You can find many industrial burners on the market, but not all are equally efficient or responsive. A high burner turndown ratio can make a massive difference in a burner’s operation and lifespan.
Keep reading to learn about burner turndown ratios and the benefits of a higher ratio.
Why Turndown Ratio Is Important
You can have a turndown ratio as low as 2:1, which means the burner will turn off when it runs at 50 percent or less. But you can also have something like a mass flow meter, which has a ratio of 1000:1. A mass flow meter can run on as low as 0.5 percent of maximum power.
The burner turndown ratio determines how low the burner can modulate before it activates the automatic shutoff valve. A higher ratio means you have more leeway and that the burner can operate on less power without turning off.
Different burners have different compressor calculations, so one burner may have a higher ratio than another. The burner with the higher ratio will have more flexibility, and it’s one of the many benefits of a high burner turndown ratio.
About Burner Cycles
When a burner reaches the lowest percentage and turns off, it engages in a cycle. Having more cycles can work the burner more than if the burner stayed on, especially if the power frequently moves around the turndown ratio.
In that case, the burner may turn on for a few minutes before turning off again. The more those on-off cycles continue, the more the burner can wear down. When a cycle happens, the burner goes through a few stages:
- Pre-purge stage
- A firing interval
- Post-purge stage
An automatic shutoff system can offer many safety benefits, but it isn’t always the best for your burner because it can lead to more of these cycles.
So if you know the power will stay around a certain percentage, you’ll want a high enough burner turndown ratio to compensate for small changes. Consider a few other benefits of having a high burner turndown ratio:
Better Stability and Control
When a burner has a high turndown ratio and can stay on longer, it offers better stability and control. Burners can have multiple types of compressors, such as a multistage centrifugal compressor or a single-stage centrifugal compressor.
Both compressor types help recycle steam and condense it for more stability and control over the steam pressure. Having more control over the steam pressure can help your burner heat more evenly.
Even without a recycling compressor, a high burner turndown ratio can improve steam pressure stability and keep it from getting too high or low. That way, you don’t have to worry about power fluctuations.
A centrifugal compressor can increase the steam pressure and also control water temperature. You won’t need any outside power to keep the water from getting too hot or cold. All of that can help you get more power and efficiency from your burner.
More Energy Efficient
Because a high burner turndown reduces the amount of on and off cycles, it can make your burner more energy efficient. The fewer cycles you have, the fewer purge losses you have to worry about.
When a purge cycle happens, the burner combustion air fan pumps room temperature air through a heat exchanger. The heat exchanger contains water at the system temperature, and the water is hot enough to warm up the air.
Some purge cycles can keep the burner from overheating and becoming unsafe. But having that happen too often uses up a lot of energy. If you understand how to calculate work done by a compressor, you can quickly determine if you have the optimal burner turndown ratio for your burner.
Lower Maintenance Costs
Another benefit of a high burner turndown ratio is that it can lower your maintenance costs. Every purge cycle not only uses energy but can also break down your burner over time. More purge cycles mean more switching between on and off.
Stopping and starting can cause a lot of wear and tear, especially as those cycles add up. Obtaining a burner with a slightly higher turndown ratio can be enough to make a significant change. Still, an even higher burner turndown ratio can lower your maintenance costs considerably.
If you have a lot of alternative costs associated with power or other equipment, you should save whenever you can. Switching to a burner with a higher turndown ratio is simple, and you can save a lot of time and money on maintaining the new machine.
More Responsive
Every burner has a load, which refers to the horsepower, BTU, or pounds of steam produced per hour. No matter the type of energy determining the load, your burner may experience load changes, and it will need to adapt to those differences.
Having a higher burner turndown ratio can make your burner more responsive to different burner loads. That means your burner can keep operating even when there’s a significant increase or decrease in the horsepower or BTU.
Burners with lower turndown ratios aren’t as responsive to these changes. Being slow to adapt can waste a lot of time and energy. Even if you choose a low-maintenance burner, having a responsive one can make a big difference in the overall operation.
Less Thermal Shock
Thermal shock occurs when an object heats or cools more quickly than it should. It can produce cracks and lead to other stresses, shortening an object’s lifespan. When a burner turns on and off more often, it can lead to thermal shock.
Using a burner with a higher turndown ratio reduces those on and off switches, thereby minimizing the opportunity for thermal shock. It can help reduce that shock to the boiler and refractory.
If you want to keep all of your equipment in good condition, you should consider thermal shock very carefully. Even if a burner doesn’t waste much energy and is responsive, it’s crucial to be aware of thermal shock prevalence. You can switch to a higher burner turndown ratio to avoid all of these issues.
What Else to Consider
While there are many benefits of a high burner turndown ratio, you may still have trouble deciding on the best burner for you. Selecting an industrial burner involves a lot more than just the turndown ratio. Here are a few more things to consider:
- Burner temperature
- Overall capacity
- Chamber flame geometry
- Burner mounting
- Ignition type
You can choose from high-temperature burners that go above 1000 degrees Fahrenheit and low-temperature burners that are below that threshold. Both can be good, but your needs should dictate which you use.
You should also consider the capacity in BTUs that you need. Think about the burner’s function and if it will be able to do the job. Certain chambers may also require a specific flame geometry, so you need to make sure your burner fits those specifications.
Don’t forget about these other features when choosing a burner. Of course, the burner turndown ratio can make a big difference. However, it’s not the only factor that can help you decide on the best burner.
Remember Burner Tips
Another thing to consider when using a burner is burner tips. Burner tips can help you get better performance from the burner. Installing and maintaining burner tips can also help you avoid flame-to-flame interaction, unstable flames, and improper heat transfer.
Make sure to clean your burner tips whenever you perform maintenance on the burners. Take the burner tips off and let them cool before you wash them. After you clean the tips, reinstall them on the burner before using it again.
The Best Burner Turndown Ratio
When choosing a burner, you should consider many factors. It’s essential to look for a high burner turndown ratio. A higher ratio offers many benefits, from energy efficiency to a reduction in thermal shock.
All of these advantages make the burner easier to use and help extend its lifespan. High burner turndown ratios allow you to maintain your operations without worrying about wasting time, money, or resources.
