Design and principle of operation of steam boilers

In order to heat homes and buildings and provide warmth and comfort, steam boilers are essential components of heating systems. Homeowners and professionals working in the heating and insulation industries must comprehend the fundamentals of their design and operation. Steam boilers are a common option for heating applications because they effectively use the power of steam to generate heat.

Steam boilers are powered by a straightforward but clever mechanism. Steam is created by heating water, and it is subsequently distributed throughout the building via pipes to heat exchangers such as radiators. The cycle is completed when steam returns to the boiler to be reheated after releasing its heat energy and condensing back into water. This ongoing procedure guarantees a constant flow of heat to sustain cozy interior temperatures.

A steam boiler’s design consists of multiple essential parts that function as a unit. The boiler is a robust container that heats water to a boiling point and generates steam under intense pressure. After that, the steam is routed via pipes to different areas of the structure, providing heat where it is most needed. Boilers that use steam also have safety features that guard against overpressure and guarantee constant, safe operation.

The variety of fuel sources available to steam boilers is one of their unique characteristics. While steam boilers can run on electricity or alternative fuels like biomass, traditional boilers are typically powered by natural gas or oil. Because of this flexibility, homeowners can select the heating solution that best suits their needs while also being economical and ecologically friendly.

It is essential to comprehend the fundamentals of steam boiler operation in order to heat effectively and efficiently. Understanding the creation, circulation, and application of steam for heat transfer allows heating professionals and homeowners to maximize system efficiency and reduce energy use. Steam boilers continue to be a dependable and effective way to maintain comfortable interior spaces, regardless of whether they are used for residential or commercial purposes.

Design Principle of Operation
Steam boilers are typically comprised of a large metal vessel called a boiler shell, inside which water is heated to produce steam. The principle behind steam boilers involves heating water to create steam, which can then be used for various purposes such as heating, power generation, or industrial processes.

It’s essential to comprehend the layout and operation of steam boilers in order to comprehend them for heating purposes. In essence, steam boilers are containers that heat water to produce steam, which is then circulated. They are made up of a burner, a combustion chamber, and tubes that produce steam from water. Fuel is first burned in order to heat the water and produce steam. Heat is then released from this steam and distributed throughout the house via pipes and radiators. This system’s efficiency is dependent on things like insulation and regular maintenance. Maintaining a warm and comfortable home requires an understanding of the design and operation of steam boilers.

What steam is needed for

Efficient equipment selection is made possible by understanding the locations and modes of use of steam boilers.

PCs are employed in these sectors:

  1. Housing and communal services in central heating install modifications of low or medium pressure PCs for steam heating. The heat carrier goes either directly into the network, or through the heat exchangers prepare water for central heating and DHW.
  2. The industry uses more powerful steam generators, which produce superheated steam with increased heat output.
  3. Energy, high-pressure steam boilers are involved in power generation schemes, transferring steam to the turbine.
  4. Industry, PCs provide the mechanical movement of production apparatuses.
  5. Railway transport, PCs are installed on diesel locomotives.

Principle of operation of the steam boiler

Chemically treated water is heated through screen tube packs in high-pressure steam boilers by hot flue gases generated during the burning of natural fuels.

Steam is created when the water’s temperature rises and enters the application area to transfer the jet’s kinetic or thermal energy.

  1. Natural water enters the water treatment plant, where it is purified from suspended solids and softened. It is then fed into the chemically treated water tanks and supplied to the unit by feed pumps for the steam units.
  2. Before entering the drum, the feed medium enters through the economizer – a cast-iron heating device located in the tail part of the unit to reduce the temperature of flue gases and increase the efficiency of the steam boiler.
  3. From the upper drum, water flows through unheated pipes into the lower drum, and rises from it through lifting convective pipes in the form of a steam-water mixture.
  4. In the upper drum the process of its separation from moisture takes place.
  5. Dry steam is sent to consumers through steam lines.
  6. If it is a steam generator, the steam is reheated in the steam superheater.

Steam boiler device

A tank where water is turned into steam could serve as a simplified design for the PC. It is constructed from pipes with various diameters. The PC has a furnace area where natural fuel is burned in addition to the pipe system.

The type of fuel affects the design features of the steam boiler device. For instance, the burning fuel bed in a coal furnace is positioned on grates that allow oxygen to enter the furnace.

The installation of a chimney at the top of the furnace maintains the regular regime by causing a draught in the steam-gas path of the appliance. Oil or gas burners are found in gas-fired steam boilers.

Water is heated to a boiling point by hot flue gases produced during fuel combustion. Vapor is then released from the vaporization mirror and supplied to the consumer, while flue gases exit the chimney and enter the atmosphere.

With the aid of garnish, valves, circulation pumps, instrumentation smoke pumps, and fans, the major structural components of steam boilers are united into a single boiler system.

Scheme of the steam boiler unit

The boiler room, which can be found in built-in, attached, or detached non-residential buildings, is where PCs are installed.

Assignations in accordance with the plan:

  1. Fuel supply system of the gas steam boiler, No1.
  2. Combustion device – furnace, No2.
  3. Circulation pipes, No3.
  4. Vapor-water mixture zone, vaporization mirror, No4.
  5. Feed water flow direction, NoNo5,6 and 7.
  6. Partitions, No8.
  7. Gas duct, No9.
  8. Chimney, No10.
  9. Circulation water outlet, from the steam boiler tank, No11.
  10. Purge water drain, No12.
  11. Boiler feeding with water, No13.
  12. Steam collector, No14.
  13. Steam separation in the drum, NoNo15,16.
  14. Water glasses, No17.
  15. Saturated vapor zone, No18.
  16. Steam and water mixture zone, No19.

Types of steam boilers

PCs are categorized according to a number of factors, which are important to understand since they affect how the steam boiler operates.

Based on the kind of fuel used:

  • gaseous fuel;
  • steam boilers on solid fuel;
  • liquid-fuel: fuel oil, solar oil;
  • electrical energy.
  1. Utilizer boiler – is involved in fuel saving schemes and recycling of secondary heat emitted during production or from waste gases at CHPPs.
  2. Power – steam boiler plants participate in the scheme of power generation, as a source of steam for turbines, operate with high flow rates and steam parameters.
  3. Heating for central heating and DHW, which are subject to the rules of device and safe operation of steam and hot-water boilers.
  4. Industrial – involved in the production processes of the enterprise.

Steam boiler classification based on the furnace’s construction:

  1. Chambers – use pulverized fuel.
  2. Layer solid fuel – burning solid fuel.

Water pipe

The primary coolant, feed water, travels through the screens during water-tube boiler (WTB) operation, while flue gases travel through the intertube gap. When water reaches its boiling point, steam is produced.

Before determining the capacity, consideration is given to the configuration of the screen tubes and the type of feed water circulation, both of which affect the efficiency of steam generation. The most popular AC schemes are direct-flow and drum. The first type of steam boiler is designed either vertically or horizontally.

Typical drum boiler design: the top is fixed in the upper drum, and the furnace is restricted by tube screens. Packages are connected by bottom collectors. Both AC drums are joined by the second bundle of boiler tubes to form a single circuit that runs in the lower temperature range.

Convection and radiation from the burning fuel in the tube system transfer heat to the water, which then enters the upper drum where steam and moisture are separated.

Water was released into the furnace headers and bottom drum. Depending on the type of boiler, the internal circuit circulation rate varies. In the Russian market, natural circulation boilers are the most widely used type.

The Biysk Boiler Plant (DKVR-2,5,4,6,5,10, and 20) is where steam boilers are produced.

Fire tube

Water flows through the intertube gap and flue gases pass through one or more pipes in gas-tube or flame-tube boilers, which operate AC "vice versa." These small-scale steam boilers have been in use since the 19th century’s pre-war era.

The method by which steam is produced:

  1. The furnace is placed directly in the tube part of the boiler, where the combustion of the fuel mixture and the formation of flue gases takes place.
  2. These devices are made with flame or smoke tubes.
  3. In the first process of combustion takes place directly in the pipe, for which at the inlet is installed oil-gas burner with a fan that promotes uniform combustion along the length of the furnace.
  4. In chimney stacks, fuel is not directly burned, but water is heated by the heated flue gases.

The regulations governing the safe operation of steam and hot water boilers do not apply to these boilers because their steam pressure is less than 0.7 MPa. Steam is created by heating boiler water as it travels through the intertube space. This process is finished in the upper portion of the boiler, and steam is then directed into the main line with the aid of a bypass valve.

The maximum temperature that flue gases can reach at the outlet of a diesel boiler is 150 C. The necessity for technological draught in the chimneys is the reason for this requirement. Because of this, boiler power is reduced to about 400 kW, with steam pressure reaching up to 10 kgf/cm2.

Sectionalized cast iron

In heating andDHW networks, boilers with cast iron packages or sections are common. These units’ designs have advantages in that they can be quickly assembled or disassembled, and by adding sections, the boiler’s capacity can be increased.

One major drawback of operating steam boilers with successful designs is that all unit sections will need to be disassembled if one package breaks.

Permits are not needed for boiler owners because they are exempt from the regulations governing the safe operation and maintenance of steam and hot water boilers.

Because the inner surfaces of the sections directly form the furnace chamber, these boilers are efficient and heat up quickly.

The units have improved thermal conductivity and can withstand corrosion processes in the harsh flue gas environment, but they cannot run at high steam parameters; the maximum pressure is less than 100 kPa, the power is limited to 200 kW, the steam capacity is up to 4.3 tons per hour, and the solid fuel consumption is 300 kg per hour.


The circulation ratio in direct-flow steam generators, which are a subset of vertical steam boilers, is one because they are made to force the water in the screen tubes to go through just one cycle while also being entirely transformed into vapor.

These boilers have far simpler structural designs and don’t need sophisticated combustion process automation. They produce less steam and have a low thermal efficiency compared to circulating boilers, but they are much more explosive because they require a feed pump and are energy independent.

Water moves in a straight-flow unit by gravity convection because it is heavier than steam. Steam boilers are now being switched to the hot-water mode in order to lower the load on devices that have reached the normative resource level.

Peculiarities in a single-screw PC’s operation:

  1. The furnace is made of pipes, which are heated by flue gases.
  2. Boiler water enters the lower part of the water heating circuit, and dry steam is withdrawn from the opposite upper part of the water heating circuit.
  3. In the economizer, the incoming coolant is heated to saturation temperature, and in the screen tubes and superheating circuit – there is a further growth of steam parameters to design values.
  4. These surfaces are not clearly separated from each other, and their geometry depends on the design load of the unit. As the temperature of flue gases decreases and boiler water velocity increases, the economizer and evaporator boundaries shift, and the length correspondingly increases and vice versa.
  5. Steam capacity is limited by the growth of hydraulic resistance and cannot be more than 10 t/h. For more powerful boilers, it is required multifilament designs of the unit.

Steam BMK

Block-modular boiler houses (BMKs) are small modules that come complete with auxiliary equipment.

It is intended to meet the process needs of businesses situated in areas with an energy deficit by providing steam generation, heating, and domestic hot water. BMK eliminates the need for operational staff to be involved all the time, and it activates protection through signaling in an emergency.

The entire operation of the unit is automated: sensors keep an eye on the temperature inside the room, sending the information to the control panel so that the BMK can be adjusted.

The unit can function as a stand-alone source of heat energy in an emergency by being operationally connected to the current heating system.

Only the current engineering networks are connected to the BMK on site; it is transported there with a chimney and in complete factory readiness. This kind of factory assembly reduces the need for installation and adjustment work and boosts unit efficiency to 93%.

Scheme of steam boiler piping

The kind of steam generator and its settings determine the typical PC piping layout.

The standard plan for the housing and communal services system’s district heating systems includes:

  1. Steam generator.
  2. Deaerator.
  3. Softener by chemical purification scheme.
  4. Reagent doser and tank.
  5. Receiver.
  6. Pressure regulators.
  7. Boiler feed water pump.
  8. Water supply pump from deaerator to receiver.

The boiler’s design may additionally comprise:

  • superheater – to increase the temperature of saturated steam;
  • steam separator and in-drum devices – to remove moisture from steam.

How to operate correctly

Since steam boilers are among the objects that pose an increased risk, a number of regulatory documents pertaining to boiler inspection, installation projects, manufacturer technical documentation, and device and safe operation guidelines for steam and hot water boilers are fixed requirements for the safe operation of such vessels, which must be met by accountable officials and service personnel.

Chemical water treatment is the first step toward safe operation and is crucial for the upkeep of contemporary boilers and steam generators. At temperatures higher than 70 oC, mineral salts found in natural water cause scale to form on the inside surfaces of the pipes.

This results in a sharp drop in pressure within the unit’s internal circuit, a rupture of the walls, the instantaneous vaporization of superheated water, and a boiler explosion. It also deteriorates the heat transfer from flue gases to feed water and stops cooling the tubes, which overheat and burn out.

The degree of raw water purification is determined by experts in the boiler unit’s water treatment project, which details both the modes and the equipment’s connection diagram, and it is contingent upon the source of water supply.

Both manual and automated boiler controls are available. It is forbidden to operate modern PCs without automation and safety precautions. Only low-power, low-pressure coal-fired boilers that have manual control and safety protection are permitted.

Structure of the boiler control:

  1. Devices for ignition and shutdown of fuel combustion.
  2. Flow controls: fuel, air and water.
  3. Collection and analysis of PC operation data.
  4. Boiler emergency stop system.

Anyone wishing to enhance their home’s insulation and heating systems must comprehend the construction and functioning of steam boilers. These components are essential to heating systems because they effectively harness the power of steam to produce heat. Homeowners may choose their heating system with knowledge if they understand how they operate from the inside out.

Steam boilers work by heating water to create steam, which is then distributed via pipes and radiators throughout the house. The process starts when a fuel source ignites inside the combustion chamber of the boiler, such as gas, oil, or biomass. The water receives this heat energy, which raises its temperature and produces steam under pressure.

After that, the steam is transported by the distribution system to different rooms of the house, where it releases heat energy to warm the surrounding air. Steam cools and condenses back into water, which is then brought back to the boiler to complete the cycle by being heated again. The consistent heating performance and effective energy use are guaranteed by this closed-loop system.

Maintaining and insulating steam boilers properly are essential to optimizing their efficiency. Frequent maintenance, upkeep, and repairs support efficient operation and avert possible malfunctions. Enhancing the insulation of radiators and pipes also reduces heat loss during distribution, making the system function better.

To sum up, steam boilers are essential parts of heating systems because they effectively use the power of steam to produce heat. Homeowners can maximize their home’s insulation and heating by making educated decisions based on their understanding of the products’ design and functionality. For many years to come, steam boilers can dependable provide warm comfort with the right upkeep and insulation installed.

Video on the topic

I&C service. How a steam boiler works. Accident on a steam boiler

Steam boiler how it works ☼ Principle of steam boiler operation ☼ Detailed explanation.

Operation of steam boilers

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Sergey Ivanov

I like to help people create comfort and comfort in their homes. I share my experience and knowledge in articles so that you can make the right choice of a heating and insulation system for your home.

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