Estimation of Mean Time between Failures of a Two Tandem Mill of a Sugar Plant

When minutes of down-time can negatively impact the bottom line of a business, it is crucial that the physical infrastructure supporting be reliable. The equipment reliability can be achieved with a solid understanding of mean time between failures. Mean time between failures (MTBF) has been used for years as a basis for various maintenance decisions supported by various methods and procedures for lifecycle predictions. To quantifying a maintainable system or reliability we can use MTBF. For developing the mean time between failures model we can use make use of Poisson distribution, Weibull model and Bayesian model. In this paper we will be talking about complexities and misconceptions of MTBF and clarify criteria that need to be consider in estimating MTBF in a sequential manner. This paper sheds light on MTBF using examples throughout in an effort to simplify complexity. Keywords: MTBF, Two Tandem Mill, Sugar Mill, Reliability, Maintenance

FAILURES PREDICTION APPROACH IN AGILE SOFTWARE DEVELOPMENT

Software failure prediction is an important activity during agile software development as it can help managers to identify the failure modules. Thus, it can reduce the test time, cost and assign testing resources efficiently. RapidMiner Studio9.4 has been used to perform all the required steps from preparing the primary data to visualizing the results and evaluating the outputs, as well as verifying and improving them in a unified environment. Two datasets are used in this work, the results for the first one indicate that the percentage of failure to predict the time used in the test is for all 181 rows, for all test times recorded, is 3% for Mean time between failures (MTBF). Whereas, SVM achieved a 97% success in predicting compared to previous work whose results indicated that the use of Administrative Delay Time (ADT) achieved a statistically significant overall success rate of 93.5%. At the same time, the second dataset result indicates that the percentage of failure to predict the time used is 1.5% for MTBF, SVM achieved 98.5% prediction.

Increasing the Time between Failures of Electric Submersible Pumps for Oil Production with High Content of Mechanical Impurities

The main principles of hydroabrasive wear of parts of the pumping stages of well’s electric submersible pumps are considered in this article. The concentration, grain-size distribution and shape of solid particles have the greatest impact on the abrasion ability of particles of mechanical impurities interacting with the parts of pumping equipment. The implementation of filters is the most effective and affordable way to protect borehole electric submersible pumps from hydroabrasive wear. Filters reduce the concentration and decrease the average grain-size of mechanical impurities going through the pumping stages. The authors propose variants of constructive and schematic solutions of self-cleaning slot filters, providing an increase in the operating time of electric centrifugal pump units during production of well fluid with a high content of mechanical impurities. The operating principle of the proposed filters is described. The results of calculations of deformation of tubing string during the increase in pressure at the oil wellhead are presented, confirming the possibility of restoring the permeability of spring filter elements without lifting the pump unit to the surface.

Retrofitting in Fabric Finishing Machine - Sanforizadeira

With the advancement of technology in all fields, mainly in the industrial sector, which is manifested in more modern and self-contained equipment. Many equipment in the industry are obsolete with the electrical and electronic parts, but the mechanical parts are in perfect condition and can often be used for a long time. This paper demonstrates the retrofitting of a fabric finishing machine (Sanforizadeira) in the textile process thet was obsolete. In these conditions, it became necessary to retrofit the automation system. Through the study of the machine and the process, involving the fields of production and mechanical maintenance, the critical points and the improvements that should be implemented were found, thus raising the materials needed to carry out the work. The automation system was modernized, the control panels were replaced and improvements were implemented. The final result was achieved through the objectives outlined in this work, guaranteeing the company a system with considerable improvements, with a reduction in the number of stops and time spent for maintenance. The results were demonstrated by the graphs of the maintenance indicators. Comparing the before and after retrofitting, the following indicators were analyzed for six months: Failure rate, with an average reduction of 50\% in the failure rate per hour; Mean time between failures, showed an average increase of 140 hours in the prediction of the next failures; Average time to repair, presented an average reduction of thirteen minutes in the resolution of the failures; Availability, there was a 16\% increase in the availability of the machine, leaving the indicator above 90\% where the ideal is 100\%. Finally, the total cost of the project represented only 9.5\% of the total value of a new machine, being also considered a positive result for the work.

Reliability and maintainability of scraper conveyor used in coal mining in the Jiu Valley

Purpose.The aim of the study is to determine and analyse causes of faults in the operation of TR-7A scraper conveyor and to estimate the required time for their remediation and select the methods of their prevention and elimination. Methods. The characteristic of a system, such as the scraper conveyor, intended to fulfil its specified function in time and operation conditions, can be studied, theoretically, by determining its operational reliability. This implies the existence of a framework that incorporates several interconnected components of technical, operational, commercial and management nature. The quantitative expression of reliability was based on elements of mathematical probability theory and statistics (exponential distribution law), failure and repair mechanism not being subject to certain laws. Findings. The following TR-7A subassemblies, if defective, could have been the cause of a failure: chains, hydraulic couplings, chain lifters, drive, return drums, some electrical equipment. After 28 months of monitoring the TR-7A operation, we have established the number of failures (defects) ni, the operating time between failures ti, frequency of failures fc, time to repair tri, weight repair time pr, mean time between failures (MTBF), mean time to repair (MTR). Originality.Data collection and processing involves the adoption of specific procedures to allow the correct highlighting of the causes and frequency of failures. The accomplishment of this approach allowed finding the solutions for increasing reliability of some subassemblies of TR-7A conveyor (i.e., those subjected to abrasive wear). Practical implications.One solution was to use materials with compositional and functional gradient in the case of worn surfaces of some subassemblies. It was successfully applied for the chain lifters where a significant increase in the mean time between failures was obtained. The field of application of these materials can be extended to the metal subassemblies of machines and equipment with abrasion wear that occurs both in underground mines and in quarries.

Safety Analysis of a Certifiable Air Data System Based on Synthetic Sensors for Flow Angle Estimation

This work deals with the safety analysis of an air data system (ADS) partially based on synthetic sensors. The ADS is designed for the small aircraft transportation (SAT) community and is suitable for future unmanned aerial vehicles and urban air mobility applications. The ADS’s main innovation is based on estimation of the flow angles (angle-of-attack and angle-of-sideslip) using synthetic sensors instead of classical vanes (or sensors), whereas pressure and temperature are directly measured with Pitot and temperature probes. As the air data system is a safety-critical system, safety analyses are performed and the results are compared with the safety objectives required by the aircraft integrator. The present paper introduces the common aeronautical procedures for system safety assessment applied to a safety critical system partially based on synthetic sensors. The mean time between failures of ADS’s sub-parts are estimated on a statistical basis in order to evaluate the failure rate of the ADS’s functions. The proposed safety analysis is also useful in identifying the most critical air data system parts and sub-parts. Possible technological gaps to be filled to achieve the airworthiness safety objectives with nonredundant architectures are also identified.

Evaluation and optimization of CES performances: application of Pareto principle to KPIs

In recent times the approach to health care has been mostly influenced by the growing number of biomedical equipment used in hospitals, which needs the presence of the Clinical Engineering Service (CES). The aim of this work is to suggest a methodology to improve the performance of a CES through the application of Pareto principle to main Key Performance Indicators (KPIs). The methodology is applied by focusing on the use of KPIs that represent a quantifiable measure of achieving goals set by an organization. In this study five KPIs are considered: Uptime, MTTR (mean time to repair), PPM (percentage preventive maintenance), MTBF (mean time between failures) and the COSR (cost of service ratio). The first three indicators express the measure of CES efficiency in ensuring regular maintenance. The first step consists in retrieving data related to work orders for the years 2015-2016 on 6000 installed devices, carried out by a management software. The second step is to get the results through the use of an environment for numerical calculation and statistical analysis. In order to identify the main critical issues that may be present, three indicators (Uptime, MTTR and MTBF) are analyzed by applying the Pareto principle (i.e. 20% of the causes produce 80% of the effects). Considering the totality of work orders, therefore, it is possible to concentrate on only 20% of them in order to focus on a small group to understand the correlations between them. Identifying these characteristics means identifying the main critical issues that are present, on which action must be taken, and which affect 80% of the overall behavior. The COSR and PPM indicators, instead, suggest distribution models that allow to focus attention on the most critical devices. In conclusion, the way to analyze the results is obtained, when possible, by applying Pareto principle. Therefore, a CES will be able to focus on a few causes of poor performance. The achievement of these results could allow the standardization of the method used, enabling it to be applied to any healthcare system.

Reliability and Economic Efficiency Analysis of 4-Leg Inverter Compared with 3-Leg Inverters

The 4-leg inverter can adjust the load current or output voltage even under unbalanced load conditions, but it is known that the additional switch arm to the 3-leg inverter can increase the overall cost and the failure rate. This paper aims to analyze the failure rate and mean time between failures (MTBF) of 3-leg inverters and 4-leg inverters using part count failure analysis (PCA) and fault-tree analysis (FTA), and to compare the price of the inverters. The FTA can analyze the failure rate, including the type, number and connection status of the circuit components, and moreover the redundancy effect of the 4-leg inverter. For more accurate failure-rate prediction, the failure rate and MTBF of the 4-leg inverter according to the lifecycle of the controller are analyzed. Finally, by comparing the price of 3-leg inverters and 4-leg inverters using the cost model of major parts, the degree of reliability improvement against price increase is quantitatively analyzed.