Did you know we rely on heat exchangers for all kinds of daily needs? They are essential for various heating and cooling applications, including air con, refrigeration, and even the humble electric kettle. Additionally, they are vital for industrial processes like power generation, food and beverage manufacturing, and transport. With techniques like bending, tube reduction, and ring rolling, it’s possible to create effective heat exchangers for all kinds of situations.

While they are important, sadly a heat exchanger can fail prematurely in some cases. We want to have a closer look here, including exploring findings from a recent study.

Stainless steel

Often, heat exchangers are made of stainless steel tubing because it has a number of desirable characteristics. Crucially, it is strong and tough, has good thermal and electrical resistance, and can withstand various corrosive elements.

There are two very popular types of stainless steel for heat exchangers. Firstly is 304L (aka 1.307 or its old name 18/8). It’s an interesting alloy, with 18% chromium plus 8% nickel. Donated by the L, it has a low level of carbon. Crucially, it has excellent corrosion resistance and weldability.

The main alternative is 316L (aka 1.4404). The main alloying elements are also chromium (16.5-18.5%) and nickel (10-13%). It is another a low carbon alloy. However, significantly, it contains 2-2.5% molybdenum to increase corrosion resistance and formability. The latter means you can use techniques like tube reduction and bending with relative ease.

Corrosion

While 304L and 316L stainless steels can provide incredible corrosion resistance, there are situations where problems can occur. A recent study found premature leakage due to tube corrosion in two heat exchangers. It began after just 70 days of service.

Most crucially, the study found that dew point corrosion was the main issue. Because the tubes were handling flue gases, there was a substantial amount of carbon dioxide. That, plus the condensation of aggressive hydrochloric and hydrofluoric acids on the tubing, caused rapid pitting. Also notably, the fact the operating temperature of the flue gas was low meant higher concentrations of the acids.

The key conclusion from the study is 316L stainless steel is not suitable for heat exchanger applications where dew point corrosion with hydrochloric and hydrofluoric acid is a risk. Instead, operators should choose alternative materials. Proper material selection here can reduce the risk of leaks and premature failure.

Do you want to arrange tube reduction services?

Multiform Tubes Engineering Ltd is a leading specialist in the field of tube manipulation. We stand out because of our knowledge of different materials and ability to adapt to ensure accuracy. This is crucial for many applications where minimising the risk of leaks is key, such as heat exchangers and pipelines.

So, if you want tube reduction, bending, or any of our other services, please get in touch. We can support clients in various industries, delivering the highest standards every time.