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Availability Simulation Model for Stochastic Analysis
of Coal Supply System in a Thermal Power Plant
--Ravinder Kumar, Avdhesh Kr Sharma and P C Tewari
The paper evaluates the availability simulation model (Av.) for the performance analysis of coal supply system in a coal-fired power plant using Markov approach. Coal supply system ensures proper supply of coal for sound functioning of thermal power plant. This system consists of four subsystems, i.e., Wagon tippler, Crusher, Conveyor belt and Coal mills. For the analysis, an availability simulation model (Av.) is developed with the help of mathematical formulation based on Markov Birth-Death process using probabilistic approach. For this purpose, first order differential equations are developed based on the transition diagram developed for the system. Then these equations are further solved by using normalizing conditions so as to determine the availability simulation model (Av.), i.e., measure of performance of the coal supply system. This performance evaluating model deals with the quantitative analysis of all factors (courses of actions and states of nature), which influence all maintenance decisions associated with this system. The results show that coal mill subsystem is the most sensitive and demands more improvement in maintainability as compared to other subsystems. © 2013 IUP. All Rights Reserved.
The Effect of Process Parameters on Mold Properties Manufactured
by Silicon Molding
--Rupinder Singh and Vipul Sharma
In the present study, polyurethane replicas (to be used as pattern) were prepared by Silicon Molding (SM) process. The prototype with three different types of materials (polyurethane) was prepared under three different conditions of de-mold time, de-mold temperature and mixing ratio (hardener:softener). Relationship between these input and output parameters (dimensional accuracy, surface roughness and micro hardness) was deduced by using Taguchi L9 Orthogonal Array (OA) for industrial applications. The results of study suggest that polyurethane replicas produced by SM are acceptable as per ISO UNI EN 20286-i (1995) and DIN 16901 standards. Further, the type of material is a significant factor contributing dimensional accuracy and micro hardness to SM process. For surface roughness, mixing ratio is the most significant factor. © 2013 IUP. All Rights Reserved.
Fabrication of PRAl-SiC-MMC Using Melt-Stirring Technique
and Analysis of EDM Parameters
--K L Meena and Alakesh Manna
The paper explains the melt-stirring technique for fabrication of Particulate Reinforced Al/SiC Metal Matrix Composites (PRAl-SiC-MMC). The MMCs of different size bars are prepared varying the weight fractions of SiC reinforced particles and mesh size such as 5 wt%, 10 wt%, 15 wt%, 20 wt% and 220 mesh, 300 mesh and 400 mesh. The stirring is performed at 200 rev/min constant rotating speed by graphite impeller for 10 min. A series of machining tests are performed on Electrical Discharge Machining (EDM). The effect of different parameters of EDM on machining response characteristics, such as Tool Wear Rate (TWR) (g/min), Metal Removal Rate (MRR) (g/min), average surface roughness heights Ra (m) and Rz (m), are investigated through various graphs. The experiments are performed by changing the parametric setting values such as pulse peak current (IP: 2, 6, 10, and 14 amp), pulse on time (Ton: 30, 50, 70 and 90 s), pulse off time (Toff: 3, 5, 7 and 9 s) and gap voltage (Vg: 25, 30, 35 and 40 Volts). The investigated results are plotted in various graphs and their effects on various response characteristics explained. © 2013 IUP. All Rights Reserved.
Designing a System for Capturing and Analyzing Data,
and Improving Machine Utilization
--Deepak Kumar, H Ramakrishna and Praveen Gowda
An organization has more than 1,000 machines which are continuously operating. Out of these machines, about 148 machines are bottleneck machines. Bottleneck is a process or a machine in a value stream which has the highest cycle time and decides the maximum technical capacity of the value stream/line, hence affecting the Overall Equipment Effectiveness (OEE). OEE is a worldwide established metric for the current process control of Total Productive Maintenance (TPM) activities, and it is a metric for the output of MAE during a selected period. Currently, to record the utilization of these machines, workers enter hourly production and losses of the unit on Hourly Monitoring Chart, and at the end of the day, the foreman sums up all these, enters them on an Excel sheet according to cell. Excel sheets are stored on the server that can be accessed by anyone in the organization. These Excel sheets are used to produce important charts like OEE with losses and Pareto chart, which are very essential to management heads to take decisions. For plant manager and department head to get the Pareto chart, they have to go about searching for relevant Excel file on the server. To look into the Pareto of whole plant or department, the Excel sheets need to be consolidated manually, which takes 3-4 days and causes delay in the preparation of Pareto. The aim of this paper is to streamline the whole process by an IT solution, which helps to reduce the delay in the preparation of charts and improve OEE of bottleneck machines at shop floor. Overall, the paper helps XYZ Production Systems—BPS with a system that will be reliable and at the same time more effective and less time-consuming, hence boosting OEE. © 2013 IUP. All Rights Reserved.
Effect of Sample Size on X
Chart for Correlated Data
--D R Prajapati and Sukhraj Singh
Shewhart X charts are often used in industries to detect the larger shifts in the process mean. One of the assumptions while implementing these charts is that the observations from the process output are Independent and Identically Distributed (IID), but in actual practice, the observations are correlated for many processes. This correlation has a significant effect on the performance of the Shewhart (standard) X chart. The performance of the X chart is studied for the IID and correlated data at different sample sizes. The Average Run Lengths (ARLs) at various sets of parameters of the X chart are computed by simulation, using MATLAB. Various optimal schemes of the X chart for different sample sizes and levels of correlation are suggested in this paper. The larger sample size (n) is recommended to detect the shift in the process mean quickly. The suggested schemes may be very useful at the shop floor level for industries and service sectors. © 2013 IUP. All Rights Reserved.
Cost-Effective Rapid Manufacturing
of Shell Casting Using 3DP
--Mukesh Verma and Rupinder Singh
During the development cycle, the task that often takes longest time is production of prototype, which may itself be costly and also delay testing. If the prototype performance is not adequate, the design may have to be changed and the prototypes have to be reproduced until they meet the design specification and execute the task for which they are intended. In the present work, 3D printing technique was used for cost-effective, rapid shell casting of aluminium alloys. Efforts were made through experiments to study the feasibility of decreasing the shell wall thickness from the recommended one (12 mm) to 2 mm, in order to reduce the cost and time of production. Some important mechanical properties are also compared to verify the suitability of the castings. The results of study suggested that with decrease in shell wall thickness, there is hardly any effect on mechanical properties and microstructure of casting obtained; however, cost of production and production time are appreciably reduced. © 2013 IUP. All Rights Reserved.
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