Investigation of the Mechanical and Microstructural Properties of Welded API X70 Pipeline Steel

The mechanical properties of pipelines particularly those in marine environments are influenced by corrosion activity of seawater throughout their service lives. The degree to which these properties are influenced in seawater compared to those exposed to air needs to be better understood. In this study, the chemical composition of API X70 pipeline steel plate, microstructure and mechanical properties of the welded joints of same steel plates exposed to ambient air and seawater respectively were investigated. It was found that the base metal consisted of manganese (0.51wt% Mn), low carbon content (0.051 wt% C) and small quantities of alloying elements such as vanadium (0.021wt% V), molybdenum (0.118 wt% Mo), chromium (0.240 wt% Cr), copper (0.002 wt% Cu), and a carbon equivalent (CE IIW) of 0.38. Scanning Electron Microscope (SEM) showed that the microstructure of base metal sample has large grains formed in packets which have certain crystallographic orientation but contain submicron grains arranged in a chaotic interlocking manner. The tensile tests performed using a UNITED type universal testing machine confirmed that the yield strength of the base metal was 573.045MPa which conforms to API standard for X70 steel pipe. The manual metal arc (MMA) welding technique was applied to produce the welded joints.  For the welded joints exposed to ambient air at room temperature, the yield strength was 680.624MPa while the compressive strength was 1500.2MPa, and the impact energy at -10°C was 112.68J. Air tests referred to tests conducted in the laboratory at room temperature. For the welded joints exposed to seawater for 12 weeks, the yield strength was 609.154MPa while the compressive strength was 1219.34MPa, and the impact energy at -10°C was 61.48J. The above results for air and seawater exposures were used to determine the environmental reduction factors of the two environments.  Hardness tests conducted using Vickers hardness tester revealed variations in hardness across the base metal, the HAZ and the weld, with the weld having the highest average Vicker’s hardness value (223.8HV) followed by the base metal (217.3HV) and the HAZ had the least (214.5HV

Development of a petroleum pipeline monitoring system for characterization of damages using a Fourier transform

Significant damage to the environment and huge economic losses are potential problems caused by leakage from petroleum pipelines. The occurrence of a leakage in a pipeline throughout its lifetime is very difficult to prevent. To minimize environmental damage and high economic losses, an efficient pipeline monitoring system is required to carry out damage characterization thereby enhancing quick response. The signal processing technique of sampling and reconstruction was adopted and mathematical algorithms for the characterization of damages in pipes were developed using the Fourier transform method. These were simulated with the results showing a good agreement between the shapes and magnitudes of the measured original and reconstructed pulses. The simulation was verified with experiments on the test rig. The results showed an underestimation in the magnitudes of the reconstructed pulses in the range of 40 – 45 %. This problem was solved by using a factor K obtained by dividing the maximum amplitude value of the original pressure pulse by that of the reconstructed pulse. Reconstruction of the measured original pulse at a damage location was achieved from combining the measured pulses from two other close locations using the developed Fourier transform based model. Keywords: Damage Pipeline-monitoring Characterization Fourier transform Reconstructio

AN ASSESSMENT OF NIGERIA WIND ENERGY POTENTIAL BASED ON TECHNICAL AND FINANCIAL ANALYSES

The energy requirement of Nigeria is increasing exponentially with little projects available to carter for this increasing demand. The primary source of energy in the country which is fossil fuel creates environmental pollution and is also finite in nature. Hence, there is a serious need to look for other alternative ways to meet up with the energy requirement of the country. This paper analysed some of the economic and sustainability benefits for Nigeria by deploying and integrating wind energy into her energy mix. The study was done with the RETScreen Clean Energy software tool, designed by Natural Resources Canada. The study began with a brief review of the various wind energy resource assessment done previously in the country and Maiduguri town was selected as the area of study from the reviews. The technical and financial analyses of the study showed that if the project is implemented it will be beneficial to Maiduguri town and Nigeria in the long run. The process of electricity generation from 100 units of VESTAS V80 in Maiduguri yielded MWh 525,600 and saves about 202,881.6 tonnes of CO2. Without incentives, the financial analysis showed that the project is not financially viable with the equity payback greater than the project life. Key issues affecting the development of wind energy technology in Nigeria were also discussed