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Corrosion monitoring is an important tool to control and predict corrosion in piping, vessels, furnace tubes, etc. of chemical plants. This study shows results from ultrasonic wall thickness measurements in crude oil and high vacuum distillation units of a German crude oil refinery. Wireless ultrasonic sensors were installed on the external surface of selected piping to continuously monitor internal corrosion. The focus was on high-temperature corrosion (>220°C), which is mainly caused by sulfur and acid components that are present in crude oil and its fractions. Two corrosion parameters were calculated: corrosion rates (from wall thickness over time) and the change in shape of the ultrasonic back wall reflection over time (PSI). This latter parameter is derived from the ultrasonic waveform measured by each sensor. Both corrosion parameters showed different results regarding corrosion activity over time. This was explained by variations in process temperature that significantly influence wall thickness readings but not PSI. Furthermore, only limited correlation was found between corrosion and flow velocity/internal pressure. Finally, three crude parameters (total sulfur content, total acid number, and mercaptan content) were obtained from crude run history and compared to measuring data. Significant correlations between shape change and crude parameters were found, dependent upon sensor location/ corrosion loop.

Grain refinement is an important possibility to enhance the mechanical properties such as strength, ductility and toughness of aluminium weld metal. In this study, grain refinement was achieved through the addition of commercial grain refiner Al Ti5B1 to gas tungsten arc weld metal of the aluminium alloys 1050A (Al 99.5) and 5083 (Al Mg4.5Mn0.7). The grain refiner additions led to a significant reduction of the weld metal mean grain size (Alloy 1050A, 86 %; Alloy 5083, 44 %) with a change in grain shape from columnar to equiaxed. Tensile tests showed for Alloy 5083 that the weld metal's ductility can be increased through grain refinement. No improvement in weld metal strength (i.e. yield strength and ultimate tensile strength) was observed. Furthermore, tear tests with notched specimens revealed that the resistance against initiation and propagation of cracks in the weld metal can be enhanced through grain refinement. The toughness was observed to increase clearly by grain refinement in weld metal of commercial pure Al (Alloy 1050A). In Alloy 5083 weld metal, the toughness was not improved through grain refinement, likely because of a semi-continuous network of brittle intermetallic phases that facilitate crack propagation