Maintenance and Reliability Tensile test results are provided in These conform to the ASTM 516M-17 Grade 60 specification. The chemical composition of all three parent materials and both welds are given in TABLE 4. This is compared to the ASTM 516M-17 Grade 60 specification. Both the shell and reinforcement pad materials fall within this specification. The nozzle material falls within the limits of the ASTM A106-18 Grade B specification. TABLE 3. Discussion. This component has suf- fered cracking through the thickness of the shell due to a fatigue mechanism. This cracking was initiated from the root of the weld in multiple locations. Nearly all fatigue failures are multi-initiation failures. In this case, initiation has occurred at several locations along the length of the weld due to the poor root profile. These have then coalesced to form a single crack front. This is the usual progression for fatigue failures. Evidence of the multiple initiations is shown by ratchet marks on the fracture surface. The flat, featureless fracture surface is typical of high-cycle fatigue. This fracture face is not typical of low-cycle fatigue failures, as there would need to be more evidence of plastic deformation. Considering the geometry of the weld, it would be classified as a butt weld on a backing bar. The full-penetration weld between the shell and the nozzle is functioning as the butt weld, and, since TABLE 1. Vickers hardness data for Weld 1 (taken as per BS EN ISO 6507-1:2005) Indent no. Ocular 1 Comments Ocular 2 HV Cap Indent no. Ocular 1 Comments Ocular 2 HV Root 1 233 237 168 Parent metal 18 245 241 157 Parent metal 2 241 242 159 Parent metal 19 252 243 151 Parent metal 3 245 244 155 Parent metal 20 240 235 164 Parent metal/HAZ 4 243 242 158 Parent metal/HAZ 21 228 227 179 HAZ 5 237 239 164 HAZ 22 220 221 191 Fusion boundary 6 232 234 171 Fusion boundary 23 214 214 202 Weld metal 7 219 229 185 Weld metal 24 212 211 207 Weld metal 8 217 220 194 Weld metal 25 216 213 202 Weld metal 9 223 225 185 Weld metal 26 187 192 258 Fusion boundary 10 224 230 180 Weld metal 27 217 218 196 HAZ 11 214 210 206 Fusion boundary/HAZ 28 241 241 160 Parent metal 12 225 225 183 HAZ 29 234 238 166 Parent metal 13 227 228 179 HAZ 30 234 232 171 Parent metal 14 234 238 166 HAZ/parent metal 15 235 231 171 Parent metal 16 228 228 178 Parent metal 17 234 233 170 Parent metal Location of indentations TABLE 2. Vickers hardness data for Weld 2 (taken as per BS EN ISO 6507-1:2005) Indent no. Comments Ocular 1 Ocular 2 HV 1 234 240 165 2 239 244 3 233 239 Comments Cap Indent no. Ocular 1 Ocular 2 HV Root Parent metal 13 235 237 166 Parent metal 159 Parent metal 14 238 239 163 Parent metal 166 Parent metal 15 218 223 191 HAZ 4 209 211 210 HAZ 16 221 220 191 HAZ 5 185 179 280 Fusion boundary 17 201 203 227 HAZ 6 209 206 215 Weld metal 18 199 201 232 Fusion boundary 7 220 220 190 Weld metal 19 217 221 193 Weld metal 8 203 203 225 Weld metal 20 223 218 191 Weld metal 9 209 218 203 Fusion boundary 21 208 221 202 Weld metal 10 235 242 163 HAZ/parent metal 22 221 220 191 Fusion boundary 11 250 243 153 Parent metal 23 229 234 173 HAZ 12 258 253 142 Parent metal 24 235 237 166 HAZ/parent metal 25 240 237 163 Parent metal 26 241 245 157 Parent metal 32 MAY 2021 | HydrocarbonProcessing.com Location of indentationshttp://www.HydrocarbonProcessing.com