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4 Different Designs of the Fire Tube Boiler: Which Is Best for Your Facility?

4 Different Designs of the Fire Tube Boiler

Fire tube boilers are designed to transfer hot gases from the heating source and cycle these gases through tubes that circulate through a drum filled with water. This process effectively transfers the heat from the gas into the water, which effectively generates steam.

Due to this relatively simple design, fire tube boilers are easy to operate and inexpensive to purchase. With the ability to generate medium to low degrees of pressure, fire tube are exceptionally versatile and able to be configured in a variety of designs. The following information explains some of the most common designs for fire tube boilers.

1. Horizontal Return Tubular Fire Tube Boiler

As one of the oldest and most simple designs for industrial boilers, the Horizontal Return Tubular fire tube boilers are still being produced today. It features a shell, a tube sheet on each end of the shell, and tubes that connect both tube sheets.

The boiler is mounted above the masonry or steel furnace. Once the combustion products leave the furnace, it's directed through the tubes on the end of the boiler. After going through the tubes, the combustion products leave the other end of the boiler. The combustion products are directed to the chimney or stack.

2. Firebox Boiler Design

The firebox boiler design utilizes locomotive boilers and fire tube firebox boilers. As a one-pass boiler design, the combustion products pass through the locomotive boiler once. Depending on the arrangement of the tubes and baffles, some firebox boiler designs may be a three-pass or two-pass.

The most common characteristic of the firebox boiler design is a furnace that may be contained partially in the boiler. The furnace is cooled by water for the majority of its entire surface area.

Multi-pass boilers are an extremely common option. These boilers are typically found in colleges, universities, or areas where the system is used to produce steam for space heating or use to create hot water.

3. Scotch Fire Tube Boiler Design

The scotch fire tube boiler design is most commonly referred to as the scotch marine boiler. With this design, the furnace is a big diameter tube located inside of the boiler. The furnace and boiler are circumferenced by water.

Some of the larger, older scotch boilers would have two or even three different boilers. However, most of today's modern scotch boilers only have one. Depending on the arrangement of the tubes and baffles, these systems can be two, three, or even four-pass.

Systems with four passes are typically recognized as the best option when balancing condensation induced corrosion and economic heat transfer. With every pass through the boiler, heat from the combustion products is transferred to the water located in the boiler. After a certain number of passes, it increasingly becomes economically difficult to extract heat from cooling products of combustion. At the same time, if the combustion products cool too much, the gases for combustion will condense, which can lead to corrosion.

Wet-Back & Dry-Back Scotch Boilers

Wet-back scotch boilers feature a design where the end closure is opposite of the burner end of the boiler. As the name suggests, wet-back refers to the fact the end closure is cooled by water. On the other hand, a dry-back design means the end closure isn't cooled by water. Dry-back designs rely on a refractory, fire brick, or some combination of the two to avoid the end closure from overheating.

4. Vertical Fire Tube Boiler Design

As a one-pass boiler design, vertical fire tube boiler has the furnace on the bottom. The tubes run between the upper and lower tube sheets. With this type of design, the furnace may be comprised of masonry or enclosed on its sides with a water-cooled jacket.

Wet-Top & Dry-Top Vertical Tube

The top tube sheet can be below or above the water line. When the top tube sheet is below, it's known as a wet-top; but when it's above the water line, it's known as a dry-top. One of the most attractive facets of vertical boilers is a relatively small footprint.

These types of systems are optimum for facilities with space restrictions. Due to this facet, vertical boiler systems are extremely popular within the dry cleaning industry.

Contact Applied Technologies of New York

Anytime someone begins constructing a new industrial facility, one of the first considerations is the type of boiler that will be used for the plant. Firetube boilers offer several advantages over other types of boilers, but the type of boiler you choose should be based on the needs of your facility.

The experts at Applied Technologies of New York offer decades of experience helping facility managers choose the best boiler system. We specialize in helping business within:

Contact Applied Technologies of New York for a consultation today.

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