Mey Structure degradation of heat exchanger’s stream plates as effect of corrosion 
OS bw u fatigue 
Fr . 
LE Krzysztof Palka, Andrzej Weronski 
i Technical University of Lublin, Department of Materials Engineering, Poland 
Introduction 
The corrosion fatigue behaviour of type 304 and 316L stainless steels have received little 
attention despite its importance from an engineering and design standpoint. These types of steels are 
„06, 86, (1995), used in food industry, especially on elements of heat exchangers, homogenizers, pumps, etc. This 
elements work in changing loads of pressure, usually in corrodants. Those working conditions 
i deformation initiate the corrosion fatigue of stainless steels. 
EUR Most studies presents results obtained in chloride, sulphide or phosphate solutions [1,2,3]. 
2 es se] Corrodants in food industry are different, but may also contain chloride ions [4,5,6]. In this paper 
Sir ® were presented results obtained in air, 5% citric acid and 5% sodium hydroxide water solutions, 
— which are used as cleaning solutions in CIP process. 
MER of de 
Experimental 
D978! nden in The solution was 5% citric acid (pH=0,5) and 5% sodium hydroxide (pH=13,8) water 
ge solutions. Both solutions contained 0,015% Cl to simulate municipal water. Specimens were 
fatigued under one-sided bend stress at a frequency of 45 Hz. A square loading waveform was 
specified because its maximises the time at maximum load and therefore maximises also the 
probability of promoting corrosion fatigue [7]. After fracture specimens were observed by SEM. 
Additionally structure of failure heat exchanger element was observed (Fig. 1). 
After tests there were calculated values of the fatigue life ratio (FLR), defined as: 
FLR = Fatigue Life in Corrodant 
Fatigue Life in Air at the Same Stress 
Results of the fatigue tests are summarized in Table 1 and Figure 2 and 3. They were 
obtained in limit fatigue life range. 
Fig. 1: Structure of failure heat exchanger element with trans- and intergranular crack. 
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