F-A. Chen et aL/ Engineering Failure Analysis 37(2014)42-52 3 Comparison of mechanical properties of in-service tube and the standard values. Yielding strength(oo.2/MPa) Tensile strength(ob/MPa) Elongation percentage(6s/6) 445 B338 value International value 370-530 Note: International values are from Chinese standard GB/T 3624-1995 110]. Fig. 5. Macro-and microscopic morphologies of tensile fracture of titanium tube(a)macroscopic appearance of tensile fracture(b)magnified fracture edge. 2. Experiments and results 1. Material analysis of titanium tubes 1. 1 Chemical composition To better analyze this individual case, we started from its material analysis and tried to decide whether the failure came from material pre We analyzed the material of one failure tube of condenser 1B in unit 1 as a sample ICP-AES, infrared carbon sulfur analyzer and nitrogen hydrogen oxygen gas chromatograph were applied to measure the content of Fe, C, and n, H, o respec- tively. The results are listed in Table 1. It presents that the content of impurity element in the in-service titanium tube is strictly controlled, far below the upper limit of requirements of ASME SB338 titanium specification [7(equals to the TAl industrial pure titanium in GB/T 3620 1-2007 standard of China 8), indicating that the material of the in-service titanium ubes is qualified.2. Experiments and results 2.1. Material analysis of titanium tubes 2.1.1. Chemical compositions To better analyze this individual case, we started from its material analysis and tried to decide whether the failure came from material problems. We analyzed the material of one failure tube of condenser 1B in unit 1 as a sample. ICP-AES, infrared carbon sulfur analyzer and nitrogen hydrogen oxygen gas chromatograph were applied to measure the content of Fe, C, and N, H, O respec￾tively. The results are listed in Table 1. It presents that the content of impurity element in the in-service titanium tube is strictly controlled, far below the upper limit of requirements of ASME SB338 titanium specification [7] (equals to the TA1 industrial pure titanium in GB/T 3620.1-2007 standard of China[8]), indicating that the material of the in-service titanium tubes is qualified. Table 3 Comparison of mechanical properties of in-service tube and the standard values. Item Yielding strength (r0.2/MPa) Tensile strength (rb/MPa) Elongation percentage (d5/%) Ti tube sample 327 445 37.9 SB338 value 275–450 P345 P20 International value P250 370–530 P20 Note: International values are from Chinese standard GB/T 3624-1995 [10]. Fig. 5. Macro- and microscopic morphologies of tensile fracture of titanium tube (a) macroscopic appearance of tensile fracture (b) magnified fracture edge. F.-J. Chen et al. / Engineering Failure Analysis 37 (2014) 42–52 45