Particle size of disintegrated particles as a function of time measured by modified spatial filtering velocimetry. Left column is the data of SSG (Primojel, DMV-Fronterra Excipients, Goch, Germany) and the right one is the data of PP (AmberliteIRP88, Rohm and Haas France SAS, Chauny, France). (a) and (b) show particle size distributions (contour plots) of disintegrating tablets. The rows he colour codes are the relative percentage of a given particle size. The particle size developing over time is depicted in (c) and (d) for SSG and PP, respectively (modified from [154]).
Many metals used in code fabrication are very sensitive to rapid quenching including many of the basic P-No. l metals. Very hard, brittle, crack sensitive micro structures, such as martinsite and upper bainite, are formed in many metals when rapidly quenched from an elevated temperature. The brittle micro structures are likely to crack during the solidification of the weld metal or when highly stressed during operation of the pressure vessel. The cracks are usually an underbead crack not detectable by visual or dye penetrant examination and difficult to detect by radiographic or magnetic particle examination. Yet these small cracks may lead to the product failure, if not at hydro test, at some future time due to cyclic fatigue of the pressure vessel. There are many preventive measures to circumvent this problem such as preheat, high heat input processes, subsequent Post Weld Heat Treated (PWHT), etc.