Drum boilers: types, principle of operation, peculiarities of service

It is crucial to comprehend the various heating systems available in order to maintain a warm and comfortable home environment. The drum boiler is one such device that is indispensable in a lot of homes. An exploration of the types, principles of operation, and service peculiarities of drum boilers can provide insight into how these systems function and how to maintain them, whether you’re thinking about replacing your heating system or just want to learn more about your current setup.

One kind of heating system that is frequently found in both residential and commercial buildings is the drum boiler. Drum boilers are different from conventional boilers in that they have several smaller drums, each of which has a distinct function in the heating process. Together, these drums effectively heat the water and distribute it throughout the structure, warming various rooms and areas.

Gaining an understanding of the fundamental workings of drum boilers is essential to comprehending their role in a heating system. In essence, drum boilers work by heating water to create steam, which is then distributed throughout the building’s pipes and ducts to provide heat. This method successfully raises the temperature and creates a cozy interior atmosphere by transferring thermal energy from the steam to the surrounding air.

Drum boilers are renowned for their adaptability and versatility to various heating requirements. These boilers are available in different varieties, such as water-tube and fire-tube boilers, each with special benefits and uses in mind. For example, water-tube boilers are more appropriate for larger buildings with higher heating demands, while fire-tube boilers are more compact and efficient, making them perfect for smaller residential properties.

Drum boilers need to be maintained on a regular basis to ensure maximum efficiency and longevity, just like any other heating system. Tasks like cleaning and inspecting the drums, looking for leaks or corrosion, and making sure all the parts are working properly are all part of proper servicing. Through proactive maintenance and timely resolution of issues, homeowners can guarantee the continuous operation of their drum boilers, thereby ensuring year-round warmth and comfort in their homes.

Technical characteristics

The initial design of the apparatus was to produce a large amount of steam-water mixture at high pressure and temperature. Any grade of metal is strongly oxidized by red-hot steam, and heating boiler steel is always linked to the development of thermal deformations.

The primary component of the construction, the heat exchanger, is protected from potential issues related to intense steam generation inside the heating tubes even when the boiler is operating at full load thanks to the unique design of the drum boiler.

Key features of the steam boiler in a drum:

1. High steam capacity. Depending on the water regime, drum boilers can produce from 300 kg/h to 20 tons/h (depending on the model and purpose).
2. High efficiency – 90% on average. Small drum boilers, used as equipment of heating stations and heating stations, work with efficiency of 85-90%. The efficiency factor of power plant boilers is 90-93% and more.
3. Working pressure of the coolant – from 15 to 180 bar.
4. Boiler equipment can operate on gas, fuel oil, mixed fuel, coal and coal dust.

An atmosphere of high temperature and pressure, along with the presence of water vapor and glowing gases, is perfect for the development of corrosion. For this reason, boiler steel with a significant thickness (10–40 mm) is used to make drums.

It is evident that the boiler tank’s safety margin exceeds what the drum boiler’s strength or stability require. However, in situations where there are temperature variations and thermal stresses on the tank’s welds, this is the only way to prevent the tank from being destroyed.

In understanding drum boilers, it"s vital to grasp their types, how they work, and what makes them unique in service. Drum boilers come in various forms, each tailored to specific needs, whether it"s industrial, commercial, or residential. Their principle of operation relies on heating water to produce steam, utilizing either fire-tube or water-tube designs. Fire-tube boilers feature a cylindrical shell filled with water, with hot gases flowing through tubes submerged within. Water-tube boilers, on the other hand, have water-filled tubes circulating hot gases. Maintenance and service for drum boilers are crucial, ensuring efficiency and safety. Regular inspection, cleaning, and monitoring are essential to prevent issues and prolong their lifespan. Understanding these basics helps in optimizing heating systems and ensuring cozy homes or efficient industrial operations.

Boiler design

The device’s use in the creation of unique drums—cylinder-shaped containers—gave rise to its name. This boiler equipment component was taken from steam engines that run on superheated steam.

Strong machinery with a high heat load emits steam and boiling water at the output.

The vapor phase’s content can range from 5 to 20%. The mixture is fed via a drum-style separating device since it cannot be fed straight into the machine or turbine.

The furnace with its grates and chimney was housed inside the main tank, which was designed like a cylindrical vessel. Even though contemporary high-pressure superheated steam boiler plants don’t look much like the old steam engines, large capacity equipment still goes by the term "drum boiler."

The following technical characteristics of the contemporary drum boiler unit:

1. The heat exchanger is made in the form of a bundle or package of small diameter pipes covering the hot zone of the furnace, in which gas or fuel oil is burned.
2. The pipes of the heat exchanger are looped with the accumulating drum tank. The vapor phase is separated and vaporized from liquid water in the drum.
3. Furnace chamber – fuel is burned in it. The tubes cover the combustion zone in a "cocoon" so that most of the convective and radiated heat is absorbed by the walls of the tubular heat exchanger and not by the thermal resistant materials lining the chamber.

Despite their seeming simplicity, drum boilers are among the hardest to maintain and repair, mostly because of issues with the metal heat exchanger pipes corroding. The high concentration of sulfur oxides in flue gases is the cause of this.

Types of drum boilers

There are very few universal designs in the model nomenclature that can be used to produce high-pressure superheated steam in addition to hot water. Every variation of the drum-type boiler equipment is specialized. They are typically separated into two major groups: those that generate steam and those that heat, based on their design and intended use.

As a result, the water circulation schemes in the pipes vary. Water can flow through the heat exchanger in a straight line or looped hot circuit multiple times before returning to the drum accumulator.

A cursory glance at the scheme will suffice to comprehend the key differences between a direct boiler and drum boiler.

Water circulates through the ring in drum-type models, while in direct-flow models it passes through the heating tubes once.

Drum boilers

Their primary function is to produce hot water under high pressure. Because the drum boiler produces superheated boiling water and a small amount of steam at its output, they are frequently referred to as steam-water or boilers.

A battery heater is structurally similar to a large cylinder with multiple heating circuits of heat-resistant tubes inside of it.

Because they don’t take up much room, boilers are grouped together or placed in batteries. There is one drum collector-separator of water and steam installed in each battery of four to six boiler units because the amount of steam at the heat exchanger’s outlet is rather little.

Batteries can only be powered by gas.

Water tube boilers

Their more intricate design sets them apart from the boiler models. You can comprehend the device by using the example of a drum-style domestic heating boiler.

The water tube boiler is a large water-filled tank or drum. It may have very large dimensions.

Along the walls of the drum, two rows of heating pipes are welded on both sides. Beneath the heating circuit are one or two burners. In this instance, the drum boiler’s natural circulation is employed. Pumps are not required to guarantee steady heat extraction from the heated walls of the water tube registers.

As the water in the pipes heats up, its density drops and, in accordance with Archimedes’ law, colder water from the container placed in the upper section of the drum boiler replaces the expanded water. Because the register is designed like two pipes, a natural liquid circulation forms and will continue to do so for as long as the burner is operating.

Since water-tube boilers run on any fuel, the technology is frequently employed in the production of DIY heating appliances. The water-tube heat exchanger configuration is found in residential coal-fired boilers that are produced in factories by manufacturing firms.

Drum boilers, which are very powerful steam generators, use a lot of water-tube technology for both steam generation and water heating. In this instance, the furnace is constructed like an arch.

The furnace occupies one section of the building, and the walls are lined with vertical heat exchanger pipes, also known as pipe screens. They extract heat, which is then naturally circulated to the boiler’s upper drum tank. Air heating and the economizer are located in the second section of the arch.

Principle of operation

Similar to direct-flow boilers, drum boilers operate. The heat exchanger is constructed from tubes that are wound spirally to resemble a drum or cylinder. Several circuits are typically nested inside one another in a single drum boiler. The heated flue gases circulate around each row of coiled tubes in the heat exchanger in a sequential manner after leaving the burner zone and entering the rotary collector.

These kinds of devices can’t work in the mode of natural circulation. The water heats up quickly because of the high density of the coiling steps and the gas plume’s high heat output. In the event that the circulation pump is turned off, boiling water will erode the heat exchanger’s walls.

An emergency hatch built into the boiler design allows hot gases from the heat exchanger to be directed straight into the chimney.

Small steam generators have two modes of operation: forced coolant circulation and natural convection, which is typically used during warm-up.

Since steam is the primary output of large capacity drum boilers, the heated water that has been in the drum-steam separator is pumped by means of the pump.

Before reaching the consumer, the liquid that has been separated from the vapor must go through a superheater at the heat exchanger to remove any remaining water microdroplets.

The separating drum is an intricate apparatus. It is employed to simultaneously carry out the following boiler operations:

1. The cooled steam is condensed. Accordingly, heat is released, which is used to heat the water discharged into the heating circuit.
2. Adjusts the amount of water and pressure in the boiler circuit.
3. The coolant is treated with chemical reagents.

In the final scenario, the drum storage tank is filled with an aqueous solution of orthophosphoric acid salts.

Because of this, it is feasible to lower the water’s hardness to the necessary degree and move some of it into a dissolved state, which allows for the removal of the flushing solution and additional cleaning and flushing of the boiler’s water tube registers using clean heat transfer medium.

Peculiarities of repair

The majority of the salts are precisely gathered in the drum tank. Therefore, the water tube registers for heavy-duty boilers are flushed and blown out of deposits at least once every 20 days. Flushing is typically done on domestic boiler equipment prior to the start of the heating season. During operation, the coolant’s hardness is already adjusted.

Large volumes of water and steam can be heated by drum designs. Refilling the system with desalinated water that has gone through a reverse osmosis filter is therefore not financially advantageous. Flush costs are lower than the price of distilled water.

Not only is salt sludge removed, but water pipe register wall thickness is measured as well. The heat exchanger section is overhauled and replaced with a new one if a cavern has formed. Repairing pipes requires industrial equipment only. Patching and welding are not permitted.

Drum boilers have shown to be a dependable and effective option for home insulation and heating. Homeowners can choose from a variety of types, each with distinct benefits, to meet their individual needs. Flexibility in installation and operation is made possible by the variety of designs, which range from single drum to bi-drum to even tri-drum.

Because of their simple operating principle, drum boilers are suitable for a broad variety of applications. The drum heats the water, creating steam that can be used by radiators and pipes to distribute throughout the house. This procedure guarantees constant warmth and coziness, particularly in the winter.

Drum boilers’ ease of maintenance is one of their main advantages. Compared to other heating systems, this system has fewer moving parts, which makes maintenance and repairs easier and less frequent. This minimizes disruptions to daily life while also saving homeowners money and time.

That being said, there are a few unique aspects of drum boiler maintenance that need to be considered. Maintaining optimal performance and safety of the boiler and its associated components requires routine inspection and cleaning. To further avoid potential risks, adequate ventilation and fuel consumption monitoring are required.

To sum up, drum boilers provide a dependable and effective way to heat and insulate homes. When paired with a variety of options, their ease of use makes them a sensible option for homeowners looking for convenience and comfort. Through comprehension of their principles of operation and compliance with maintenance protocols, homeowners can experience reliable warmth and peace of mind all year long.

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