When a facility’s boiler is seemingly operating without issues, it is easy to put off cleaning for a few weeks, months or even years. But, what seems like a time-saving trick or a way to stretch a budget allocation can lead to inefficiency, safety concerns and a shorter equipment lifespan.
Even a small amount of soot or scale buildup can impact the energy efficiency of an industrial boiler. In fact, the effects are noticeable nearly as soon as buildup starts to occur. An insignificant-looking 0.125” of scale can increase an industrial boiler’s fuel consumption by 8 percent. Imagine the loss of fuel output as that thickness increases.
The result of dipping efficiency? The boiler has to work much harder to maintain the same steam throw, water or air temperature. In the long run, the equipment may have a shorter lifespan and require otherwise avoidable repairs. In the short term, climbing fuel costs will be the most noticeable change (at first).
Moreover, the harder the boiler works, the more fuel it consumes. For instance, a 450,000 million BTU industrial boiler that produces 150 psig steam at the rate of 45,000 lb/hr might result in annual fuel costs around $3.6 million. According the U.S. Department of Energy, even 0.03125” of scale on the water-side surfaces of your tubes could increase energy costs by 2 percent. That means an additional $72,000 in just one year.
Buildup does more than just lower the energy efficiency. Excessive soot and scale can damage the boiler structure. When left unchecked, scale and soot buildup can lead to corrosion within the boiler tubes. The integrity of the tubes is weakened, which can lead to tube failure. The costs related to repairs after tube failure or the potential total replacement of the boiler come on the heels of those increased fuel costs. In effect, required repairs and increased fuel usage often cost more than what a proper preventive maintenance program would. Additionally, a good preventive maintenance program will prolong the boiler lifespan as well.
Boiler cleaning is part of a responsible maintenance program. When it is ignored — along with any other element of a maintenance program — the facility staff is put at risk. Even a relatively small boiler can cause significant damage if maintenance is ignored, and the equipment fails. For instance, according to the National Board of Boiler and Pressure Vessel Inspections, explosive failure of a 30-gal home hot water heater can create enough force to push 2,500 lb more than 100’ into the air. While that is a small residential boiler, the consequences of an industrial boiler explosion can include facilities being destroyed or even casualties.
Soot and scale build up naturally as a result of using the boiler. Regular cleaning can help protect the equipment from lasting damage. But, what exactly does regular cleaning entail, and how often should it be done?
Even a small amount of soot or scale buildup can deeply impact the energy efficiency of your boiler.
Identify the Equipment
This might seem obvious, but identifying the equipment type is the first step. The cleaning process varies among the different types of boilers.
In firetube boilers, hot gases move through tubes surrounded by water to help create steam. Cleaning these tubes with water can have disastrous results: When water mixes with the ash and soot inside firetube boilers, it becomes acidic. This fluid should not be washed down the drain. Instead, firetube boilers can be cleaned using rotating brushes or scrapers that loosen soot and a vacuum to pick up the dust. Tools that combine these functions help avoid a second cleanup when soot covers the floor after boiler cleaning.
In a watertube boiler, a heat source outside of the tubes heats the water inside to create steam. Because some watertube boilers have tubes that bend, these boilers can be more difficult to clean. Watertube boilers often are cleaned using air motors.
Evaluate the Facility and Environmental Conditions
Several factors can determine how quickly a boiler builds up soot, ash or scale. Keeping an eye on these key points throughout the year can help suggest the cleaning schedule that should be used. Factors to consider include:
- What kind of fuel are you burning?
- What does your water quality look like?
Fuel Type. Different fuels create different levels of buildup in their wake. For instance, natural gas is known to burn cleaner than many other fuels. Boilers using natural gas collect ash and soot at a slower rate. Fuels that do not burn as clean — for example, coal, fuel oil or medical waste — tend to accumulate more buildup. They need to be examined and cleaned more frequently.
Water Quality. If the water in the boiler is high in mineral deposits, scale buildup will occur more often. Having a water treatment plan in place can help prevent that from happening as long as it is tailored to the needs of the facility’s water source. Having the wrong water treatment can mean having to clean just as often as if the facility did not have one.
Conduct a Visual Inspection
The best way to understand the state of the boiler is to conduct a visual inspection. Keep an eye out for scale or buildup. When necessary, clean the tubes to rid them of buildup.
Before beginning cleaning, make sure to identify the type and amount of buildup present. Tools like videoscopes can help show the condition of the tubes. After the cleaning, plan to take a second look at your equipment. Inspection after cleaning is a good time to check the tubes for damage or weak points.
The best way to understand the state of the boiler is to conduct a visual inspection. Keep an eye out for scale or buildup.
Consider Chemical Cleaning
Sometimes, brushes and air motors are not enough to remove scale buildup, especially in difficult-to-reach places. In such cases, chemical cleaning can help remove the tough-to-remove scale lowering the equipment’s energy efficiency and making the equipment work harder. A chemical descaler will flow through the tubes to dissolve and flush out the scale. It is important to understand the type of scale present in the tubes in order to match the descaling product to the need.
Monitor Boiler Outputs
Taking a look at how the boiler is performing is one of the best ways to understand whether a cleaning may be in order. Most facilities with boilers track several factors — including CO2, O2 and flue gas exhausts — to keep an eye on how well the boiler is performing. Constant monitoring allows facilities to gather data and get the clearest understanding possible.
In facilities where tracking is not already in place, for a quick understanding of how the equipment is performing, track the monthly bills and watch for spikes in cost. These are a good indication that the boiler may need cleaning.
In conclusion, while modern boiler-cleaning methods often require minimal training, it is important to remember that these machines are powerful. And, they can be dangerous if not maintained correctly. If you are at all unsure of how to care for yours, consider hiring a third-party company to perform the boiler cleanings.
Once you understand the amount and type of buildup in the boiler, how it occurs and how often it occurs, you are well on your way to establishing a regular cleaning schedule. As with most process equipment, preventive maintenance will boost efficiency, help keep workers safe and may reduce fuel and repair costs.