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Boilers Manufacturers and Suppliers

IQS Directory provides a comprehensive list of boiler manufacturers and suppliers. Use our website to review and source top boiler manufacturers with roll over ads and detailed product descriptions. Find boiler companies that can design, engineer, and manufacture boilers to your companies specifications. Then contact the boiler companies through our quick and easy request for quote form. Website links, company profile, locations, phone, product videos and product information is provided for each company. Access customer reviews and keep up to date with product new articles. Whether you are looking for manufacturers of outdoor boilers, double boilers, electric boilers, or customized boiler of every type, this is the resource for you.

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We strive for the best at Unilux Advanced Manufacturing LLC. Our boilers are designed with superior materials. We are proud to say that we produced the world`s first UL/FE boiler and our units provide the highest levels of safety and accountability. Our systems feature large volumes of totally isolated positive circulation. Rest assured with our company and our 30 years of manufacturing experience! Contact us today!
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As the inventor of the vertical tubeless boiler, Fulton has a reputation for success dating back to 1949. We`re a global manufacturer of steam, hot water and hydronic boilers; thermal fluid heaters; custom engineered systems; and a full range of ancillary equipment. We continue to make advancements in the boiler market and are committed to improving life through heat transfer solutions.
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Johnston Boiler Co has been manufacturing, designing, engineering and servicing gas, oil, coal, wood, solid waste, biomass & hybrid fuel-fired steam & hot water boilers since our inception. With installations across all industries worldwide, We are recognized for the highest code standards, innovative engineering and design, Energy Star rating, fully Integrated controls, and renewable, sustainable solutions for green building design and operational efficiency. Call us today for more information.
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Biomass Combustion Systems designs and manufactures high-quality wood-fired energy systems. Our systems include new wood boilers from 100HP to 1200HP. In addition to our years of experience, we offer turnkey installations, retrofitting existing wood boilers to make them more efficient.
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AERCO has been an industry leader in water heating design for over 50 years. We have solutions that fit all segments of the water heater and boiler market. From the smallest elementary school to the largest of Las Vegas` hotel casinos, AERCO provides the highest-quality products and system designs that deliver hot water and space heating with the greatest efficiency and performance.
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Industry Information


Boilers are industrial, commercial and domestic utilities that provide heated air and hot water in homes and businesses as well as steam for use in steam-operated machinery. The most common boiler varieties are often denominated according to their method of heat generation; gas boilers, electric boilers and oil boilers are the most widely used steam boilers.

Almost all boilers can be placed into one of those three categories (there are exceptions: Central Boiler's systems are wood fired). Combi boilers are different from conventional models because they do not store hot water but rather heat it rapidly on demand. They have a second heating element to speed the heating process and maintain a steady supply for as long as the boiler runs. Condensing boilers are able to recover energy that would normally be expelled through the flue by condensing the escaping water vapor back into liquid water. Because the boiler uses latent heat to boost its efficiency to above 90%, it is considered a high efficiency boiler. Another way to increase efficiency is through a high pressure boiler, which maintains an operating pressure greater than 15 PSI; some models achieve pressures as high as 1,000 PSI. Low pressure boilers have pressure less than 15 PSI and are used mostly in smaller buildings for heating a space. Industrial boilers are used either as part of a heating system or to individually generate hot water or steam for various industrial and manufacturing processes. They are much larger in size and built from heavy duty materials to ensure safety, durability and performance.

Boilers provide residential, commercial and industrial heating and are a key part in hydronics, which is the use of water as a heat-transfer medium. Boilers are constructed of stainless steel, aluminum or cast iron and are composed of a furnace with various heat exchanger components and a pump or fan. The two basic designs include fire-tube and water-tube boilers. Fire-tube boilers work by distributing heat through tubes immersed in water; water-tubes circulate water through heated tubes within the enclosure. Hot flue gases are passed over the tubes, heating the water, and then are discharged through a stack. Both designs are comparable in efficiency but are not interchangeable, because of structural considerations. Boilers rely on radiant heat and the transfer of thermal energy to guide the movement of the water or steam. Because heat moves from areas of high temperature to low temperature, the furnace is able to heat the tubes that heat the water, which in turn heats the pipes or radiators that heat the room; virtually the entire process relies on the behavior of high temperature fluids.

The purpose of a boiler is to provide hot water or to generate steam. Steam boilers produce steam for heating large buildings such as factories and warehouses; in other industrial applications the steam can be used for power. Hot water boilers are an important part in hydronics because they heat the water that circulates through a series of pipes and into radiators, baseboards and other heat exchangers. Boilers generally use one of three sources of fuel: gas, oil or electricity. Gas boilers are fueled by natural gas and use a natural gas flame to heat water to a specified temperature or to its boiling point, thereby producing steam. They are the most common type of boiler used for heating applications in the United States. Oil boilers use oil either as fuel for the furnace or to replace the water generally found in boilers and produce hot gases that travel through the piping system. Electric boilers offer efficient, clean and safe water heating. Unlike appliances that provide heating through the process of combustion, electric boilers eliminate the problems with carbon monoxide, back drafting, pilot lights, gas piping and venting.

Boilers have historically been used to produce steam for power. The steam locomotive and steam engine are two examples of this application. They were used industrially and were fairly dangerous, as early operators did not fully understand the relationship between temperature and pressure. Concerned citizens and workers contemplated getting rid of steam boilers altogether until advances in safety and knowledge were made. Today, boilers operate in many different settings such as schools and office buildings. The materials, design and construction have all improved to the point that fear is no longer a factor. Accidents do still occur but with less frequency and with fewer injuries or fatalities. Boilers are now an extremely valuable part of life and can be found in almost any environment. Once quite large, boilers are becoming smaller and smaller in order to fit into tight spaces, though some boilers, like those used industrially, must remain their size in order to produce the necessary amounts of steam and water. Mobile boilers are now available and can be used in military, emergency or temporary situations to provide steam for heat or power. Even as technology continues to make significant advances, boilers will most likely remain a critical part of life for years to come.

Boilers Manufacturers
Boilers Manufacturers
Boilers Manufacturers - Fulton Boiler Works, Inc.
Boilers - Fulton Boiler Works, Inc.
Boilers Manufacturers - Unilux Advanced Manufacturing, LLC
Boilers Manufacturers
Boilers Manufacturers
Boilers Manufacturers - Unilux Advanced Manufacturing, LLC
Boilers - Fulton Boiler Works, Inc.
Boilers Manufacturers - Unilux Advanced Manufacturing, LLC

Industrial Boilers - Construction and Application

Industrial boilers have been an important device in number of industries since they were first used in steam engines. Steam engines may have been phased out, however, boilers are still extensively used for various industries, ranging from laundry to food, and from sewer maintenance to breweries.

Industrial boilers' working principle is the same as pressure cookers in your kitchen. The difference is in the scale and ability to withstand high pressure. They are specially designed to manage pressure as high as 30 bars, and are thus made from chunky steel plates that are welded together. However, just like pressure cookers, they are enclosed vessels made to withstand high pressures and to heat water by a fuel source. The steam generated by the boilers is used for humidification and for industrial heating. In the times of steam engines, the steam was used to expand the cylinder, which moved the piston, giving momentum to engine.

Construction of a standard boiler

An industrial boiler consists of a heating chamber, also known as a vessel, which typically is in the shape of a cylinder. In the cylinder, a heating source in the form of a burner is installed, and the heat produced by the burner is transferred to the water. The heat is transferred by the heat exchanger, which includes pipes and tubes to transfer the steam to the desired end. When hot water is the requirement rather than steam, pumps are usually employed. The steam moves under its own pressure and is transported to the desired place with a cache of tubes. To make boilers work efficiently with less water loss, the condensed steam is returned back to the furnace to be heated again, and the furnace is furnished with water continuously to compensate for the lost water. The other parts include a chimney to emit combustion gases, and a pressure safety mechanism.

Application of industrial boilers

  • Boilers are most commonly used in the food processing industry, as all food items need to be heated to inhibit microbial growth. Moreover, steam is used for cooking, sterilization of vessels, pasteurization, sanitization of packaging material and general cleaning.
  • The other industry that makes use of boilers is laundry. Heated water makes it easy to clean dirty clothes efficiently and remove tough stains. Moreover, the steam produced by boilers are also used for ironing, just like a home steam press.
  • Wineries and breweries use boilers at large scale. In the large boilers, a combination of raw materials is heated for numbers of hours to start the fermentation process, which breaks the material into alcohol. The steam also is used for cleaning barrels and other equipment so that nothing mixes with your favorite drink.
  • Boilers also have application in building industry and sewer cleaning. In building industry, the manufacturing of bricks involves use of boilers. Steam hardens the brick under high and in a special chamber. In sewer cleaning industry, steam is used to clean jammed piping systems by exposing the pipes to high-pressure steam, which cleans the blockades.

Factors to Consider while Buying Industrial Boiler

Industrial boilers consume huge amounts of energy, thus, it is important that they run efficiently in order to be cost effective. A single parameter cannot determine the efficiency of an industrial boilers; therefore, a number of things need to be considered before buying a boiler.

Combustion efficiency versus thermal efficiency

For industrial boilers, two types of efficiencies are normally used, one is the combustion efficiency and the other is thermal efficiency. So what is the difference between them?

In a combustion process, chemical potential energy of a fuel is changed or converted to produce thermal energy, and the percentage of potential energy that is converted is defined as the combustion efficiency. Whereas, the thermal efficiency is the percentage of potential fuel energy converted to thermal energy for producing steam or heated water. While looking into the efficiency of industrial boilers, it is advised to check the thermal efficiency, not the combustion efficiency.

Boiler controllability

The other parameter that defines the efficiency of boilers and heating system efficiency is the boiler controllability. It is reported that for maximum boiler efficiency, the boiler controllability, which also is known as turn down ratio, should be considered.


With the advent of stricter environmental regulations, it is important that you consider the rules and codes implemented regarding boilers. The rules that you must research, include the American Society of Mechanical Engineers rules, insurance guidelines, and state rules regarding boilers.

System Load

A system load is measured at specific temperature and pressure in terms of Btus or pounds of steam. Typically, there are three types of loads, heating load, process load, and combination load. System load helps to select the size of a boiler that will serve the requirement.

Single or multiple boilers

While selecting a boiler, considering a back-up for the boiler is important. However, some systems do not need a backup; those are usually not associated with production. Moreover, emergency repairs, future expansion and maintenance should be considered.


In a standard operation, almost 10 percent of an operating budget goes to fuel, thus fuel options must be deeply considered. You can choose from a number of fuel sources, including propane, natural gas and light oil. Fuel such as heavy oil and solid fuels are being phased out under new guidelines. Natural gas is recommended, as the best fuel as it leaves few residues, which determines maintenance cost.

Parameters that you need to calculate

For understanding how a boiler will perform over time, it is important to estimate number of things, including boiler-fuel consumption rate, annual fuel use, annual fuel cost, and potential annual fuel savings. After estimating all these parameters, you need to determine potential incremental efficiency, as well as, what will be the payback period against the investment.

The factors and parameters discussed for industrial boilers need further research to understand how they all together and individually affect the performance of a boiler. Therefore, it is recommended to review the literature given in American Society of Mechanical Engineers (ASME), which explores the factors with better insight.

How to Choose an Efficient Industrial Boiler

With the number of options available on the market, choosing an industrial boiler can be a daunting task. Boilers may look like large pressure cooking units; however, they are complex devices with varying designs to serve different purposes. The best way to select a suitable boiler is to look at two factors, the application and design.

The primary decision that you have to make is regarding the application, since boilers are used either for hot water or for steam generation. This is how boilers are classified. Hot water boilers provide hot water for heating systems, which are commonly used for providing optimum room temperature, used as protection against freezing, for dishwashing at large scales, car washing, along with many other applications. Whereas, industrial boilers, that generate steam, have application in power generation, cement and brick production, as well as soil steaming in agriculture.

All standard boilers have a furnace. The heat exchanger distinguishes one from another design. In general, three types of boilers are available, with different heat exchangers.

Water-Tube Boilers

In this design, water tubes are installed in the boiler drum. When the water filled tubes are exposed to heated gases, the water boils and evaporates to make steam. This type of boiler is more thermally efficient and saves a significant amount of energy. However, the design has downfalls too. First, their construction is complex. Second, the water fed into the system needs to be treated, since water with contaminants can clog tubes; all solids in the water are required to be filtered out before water enters the boiler. This design is preferred when the demand of the steam is high and when high pressure is required, therefore, they are also called high pressure boilers.

Fire Tube Boilers

As the name implies, tubes carrying hot gases from the furnace pass through the water-filled drum to generate steam. This design is a common construction found in the industry and is relatively easy to operate compared to the water-tube design. Unlike the water tube design, they are not complex, which makes them less expensive than the alternative. However, they are bulky because of the chunky outer shell. The design is used when low pressure steam is required, thus they are also known as low-pressure boilers. This design has evolved over time and three variations are available on the market. The first is the horizontal return tubular boiler, which has a horizontal tubes and a separated furnace. The second design is known as scotch marine or shell boilers, in which both the fire-tubes and combustion chamber are designed in a single shell. The last variation is known as firebox boilers, which has a specialized water-jacketed firebox.

Sectional Boiler

Sectional Boilers have the most basic design, in which different sections are casted and bolted together. The combustion chamber surrounds the water chamber and heat is exchanged directly. The boilers are used for hot water needs, since it is made from cast iron.

The last option that you can come across is the hybrid design, which uses a different arrangement of heat exchangers and combustion chamber to achieve high efficiency.

Boiler Types

  • Cast iron boilers are modular boilers that are limited to low-pressure steam or hot water applications.
  •   Central boilers provide steam and heat for a larger complex heating system. Central boilers are often housed in a special environment with cooler temperatures surrounding them to prevent overheating.
  • Combi boilers are tanks or vessels used primarily to transfer thermal energy from a heat source to water or stream in accordance with the demand for hot water.
  • Condensing boilers are tanks or vessels that transfer thermal energy from a heat source to water or steam while recovering energy that would normally be expelled through the flue. By condensing the escaping water vapor back into liquid water, the boiler uses latent heat to boost its efficiency up to 98%.
  • Double boilers allow for fine-tuned control and provide high thermal efficiency.
  • Electric boilers are water or water/steam units powered by electricity rather than gas or other fuel.
  • Firebox boilers use tube attachment techniques that are similar to those of the firetube boiler, but their combustion chambers are not round. Firebox boilers are compact, economical units that are typically used seasonally in low pressure steam or hot water applications in which efficiency is not a primary factor.
  • Fire-tube boilers are cylindrical vessels with the flame in the furnace and the combustion gases inside the tubes. The furnace and tubes are within a larger vessel, which contains the water and steam.
  • Flexible water-tube boilers, also called "bent tube boilers," are a common type of boiler valued for their resistance to thermal shock. Flexible water-tube boilers are used in low pressure steam or hot water applications and can be a part of a field-erectable package.
  • Gas boilers use natural gas to heat the water and generate the steam necessary for heating applications.
  • High efficiency boilers are tanks or vessels that transfer thermal energy from a heat source to water or steam and then recover heat that would typically escape through the flue. Condensing boilers are the most efficient boilers with efficiencies above 90%.
  • High pressure boilers are tanks or vessels that facilitate the transfer of heat from its source to water or steam while maintaining a high internal pressure.
  • Hot water boilers are tanks or vessels that transfer thermal energy from a heat source to water that is then circulated to provide residential, commercial and industrial heating. Hot water boilers are an important part in hydronics.
  • Industrial boilers are used either as part of a heating or HVAC system or to individually generate hot water or steam for various industrial processes. Boilers may be powered by oil, natural gas, or electricity.
  • Low pressure boilers are tanks or vessels that facilitate the transfer of heat from its source to water or steam at pressures below 15 pounds per square inch.
  • Membrane watertube boilers are compact boilers with high outputs that are used in high or low pressure or hot water applications. Membrane watertube boilers are ideal for applications in which space is limited.
  • Mobile boilers are used often in temporary shelter environments, such as military camps or for emergency boiler breakdown situations. Mobile boilers can vary greatly in size and capacity and be towed to a location via semi-trucks or small vehicles.
  • Oil boilers are tanks or vessels that either use oil as fuel for the furnace which in turn heats water that circulates through radiators, baseboards or other heat exchangers or as a replacement for the water generally found in boilers and produce hot gases that travel through the piping system.
  • Packaged boilers are units that produce both heat and hot water to an environment.
  • Steam boilers are boilers whose primary function is to produce steam. Steam boilers are a general type of boiler.
  • Tubeless boilers are vertical boilers that have the burner located either at the bottom, middle or top. Tubeless boilers are easily operated boilers that have no tubes but collect the steam over the water in a large jacket or "U" tube.
  • Vertical boilers are commonly used in steam trucks, buses, trams and portable equipment, such as donkey engines utilized for sawmilling and dock work. The design of the vertical tube boiler lends itself to rough handling while in steam, making it ideal for use in situations in which the work plant has to be moved frequently over rough terrain.
  • Waste-heat boilers make use of the rejected heat from other processes, such as gas turbines.
  • Water tube boilers are safe boilers that consist of a header drum to which the water tube pipes connect. The drum and the tubes are usually surrounded by an insulating jacket or brickwork, and the fire and products of combustion are directed to pass through the tubes a multiple number of times, horizontally or vertically.

Boiler Terms

Accumulation Test - A test that measures the relieving capacity of boiler safety relief valves.

Ambient Air - The air that surrounds the equipment.

Aspirating Burner - A burner in which the fuel, in either a gaseous or finely divided form, is burned in suspension. The air for combustion is supplied by bringing it into contact with the fuel as it is drawn through one or more openings by the lower static pressure created by the velocity of the fuel stream.

Boiler Lay-Up - The removal of a boiler from service for a length of time. A boiler may be laid-up dry or wet.

Boiler Pressure - Pressure of the steam of water in a boiler, generally expressed in pounds per square inch (psi) and corresponding temperature.

Boiler Vent - A valved port used to vent air from a full boiler and to prevent a vacuum from forming when the boiler is drained. Boiler vent openings are located on the highest part of the waterside of the boiler.

Bottom Blowdown - The draining of a portion of the water in the boiler in order to remove the heavy sludge that tends to settle at the bottom. This process is done periodically.

BTU (British Thermal Unit) - Amount of heat needed to raise or lower the temperature of one pound of water by one degree Fahrenheit under standard pressure.

By-Pass Line - A pipeline that passes around a control in order to allow the boiler to be operated manually without having to use the control.

Continuous Blowdown - A small, continuously draining stream of water that controls the quantities of impurities in a boiler.

Cut-In Pressure - A pressure control setting at which the boiler automatically turns on.

Equalizer - Connections between parts of a boiler to equalize pressures.

Explosion Door - A door in a furnace or boiler setting that is designed to be opened by a pre-determined gas pressure.

Flash Point - The lowest temperature at which, under specified conditions, fuel oil gives off enough vapor to flash into a momentary flame when ignited.

Furnace - An enclosed space of a boiler in which the fuel undergoes combustion.

Pilot - A flame which is utilized to ignite the fuel at the main burner or burners.

Stack - A vertical conduit that, due to the difference in density between internal and external gases, creates a draft at its base.

Steam - The vapor phase of water, unmixed with other gases.

Vaporization - The change from liquid or solid phase to the vapor phase.

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