Natural gas boilers are heating systems that use natural gas as fuel. These types of boilers are common in the urban areas of cold climates, where the natural gas circulates through pipelines located under the streets.

In rural areas, it is more common to use propane gas as fuel. The long distances between homes make more efficient distributing gas by trucks and delivering it to large storage tanks located in the home’s yards. Propane is more expensive than natural gas, but both of them are more affordable than heating oil or fuel. 

A boiler system heats water in a tank that supplies either hot water or steam that flows through pipes and radiators to heat different spaces. There are two types of natural gas boilers, hot water, and steam boilers. 

Types of Natural Gas Boilers

Steam boiler systems heat water to create steam, which is distributed through the house’s radiators. Hot water boiler systems heat water and pump it through the house’s radiators and baseboards. They also distribute water for purposes other than heating. As a result, they eliminate the installation of a separate system for bathing and cooking. Both boiler systems heat water as the primary source of heat. Nevertheless, they differ in the way that they produce the heat.

Heat Production

Steam boiler systems heat the water beyond the boiling point to create steam. The steam travels through a series of pipes to the radiators located in the house. Hot water boiler systems do not need to heat the water to produce steam. They pump warm water through the series of pipes, radiators, and baseboards around the home, heating the different spaces. The condensed steam, in one case, and the cold water in the other, travel back to the boiler to repeat the cycle. 

Accessory Parts

Hot water boiler systems need a pump to distribute the hot water through the different spaces of the house, and to bring the cold water back to be reheated. A steam boiler system, on the contrary, does not need a pump because the steam travels through the pipes by pressure, and the condensed steam travels back via gravity.

Hot water boilers require other series of accessories, like temperature and pressure regulators, check valve, radiator bleeders, and expansion tank. 

Cost and Energy Usage

Both systems have around the same installation costs. However, their energy efficiency differs because of operational reasons. Steam boilers use more energy to boil the water because they need to produce steam. But they use less energy because the steam travels by pressure and has a more efficient heat transfer. Although hot water systems need less energy to heat the water, they consume more energy to transport and transfer the heat. 

High-Efficiency

The Federal Trade Commission requires that new boilers display their AFUE (Annual Fuel Utilization Efficiency) so that the consumers can compare them. For instance, an AFUE of 70% means that 70% of the energy produced heat, while 30% was wasted. They have a rating system that goes from old, low-efficiency, to new, high-efficiency.

  • AFUE of 56% – 70%. Old Low-efficiency Boilers.
  • AFUE of 78%. New, Minimum- Efficiency Standard Boilers.
  • AFUE of 80% -83%. New, Mid- Efficiency Boilers.
  • AFUE of 90% – 98%. New, High – Efficiency Boilers.

Because High –Efficiency Boilers convert almost all the fuel consumed into heat, they significantly lower the amount of fuel used by the boiler, which translates in energy savings. 

According to the U.S. Department of Energy, the use of a High-efficiency Boiler, reduces the fuel bill in half, compared to the fuel consumption of an old, low-efficient boiler. 

Conclusion

Natural gas boilers of the two types – Steam Boilers and Hot Water Boilers – are highly efficient heating systems that can last a long time if the owner maintains them according to the manufacturer’s instructions. They have different ways of operating and of heat distribution and exchange. If you know the fundamental differences between the two types of boilers, you have a higher probability of selecting the one that will offer you the most advantages in comfort and cost.

If you need a natural gas boiler, consult the experts here.

To know which of these boiler types is the most convenient for you, let us see what a boiler is. “A boiler is an enclosed vessel in which a fluid such as water is heated to produce steam or the vaporized form of a liquid. The steam or hot water is then circulated through a piping system to transfer heat for various applications such as heating, power generation, and other processes. Boilers and associated pieces of equipment are efficient heat exchange systems. However, they can be dangerous if not properly maintained and operated”.

There is a wide variety of boilers for a myriad of applications; from heating a room, to drive the turbines of a utility company. Although all of them produce steam and hot water, they have different designs, differ in their operation, and use various types of fuel. As a result, it is convenient to know more about the boiler types available, so that you can decide which one is the most suitable for your application.    

Industrial Boilers

Fire-tube Boiler

Fire-tube steam boilers are cylindrical vessels that hold water that surrounds a set of tubes conducting hot gases produced by a furnace. Consequently, the heat in the tubes transfers to the water surrounding them, producing steam.

The installation and relocation of modern fire-tube steam boilers are possible because they are available as portable packages. Also, they are easy to maintain. Nevertheless, due to the massive amounts of water at high pressure that the boiler holds, it requires safe operating procedures. The users of fire-tube boilers are industrial and commercial facilities whose processes demand lower steam pressures from this type of boilers. 

Water-tube boiler

Water-tube boilers are highly efficient machines that, by their design, produce superheated dry steam at very high pressures. It feeds large amounts of vapor (several million pounds-per-hour), at very high pressures, up to 5,000 PSIG, to industrial processes. A water-tube industrial boiler has a larger size than a fire-tube.

They are the kind of boilers capable of feeding the processes of heavy industry and utility companies. However, the acquisition and installation costs are high. In the case of heavy industries, they are custom made on the installation site, which can be complicated and time-consuming. Furthermore, they are challenging to maintain. Thus, they require highly skilled personnel for operation and maintenance. 

Commercial Boilers

Commercial boilers have different ways to generate heat; firetube, small water tube, and electric resistance. Their ideal users are universities, libraries, office buildings, schools, laundries, hospitals, and other similar facilities,

Among the different boiler types, commercial boilers are some of the most diverse. These units can use propane, natural gas, electricity, or light oil to provide hot water or steam for process requirements or comfort heating. Based on the type of boiler selected and its application, these systems boost fuel efficiency as high as 99%.

A central heating boiler’s size is proportional to the size of the facility. The ideal size for a boiler is one that can cope adequately with the heating needs the coldest season of the year. A typical commercial heating system has four main components: The boiler produces the heat. The pipes, pumps, and valves, distribute the heat. Radiators and convectors, irradiate the heat to the specific room. Finally, there is a control system that regulates everything.

Home Boilers

Condensing Boilers

Condensing boilers typically extract over 90% of the heat from the fuel they burn, making them both cost-effective and energy-efficient. 

Combination Boilers

A combination boiler is a type of condensing boiler. They are highly efficient and compact, making them ideal for smaller homes. They can act as both, a water heater and also a central heating unit. 

System Boilers

A system boiler directly heats a house’s central heating and also produces hot water for the storage cylinder. It is a heat-only boiler. 

Boiler Types by fuel consumption

Another way that boilers can be classified is by the type of fuel that they burn. The most common are:

Coal 

Most industrial coal-fired boilers run on crushed or pulverized coal, which burns more efficiently than large coal clumps.

Gas and Oil

Gas-fired boilers operate using natural gas, most often a mix of methane, ethane, butane, pentane, or propane. Oil-fired boilers burn gasoline, diesel, and other fossil fuels.

Biomass

Biomass boilers burn plant materials like wood chips, wood construction debris, and corn husks.

Boiler Types by Combustion System

All the boilers mentioned before typically fall into one of the following combustion method categories.

Thermic Fluid

Thermic fluid heaters use fossil fuel inside a closed system. The sealed system can lead to greater efficiency, although it is not ideal for specific applications.

Fluidized Bed

It is the most common method used for burning solid fuels in boilers today; fluidized bed technology involves a bubbling hot mixture of water and material particles (like sand) with fuel in suspension. This mix allows for rapid heat transfer and cleaner, more efficient operations.

If you need one of these boiler types, Teems Steam is here to provide solutions for all of your boiler rental, sales, installation, and operation needs.

Sources: Superior Boiler, Odesie

An industrial Boiler is a closed pressure vessel that produces high or low-pressure steam or hot water for industrial use. Generally, there are two types of boilers used in industrial applications—Fire-tube and Water-tube boilers.

The use of a fire-tube or water-tube industrial boiler depends on the industrial process for which they are going to generate steam or hot water. 

Fire-tube Industrial Boiler

Fire-tube boilers are a cylindrical vessel in which the flames in a furnace produce hot gases that pass through tubes surrounded by water. Consequently, the heat contained in the tubes transfers to the water, heating it, and producing steam.

A fired-tube industrial boiler is employed in processes that require low pressures, up to 250 PSIG. Furthermore, due to their size limitations, up to 50,000,000 BTU/hr, do not produce large amounts of steam. 

Operation 

The fire-tube boiler holds a firebox where flames produce hot combustion gases. A cooling jacket that contains water surrounds the firebox and connects to the long cylindrical boiler shell. The water surrounds a series of fire-tubes or flues that heat the water, generating saturated (wet) steam. That steam rises to the boiler’s highest point, called steam dome, where it accumulates.

A regulator located in the steam dome controls the exit of the steam. A series of larger flues (tubes) situated at the top of the boiler, conduct the saturated (wet) steam back, turning it into dry or superheated steam. The boiler produces superheated steam and exhaust gases, feeding a steam engine’s cylinders. Those machines turn the energy of the steam into mechanical work. The exhaust gases are recycled to preheat the water that enters the boiler, thus increasing its efficiency.

Maintenance

  • The maintenance and cleaning operations of a fire-tube steam boiler relatively simple. They have easy access to its firesides, allowing the change of the fire tubes without further repair of the boiler.
  • The control systems are less complicated than the ones on water tube boilers.
  • The accessories required by a fire-tube boiler are available at economical prices, due to the relatively low pressures that they have to stand.
  • They are not only easy to operate, but they are also fuel-efficient.

Water-tube Industrial Boiler

A water-tube industrial boiler has a larger size than a fire-tube. It feeds large amounts of steam (several million pounds-per-hour), at very high pressures up to 5,000 PSIG, to industrial processes.

Water-tube boilers are highly efficient machines that, by their design, produce superheated dry steam at very high pressures. They are the kind of boilers capable of feeding the processes of heavy industry and utility companies.

Operation

In general, the water tube boiler design includes several drums. Specifically, the lower water drum and the upper steam drum. They are connected by tubes that form the furnace and convection section. The tubes that make up the furnace walls receive the heat and transfer it to the water contained in them, producing steam. Afterward, the hot water rises and enters the upper steam drum. There, the saturated (wet) steam exits off the top of the drum to feed processes or to produce superheated steam.

Maintenance

  • The larger the amount of steam and pressure produced, the larger the size of the boiler. As a result, they have to be assembled and installed on the site of their operation.
  • The preassembled “packaged” boilers, up to 1,500 PSIG, are easier to maintain than the larger ones.
  • The assembly and installation process of the boilers at the site where they are going to work can be comparatively difficult and time-consuming.
  • The difficulty of the cleaning process makes the maintenance process a complicated task that requires highly skilled personnel.
  • It is not possible to replace the tubes, because there is not a common standard of fabrication.

Conclusion

Fire-tube boilers are widely available in packaged form, allowing smooth relocation and installation. They are also easy to operate, control, and maintain. Nevertheless, due to their design, they are limited in their capacity to produce both–Large amounts of steam and very high pressures.

Water-tube boilers are highly efficient, produce large amounts of steam at very high pressures. The packaged type boilers are easier to maintain than the larger ones. Most water-tube boilers with a pressure capacity beyond 1,500 PSIG have to be custom assembled and installed in their working location. Due to their design and large sizes, they are challenging to maintain.

For information about the operation and maintenance of industrial boilers, contact our steam team here.

Sources: Superior Boilers

Fire-Tube Steam Boilers

Fire-tube steam boilers are cylindrical vessels that hold water that surrounds a set of tubes conducting hot gases produced by a furnace. Consequently, the heat in the tubes transfers to the water surrounding them, producing steam. 

Advantages of Fire-Tube Steam Boilers

  • Fire-tube steam boilers are widely available as “packaged” systems. Thus, their transportation and relocation are rather easy. 
  • Their installation is rather simple, if previously an adequate foundation and the connections to water, electricity, fuel, and steam systems are in their place by the time of arrival.
  • The maintenance and cleaning operations of a fire-tube steam boiler relatively simple. They have easy access to its firesides, allowing the change of the fire tubes without further repair of the boiler. 
  • The control systems are less complicated than the ones on water tube boilers.
  • The accessories required by a fire-tube boiler are available at economical prices, due to the relatively low pressures that they have to stand.
  • They are not only easy to operate, but they are also fuel-efficient. Their range of operation is between 600,000 BTU/hr to 50,000,000 BTU/hr.
  • They are used for space heating and diversity of industrial operations.

Disadvantages

  • Although fire-tube boilers are smaller in design, they have a larger water volume than similar size water-tube boilers, causing them to take longer to bring up to operating temperature from a cold start. 
  • Generally, this type of steam boilers generates a maximum output of 27,000 kg/h. Most commercial and industrial users that demand a higher output install multiple fire-tube boilers in tandem.
  • Fire-tube boilers can’t work with applications that require high pressure, beyond 250psig.
  • The cause is the large diameter that the cylindrical bodies of fire-tube boilers have.

Water Tube Steam Boilers

Water-tube boilers have a furnace that burns gas or another type of fuel, whose combustion heats water-containing tubes. As a result, the tubes produce steam by transferring the heat received to the water circulating inside them. Next, the resulting vapor reenters the furnace through a superheater to generate extra pressure. In particular, this device heats the saturated steam above the boiling point at very high pressure, turning it into superheated dry steam, which leaves the boiler with pressure high enough to drive large turbines. They are used by industries and utilities that demand high-pressure steam for their processes.

Advantages of Water-Tube Steam Boilers

  • They contain minimal amounts of water; therefore, they have a high capacity to respond to fluctuations in load and heat supply.
  • Their design containing small diameter tubes and steam drum, allows for the toleration of very high steam pressures, up to 160 bar. 
  • Water-tube boilers are highly efficient because they economize fuel by the use of an induced draft that feeds the furnace fire. Also by the recirculation water for preheating purposes, and for their capacity to produce superheat.
  • They can produce high steam pressures, up to 5,000 psi.  

Disadvantages

  • The degree of pressure that they produce limits their availability as preassembled “packaged” boilers, up to 1,500 psi.
  • The assembly and installation process of the boilers at the site where they are going to work can be comparatively difficult and time-consuming.
  • Their cost, including the installation, happens to be higher than fire-tube boilers.
  • The difficulty of the cleaning process makes the maintenance process a complicated task that requires highly skilled personnel.
  • It is not possible to replace the tubes, because there is not a common standard of fabrication.

Conclusion 

Fire-tube boilers are widely available in packaged form, allowing smooth relocation and installation. They are also easy to operate, control, and maintain. However, they take longer to respond to fluctuations in the pressure demand. Their uses are for space heating and diversity of industrial operations that do not require high pressure.

Water-tube boilers are highly efficient, produce very high pressures, and for their low water content, respond fast to fluctuations in demand for steam. The degree of steam pressure limits its availability as ‘packages” because as the pressure generated increases, so does the size of the boiler.

There is a point beyond which they have to be custom assembled and installed in their working location. They have big sizes, are challenging to maintain, and the cost of acquisition and installation is higher than fire-tube boilers.

If you require information or assistance for buying, renting, installing, and operating Fire-tube or Water-tube steam boilers, contact us here.

Sources: Superior Boilers

Fire-tube steam boilers are a cylindrical vessel in which the flames in a furnace produce hot gases that pass through tubes surrounded by water. Consequently, the heat contained in the tubes transfers to the water, heating it and producing steam.

Fire-tube can be either low or high pressure. Most low-pressure boilers produce hot water for heating purposes, while the high-pressure boilers produce steam for process use.

This article contains technical descriptions. Hence, go directly to the CONCLUSION section at the end of the post if you are interested in a summary.

Design

They have two types of design, wet-back or dry-back. In the first, the boiler has a water-cooled turn around a chamber used to channel the gases from the furnace into the tube banks. Tube removal and cleaning can be more complicated than in the dry-back design.

The dry-back design has a larger and swingable refractory-lined rear door integrated with the vessel. Through this door, combustion gases transfer from the furnace into the tube banks. It requires more refractory maintenance than the wet-back design.

Operation.

The fire-tube steam boiler holds a firebox where flames produce hot combustion gases. A cooling jacket that contains water surrounds the firebox and connects to the long cylindrical boiler shell. The water surrounds a series of fire-tubes or flues that heat the water, generating saturated (wet) steam. That steam rises to the boiler’s highest point, called steam dome, where it accumulates.

A regulator located in the steam dome controls the exit of the steam. A series of larger flues (tubes) situated at the top of the boiler, conduct the saturated (wet) steam back turning it into dry or superheated steam. The boiler produces superheated steam and exhaust gases. The superheated steam, most of the time, feeds a steam engine’s cylinders and rarely feeds a turbine. Those machines turn the energy of the steam into mechanical work. The exhaust gases are recycled to preheat the water that enters the boiler, thus increasing its efficiency.

The fire tubes run through the length of the boiler and make a turn. That run before making the turn is called a pass. Therefore, a three-pass boiler has three sets of tubes, while a four-pass boiler has four. A boiler with more passes has a higher heat extraction rate and is more efficient than one with fewer passes. The fire–tube steam boilers hold pressures to a maximum of 250 psi and 750 horsepower.

Thermal Efficiency

The addition of tubes to the drum containing the water increases the heating surface of the boiler. The higher the heating surface, the more significant the amount of heat that transfers from the hot gases to the water, thus, increasing the thermal efficiency of the boiler. The thermal efficiency is the ratio of the heat transferred from the fuel to the heat absorbed by the water. Steam boilers that have an improved design and high heat transfer rates reach a thermal efficiency of 80% – 85%.

Safety

Every boiler technician must know the basic principles of boiler operation and maintenance because the safe operation of a boiler can prevent accidents. Steam boilers hold large quantities of very hot water under high pressures. When the pressure in the boiler is close to 100 psi, the temperature of the water reaches more than 300 degrees F. If the pressure suddenly drops to zero, without a corresponding drop in temperature, the water instantly turns to steam, increasing its volume enormously. The result of this reaction may be an explosion. Modern fire-tube boilers have built-in safety controls that prevent this type of event from happening. For more information, contact us here.

Conclusion

Fire-tube steam boilers are cylindrical vessels that hold water that surrounds a set of tubes conducting hot gases produced by a furnace. Consequently, the heat in the tubes transfers to the water surrounding them, producing steam.

Modern fire-tube steam boilers are sold as packages that can be installed rather fast and can be relocated elsewhere. They are easy to maintain. Nevertheless, due to the massive amounts of water at high pressure that the boiler holds, they require safe operating procedures.

Industrial and commercial applications whose processes require lower steam pressures demand this type of boilers. If you require information or assistance for buying, renting, installing, and operating Fire-tube steam boilers, contact us here.

Sources: Superior Boilers

A boiler is a crucial piece of equipment in most industrial, commercial facilities and power plants. Specifically, it is a closed pressure vessel that produces high or low-pressure steam or hot water for industrial or domestic use, and have a wide variety of uses. Consequently, there are several types of boilers serving every need. Here we present their classification so that you have a better idea of the kind of boiler that you need.

Classification of Boilers

Industrial Boilers

Fire Tube


They are the type of industrial boilers where heat and gases of combustion (from the furnace) pass through tubes that are enclosed on water. (1)

Water Tube


They are the type of industrial boilers where water passes through tubes while the hot combustion gas flows on the other side of the pipes. Water Tube boilers are more efficient and less dangerous than fire tube boilers. (2)

Fire Box

They are the traditional “locomotive” type of boiler. The “firebox” is the space where the heat originates, producing hot gases that pass through the tubes, heating the fluid. It is reliable but limited.

Packaged Type


The packaged type comes as a factory-assembled package with mountings, accessories, and control instruments installed on it. Either they can be of the fire tube or the water tube type. (4)

By the Type of Fuel Used by Boilers

Coal-fired


They generate thermal energy by burning pulverized coal. (21)

Oil-fired


They are used for application in low-pressure steam or hot water central heating system. (22)

Gas-fired


They, as its name indicates, are gas-fired by either natural gas or propane. (23)

Biomass


They are very similar to the conventional gas types, but instead of using gas (or oil) to produce the heat, they combust sustainably sourced wood pellets. (24)

Circulating Fluidized Bed (FBC Boiler)

CFB is a combustion technology that allows burning solid fuels in steam boilers. When air or gas passes through an inert bed of sand supported by a fine mesh, as the velocity of the air bubbles increases the bed particles, and the air attains a state of high turbulence and the bed assumes the appearance and exhibits the properties of a fluid, and hence its name. (5)

Pulverized Coal (PC Boiler)


Their use is commercial or industrial, and they generate thermal energy by burning pulverized coal or other combustible material. Specifically, compressed air blows the pulverized coal through a suitable nozzle where it burns. (6)

Waste Heat Recovery


It is an energy recovery heat exchanger that recovers heat from hot streams with potential high-energy content. In particular, hot fuel gases from a diesel generator or steam from cooling towers or even wastewater from different cooling processes such as in steel cooling. (7)

Nuclear Steam Generators


Nuclear Steam generators are heat exchangers that are used to convert water into steam from heat produced in a nuclear reactor core. Specifically, pressurized water reactors (PWR) use them in between the primary and secondary coolant loops. Then, his primary coolant is pumped through the reactor core, where it absorbs heat from the fuel rods. (8)

By the Steam Pressure of Boilers

Low-Pressure


They are of the steam or hot water types that have a maximum pressure of 15 pounds per square inch for steam and a maximum of 160 pounds per square inch for hot water. (9)

High-Pressure


A high-pressure is a boiler that generates steam or other vapor at a pressure of more than 15 PSIG or heats water to a temperature higher than 250°F and pressure greater than 160 PSIG for use external to itself. (10)

By the Boilers’ Steam Uses

Process Boilers.


They produce a heated or vaporized fluid for use in various processes or heating applications. For instance, water heating, central heating, boiler-based power generation (11)

Utility Boilers


It is a combustion unit of more than 25 megawatts that serves a generator that produces electricity for sale and fires fossil fuel. (12)

Marine Boilers


They are usually of the two-drum water-tube type with water-cooled furnaces. Likewise, heat recovery equipment of the economizer or air-heater type. The majority of ships are fitted with two units, although some large passenger ships may have three or more. (13)

By their Portability

Stationary and Portable boilers.

By the Furnace Position

Externally Fired Boilers


It has the combustion chamber outside of the shell. This type of furnaces are not surrounded by water but by brickwork (14)

Internally Fired Boilers


It is one whose furnace is wholly or partly surrounded by water. (14)

By the Axis of the Shell

Vertical (Cochran)


It is a vertical drum axis, natural circulation, natural draft, low pressure, multi-tubular, solid fuel fired, fire tube boiler with an internally fired furnace. (15)

Horizontal (Cornish, Lancashire)


Lancashire is a simple horizontal boiler which belongs to the shell and tube class. While Cornish is much like the Lancashire boiler, it is a fire-tube type of boiler that its hot gases flow in tubes and water surround these tubes in shell. (16)

By the Number of Tubes in the Boiler

Single-tube Boilers


It is a type of boiler in which hot gases pass from a fire through one tube running through a sealed container of water. (17)

Multi-tube Boilers


It is a type of boiler in which hot gases pass from a fire through many tubes running through a sealed container of water. (18)

According to the Circulation of Water and Steam in the Boiler

Natural Circulation Boilers


Inside them, the heating of water sets up convection currents that make the water flow. Consequently, as the temperature of the water in the boiler increases, the difference in density makes the water circulate. (19)

Forced Circulation Boilers


It is one where a pump circulates water inside the boiler. Notwithstanding, it differs from a natural circulation type, which relies on current density to circulate water inside the boiler. Furthermore, in some forced circulation boilers, the water flows at a speed of twenty times the rate of evaporation. (20)

Conclusion

Independently of the type of boiler that you need, our steam team has over 100 years of combined experience and is prepared to serve you! We provide solutions for all of your industrial boiler rental and boiler sales needs for all market segments, request a quote today here.

Sources: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24