Comparative Analysis of Soaking Time on Hardness and Tensile Strength for Mercerization Treated Raffia Palm Fibre

The paper aims to study the soaking time on hardness and tensile strength for mercerization modified raffia palm fibre, which will be gathered, extracted, retted, processed and treated with 5% and 10% NaOH concentration using a soaking time of 60(1hr), 120(2hrs), 180(3hrs) and 240 minutes(4hrs) at a varying fibre length of 50, 60, 70 and 80mm. From the experiment conducted for hardness, the maximum optimum value of 395 HB was recorded at 60mm fibre length for 2 hours using 10% NaOH concentration. While the strength gave an average optimum value of 768Mpa at 70mm fibre length for 3 hours using 5% NaOH concentration at varying the soaking time for mercerization modified fibre. The fibre was grounded into smaller particles size and reinforced with high-density polyethylene (HDPE). Different test samples for the production of oil and gas facilities like pipes and pipe joints, a storage system (pressure vessel), etc. and also for producing interior paneling for aircraft and automobiles, household tables and chairs, window frames, laptop cases, and another consumer item.Keywords: Raffia Palm, Soaking Time, Mercerization, high-density polyethyleneDOI: 10.7176/ISDE/10-6-02Publication date:July 31st 201

Risks Associated with Maintenance Decisions Concerning the Afam Electricity-Generation Station

For the nationally-deregulated Nigerian electric-power industry, an increasingly competitive environment has resulted to an important question being asked, the costs of maintenance in the plants. To survive the competition, the power stations have to reduce maintenance costs, i.e. handle maintenance effectively. Risk analysis is one tool decision makers in the power stations can use to help them prioritize as their plan maintenance actions. The results of such analysis will form a reliable basis for decision making, it is important to consider whether the quality of the results will vary significantly with the risk analysis approach chosen. This paper presents a factual dataset, with few risk of failures used to illustrate how Weibull analysis can forecast the risk of failures based on a small dataset. Using Gas Turbine number 17 of the Afam thermal power station, two perspectives are described: the statistics and engineering views. The study establishes the importance of the need to analyze and interpret risk analysis results, before making maintenance decisions Keywords: risk analysis, statistical/engineering methods, and optimization. Afam thermal power statio

Model Formulation for the Exact Position of Dew Point along a Gas Pipeline

Natural gas piping network are often laid under the sea bed, under or above earth surface through places of diverse temperature gradients. In such environments, if the temperature of the flowing stream of gas is below the water or hydrocarbons dew points temperatures condensation occurs. The condensates so formed accumulate at low points in the pipes thereby obstructing flow of gas. Flow obstruction leads to pressure drop along the line. Hydrates can also be formed if there is excessive cooling of the gas due to pressure drop. The end result of this is obstruction of flow or freeze up of the valves, a worst case situation leading to total obstruction of flow. This necessitates the need to find at what point along a pipeline at which condensation will commence after attainment of dew point for natural gas gaseous mixtures. The mathematical models so generated help to determine the dew point of such hydrocarbons mixtures and the extent of the length from the upstream end of the pipeline at which dew point will be attained. To prolong the pipe length or stop attainment of dew point temperature, the pipe is covered with a layer of insulating materials of low thermal conductivity. Keywords: Mass Flowrate; Specific Heat Capacity; Burial Depth; Convective Heat Transfer; Thermal Conductivity; Residual Heat; Dew Point Temperature; Flow Resident Time

Computer Simulation of the Mathematical Models for the Determination of the Uplift Resistance of a Gas Pipeline

Mathematical models for the determination of the uplift resistance of gas pipelines network system have been developed. The computer simulation of the mathematical models is the bane of this work. The paramount parameters in view to be determined by computer simulated algorithms are optimal wall thickness, the restoring moment, pipe deflection and pipe support spacing for a laid pipeline to avoid buckling of the pipeline subject to the different loading conditions. At nominal pipe wall thickness of 11cm, the simulated optimal wall thickness is 17cn. The simulation results confirmed the deflection of the pipe as -2.698m,  the restoring force as -3.33x1017N. Subject to these findings, three pipe supports are required to bear restoring the load of 1.11x1017N at each support. Keywords: Uplift Resistance; Earth Mass Centroid; Pipe Thickness; Maximum Deflection; Internal Fluid Pressure; External Loads; Support Reaction; Buckling Load.

Fatigue Analysis of Steel Jacket Platform in Shallow Water Depth in the Gulf of Guinea

This work investigates the fatigue life of a steel jacket installed at a water depth of 22m in the Gulf of Guinea, both deterministic and spectral analysis was done using the Bentley SACS software. Wave data was collected every 3 hours for seven years resulting in 20440 sea states. The analysis was carried out using industry codes and standards for critical inspectable and non-inspectable members. The result of the analysis was obtained for 50 modal shapes, and the mass participation factors show the highest vibration at the mode shape of 2. The fatigue life of the joint was determined for a life of 50 years and applying the factor of safety of 5; the spectral analysis shows that none of the members investigated to meet the fatigue life of 250 years. However, the deterministic analysis shows some members that meet the fatigue life of 250 years. The analysis was also conducted for the piles both above and below the mud line, and the spectral and deterministic analysis show that the piles meet a fatigue life of 500 years using a factor of safety of 10. It was concluded and recommended that the joints on the jacket that do not meet the fatigue life should be rewelded and inspected for structural integrity. Also, the result shows that the spectral analysis is more detailed than the deterministic analysis. Keywords: jacket, fatigue analysis, Gulf of Guinea, SACS, spectral analysis, deterministic analysis, fatigue damage. DOI: 10.7176/ISDE/11-3-01 Publication date: April 30th 202

Approach to Two-Phase Flow in Gas Transmission Pipeline Network System

Flow of natural gas in a gas pipeline is not entirely single phase flow situation. Even from the well or treatment plant the gas stream might carry along with it appreciable amount of dirts, debris, water or corrosion products from the walls of the pipes, resulting in two or three phase flow situation [1]. Oftentimes the gas might be transported above or below the earth surface or below the sea bed through places of diverse temperature gradients, giving rise to certain undesirable problems. Condensates and hydrates formation are such problems.  The condensates so formed accumulate at low points in the pipes, thereby obstructing flow of gas. Hydrates do form around valves resulting in total blockage or freeze up of the valves. A worst case situation is total obstruction of flow. The end result is increased pressure drop along the pipeline. The approach in the two-phase flow analysis in gas transmission line is to separate the liquid phase from the dry gas phase and develop or deduce the governing expressions for friction factor. The friction factor for two phases so deduced can be injected into any appropriate flow equations to determine the various pressure drop components, overall pressure drop, line throughput or any other flow variables of interest. Two-phase flow analysis approach in this work has enabled the deduction of mathematical models that would be more precise and accurate in predicting flow situations. Keywords: Mean Flow Velocity; Compressibility Factor; Friction Factor; Liquid Holdup; Gas Holdup; Liquid Velocity Gradient; Gas Velocity Gradient; Liquid and Gas Acceleration Gradient; No Slip; Equivalent length;  Two Phase; Pipeline Efficiency; Equilibrium Constant

Prediction of Pressure Drop in Subsea Pipeline Using Pipesim Software

The number of offshore developments for which long-distance tie-back is usually implemented has increased recently, leading to increasing pressure loss concerns from such systems. In the literature, it revealed that pressure drop in multi-phase transport is quite complex to compute manually. Hence the need for multi-phase flow simulation software. PIPESIM is a leading industry software currently used in the oil and gas industry for multiphase flow simulation. In this study, a 64km subsea pipeline system comprising two sections; 23km, 22.064in ID and 41km, 24inch ID, coated with 3mm (0.003m) polyethene insulation and transporting multiphase hydrocarbon fluid in an ultra-deep-water field was modelled in PIPESIM. Network simulation for the base case was carried out at 114barg (114MPa) inlet pressure and 18.7MMSCfd gas flowrate. The observed system pressure drop was dependent on pipeline inlet pressure, flowrates, and internal pipe diameter. 13.8barg (13.8MPa) was lost from the system for the base case simulation. Sensitivity analysis carried out using Gas volumetric flowrates of 3, 12 and 18.7 MMSCFd. The inlet pressures of 57, 114 and 171barg combined with six different pipe diameters generated a unique combination of 81 data points that were used in the development of a pressure drop correlation using the LINEST regression analysis tool in Microsoft Excel. At high flowrate and high inlet pressure, the pressure-drop observed was minimal and vice versa. Also, at constant flowrates and inlet pressures, the pressure drop was observed to increase with increasing pipe sizes. An R2 value of 0.9226 was obtained from the analysis. The plot of Predicted Pressure-drop against Calculated pressure-drop similarly gave an R2 value of 0.8025. Both results showed usefully, and hence the developed correlation can be used as an estimate in the absence of PIPESIM software for pressure drop prediction purposes. Keywords: Pressure drop prediction, Multi-flow Simulation, PIPESIM, Pipe sizing, Regression Analysis DOI: 10.7176/IEL/10-2-06 Publication date:March 31st 202

Applicability of Heuristic Approach in Planning and Scheduling Project

This paper focuses on the application of heuristic approach in solving scheduling problems of ongoing project. This study is primarily aimed at providing a suitable heuristic for finding an optimum resource level, which ought to be kept over the project execution period, and a sensitivity analysis of which resource type ought to be increased in order to reduce the project completion time towards the ultimate. The use of resource utilization and a “constraining index” in the search for optimal solutions to this problem of meeting delivery date requirements, and optimize utilization of multiple resources in project and minimize other resources. Keywords: Heuristic; resource constraints; constraining index.

Comparative Analysis of Vortex-Induced Vibration Models on Risers Caused by Vessel Motion

Over the past recent years, several models for prediction of vortex-induced vibrations on risers and cables in slender marine structures have been proposed. This study provided a consistent discussion and critical evaluation of the most commonly applied models, highlighting their strengths, mathematical equations, principles, assumptions and their implications, and the apparent limitations associated with each model. The study critically evaluated and compared vortex-induced vibration models for dynamic response of water risers induced by vessel motion using a multi-criteria analysis tool (AHP). Seven alternatives which include: the DNV model, the LIC engineering model, the MARINTEK model, the MIT-Trianfyllou model, the MIT-Vandiver model, the NTH model and the UCL model were compared against a set of five broad criteria which include: Robustness, Reliability, and Accuracy, Time, Ease of application and cost. The robustness as a broad criterion contains sub-criteria like Reynold’s number range for which the simulation is valid, ability to be deployed for multimode problems, ability to describe spatial attenuation, ability to define excitation zones and how the load process is correlated in the zone. From the AHP analysis, the UCL model came out on top as the best and optimum VIV model compared to the other alternatives with an overall priority score of 1.3694. MIT-Vandiver came second with an overall priority score of 0.9656. The worst model from the outcome of the AHP analysis is the DNV model with an overall priority score of 0.6972. Keywords: vortex-induced vibration, optimum VIV model,  multi-criteria analysis tool, vortex-induced model comparison DOI: 10.7176/IEL/10-2-05 Publication date:March 31st 2020

Investigation of the Effects of Flowline Sizes, Flow Rates, Insulation Material, Type and Configuration on Flow Assurance of Waxy Crude

The recovery of hydrocarbons has gone into deep and ultra-deep waters. Typically, operations from such an environment make the system susceptible to flow assurance challenges. Operations with long subsea flowlines need special attention with respect to flow assurance problems, especially with respect to wax deposition and risk of hydrate formation. As a result, during such operations, it becomes very crucial to evaluate the flowline sizes, flow rates and subsea flowline lengths to minimize flow assurance problems. For the wax deposition control, the operating temperature must be maintained above wax appearance temperature (WAT) by either insulation or electrical heating depending on the cost and energy efficiency factors. In this study, several multiphase simulations were carried out using PIPESIM software to investigate the effects of flowline sizes, flow rates, insulation material, type and configuration on flow assurance of waxy crude over 10.2 km between the wellhead and the first stage separator on the platform. Considering the implications of these factors for flow assurance. The data and results obtained from this study suggest that line size of 0.29 m, the flow rate of 3280 m3/d, poly-urethane foam, and pipe-in-pipe insulation type are favourable to flow assurance of waxy crude with respect to maintaining the temperature of the fluids above the wax appearance temperature of 26 oC; and also to deliver the fluids to the platform at the recommended pressure of over 11 bar. Keywords: Waxy Crude. Flow Assurance. Flow Rates. PIPESIM software, wax control. DOI: 10.7176/ISDE/11-3-02 Publication date: April 30th 2020