Flow regimes and pressure drop of a composite tridimensional rotational flow sieve tray under concurrent gas--liquid flow

A new type of composite tridimensional rotational flow sieve tray is proposed. The flow pattern and operation domain of the tray were defined and divided by the image shooting method, combined with the standard deviation of the pressure difference sequence. There are membrane–drip column and foam–embolic flow in the TRST area of the internal packing–type tray, while bubbly and milk froth-ribbon flow are present in the packing area of the external packing-type tray. This study focused on the influence of the tray structure parameters on the pressure drop. Under the experimental operating conditions, the dry pressure drop was within 160 Pa, while the wet pressure drop was within 900 Pa. Under the same structural parameters, the internal packing–type pressure drop of the tray was higher than that of the external packing-type tray. A mathematical model of the pressure drop between dry and wet trays was established.

Designing and Optimising Duplex/Superduplex Compact Flanges to Negate HISC in Subsea Applications

Hydrogen Induced Stress Cracking (HISC) is a phenomena related with metals, with potentially severe consequences when utilizing Duplex / Super Duplex stainless steels in subsea equipment exposed to Cathodic Protection (CP). In general, the three conditions need to be present: hydrogen source (CP), susceptible material (Duplex/Super Duplex stainless steel) and high stresses/strains. The third one can be related with loads, calculation promises and parts design in general (for example risers). The designing rules to minimize the risk of HISC failure are still in development and the latest state of art is presented in DNVGL-RP-F112 June 2018 edition. The Compact Flange (CF) is much lighter and more robust connection than standard ASME or API types as the CF design methodology is based on plastic capacity which is presented in the ISO-27509 code. However, ISO standardization covers only topside applications (with IX seal ring type), pressure class range up to CL2500 and simplified face angles methodology. The ISO-27509 flanges are not HISC proven. Therefore, to deal with HISC requirements and subsea conditions the SPO-S (Subsea) flange series with HX seal ring type was defined and type approved by DNVGL based on extensive FEA documentation, testing and field experience. The SPO-S range has, currently, only HISC compliant designs for the 5K, 7.5K, 10K and 15K flange ranges. For the projects where the Duplex / Super Duplex flanges are used subsea with CP, consideration for HISC still must be addressed. For such cases, the process is not straight forward and often many FEA rounds are needed depending on the engineer’s experience and project related restrictions. The process is time consuming and every decision reflects many aspects to finalize the design. Genetic Algorithms (GA) are a good optimization tools to use in such situations, because at the end, the engineer will only get few design propositions to choose from, and the process itself, is highly automated. In the following paper the results for HISC optimized CF flange connection will be presented and compared with standard ISO-27509 flange design. The GA optimization steps and designing process will also be presented in the same example. Commercial FEA code ANSYS will be used for calculations based on parametrical model and GA implemented by APDL scripting. The following optimization method is already in use for HISC related projects.

Skin Darkening in COVID-19 Patients: Case Series of Eight Patients in a Hemodialysis Unit.

The Pandemic of COVID-19 has grasped the whole world and changed dramatically, together with our social, occupational and personal life with high mortality and morbidity with other consequences since December 2019 started from Wuhan and then declared pandemic in March. It has been observed to involve every organ of the body including skin. Various skin manifestations, but most cases reported were like urticarial rash, xanthemas, chickenpox-like vesicle, vasculitidic type, pressure sores, contact dermatitis and a single case was reported in china with skin darkening. The COVID-19 and cutaneous manifestations are recognized by physicians and dermatologist treating COVID-19. We have observed around eight cases of COVID -19 who had skin darkening in our center Baluchistan Institute of Nephrology and Urology Quetta, among these included were six dialysis technicians one chronic maintenance dialysis patient and a physician. We present the representative cases and discuss the skin manifestations of COVID-19.