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Humans have dabbled in alloys and iron for 4,000 years. The additions of elements such as chromium and titanium gave rise to the stainless steel used today, but despite the best efforts of engineers, it is far from indestructible. For industrial-scale heaters to perform well, heat exchanger materials must be compatible with the environment in which they are used. Different humidity levels and the presence of airborne corrosives dictate the type of steel used in heater design. Here are some things to keep in mind when selecting an industrial heater to ensure the heat exchanger will perform well over the long haul.

Use dictates form

The application and environment in which these heaters are used are critical in determining what exchanger type should be used. The standard material used in a heat exchanger is aluminized steel. That works well in the majority of applications. Aluminized steel, however, will corrode much more quickly than stainless steel in humid environments.

There is a downside to stainless steel, though. It helps prolong the life of heat exchangers, but in a corrosive environment it’s likely to break down. While it’s a very robust product, it’s really best suited for high-humidity, noncorrosive applications, such as greenhouses. It would not be a good choice for a pool environment where chlorine is present. Stainless steel is also a good option for areas with consistently high levels of humidity, such as the Southeast or coastal environments.

There are multiple types of stainless steel, including 430, 321 and 409. Each has different types of elements that serve as protection against corrosion, and each must be weighed in terms of economy, usage and longevity. Thermal expansion properties must also be considered. There is no “one size fits all” option for use in gas-fired industrial heaters. The use of a particular type of stainless steel must be chosen on the basis of wide criteria that include stability, durability and how it welds together with different alloys.

The origins of type 409

Some companies have opted to use 409 stainless steel in heat exchangers because the steel type offers the best expansion rates and heat transfer. The 409 alloy was originally developed for use in auto exhaust systems that needed to withstand condensate in short commutes in cold environments. It is robust, proven and reliable. Its thermal expansion is less than other types of stainless, therefore it is less prone to cracking. It is also easier to weld, a key factor in construction of industrial heaters.

Type 409 is slightly more expensive than its aluminized counterparts, but is still economical over the long term when used in the proper environments. It will last years longer. It is a product originally designed for use in one of the harshest possible applications, and its durability to this day makes it a perfect fit for heat exchangers in challenging environments. Builders, owners, architects and contractors in search of superior and durable industrial heaters should do their homework and make sure they make the right choice for what can be a challenging application. It will pay off in the long run.


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