Whether you have purchased, leased, or operated a boiler, it is likely that you have plenty of questions about how industrial boilers work and what exactly happens during the combustion process. At Manley’s Boiler, one of the most important parts of our job is to educate customers on boiler function, safety, and maintenance. The industrial boiler vocabulary can be full of convoluted terms and complex phrases, leaving you to wonder how these terms apply to the day in and day out operation of your facility. That’s why we’ve put together our industrial boiler guide that’s simple and easy to understand. We’re here to explain and demystify some of the most common boiler terms, parts, and operations. The more you know about your boiler system, the better prepared you are to operate it safely and efficiently. Have more questions? Give us a call. We’re always here to help.
Starting with the Basics: What Is a Boiler?
To start our boiler guide, we’d like to define for you exactly what a boiler is. At the most essential level, a boiler is a water-containing vessel that creates heat by turning water into steam.This vessel is the site for combustion, the process that uses fuel to create heat. Combustion depends on a fuel source to power this transformation and there are a variety of options when it comes to the type of fuel used in this process.
The most common fuels are oil, gas, and coal. Keep in mind that fuel considerations and efficiency are an extremely important aspect of your boiler usage. A boiler is the heart of a central heating system-by far the most important part, actually. Generally, whether you are looking at a commercial or a residential boiler, the boiler is receiving a supply of gas connected to a supply line in the nearest street to the facility.
Closed Systems vs. Open Systems
Once you dive deeper into the discussion of what a boiler is, you are likely to encounter two terms: ‘closed system’ and ‘open system.’ A closed system is one where 100 percent of the steam is returned and reused within the system. Closed systems are, by necessity, a one pipe system. In many cases, older heating systems are one pipe systems and are generally antique or out of date.
Open systems are defined as systems that don’t feed steam back into the feedwater system. With open systems, there is always some degree of contamination, including dissolved oxygen, hydrazine, sodium, and silica, that need to be monitored.
More Boiler Types: Firetube Boilers vs. Watertube Boilers
Another set of terms that you’ll frequently hear are ‘firetube boilers’ versus ‘watertube boilers.’ Firetube boilers are also commonly referred to as shell boilers. In a firetube boiler, fire or hot gases are directed internally through tubes within a boiler shell. They are surrounded by water and the tubes are arranged in banks so that the gases pass through the system up to four times before passing through the stack. Firetube boilers can produce an amazing amount of energy—up to 750 horsepower of energy, or 250,000 pounds of steam per hour of operation. About 80% of boilers manufactured today are firetube boilers.
A common configuration for firetube boilers is the packaged boiler, in which a boiler is shipped in a single, complete unit, including fuel burning equipment, mechanical draft equipment, automatic controls, and all accessories. As a result, these firetube package boilers are very easy to order, ship, and install. They also represent considerable square footage and cost savings. Another benefit of package boilers is that their design lends itself to more automated function. They are engineered to function automatically with less attention and less maintenance than a standard, non-package boiler.
A watertube boiler, on the other hand, is designed so that any fire or hot gases are directed externally around tubes containing water. This requires that watertube boilers are designed with tubes in a vertical position for optimal functionality. A watertube boiler has a rectangular shape and includes two or more drums that serve as storage containers for tubes and water. These drums are the sites where steam and water separation occurs, and the lower drums serve to collect any sludge that results from the process. The average watertube boiler has a horsepower of up to 750, and can produce up to 200,000 pounds of steam.
Aside from their design and output, it is generally thought that watertube boilers are slightly safer than firetube boilers, and that they may last longer, too. Firetube boilers, on the other hand, tend to be lower in cost and are easier to clean and maintain. But because a firetube boiler relies on a larger volume of water, it takes longer to start up and reach operating temperatures. With watertube boilers, the lower water volume allows for better handling of load swings and, in general, has better turndown.
How A Boiler Functions: A Guide for Boiler Operation
In every boiler, there is an electric switch that opens a valve which controls a mechanical device and allows or blocks fluid or gas from flowing through it. Once the switch is flipped and the fluid or gas is allowed to flow through the pipe, the gas enters a combustion chamber via a series of small jets. These small gas jets contribute to a heat exchanger. The heat exchangers are connected to a pipe carrying cold fluid. The heat exchanger interacts with the heat from the gas jets and raises the temperature of the liquid until it is an extremely high temperature. The hot liquid then travels through a series of pipes that run through hot water radiators and then return to the boiler system. Typically, each room in a house or a facility has its own radiator, which provides heat to the immediate area.
When the water returns to the boiler after flowing through the radiators, it has cooled significantly. The boiler will fire another time in order to heat the water once more and recirculate it through the system. Constant, regular water circulation is key to effective heating, and an electric pump within the boiler system makes sure that water flows through the system and radiates in a consistent fashion.
Heat Exchangers: Keeping Heat Moving
Heat exchangers are key to an efficient industrial boiler, and no boiler guide would be complete without a discussion of the role heat exchangers play within a boiler. A heat exchanger is a device that allows heat from water or vapor to pass through a radiator system and provide heat through those radiators. How? A heat exchanger burns natural gas in either a line formation or a grid formation of gas jets that fire upward, over a water source allowing the water pumps to absorb the heat energy. The heat exchanger is crucial in allowing the heat from water or vapor to transfer to a secondary liquid or gas without allowing the two to come in contact.
There are several types of heat exchangers that any consumer should be aware of. The first is the shell and tube style of heat exchanger. The shell and tube is defined by water flowing through a set of metal tubes as the second source of fluid passes through a sealed-off shell enclosing both tubes. Both fluids flow in the same direction (parallel flow), in the opposite direction (counter flow), or in a cross direction. The shell and tube heat exchanger is most commonly seen in steam locomotives.
Another type of heat exchanger is the plate/fin style. As with the shell and tube model, a plate/fin heat exchanger is named after its design, which features thin metal plates or fins that have a large surface area, allowing them to exchange heat for gas furnaces.
Essential Functions: How a Boiler Creates Hot Water
Depending on the type of boiler you have, your system may store water in a variety of ways. There are three primary types of boilers you should know about and each have their own design and styles of operation.
First are open-vented boilers. These boilers store hot water in a tank. The second type of boiler is a combi-boiler. Unlike open-vented boilers, this type of boiler stores water in tanks and then heats it on demand. When a valve in the system of a combi-boiler is opened, the boiler fires and heats the water prior to sending it through the system to where it is needed (i.e., a faucet.).
A third type of boiler, called a condensing boiler, burns carbon-based fuel with oxygen in order to produce steam and carbon dioxide. The gases that escape this process (through a chimney) as exhaust are called flue gases. Flue gases in and of themselves are not necessarily problematic, but the primary drawback of these gas boilers is that a significant amount of heat also escapes from the system along with the flue gases. However, with condensing gas boilers, one of the major advantages is that they offer up to a 90% improvement in terms of efficiency when compared to standard gas boilers. Overall, condensing boilers are considered much more efficient in contrast to non-condensing gas boilers, a major consideration for any business running on a budget.
When You Need Professional Service
We know it’s important to keep our clients educated and help them make the right decisions when it comes to leasing or buying an industrial boiler. Manley’s Boiler has decades of boiler service, installation, and repair experience, and can help you with all of your industrial boiler needs. We offer 24/7 emergency service, including weekends and holidays, and we are always available to educate and assist our customers. We have experience working with some of the largest industrial and commercial facilities in the California region, and we would be happy to offer our expertise to your business.
Manley’s Boiler is an authorized rep for several major boiler brands, and we are always available to consult with you on your boiler lease or purchasing options. Whether you are looking for immediate emergency service, an annual maintenance visit, a part replacement, refractory repair, or anything in between, we are happy to be a quality, dependable resource for our customers.