Combustion Dictionary

Burner Combustion Systems has put together this combustion dictionary to help you understand these industry terms. 


A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The vaporized or heated fluid exits the boiler to be used in a variety of processes or heating programs, including water heating, central heating, boiler-based electricity generation, cooking, and sanitation.


Also referred to as a gas burner, coal burner, or oil burner, a burner is a mechanical device that burns a liquid or gas fuel in a controlled manner.


A boiler stack, also sometimes called a smoke stack, chimney stack or just as a stack, is a sort of chimney, a vertical pipe, channel or comparable structure through which combustion product gases called flue gases are exhausted to the outside air.

Blow Down

Blow Down is an important process in the operation of boilers. Blow Down is the process of safely releasing a portion of the hot water and/or steam from a boiler in order to reduce the level of dissolved solids and/or to reduce the pressure inside the boiler. This process helps to maintain the quality and safety of the steam and water produced by the boiler.

The amount of water that is released is typically determined by the type of boiler and its operating conditions. The blow down process is typically done on a regular basis, such as once a day, or more often if the boiler is operating at a higher pressure or temperature.

It is important to use the proper safety equipment when performing a blow down, such as safety glasses, hearing protection, and other protective clothing. If the blow down is done incorrectly, it can lead to dangerous levels of steam and pressure buildup inside the boiler, resulting in possible injury or even death.

In order to ensure the proper operation of a boiler, it is important to perform regular blow downs. This will help to maintain the quality of the steam and water produced, as well as help to keep the boiler running in a safe and efficient manner.

Cycles of Concentration

Cycles of Concentration is a measure of the total amount of dissolved solids in a boiler system. It is used to monitor the concentration of a boiler‘s steam and water, and is typically measured using conductivity. Boilers are typically operated at a certain cycles of concentration, which is determined by the type of water and the type of steam used in the boiler. By measuring the concentration of the steam and water, it is possible to determine the total dissolved solids in the boiler system, which can then be used to adjust the operating cycles of the boiler. The higher the cycles of concentration, the lower the amount of water that is used, and therefore the less water that must be discharged into the environment. The proper cycle of concentration helps to reduce energy costs and maintain the boiler in optimal working condition.

Fuel To Steam Efficiency

When it comes to producing steam, fuel efficiency is an important factor to consider. Boilers, which are used to create steam, require a significant amount of fuel to heat the water and turn it into steam. As such, choosing an efficient boiler is a great way to reduce fuel costs and improve fuel to steam efficiency. The most efficient boilers use a combination of modern technologies, such as condensing and premix burners, to achieve maximum fuel efficiency. Condensing boilers are designed to extract as much energy from the fuel as possible, while premix burners are designed to reduce fuel consumption by precisely controlling the airfuel mixture. The most efficient boilers also use advanced insulation and airtight construction to reduce heat loss and improve fuel to steam efficiency. This helps to ensure that as much heat as possible is transferred to the water and converted into steam. In addition to selecting an efficient boiler, fuel to steam efficiency can also be improved with regular maintenance. Boilers need to be checked and serviced on a regular basis to ensure that they are operating optimally and that all parts are in good condition. Regular maintenance also helps to identify any issues that could be causing the boiler to use more fuel than necessary. By choosing an efficient boiler and performing regular maintenance, businesses can improve their fuel to steam efficiency and reduce their overall energy costs.

Thermal Efficiency

Thermal Efficiency is the measure of how efficiently a boiler converts energy sources into usable energy for a given application. A boilers thermal efficiency is determined by the ratio of the useful energy output from the boiler to the energy input from the fuel source. The higher the thermal efficiency of a boiler, the more efficient it is at converting energy sources into usable energy. Thermal Efficiency is especially important in steam boilers, as they are used to generate steam for many industrial processes. Steam boilers must be able to generate steam efficiently and reliably in order to ensure their efficient operation. As such, the thermal efficiency of a steam boiler is critical to its overall performance and can have a major effect on the productivity of an industrial operation.

Combustion Efficiency

Combustion efficiency is a measurement of how well a boiler utilizes the energy it consumes to generate steam. Boilers, such as steam boilers, are used to produce steam by burning fuel such as natural gas, oil, or coal. The combustion efficiency of a boiler measures how much of the fuel is being transformed into usable energy, as opposed to unusable byproducts such as carbon dioxide and water vapor. Boilers with higher combustion efficiency are able to generate more steam while using less fuel, while boilers with lower combustion efficiency use more fuel to generate the same amount of steam. Improving combustion efficiency can help to reduce the environmental impact of the boiler, as well as reduce energy costs.


The American Society of Mechanical Engineers (ASME) is the leading professional organization for mechanical engineers. Founded in 1880, ASME is dedicated to advancing the art, science, and practice of mechanical engineering. It is also a global leader in developing and promoting standards for the design, manufacture, and inspection of boilers and pressure vessels. The ASME Boiler and Pressure Vessel Code (BPVC) is one of the most comprehensive collections of standards for boilers and pressure vessels, providing safety regulations and requirements for the design, fabrication, and inspection of boilers, pressure vessels, and nuclear power plant components. It is used by engineers, inspectors, and regulators to ensure that boilers and pressure vessels are safe and reliable. ASME boiler standards provide guidance for the design and construction of steam boilers, hot water boilers, thermal fluid boilers, and other related components. These standards include requirements for materials, processes, and design, as well as testing and inspection requirements.


A deaerator is a device used in boilers and steam boilers to remove dissolved gases, such as oxygen, from the feedwater. It is also known as a deaerating heater, deoxidizer, or deoxygenator. Deaerators are important components of steam boilers because they help reduce corrosion and improve the performance of the boiler. Without a deaerator, dissolved gases in the feedwater can react with the metal components of the boiler, leading to corrosion and other damage. The deaerator functions by heating the feedwater to boiling and then cooling it in a vessel where the gases are allowed to escape. This process is known as deaeration. The deaerator can be used with a variety of boiler systems, including steam boilers, firetube boilers, and watertube boilers.

Hotwell Tank

A Hotwell Tank is a type of boiler accessory used to store hot water for use in steam boilers. The water is heated to a high temperature and stored in the tank until it is needed, at which point it is pumped from the tank and into the boiler. Hotwell Tanks are used in a variety of industrial and commercial applications, such as in power plants, chemical plants, and manufacturing facilities. They are designed to provide a reliable source of hot water for steam generation, helping to ensure steam boiler efficiency and optimal performance. Hotwell Tanks can be made of a variety of materials, including steel, cast iron, and stainless steel.

Feedwater Pump

A feedwater pump is an important component of a steam boiler, as it is responsible for supplying the boiler with water. The feedwater pump takes in water from a source, such as a storage tank, and pumps it into the boiler. The pump must be capable of producing sufficient pressure to push the water into the boiler, which is necessary for the steam to be created. Feedwater pumps are typically electrically powered and are designed to operate continuously, providing a steady supply of water to the boiler. The pump must also be able to maintain the water level in the boiler, as the steam produced by the boiler is converted back into water and contained within the boiler.


Cavitation is a phenomenon that can occur in steam boilers. In a steam boiler, cavitation is the formation of vapor bubbles in the liquid (typically water) inside the boiler. These bubbles form due to a decrease in pressure, and when they collapse, they cause a shockwave that can damage the components of the boiler. To prevent this, boilers must be designed and maintained to avoid cavitation. This includes ensuring that the pump and piping systems are correctly sized, that the boiler has sufficient water, and that the pressure is kept at a safe range. If cavitation does occur, it is important to take the necessary steps to address it.


Colormetry is a specialized field of measurement and analysis that involves the measurement of colors. It is commonly used in the industrial field to measure the color of textiles, paints, coatings, and other materials. Colormetry is also used in the medical field to measure the color of skin, eyes, and other tissues. The most commonly used color measurement tool is the colorimeter. A colorimeter is an instrument used to measure the color of an object by analyzing the light reflected from it. It measures the color in terms of hue, saturation, and brightness, as well as the spectral distribution of the light. Colorimeters are used in a variety of industries, including automotive, food and beverage, and medical. Colormetry is also used in the assessment of industrial boilers. Boilers are used to generate steam, which is then used to power various machines. The color of the steam produced by a boiler needs to be monitored to ensure that it is within specification. The color of steam is affected by the temperature of the boiler and the amount of impurities in the water. By measuring the color of the steam, technicians can ensure that the boiler is operating correctly.


Boilers are used to generate steam for various industrial and commercial purposes. Scale is an important factor to consider when dealing with boilers. Scale is a layer of builtup minerals, such as calcium carbonate, that forms on the interior surfaces of a steam boiler. Over time, this layer of minerals can become thick and form an insulating layer, which can reduce the efficiency of the boiler and create safety hazards. It is important to regularly inspect the interior of a boiler to check for scale buildup and to periodically clean the boiler to remove any scale that has accumulated. The most effective way to prevent scale buildup is to use a water treatment program that will keep the water in the boiler free of minerals.


NOx is the term used to describe a group of reactive gases composed of nitrogen and oxygen that are produced by combustion. Boilers, specifically steam boilers, are a major source of NOx emissions. As the combustion process in a boiler increases, the more NOx is produced. NOx is regulated and monitored by most governments due to its significant contribution to air pollution. To reduce NOx emission levels, boiler operators must take steps to ensure that combustion processes are as efficient as possible. This can include upgrading systems, switching to cleaner fuels, and using lowNOx burners. Additionally, steam boilers can be retrofitted with selective catalytic reduction technology to reduce NOx emissions.

Morrison Tube

A Morrison Tube is a type of boiler used to generate steam power. It is a horizontallymounted cylindrical boiler with two large furnaces and a single fire tube that runs through the center. The Morrison Tube was developed in the late 19th century as a more efficient and powerful alternative to traditional steam boilers. The design of the Morrison Tube allowed for a much larger firebox, which increased the efficiency and output of the boiler. It also allowed for a more even heat distribution within the boiler, which further increased the efficiency of the steam power generated. The Morrison Tube remains a popular choice for steam boilers today, due to its efficiency and power output.


Watertube boilers are a type of steam boiler that use a series of tubes to contain the water and steam. Watertube boilers are typically used for highpressure steam production, and are often larger and more complex than firetube boilers. A watertube boiler consists of a drum, also known as a steam drum, and a series of tubes that extend through the drum. The tubes are heated by a furnace, and the hot gases generated by the furnace pass through the tubes and heat the water in the drum, creating steam. Watertube boilers can be used in a variety of applications, such as to generate electricity and to provide hot water and steam for industrial processes. The water in the tubes is heated to a high pressure, which increases the efficiency of the boiler and reduces fuel consumption. Watertube boilers are also more resistant to high temperatures and pressures than firetube boilers, making them wellsuited for use in highpressure applications. Watertube boilers are often used in power plants and industrial facilities. They are also sometimes used in residential and commercial settings, where they are typically smaller and less complex than industrial boilers. Watertube boilers are typically more expensive than firetube boilers, but the higher efficiency and pressure capabilities make them a good choice for many applications.


Firetube boilers are the most common type of boiler used for heating and process applications. They are typically used in industrial, commercial and institutional applications. Firetube boilers are characterized by a cylindrical shell with a number of tubes running through it. The tubes are filled with water and heated by an external source such as a fuel burning furnace, electric elements, or a gas burner. As the water boils, steam is generated and circulated throughout the system. Firetube boilers have been used for centuries to generate heat and power. The oldest known firetube boiler was the aeolipile, which was invented by Hero of Alexandria in the first century AD. This boiler was a crude device that used steam to create a rotary motion. Over the centuries, firetube boilers have evolved to become more efficient and reliable. Todays firetube boilers are available in various sizes and configurations to meet the needs of any application. Firetube boilers are typically used in applications where steam or hot water is required in large quantities. Common applications include heating systems, process systems, power plants, and steam generators. Firetube boilers are known for their durability and low maintenance costs. They are also wellsuited for applications that require frequent cycling or rapid response times.

Flex Tube

Flex Tube is a revolutionary new product that is revolutionizing the way boilers are maintained and serviced. It is a flexible, light-weight, and durable tube that can be inserted into a boiler for the purpose of cleaning and servicing. The tube is made from a special material that is highly resistant to heat and corrosion and is designed to withstand temperatures up to 5,000 degrees Fahrenheit.

Flex Tube is specifically designed to fit into the tight spaces of industrial and steam boilers. It is a flexible and durable product that can reach hard-to-reach areas of a boiler, allowing for more thorough cleaning and servicing. The tube is inserted into the boiler using a specialized tool and is then retracted and examined for signs of damage or wear. This process helps to ensure that the boiler is running at its optimal performance.

The Flex Tube is an invaluable tool for boiler maintenance and servicing. It can help to reduce downtime and increase efficiency, while also reducing the cost of maintenance and servicing. The tube is available in a variety of sizes and lengths, so it can be customized to fit into any boiler. The tube is also lightweight and easy to install, making it perfect for any industrial or steam boiler.

If you are looking for an easy and effective way to maintain and service your boilers, then the Flex Tube is the perfect solution. It is a durable, lightweight, and flexible tube that can reach hard-to-reach areas of a boiler. This product is an invaluable tool for any boiler maintenance and servicing.

Superheated Steam

Superheated steam is steam that has been heated to a temperature above its saturation point. This means that the steam is no longer able to hold any additional water vapor and is instead a gas. This significantly increases the energy output of the steam, making it much more efficient than regular saturated steam.

The most common way to create superheated steam is by using a boiler. A boiler is a large vessel that contains water and is heated by an external source, such as a furnace or a boiler burner. As the water is heated, it begins to boil, forming steam. This steam is then passed through a superheater, which is a special device that raises the temperature of the steam. The superheated steam is then passed through pipes and used to power industrial processes.

The efficiency of superheated steam is due to its ability to transfer heat more quickly and efficiently than saturated steam. This is because superheated steam has much higher thermal energy than saturated steam, which means it can transfer more heat in less time. This makes it possible to reduce the amount of fuel needed to power the process, which in turn reduces costs.

Superheated steam is also much safer than regular steam. The higher temperatures of superheated steam make it much less likely to cause burns or other injuries if it is released, which is important in industrial settings.


When it comes to boilers, one of the most important concepts to understand is carryover. Carryover is the unwanted phenomenon that occurs when water droplets get carried along with the steam as it leaves the boiler. In industrial boilers, this can be especially damaging and costly, as the residual water droplets can cause erosion of downstream equipment.

Carryover is caused by many different factors, but primarily it is the result of improper boiler operation. If the boiler is operated at too high of a pressure, for example, the steam velocity can increase, causing the droplets to be forced out of the boiler along with the steam. In addition, if the boiler is not inspected and maintained regularly, the accumulation of scale and sludge can cause carryover and blockages in the steam piping.

When carryover occurs, it can cause major downstream damage to other equipment that the steam is being used to power. The water droplets can erode the internal components of the receiving equipment, leading to costly maintenance and repairs. In extreme cases, the damage can be so severe that the equipment must be completely replaced.

To reduce the risk of carryover, it is important to regularly inspect and maintain your industrial boiler. Any scale or sludge buildup should be removed, and the boiler should be operated at the correct pressure. In addition, it is important to install the proper equipment, such as a separator, to help reduce the risk of carryover.

Carryover is a serious issue that can be damaging to both industrial boilers and the downstream equipment that relies on the steam. By properly inspecting and maintaining your industrial boiler, you can help reduce the risk of carryover and keep your equipment running efficiently and safely.


Retube is the process of replacing a worn or damaged tube in a boiler, steam boiler, or industrial boiler. It involves removing the old tube and replacing it with a new one. The process requires specialized tools and knowledge to ensure a proper installation and to ensure the safety of the boiler and its operators.


An economizer is a device used to increase the efficiency of a boiler, steam boiler, or industrial boiler by preheating incoming air, water, or other fluids. It is typically installed in the exhaust of the boiler, where it captures the heat from the exhaust gases that would otherwise be lost. The economizer then uses this heat to preheat the incoming air or water, which lowers the energy required to heat the boiler and increases the overall efficiency of the system.

Feedwater Heater

A Feedwater Heater is a device used in boilers, steam boilers, and industrial boilers to preheat water before it is fed into the boiler. It increases the thermal efficiency of the boiler by reducing the amount of energy needed to heat the water. The feedwater heater works by transferring heat from the steam leaving the boiler to the cold water entering the boiler.

Blowdown Separator

A Blowdown Separator is a device that is used to remove unwanted solids and sediment from a Boiler system, typically used in industrial settings. The Blowdown Separator is typically installed on the outlet of a Steam Boiler, and helps to ensure that the system is operating with clean, uncontaminated water. The Blowdown Separator helps to improve the efficiency of the Boiler, as well as the safety of the personnel and equipment associated with the Industrial Boiler.

Water Softener

A water softener is a device that removes minerals such as calcium and magnesium from hard water to make it softer. The water softener can be used in a variety of applications, including in boilers, steam boilers, and industrial boilers. It can also be used in residential water systems.


Conductivity is the ability of a material to transfer heat or electricity. It is a key factor in the operation of boilers, steam boilers, and industrial boilers. Conductivity determines how quickly the heat from the boiler is transferred to the surrounding environment, and is an important factor in the efficiency of a boiler.

Flame Safeguard

Flame Safeguard is a safety system designed to protect boilers, steam boilers, industrial boilers, and other combustion systems from dangerous situations. The system monitors and controls burners, burner ignition systems, and other components of the boiler system to prevent dangerous flameouts, overfiring, and other hazardous conditions. Flame Safeguard systems can include flame scanners, flame detectors, safety valves, and other safety components.

Steam Pressure

Steam Pressure is the amount of force created by the steam created by a Boiler, Steam Boiler, or Industrial Boiler. The steam pressure is measured in pounds per square inch (psi) and is created by the vaporization of water in the boiler.

Housekeeping Pad

A Housekeeping Pad is a maintenance schedule used to keep track of the periodic maintenance and care needed for boilers, steam boilers, and industrial boilers. The Housekeeping Pad is used to schedule and document any necessary maintenance, repairs, and general upkeep needed to ensure that the boilers are running safely and efficiently.


A Head is the pressure of a fluid, typically measured in pounds per square inch (PSI). It is an important factor to consider when selecting a boiler for an industrial setting, as boilers, steam boilers, and industrial boilers require a certain amount of head to operate efficiently.

Wet back Firetube

A wet back firetube boiler is a type of steam boiler that consists of a cylindrical shell containing several fire tubes. The fire tubes are arranged in a curved shape, typically with the inlet and outlet ports located at the two ends of the fire tube. The water inside the boiler is heated by the burning of fuel in the fire tubes, and the resulting hot gases pass through the tubes and out of the boiler. The wet back firetube boiler is a common type of boiler used in industrial boilers and steam boilers, as it is able to provide a high level of efficiency, while at the same time being relatively simple in design and operation.

Dryback Firetube

Dryback Firetube is a type of boiler in which the rear wall of the furnace is lined with refractory and the tubes are surrounded by water. This type of boiler is commonly used in industrial boilers and steam boilers as it provides greater efficiency and a longer life span than other types of boilers. It is also more affordable than other types of boilers, making it a popular choice for industrial and steam boilers.


MAWP stands for Maximum Allowable Working Pressure. It is a safety limit set for boilers, steam boilers, and industrial boilers. This limit defines the maximum pressure that the boiler can safely operate at, to prevent accidents and damage to the boiler.

Gross Steam

Gross Steam is the total steam output of a steam boiler, industrial boiler, or boilers in an industrial plant or factory. It is the total of the steam coming from all the boilers together. Gross steam is the total amount of steam produced by a steam boiler or boilers, and it is used to power turbines and other machinery in an industrial plant.

Net Steam

Net Steam is the amount of steam that is delivered from a boiler or boilers in a steam boiler or industrial boiler system, after taking into account any losses due to steam leaks, flash steam, or other forms of energy loss. Net Steam is the effective energy that can be used in a process.

Boiler Horsepower

Boiler Horsepower is the amount of power generated by a boiler and is a unit of measurement used to describe the capacity of a steam boiler, industrial boiler or other type of boiler. Boiler Horsepower is equal to 33,475 British Thermal Units (BTUs) per hour, which is the amount of energy needed to evaporate 34.5 pounds of water per hour at 212°F. Boilers with higher Boiler Horsepower ratings typically produce more steam than smaller boilers.

Flue Gas Recirculation

Flue Gas Recirculation (FGR) is a technique used to reduce the amount of nitrogen oxides (NOx) emissions from combustion sources, such as boilers, steam boilers, and industrial boilers. It involves recirculating a portion of the flue gases generated from the combustion process back into the combustion chamber, in order to reduce peak flame temperatures and lower the formation of NOx.

Saturated Steam

Saturated steam is steam that is at its maximum energy level, meaning the steam is completely filled with energy and can no longer absorb any more. This type of steam is typically used in boilers, steam boilers, and industrial boilers, as it can provide a great amount of energy in a short amount of time.

N + 1

N+1 is a redundancy system applied to boilers, which ensures that at least one boiler is always running at a given time. This system is especially important for industrial boilers, which are used for highervolume steam production. By having an N+1 redundancy system, production is not disrupted in the event of one boiler failing.

Lbs / MMBTUt

Lbs / MMBTU stands for the rate of fuel input in British thermal units (BTUs) per pound of fuel burned in a boiler. It is a measure of boiler efficiency and is often used to compare the efficiency of different types of boilers, such as steam boilers, industrial boilers, and residential boilers. Lbs / MMBTU is calculated by dividing the total fuel input in BTUs by the total weight of fuel burned.


Combustion Dictionary

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