Difference Between A Wet Back Boiler And A Dry Back Boiler

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Difference between wet back and dry back boiler

Dry Back And Wet Back Boiler Design

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Yongxing wet back boiler has high thermal efficiency. It has lowest fuel consumption rate and available at extremely affordable prices.
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Our 3 pass wet back boiler design has a reversal chamber. It passes the heat three times in order to maximize thermal efficiency.
Wet Back Design
Yongxing provides a small vertical fire tube boiler design. It fits in compact places and has a panel that can adjust boiler's operating parameters.

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Why Choose Our Wet Back Boiler?

Yongxing boiler group is one of China’s largest boiler manufacturers and suppliers. Thanks to our ready-to-transport wet back boilers, our staff is ready to support you with boiler shipment internationally. But why choose our wet back boiler design?

Our 3 pass wet back boiler has the highest thermal efficiency. It consumes very little fuel and produces steam at very low pressure. All industries in need of low-pressure steam can choose our wet back fire tube boiler.

In a fire tube boiler category, we have two designs; Dry back boiler and wet back boiler. The primary difference between a wet back and a dry back boiler is its rear wall. The dry back boiler has a refractory at its rear wall, stopping furnace heat from going outside. On the other hand, the wet back boiler has water at its rear wall. It reflects the furnace heat and increases the boiler’s thermal efficiency even more.

Apart from high thermal efficiency, our wet back boiler design has a fully automatic system. It has a single panel that can manage the overall boiler operations. Plus, several settings are adjustable through the panel—for example, steam pressure and temperature. The limits are easy to adjust.

Our boilers aren’t just economical but also safe and reliable. We offer 100% safety through high-quality safety valves, pressure and temperature indicators, etc. If you aren’t sure about our product’s quality, you can check reviews from our worldwide clients. They represent our product because they have experience using it.

Both the wet back and dry back boiler have unique advantages. Depending on your industry requirements, choose one that best fits. If you have particular industry requirements, we entertain custom design orders. In other words, we will design a perfect wet back boiler for your industry. Moreover, our wet back boiler prices are very low despite number of auxiliaries with it. We will also give you free installation service if you buy from us.

So, what are you waiting for? Get yourself an inquiry now!

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Wet Back Boiler Explained

Are you looking for the best boiler that would go best in minimal space? Well, the world of boilers offers various types of boilers, but what matters is which one fulfills your requirements. When talking about a fire tube boiler, it comes in two varieties: wet back and dry back boiler. If you’re looking for an option that will save you cost and space, let’s dig into details.

You can find out the difference between wet back and dry back boiler and decide which one should be your pick.

What Is A Wet Back Boiler?

The wet back boiler is a type of boiler that is totally encased in water. It uses water as a heat-exchanging medium. Plus, it helps to transfer flue gasses to the tube bank from the furnace. The heat generated from the combustion chamber travels straight into uniformly heating water.

fire tube boiler

The water in the surrounding absorbs burner heat instead of refractory to enhance operational efficiency. When talking about the wet back boiler’s design, it comes with separate tube sheets, which makes it better tolerant of load variations. The lift-off doors of these boilers do not require a long cool-down period and can open instantly.


There are plenty of reasons that compel us to opt for the wet back boiler. Following are its major advantages.

      • Best Water Absorbers

Wet back boilers are excellent water absorbers. As water absorbs the heat from the burner, the efficiency of these boilers becomes far better than other boilers.

      • Low Maintenance

Another fantastic feature of a wet back boiler is they do not require high maintenance. Also, it doesn’t require expensive refractory to maintain; however, the maintenance of internal pressure vessels can be a bit difficult.

Kits for Sealing

The process of installing wet boilers is pretty simple. it comes with few seals, making it easy to install.

      • Doors Option

The wet back boiler design comes with lift-up doors. Due to this, there is no need to wait for a cool-down period with lift-off or split-hinged doors; you can easily open it any time you need.

      • Sheets For Tubes

Wet back fire tube boiler shows temperature differences between passes. It can cause separate tube sheets to expand and contract independently.

      • Fuel Cost Saving

The Wet back steam boiler is a suitable boiler for cost-saving. It is best when you’re looking for an option to save money on fuel consumption. Fuel cost saving is its best feature because it offers long-term fuel cost reductions.

What Is The Difference Between Wet Back And Dry Back Boiler?

A wet back boiler functions quite differently than a dry back boiler. Here are the differences below.

Comparison Wet Back Dry Back
Cost Difference When talking about a wet back boiler, they cost much higher than a dry back. It is suitable for those who have a good amount to invest initially. Dry back boilers are not as expensive as wet back boilers; therefore, these are suitable when you’re looking for an option where you cannot afford a big chunk of money to invest.
Functioning Wet back boilers have a furnace and a rear wall with a water gap in the backwall. It makes water absorb heat which is an excellent heat exchange medium. In dry back boilers, there is no water in the back wall; however, a refractory attached on its backside reflects the heat from the burner to provide heat support.
Installation The wet back boiler makes the installation process easier to install with no difficulty. The dry back boilers are also easy to install; however, the design differs. The dry back boilers come with a refractory on the backwall.
Inspection When there is an issue, or due to any reason, you want to go for inspection, it can be quite tricky. The pressure vessel inside the wet back boiler makes it challenging to inspect when required. Since no water vessel is present on the rear wall of a dry back boiler; therefore, it’s pretty easy to go when there is a need for inspection.
Heat Generation The design of these boilers makes them generate better heat than dry back due to water presence. When comparing water back and wet back, dry boilers do not produce heat as good as wet back boilers.
Durability Wet back boilers are much more durable than dry back boilers, and they do not need a periodic inspection to find out whether there’s an issue or not. Dry back boilers require regular inspection to find out whether there’s an issue or not with time to avoid any kind of risk.

How Does Wet Boiler Work?

The wet back boilers are more efficient for saving space and energy because 2-pass and even 3-pass structures are designed and used on them. Here we have the procedure in detail below.

wet back boiler

1.     Gas Travels From Fire Box

In fire tube boilers, the hot gasses surround the water, unlike the water tube boiler. After going through the heating process, the gas travels from the system’s firebox to the boiler’s main chamber. In other cases, the gas strikes the reversal chamber and bounces back toward the opposite end.

It creates a heater effect inside the boiler. Water present in the back wall helps cut down The amount of fuel required to generate optimal temperature.

2.     Heats The Water

When gas flows through the boiler, it heats the water inside, and there is a series of boiler tubes. These water tubes have a rectangular shape and are approximately the length of the boiler itself. The water tubes come with seals. and can easily withstand higher pressures. This function helps to make sure that no gas or fire can enter the tube and no water leaks out.

3.     Produces Steam

The burner’s gad and fire hover around the wet back boiler’s water tubes. It helps to heat the water inside the fire tubes. The water inside, after going through the heating process increases to the boiler’s top and passes in the steam drum.

Boiling water rests in the steam drum’s bottom and the gas created by the burner continue to heat the room. Eventually, the hot water turns into steam which the boiler releases and can be used for reheating ad other purposes.

4.     Down Comer Tube To Steam When Required

Sometimes, the steam cools and turns into water drops. As a result, the water level decreases. It can be a reason to drain the water from the steam drum. If it happens, you should fill the water to re-enter the boiler’s water supply.

Once done, then return to the tubes, and convert it into usable steam once more.

The wet back boiler works pretty faster than typical boilers. In fact, it doesn’t require a vast place; it easily fits in a far smaller space. Also, it has a far smaller footprint than traditional dry back boilers. A small footprint allows the installation of multiple boilers to deliver better efficiency.

How Does Dry Back Boiler Work?

Even though both wet back and dry back boilers are firetube boilers, they work differently due to different designs. Here we’re explaining its working principle.

dry back boiler

The design of dry back boilers comes with a reversal chamber on a rear wall. The position of the chamber is covered with an intractable position. Also, it has a core function to pass combustion gasses from the boiler to tube sheets.

These gases reach to burner heat that causes radiation losses outside. The design showcase a rear tube sheet as well as access to the waterside and a convenient fire-side. Dryback boiler comes up with a more extensive functional footprint due to its vessel-sized back door.

The door requires an adequate area to cool down before you need to open it. Plus, you don’t need a regular inspection of the tube sheet to ensure its performance. However, it has costly maintenance work.

Is Wet Back Boiler Better Than Dry Back Boiler?

There are a lot of characteristics that distinguish the wet back boiler from the dry back boiler. You can consider as per your industrial requirement. However, the following points will help you better understand the operation of wet back and dry back boilers.

1.     Shape of Back Wall

The main difference between a wetback and a dryback boiler is the shape of the back wall. A wet back boiler’s rear wall comes with water in the surrounding. In comparison, a dry back boiler’s rear wall comes with refractory. The wet back boiler is more effective than the dry-back because it utilizes the heat from combustion to heat the water.

2.     Heat Absorption

In a wet back boiler, heat from combustion travels straight into uniformly heating water instead of using refractory.

It allows the surrounding water to absorb burner heat, helping to enhance operational efficiency. On the other side, the dry back boiler uses a refractory wall, which reflects the heat from the burner, resulting in outside radiation losses.

3.     Rear Tube Design

The dry back boiler utilizes a common rear tube sheet and provides easy access to both the fire and watersides. The dry back boiler, on the other hand, has a refractory wall that reflects heat from the burner, causing external radiation losses. It helps to achieve better flexibility with load changes which is not available in dry back boilers.

4.     Separate Tube Sheets

Dry back boilers come with a single tube sheet attached inside. In reaction to temperature differences, the tube sheet may face high thermal stresses. However, a wet back boiler uses separate tube sheets making it more tolerant of load variations.

5.     Doors

The wet back boiler comes with lift-off doors that require no cool-down period and can open instantly. Also, it has an ideal functional footprint than dry back boilers. On the other side, the hefty, vessel-sized rear door in dry boilers requires sufficient space and a cool-down period before opening.

6.     Cost Comparison

Wet boilers cost higher than dry back boilers, but they offer a better return due to less fuel consumption and long-lastingness. On the other hand, dry back boilers are not as expensive as wet back but require more maintenance.

7.     Maintenance Cost

The wet back boiler doesn’t require expensive refractory maintenance. However, maintaining an internal pressure vessel can be a bit difficult in it. Dry boilers require regular inspection after a certain period, and you must replace them with time.

8.     Installation

A wet back boiler is easy to install as it comes with fewer seals than dry back boilers. Its non-proprietary design makes it easy and less expensive than dry back boilers. Moreover, each inspection and vessel service requires numerous specified sealing kits for the dry back boilers. After a thorough inspection, you will have to reinstall the boilers.

What Are the Types of Industrial Boilers?

Before opting for the right boiler, there are various factors to consider as per your industrial requirement. You can look upon your specific requirements while deciding which boiler fits best to your needs. So, here we are posting the most popular industrial boilers below.


Wet back and dry back are the two most common Firetube boiler designs. The main distinction between a wetback and a dry boiler is the shape of the back wall. A wet back boiler comes with a design in which water surrounds the rear wall. On the other hand, a dry back boiler’s rear wall comes with refractory. These boilers are more efficient than the dry back boiler since the heat from combustion utilizes to heat the water.

However, you must choose the best quality. Yongxing provides highly durable wet-back boilers. They have the highest thermal efficiency and are available at the best prices.

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