This study investigates the optimization of coal fly ash composition as a filler in Silicone Rubber (SiR) insulator materials, aiming to enhance their dielectric characteristics. Compositional optimization was achieved by evaluating and comparing three advanced meta-heuristic algorithms Particle Swarm Optimization (PSO), Genetic Algorithm (GA), and Ant Colony Optimization (ACO), using the Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) as performance metrics. The utilized fly ash, containing dominant silica, alumina, and iron oxides, was directly incorporated into the SiR matrix. Results indicate that, compared to PSO, GA and ACO exhibited superior performance and consistency. Specifically, for Relative Permittivity, the optimal composition of 80% yielded the lowest errors with GA and ACO (RMSE = 0.0751; MAPE = 0.9044). For Hydrophobicity, these two algorithms showed superior accuracy in the RMSE metric (RMSE = 0.8883) at 15.39% loading. These findings underscore the scientific contribution of this study by establishing the superior reliability of GA and ACO for optimizing fly ash composition in SiR, thus providing a robust analytical methodology to advance the use of industrial waste for high-performance dielectric materials.
Steam assisted gravity drainage (SAGD) is a technology used in Canada to extract bitumen from sandstone reservoirs. Steam is injected into the reservoir to rise and form a steam chamber. It heats up the bitumen, lower its viscosity and facilitates production. Among all the various initiatives, non-condensable gas (NCG) injection has been one of the most used elements to improve steam efficiency, particularly in mature operation and in reservoir with relatively higher water saturation. To evaluate SAGD operation efficiency, the understanding of saturation changes is important. In this context, formation evaluation and reservoir surveillance play an important role. For this purpose, the most common service is the cased hole pulsed neutron. The best-known pulsed neutron measurements are the carbon/oxygen ratios, sigma and neutron porosity outputs. These have been widely used for petrophysical analysis in cased wells, involving bitumen saturation changes from carbon/oxygen ratios and qualitative steam volumes from gamma-ray count rates decay. In SAGD projects, however, scheme efficiency monitoring requires analyzing steam and NCG movement and fractions in and around steam chamber, in addition to bitumen and water saturations. During time-lapse logging, experience indicates that changing borehole conditions (fluid type, for instance) along the reservoir surveillance period, are common in SAGD. To avoid biasing true formation response, proper borehole corrections are then required in every single monitoring job. Nuclear modelling on computed formation fluids densities for the actual temperature and pressure regimes, strongly support the understanding of pulsed neutron outputs response while ensuring representative cased hole petrophysical assessment. Pulsed neutron's inelastic and capture gamma ray measurements are used to solve for matrix mineral volumes, thus enabling matrix-corrected porosity (from the neutron and/or additional measurements such as bulk density and sonic whenever available) outputs. The bitumen volume and saturation are assessed from total organic carbon measurement and carbon/oxygen ratios, whereas volumetric analysis of low-density components (steam and NCG) is based on the hydrogen independent FNXS measurement, involving nuclear modeling that computes FNXS response as per temperature and pressure conditions. This workflow also provides steam and non condensable fractions estimations (within the total low-density fluid volume), from hydrogen independent count rates ratio and hydrogen dependent capture ratio. This volume also provides fluids corrections for total porosity output. The technique presented in this work has been tried on actual measurements and proven to be very efficient for petrophysical fluid-rock analysis in reservoir monitoring carried out during variable period (from months to years). Nuclear modeling enabled a better understanding of pulsed neutron response in specific temperature and pressure conditions and thus producing a more accurate and representative reservoir fluids analysis.
Non-ferromagnetic heat exchanger tubes are typically inspected using conventional eddy current bobbin probes to gather data on the integrity of the tubes. This technique provides operators with useful information on pitting and longitudinal cracks, but technical limitations of the conventional eddy current process leaves operators with limited ability to detect circumferential flaws and cracks. In this paper, extensive circumferential chloride stress corrosion cracks, originating from the tube outside diameter, were found by Eddy Current Array (ECA) in the front portion of SA 213 TP 321 SS tubes of a hydrocracker unit feed-effluent heat exchanger. The crevices between the tubes and the tube sheet trap chlorides in both normal operation, and in downtime. Deployment of ECA technology eliminates the limitations of conventional EC bobbin coil probes, effectively identifying circumferential cracking as well as pitting and axial cracking.
In recent years, cracking has been observed in carbon steel piping systems operating at temperatures above 70°C. These systems, equipped with mineral wool insulation and aluminum cladding, experienced cracking and failures under normal operating pressures and temperatures. Leachates from wet mineral wool insulation are suspected of causing external stress corrosion cracking (SCC) in these scenarios. A failure in a carbon steel steam condensate return pipe occurred at 50 PSI(g) and 330°F. Gaps in the insulation cladding allowed moisture to accumulate, which led to external stress corrosion cracking, particularly at the underside of the pipe where moisture collects. Material samples taken from the failed pipe showed intergranular cracking and grain elongation at the base of the cracks. This paper summarizes the findings of the investigation into the steam condensate piping failure, aiming to raise industry awareness and promote the safe operation of similar systems.
