Boilers have been around for hundreds of years, and even though they have improved greatly in safety, efficiency, and ease of use, they still do the same thing: heat water using a fuel source. Cold water enters the boiler and the boiler produces either warm water or steam, depending on the type of boiler. Industrial boilers can be found at almost any facility, so knowing the basics of how they work can come in really handy.
How Do Boilers Work?
Just like in a gasoline engine, fuels like natural gas have chemical energy in them that can be released through burning that fuel. In an engine, that energy is converted into motion. In a boiler, that energy is converted into heat. In addition to fuels like natural gas, propane, or even coal, boilers can use electricity as their energy source too.
Boilers are cylindrical pressure vessels with access doors on both ends. These boilers are often made from thick metal welded together to ensure that they stay strong even under pressure. Efficient boilers are typically well-insulated too, in order to keep as much of the heat inside as possible. In many ways, boilers are similar to the pressure cookers you may have used at home. As water is heated, the temperature of the water will increase until it hits 212 degrees Fahrenheit. If the water is at sea level, this is the point when it will begin to evaporate into steam. As more heat is put into the water, the temperature stays constant, but the liquid water turns into more and more steam.
Sometimes, however, 212 degrees just isn’t hot enough. At home, we use a pressure cooker to get the temperature up. Boilers use the same principle. Increasing the water pressure allows the water to boil at a higher temperature. At 3 Bar of pressure, water boils at a toasty 272 degrees. Depending on how the facility is using the steam, it may make sense to produce higher pressure steam, even with the added costs and safety risks. The other benefit of this higher pressure is that the steam pressure itself can be used to distribute the steam throughout the facility. Hot water must be distributed using a network of pumps and pipes.
The Two Main Types
Although they work using the same basic principles, boilers can be divided into two main types: fireside boilers and waterside boilers. Each type of boiler has its own advantages and disadvantages, along with cost differences.
In a firetube boiler, the fire and combustion gases pass through tubes inside the boiler. On the outside of the tubes, water is used to completely submerge the tubes. The fire inside the tubes warms the tubes and then gradually warms the water around the tubes. Typically, the fire and and flue gases will pass through the tubes three times before finally being exhausted. This increases efficiency by extracting a good portion of the heat from the smoke and gases. Firetube boilers tend to be cheaper than watertube boilers, and are great for low and medium pressure applications.
In a watertube boiler, the fire and water are reversed. Water is pumped through the tubes and the fire passes over the outside of the tubes. The flue gases are routed so that all of the water tubes are exposed to the hot flue gas before it is exhausted. Watertube boilers are more complex and require different maintenance to ensure that they continue operating efficiently. Another benefit of watertube boilers is that they can operate at higher pressures than firetube boilers.
What’s the Steam For?
So now you know how a boiler produces steam, but what does the plant use the steam for? Uses of steam vary from facility to facility, but the main uses of steam in industrial applications include:
- Temperature Control
- Production and Processes
- Sanitizing and Sterilization
The steam can be piped all around the facility so that it can be used by HVAC equipment and air handlers. These air handlers can have coils in them to transfer the heat energy from the steam into the air, basically reversing the process that happened in the boiler. This warm air can be used for worker comfort, or as part of a process.
Hot steam can have many uses in production. One great property of steam is that it can be used to sterilize equipment. Steam can be used at the end of a production cycle to clean and sterilize machinery or components. It may also be used during production to raise the humidity level or increase the temperature of a production process.
All of the fuel burned to produce the steam results in steam that has a lot of energy in it. This steam energy can be used to do useful work, in a similar fashion to electricity. Steam can be used to power a steam turbine, which can then produce electricity or directly power a pump or motor.
As simple as they are, boilers serve a crucial role in keeping facilities operational. Technology continues to improve boilers, making them faster, more efficient, and more reliable. However, they still operate under the same principles. Understanding how they work makes servicing them a whole lot easier. For more help on servicing them, you can contact our team or download our maintenance checklist. Keep your boilers, and your facility, functional at all times with help from Tate Engineering.