The Use of Duplex Stainless Steel Tubing in Heat Exchanger Service

 Duplex stainless steel tubing is characterised by high chromium (19–28%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. The most used duplex stainless steels are the 2205 (22% Chromium, 5% Nickel) and the 2507 (25% Chromium, 7% Nickel); 2507 is known as “super duplex” due to its higher resistance to corrosion.To improve the performance of your industrial process heat exchanger, we always use duplex stainless steel tubing.

Heat exchangers are key components for many industries, particularly in chemical and oil and gas plants where they play a vital role in process control. Industry professionals — from design engineers and fabricators to the in-plant operators who work with the equipment daily — seek new ways to improve heat transfer performance and extend the life of these units in corrosive environments. Many times, improvements are closely related to the tubing specified for use in their heat exchangers. To improve the performance of heat exchanger tubing, materials engineers have a number of options. They include specifying higher corrosion-resistant grades, selecting tube suppliers with enhanced tube manufacturing and finning processes and using state-of-the-art manufacturers that have upgraded their methods of non-destructive testing.  

Heat exchangers are often faced with extreme temperatures, pressures and corrosive media. Duplex stainless steels are designed to have high strengths while maintaining good toughness, have excellent resistance to chloride pitting corrosion and be more resistant to stress corrosion cracking than the 300 series austenitic stainless steels. 

Duplex stainless steels are useful in applications where strength is of great importance. They can help reduce the weight of components due to their increased strengths (about twice as high as typical 300 series austenitic stainless steels). The higher strength equates to thinner sections of duplex stainless steel being required to accommodate a load as opposed to lower strength materials (like carbon or austenitic stainless steels).

Utilizing corrosion-resistant duplex stainless steel tubing in place of traditional carbon steel or austenitic stainless steel can be beneficial to the performance of heat exchangers. These unique alloys have the ability to extend the lifetime of the tubing in the right applications.