Considerations for Fabrication of Flues That Are Built to Last
November 4, 2015
A flue is any type of duct that is used to transport waste gases produced by a process that burns fuel. They are an essential component of industrial facilities designed to transport the waste gases safely out of the facility. This is crucial for keeping the air quality safe for people who work in the facility. Oftentimes, the volume of emissions is quite large, requiring an extensive elimination system.
Because the gases traveling through flues come directly from a heat source, the flues themselves are quite hot. For this reason, flues must be able to withstand high temperatures without incurring damage. STI Group fabricates industrial flues that are built to last as long as possible with minimal repairs. Let’s look at some of the factors that go into the consideration of constructing durable flues.
What Are the Main Types of Flues?
Flues come in many different types. An open flue brings in heated air from its immediate surroundings and allows it to rise upwards in a vortex. This type of flue is generally not preferred because it can allow combustion materials to escape into the surroundings. Such byproducts of combustion, such as carbon monoxide, are often unhealthy. Closed flues have been developed to address this issue. Closed flues fall into two major categories: balanced flues and power flues. Balanced flues combine an exhaust outlet with an air inlet so that pressure is equalized. They use the hot air’s natural dynamism to transfer it from one area to another, so they tend to be relatively short. Power flues can be much longer and narrower because they employ a fan to drive waste gases away. Engineering takes into consideration the requirements of each specific combustion system to determine the appropriate type of flue.
What Type of Steel Should Be Used?
The type of steel used for flue fabrication should be highly resistant to both heat and corrosion. That’s because the gases that pass through the piping will likely be quite hot. Increases in temperature make corrosion more likely, especially in moist environments. In addition, the waste materials carried through the flues can cause corrosion to increase, particularly if they contain oxides.
The two types of steel most commonly used for large-scale exhaust systems are carbon steel and stainless steel. Both types of steel are quite resistant to corrosion. This means that pipes made from these materials can be thinner than pipes made from less corrosion-resistant materials, giving them a much higher carrying capacity for the same diameter. Carbon steel is particularly strong; it is sufficiently shock-resistant that it can safely be used underneath roadways. Stainless steel tends to be slightly more pleasing to look at than carbon steel, and it is quite easy to keep clean. Both types of steel are easy to cut and weld, and they withstand extreme temperatures quite well. Zinc coatings can also help stabilize the metal when temperatures reach 1000 degrees Fahrenheit.
How Is the Appropriate Thickness Determined?
The size of a flue depends primarily upon the amount of waste gases produced by a facility. However, Engineering understands that each system is unique and that the requisite thickness will depend on a number of factors. In addition to exhaust volume, factors affecting flue size include the speed of wind that must be withstood as well as stresses that may be caused by environmental factors.
How Can Weld Quality Be Assured?
Weld quality is essential for flue fabrication. Joints must be able to withstand pressure from the environment and the contents of the flues. If the welds are not made to specification, they may eventually fail. Fortunately, a number of methods have been developed to verify that all welds are made to last. After a weld is complete, various methods of NDE can be utilized to insure the weld joining quality of the weldment.
The design and fabrication of industrial flues is a highly specialized industry that requires a significant amount of detailed knowledge. STI Group’s qualified team of craftsmen are up to this challenge. We are committed to fabricating industrial flues that are safe, strong, and built to last.