10 Things You Need To Know Before Replacing Your Boilers Burner
A burner is a key component of your boiler system. It supplies heat to the boiler by mixing fuel and air, driving the combustion process, and providing heat to convert water to steam (or to heat water). The burner responds to load on the boiler by increasing or decreasing its firing rate.
Sometimes, older burners can be unreliable and require costly maintenance. They may even be out of production, making factory replacement parts hard to come by. Because of this, people may be quick to replace older burners with new ones, in hopes that the higher efficiency will be worth it. But the decision to retrofit the boiler’s burner should not be made in haste. There are several factors to consider when investing in a burner.
Here are 10 things to know before making a boiler burner replacement.
1. Choose the right type of burner design.
A poorly-designed boiler with an efficient burner can perform better than one that is well-designed but fitted with a low-quality burner. The best burner designs should maximize combustion and minimize emissions. There are various types of burners including gun-type, Windbox, Integral Head, and more, all capable of firing different fuels such as oil, natural gas, and waste-gases all of which come with different features suited for their specific purpose. You can invest in a multi-fuel burner like the Power Flame burner if you want to switch up your fuel in future, for instance, if your facility has plans to use bio-gas in the future. Burners can also be designed with corrosion resistant materials for certain applications/environments to allow for a longer service life in harsher settings.
2. Examine whether or not you have a high turndown boiler.
A burner turndown is the ratio between a boiler’s maximum and minimum output. Turndown ratios can be as small as 5:1 or as large as 12:1. For a 5:1 burner, the minimum operating load is 20% of the boiler’s capacity while that of a 12:1 machine is 8.3%. The higher the turndown ratio, the more energy you can potentially save as your system can run longer cycles (low-fire) instead of switching on and off at a higher firing rate which wastes fuel and wears down the system’s components. Also, burners with a low turndown respond slowly to load changes (instead of just increasing the firing rate, they may be off when load increases and need to go through their light-off process) and struggle to maintain the required steam pressure and water temperature, which wastes energy.
3. Quality combustion controls are the key to effective burners.
An effective burner should minimize the amount of excess air that enters the combustion chamber. Combustion controls are the brains of the entire burner system. They are a set of instruments that modulate the burner’s firing rate based on the load demand and manage the flow of air and fuel flow to the burner to ensure 100% fuel combustion with little to no unburned hydrocarbons. The controls also balances complete combustion with as little excess airflow as possible. Excess Air is not used in the combustion process and carries otherwise useful heat with it out of the stack reducing boiler efficiency. Your combustion control scheme should maintain the right amount of air and fuel balance. The type of combustion control you implement will determine burner efficiency.
The various types of combustion controls include single point positioning, parallel, and fully-metered combustion controls. Single point positioning combustion controls are the most inefficient as they can wear out the linkage joints which loosen the rod-set screws, creating hysteresis and reducing efficiency. Parallel Positioning and Fully Metered systems are more efficient, but at an increased cost. This cost needs to be compared to potential annual fuel savings (driven by boiler size, operating hours, fuel costs, etc.), determining the upgrades Return on Investment for your facility. No matter which control scheme you select, your combustion control system should be configured precisely to your application to increase operating efficiency and boiler safety. If you feel your control system isn’t up to par, it is worth investigating the costs of a new system and the potential fuel savings with the help of a qualified service company.
4. Check whether your burner management control needs replacement.
The combustion control works together with the Burner Management System (BMS). The BMS safeguards the burner before, during, and after the machine switches on and off. It provides flame safeties and interlocks to keep the boiler safe during continuous operation. In short, BMS systems ensure that it is safe to have a flame in the furnace and initiate a shutdown in cases where it’s no longer safe to run the system. You will need an expert in boiler services to check if the burner management system works or needs a replacement. Quality controls such as the Honeywell or Siemens boiler controls help you improve the safety and reliability of your boiler system. More advanced controls can even be tied in with other equipment such as Master Panels or existing Plant Control Systems to centralize monitoring of your boiler plant’s vital systems.
5. Investigate whether or not your current burner minimizes excessive air.
Highly efficient burners minimize excess air when operating. Most modern burners are designed to hold excess air at levels at 4% or less through a wide turndown range and some designs can hold this low excess air level throughout their entire turndown range.
A burners overall design affects its ability to accurately control excess air throughout its turndown range. Things such as damper design, burner head design, shape of the burner, controls used, etc. all impact the control of excess air at higher turndowns. Older designs may only control excess air through a narrower window, leading to inefficiencies at lower firing rates.
6. Your burner choice can help reduce combustion noise.
Many modern burners have options for silencers to reduce burner noise in the boiler room, improving comfort and safety. There are even options for remote fans on gun type burners to move this noise source to another room. Remote fans were and are common on Industrial Water Tube Boilers, but a newer option is available on smaller Firetube and Flexible Water Tube boilers.
7. Oxygen trim will help control varying air conditions in the boiler room.
As weather changes, the density of air changes. This will increase or decrease the oxygen available for combustion in your boiler. Seasonal tuning can help with this by tuning the boiler for warmer or cooler times of year. Without this, you will set the boiler up for situations when oxygen (by volume of air) is lower (summer) so that the boiler is safer. In the winter, this will lead to more excess air, reducing boiler efficiency. An option is the use of Oxygen Trim (O2 Trim). An O2 trim system measures the oxygen levels in the exhaust gas stream and gives feedback to automatically adjust the air damper so that excess air is kept at a preset level. Investment in an O2 trim will increase burner efficiency and can reduce downtime and maintenance. As with most upgrades in the boiler room, a payback analysis should be created to analyze the benefits versus costs. Larger boilers that are operated for more hours per year will have faster paybacks than boilers used seasonally – every facility is different – upgrades should be determined by what makes sense to your facility.
8. Consider emissions upgrades or regulations.
Consider the existing and potential regulations, as well as corporate green or efficiency initiatives, when you are researching your burner replacement. It may be a requirement to install an O2 trim system, or Flue Gas Recirculation (FGR) system (or other methods to reduce emissions) to help reduce NOX emissions depending on your location and company goals. One consideration here is ensuring adequate operator training as more advanced control systems are employed; a qualified boiler service company will be able to provide on-site, hands-on training for boiler operators and maintenance staff.
9. New burner, new gas train.
The gas train assembly consists of several components. One of these components is a pressure regulator, designed to reduce the (higher) delivered pressure from your utility company and then maintain the proper pressure for the remainder of the gas train within a narrow margin. The gas train also consists of safety control components such as pressure switches and gas valve interlocks that are tied into your boiler’s safety system. The overall components selected are driven by Code Requirements or requirements specific to your facility or insurance carrier. Although it is possible to reuse existing components, we always recommend using new components supplied with the burner. This will ensure warranties are intact and that everything is selected/designed to work as a cohesive package.
10. Other factors to consider.
Before you buy a new burner, there are other considerations, which a qualified boiler service company can help you review, such as: Burner Mounting Plate, burner selection/performance is matched to the boiler’s furnace geometry, any size change of the burner versus the existing as it relates to interference in the room, maintenance access and egress, and more.
Frequently Asked Questions
1. When should I replace my boiler burner?
Some of the situations that warrant consideration of a burner replacement include:
- Your existing burner manufacturer is no longer in business and replacement parts are becoming hard to find or have long lead times.
- You have excess air readings of more than 4%, indicating that your boiler is using more excess air than is optimal.
- Frequent cycling which could be caused by an oversized boiler/burner combination and lack of enough turndown.
- Major components of the existing burner are damaged or corroded from use.
- If the burners do not meet new emission regulations or corporate efficiency/emissions goals.
2. How long does it take to replace a burner on a boiler?
The physical process of replacing a burner once it arrives on site, depending on size, access, complexity, etc. can take from a few days to a few weeks. The entire project, including proposal generation, payback estimates, estimate approval, submittals, production and delivery to your site can take a couple to a few months. Planning ahead is key. Including anticipated upgrades in your budgeting process and staying proactive versus reactive will save potential headaches. If your facility has a backup boiler, that will need to be in good shape to operate your facility while another boiler is being upgraded. If you have only one boiler, preparation will need to be made for a rental boiler during the downtime.
3. Do you need to drain the system to change a burner?
Not necessarily. For hot water systems, as long as the boiler can be isolated from the system, the system should not need to be drained. For steam boilers, the boiler can be isolated from the steam header and feedwater to the boiler can be secured. The boiler itself may need to be drained (or partially drained), if new controls need to be fitted below the water level and thermal wells are not currently in place or need to be replaced.
A Boiler Engineer to Your Rescue
A professional in boiler room equipment can guide you on the best replacement burner for your boiler. A successful boiler retrofit is one where the money you invest in a new burner yields: a safer, more efficient, and more reliable boiler room with an overall design that best meets the unique needs of your facility. The experts at W.C Rouse will give you a detailed view of your current system efficiency, outline the potential cost savings, and help you plan for the overall project with a minimal interruption in plant operations. Is it time to replace your boiler’s burner? Contact the W.C. Rouse team for expert service.