on April 7, 2021 in Boiler Tube Cleaning
For many in the northern hemisphere, the end of the heating season is here. For facility managers, that means it’s time to look at annual maintenance and routine boiler tube cleaning. As a general rule, boilers should be cleaned and maintained at the end of each heating season to remain reliable and energy-efficient. Waiting too long can also leave little time if you identify any issues with combustion, sensors, or tube degradation.
Gone are the days of wasted labor hours using old tools to scrape scale and debris out of boiler tubes with manual rods and brushes. Modern fire tube cleaning systems are here to deliver faster, more straightforward, and better results.
Not all boilers are the same. Before deciding which solution is best for you, testing deposits and understanding your boiler’s level of “dirtiness” can help make the cleaning season run more smoothly. How often you should clean your boiler depends primarily on your system’s environmental conditions and specifically the fuel burned. This is particularly important in buildings that burn waste and garbage primarily. Still, burning other heavy fuels can present equally challenging cleaning environments.
Regularly testing your boiler’s efficiency is the best way to understand how often cleaning is needed. Testing can identify other problems including, incomplete combustion, improper firing ratios, and impingements on the flame, and more. Once testing is complete, preventive maintenance should be scheduled.
Additionally, depending on your type of boiler, make sure to look at the combustion side and the waterside. Deposits on the waterside can drastically reduce efficiency and be tackled simultaneously as combustion cleaning.
Knowing these factors can help identify the mechanical cleaning systems needed and whether should also be part of your overall maintenance plan.
■ One or more failures due to an under-deposit corrosion mechanism, particularly hydrogen damage. The first priority must be to prevent further damage by removing the deposits via a complete chemical cleaning.
■ Major contamination events or multiple small events, particularly tube leaks. Contamination events increase the amount of deposit in the boiler and its corrosiveness. Chemical cleaning removes the deposits and the contamination underneath the deposits before they corrode to failure.
■ Replacement of boiler tubing. The rule of thumb is to chemically clean if you are replacing more than 10% of the surface area of the boiler. This helps to create a uniform layer of oxide on all the tubes.
■ A major change in the boiler fuel or burner design. Changing fuels, such as from coal to gas, or modification of the burners can result in changes to the area of high heat flux in the boiler. When implementing such a major change, it is best to start with a clean boiler.
■ A change in the chemical treatment regime. Such changes would include moving from one chemical treatment to another, say from all-volatile treatment to oxygenated treatment (OT).
According to a US Department of Energy study, a firetube boiler annually uses 450,000 million Btu (MMBtu) of fuel while operating for 8,000 hours at its rated capacity of 45,000 pounds per hour (lb/hr) of 150 pounds per square inch gauge (PSIG) steam. If scale 1/32nd of an inch thick is allowed to form on the boiler tubes, and the scale is of “normal” composition, the table indicates a fuel loss of 2%.The increase in operating costs, assuming energy is priced at $8.00 per million Btu ($8.00/MMBtu), is: Annual Operating Cost Increase = 450,000 MMBtu/yr x $8.00/MMBtu x 0.02 = $72,000
Efficiency loss of a boiler due to dirty boiler tubes
So, you have done your testing and scheduling. The next steps are to determine the best solution for your system.
Mineral deposits or “scaling” can form on the boiler’s waterside, inhibiting water flow and heat transfer. Scale is removed through either mechanical or chemical cleaning methods. Mechanical cleaning removes scale with the use of tools like scrapers, brushes, or sandblasters. Chemical scale removal uses acids to dissolve the minerals through a chemical reaction between the scale and the liquid. The method used for cleaning, mechanical or chemical, differs depending on the thickness and type of deposits being removed.
The severity of fire tube corrosion and fouling is related to the fuel being burned. Natural gas, propane, and petroleum fuels like gasoline or No. 2 diesel fuel produce a light fouling removed by brushes without the need for heavy scrapers. Boilers burning wood, medical or municipal waste, and heavy petroleum fuels like No. 6 fuel oil often suffer from thick fouling that can only be removed by a powerful cleaning system with strong brushes and scraping tools.
Soot and corrosion from combustion can foul the fireside of boilers, causing tube wall temperature to get so hot that the tube itself weakens and can rupture. Fireside fouling can be mechanically removed with various methods; however, Goodway recommends using advanced technology.
Nylon brushes are best for light deposits. Steel spring brushes and brass brushes provide extra toughness for removing soot deposits in fire tube boilers. When you need just a little more soot-cleaning power than a brush can provide, an FTS tube scraper tool will get the job done. For the largest, heavily fouled fire tubes, nothing comes close to the cleaning strength of a rigid arm flare cone. See our brush basics infographic.
Choosing the correct boiler cleaning system is informed by the type of boiler you have, the severity and type of fouling to be removed, and system features like portability and power.
Get help choosing the best solution for your boiler cleaning, see this handy Boiler Cleaning Buying Guide.
Fire tube and water tube boilers need a routine maintenance and cleaning schedule and monitoring during service to operate effectively and without frequent breakdowns. Maintaining an operating log can help you identify when the system is operating at its most efficient and not. This can help identify the effective loss of efficiency, an increase in operating costs. As a maintenance professional, helping building owners and operators understand your hard maintenance work’s bottom-line impact can help them manage their buildings better – and maybe get you a nice bonus.
Industrial Boiler Cleaning – Waterside and Fireside Solutions
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Learn more about Scale Build Up
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