Journal of Scientific and Engineering Research

12-22

Authors: Tonye K Jack

The process plant maintenance planning engineer for rotating equipment is always saddled with the question: When to Repair, Replace critical or poorly functioning part or implement, complete “tear-down” or equipment overhaul? Gas turbine overhauling is usually a well planned project with the required manning and materials requirements properly put in place. The complete equipment overhaul is inclusive of the “which part(s) to repair?” and “which part(s) to replace?” questions, together with the time and costs implications. The gas turbine overhaul planning engineer must apply the concepts of Value engineering and Value analysis to ensure that the operational economic value, post overhaul, is balanced with immeasurable and defined gains to the equipment owner. In this first paper, one such field experience in answering these questions is recounted.

40-51

Authors: Ezeokonkwo John U, Okolie Kelvin Chuks, Ogunoh Peter

Concrete fails when it can no longer provide the required strength to support its designed load. This failure can be mild with visible cracks and deflections or severe, leading to partial or total collapse of the structure either during the construction or post- construction stage. It has been observed that the major cause of this collapse is the use of sub- standard materials mainly poor quality of stone aggregates materials used for concrete production. Previous study on this area centred mainly on other causes of building collapse, with little 'emphasis on coarse aggregate. Therefore, the study is aimed at establishing the qualities of coarse aggregate sourced within Anambra State. Primary and secondary data were used for this study. Samples for the laboratory experiment were obtained from quarry sites at Enugwu-ukwu, Aguleri, Nsugbe, Nikwelle–Ezunaka and Ogbunka. Sieve analysis, Slump test and Cube (crushing strength) were performed using each of the samples. The study observed that the crushing strength and/or compressive strength of the samples at 7 day are between 20-29N/mm' with Ogbunka samples having the highest compressive strength of 29.33N/mm2. Thus, at 7th day, four out of the five samples tested have attained the minimum strength of boncrete (i.e. 21N/mm'). For workability test, the study observed that the percentage of slump for the samples ranges from 21.5 – 41% with Nsugbe samples having the best slump value of 21.5%, For sieve analysis, the researchers observed that the samples were fairly graded. The percentage of the grains passaging through 19.05 diameters is between 64.3 – 84.0%. The study ended with the following recommendations that stones should be properly graded using machines rather than hand breaking. Also stones should be properly washed before using them since most of them are coated with impurities and other clayey substances and muds which may interfere with the process of bonding. Finally, more research should be carried out using un-wash samples from other quarry sites/towns not covered by this study.

71-78

Authors: Tonye K Jack

For the owner of gas turbines (GT) with top in class good history of preventive, and predictive maintenance practices, able to manage its operations efficiently within the time-between-overhaul (TBO) interval, will the repair versus replacement decisions during overhaul, be same, with an owner of questionable maintenance practices with several cases of breakdowns within the TBO interval? And, for both owner types, when is the right time to decide on, and the method to be applied for a “displacement” policy - complete replacement of old gas turbine equipments for new equipments as a result of technological changes, operational inefficiency, or increased maintenance costs? Such Costs and Usage Values, Decisions Analysis is essential in consideration of alternatives in the maintainable equipment overhaul plan. While the GT overhaul repair versus replacement decisions are present economy studies, the “displacement” decision is based on future economy studies of capital recovery. In this paper an approach to assist with the repair versus replacement economic value decision planning is shown through an example in the overhaul of a turbo-compressor, and a basic guide to assist in a gas turbines displacement policy formulation is also given.

94-98

Authors: Jitendra Kumawat

The previously used IPv4 does not deal with the issue of IPsec. It does not inherently provide any security for data transmitted across networks. Even not any integrity and encryption algorithms were used. Presently, IPsec is used widely by nearly all security vendors. It is the primary security protocol used in Virtual Private Networks; IPsec was defined in RFC 2401. The objectives are to analyze whether the IPsec VPNs configure with variety of encryption (3DES, Blowfish and AES) and authentication (HMAC-MD5, HAMC-SHA1) algorithms and to compare their TCP and UDP throughput and request/response time on the network and find out the optimal solution among these algorithm based on their performance in IPsec enable network traffic. The tests have been done with two x86 based hosts in Red Hat Enterprise 2.6.9 kernel and for configure IPsec using ipsec-tools-0.6.6 tool.The measurements are taken by the Netperf version 2.4.1 tools. This work investigates the various encryption and authentication algorithms and foreseeing the effect of these algorithms over network performance. HMAC-MD5 and AES (authentication, encryption) gives the optimum network performance parameter.

110-120

Authors: Mohanned Mahgoup, Elham Khiar

For mature fields, Excessive water production is a complex subject in the oil and gas industries and has a serious economic and environmental impact. Some argue that oil industry is effectively water industry producing oil as a secondary output. Therefore, it is important to realize the different mechanisms that causing water production to better evaluate existing situation and design the optimum solution for the problem. This paper presents the water production and management situation in Jake oilfield in the southeast of Sudan; a cumulative of 14 MMBbl of water was produced till the end of 2014, without actual plan for water management in the field, only conventional shut-off methods have been tested with no success. Based on field production data and the previously applied techniques, this work identified the sources of water problems and attempts to initialize a strategy for controlling the excessive water production in the field. The production data were analyzed and a series of diagnostic plots were presented and compared with Chan’s standard diagnostic plot. As a result, distinction between channeling and conning for each well was identified; the work shows that channeling is the main reason for water production in wells with high permeability sandstone zone while conning appears only in two wells. Finally, the wells were classified according to a risk factor and selections of the candidate wells for water shut off were presented.