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Fatigue in Heat Exchangers How to Minimize Fatigue Problems: A Fitness Scheme for Heat Exchangers

Editor: Dominik Stephan

Plate-and-shell heat exchangers have become very popular thanks to their high thermal efficiency, compact size and ability to withstand high pressures. But they are also sensitive to metal fatigue. To avoid costly equipment failures and ensure long service life, design, construction and welding must be taken into account.

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In Alfa Laval’s Duro Shell heat exchanger, the inlet and outlet tubes transverse the entire plate pack, adding strength where it is needed most. This design combats fatigue problems and improves the flow distribution, which in turn increases heat transfer efficiency.
In Alfa Laval’s Duro Shell heat exchanger, the inlet and outlet tubes transverse the entire plate pack, adding strength where it is needed most. This design combats fatigue problems and improves the flow distribution, which in turn increases heat transfer efficiency.
(Source: Alfa Laval, ©irontrybex - stock.adobe.com)

Plate-and-shell heat exchangers combine the heat transfer efficiency of plate heat exchangers with the ability to handle high pressures found in shell-and-tube types. This made them the preferred choice for a variety of applications in many industries, including high, fluctuating temperatures and/or pressures, which can cause material fatigue. The heat exchangers are often process critical, making it essential to avoid fatigue-induced failure. Unfortunately, most conventional units exchangers are designed and manufactured in a way that leads to unnecessary problems and equipment breakdown.

Material fatigue occurs when a machine part is exposed to loads that vary cyclically over time, causing it to break at stress levels that would be safe under static conditions. First investigations into the nature of fatigue by August Wöhler in the 19th century led to the discovery of a logarithmic relationship between the load that a machine part can endure and the number of load fluctuations. The logarithmic nature of the relationship means that the lifetime of a component increases dramatically with even a minor decrease in stress. Design changes that reduce stress therefore have a significant effect.