Monitor for evidence-based assessments.
- Measure the impact.
Incorporate Both Mechanical and Chemical Cleaning. The removal of contaminants on both the waterside (scale formation) and the fireside (soot and scale formation) of boilers will result in substantial energy savings. Scale deposits occur on the waterside of boilers when calcium and other minerals form insulating layers on boiler-tube metal because of normal boiler operating temperatures. Similarly, hot gases and unburned carbon from fuel on the fireside of boilers cause soot and scale buildup, which also causes insulating layers on the fireside of the tube.
An ongoing cleaning program that consists of chemical descaling for the waterside and mechanical (rotary cleaning tools) and industrial vacuums for the fireside will enhance energy efficiency and equipment life. While chemical descaling is more commonly used for watertube boilers, some firetube boilers do develop scale deposits.
In a mechanical cleaning, moving brushes operate to scrape the scale off the walls of pipes and tubes. The chemical process involves circulating a chemical through the tubes, which dissolves and flushes out the scale. Incorporating a combination of both processes to effectively rid the equipment of scale is recommended. Begin with an initial chemical treatment that helps to loosen scale, rust and other deposits before following up with mechanical scrubbing.
Conduct Visual Inspections. While one can schedule annual maintenance, it is beneficial to also perform ongoing inspections to be on the lookout for any signs of scale.
Monitor for Evidence-Based Assessments. According to Hartford Steam Boiler, evidence-based assessments are one of the best ways to determine if chemical cleaning is required. Regular monitoring of flue-gas temperature also can indicate a problem: If the temperature rises when boiler load and excess air are held constant, scale is the likely culprit. Other reasons to consider a chemical clean include one or more system failures due to corrosion or when a significant amount (more than 10 percent) of the boiler tubing is replaced.
Measure the Impact. Take the time to evaluate the impact of descaling. Compare the energy bills prior to and after the descaling. It is always good to share cost savings and positive impact on the bottom line, so make sure to highlight the successes in improving efficiencies.
Boiler cleaning is one area where making the investment pays off in the long run through increased efficiencies and cost savings.
Testing Helps Maintain Gains
Once a boiler maintenance program is in place, be sure to include regular efficiency testing. This can help identify certain trends that signify it is time to clean the boiler. For example, an increase in stack temperature can indicate soot or scale buildup. Comparing the data and results from test to test will help to identify maintenance requirements. There are many efficiency testers available that can fit within the budget and meet the process needs. Some companies offer a calculator that allows users to enter their process information, including annual operating hours, type of fuel used and basic scaling information. The tool can help calculate the potential cost savings when using liquid descaler to remove limescale from the waterside of tubes.
Boiler cleaning can be a daunting task. But there is a variety of equipment and chemicals available that are easy to use with the proper training. Boiler cleaning equipment and methods have come a long way, so the job can get done in a way that is easier, faster and utilizes less manpower. Part of the job is making sure one has the right equipment, so take the time to research the options.
Most of us understand the importance of ongoing maintenance, but the reality of reduced budgets or a limited amount of personnel resources can trump the actual implementation. Boiler cleaning is certainly one area where making the investment pays off in the long run through increased efficiencies and cost-savings.
Do yourself — and your company — a favor by developing a routine cleaning and maintenance plan for your boiler, implementing that plan and making sure that you are sharing the impact and savings with leadership and the maintenance team.