Characterization of Working Thicknesses of Some Bath-Dip-Produced Corrosion – Protective Bitumen Coatings on Polish-Prepared Low Carbon Steel Specimens
The coating thickness is an important variable that plays a role in product quality, process control and cost. Determination of the required working thicknesses for different service requirements is however a complicated task in the product finishing field. A previous study has shown that Nigeria is blessed with abundant bitumen resources for sustained exploitation as common, economical and effective coat-inhibitors of steelwork corrosion in her economy. This paper presents a testdetermination of the expected range of working thicknesses of coatings with proper bitumens from the resources. Bitumen samples were harvested at three different critical bitumen resource sites in the country for the tests. 30 specimens of the steel were properly prepared. Coatings of different thicknesses were produced on the specimens by dipping a different pair of them in each bitumen sample heated to each of five different temperatures in the range of 170 – 230 O C and removing and cooling them to 38 O C-room-temperature. The thickness of each produced coating was properly determined with a micrometer through dimensional change before and after coating. Analysis of the overall obtained data shows that the average working thicknesses of coatings with any bitumens of comparable quality to the as-harvested from the resources using temperatures in the range will decrease with increase in temperature from about 1.46 to 0.81mm respectively, and thicknesses of coatings with the separate bitumens using the same bath temperature will have minimal variations.
Assessment of Physicochemical Properties of some Bitumens from Nigerian Resources
Bitumen is a cheap, common, and important material in today’s technological world. Bitumens gotten at different locations on earth, and produced from different manufacturing processes, or crude feedstocks can however have wide variations in physico-chemical properties and levels of service performances. Hence reliability, handling, and modification in technological usage of different bitumens demands that proper information on a given harvested one should be consulted. Nigeria has large reserves of natural bitumen resources and potentials for sustained production of bitumen in large quantity, but basic applicable public information is lacking on bitumens at most locations of the resources. In this paper, proper test-obtained result of the properties is presented for three bitumen samples obtained from some important sources in the country. Assessment of the results vis-a-vis available information on bitumens elsewhere indicate that any clear surface or underground natural bitumen obtainable in the region of Agbabu village in Ondo State, and a manufactured type from Kaduna Refining and Petrochemical Company (KRPC) in the country are comparable with bitumens of good or acceptable qualities from other locations in the world. Bitumen from the region and the as-manufactured are therefore recommended to be producing in large available quantity and exploiting for different technological applications.
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.