Basim Al-Najjar

Selecting the most efficient maintenance approach using fuzzy multiple criteria decision making

We assess the most popular maintenance approaches, i.e. strategies, policies, or philosophies, using a fuzzy multiple criteria decision making (MCDM) evaluation methodology. We illustrate with two examples how the suggested evaluation methodology identifies the most informative approach. Using the fuzzy MCDM, it would be possible to select in advance, the most informative (efficient) maintenance approach. Consequently, this leads to less planned replacements, and failures would be reduced to approximately zero and higher utilization of component life can be achieved. Thus, the maintenance department could contribute more to the business objectives throughout participating effectively in adding value to the production activities.

Total quality maintenance: An approach for continuous reduction in costs of quality products

Discusses the importance of total quality maintenance (TQMain), considering that the common thread in achieving and maintaining high overall equipment effectiveness (OEE) is the availability of improved manufacturing processes capable of producing quality products without interruption. Implementing just‐in‐time (JIT) philosophy demands healthy processes. Any interruption of the line caused by any equipment malfunction or failure will result in a major disruption of output or even line or factory shutdown. Thus, an effective maintenance programme should be evolved to provide the required availability of machinery and output quality. A new concept of condition‐based maintenance, total quality maintenance, is presented. It aims to maintain not only machinery but all the elements constituting a manufacturing process, e.g. production/ operation, environmental condition, personnel, methods, material, quality control. TQMain is a result of establishing a common database through integrating the maintenance program with other plant programs to form an overall plant information technology system. Identifying and “eliminating” quality deviations and failure causes at early stages, and extensive use of data feedback are the suggested tools to accomplish continuous improvements and to assure high quality products.

Enhancing a company's profitability and competitiveness using integrated vibration-based maintenance: A case study

In this paper a model is developed for identifying, monitoring and improving the economic impact of vibration-based maintenance (VBM). This model provides an additional possibility of identifying w ...

Improving Effectiveness of Manufacturing Systems using Total Quality Maintenance

In manufacturing systems intelligent techniques are being used to integrate and interpret data from multiple sensors to predict tool wear and tool life. Less attention is devoted to developments of integrated condition monitoring systems, which enable the user to evaluate a multi‐variant system based on the data collected from, e.g. maintenance, quality, production, etc. In this paper we discussed different approaches of how to keep availability, quality and productivity at high levels. Also, we proposed a new approach for an expert system concept, which is characterised by using a total quality maintenance (TQMain) concept; having a common database, and a continuously improved knowledge base with an intelligent inference engine. It can enhance data reliability, decision making certainty, remove the redundancy in monitoring systems, and allow the user to detect and eliminate reasons behind variations through effective diagnosis and prognosis. This will enhance the performance‐efficiency, availability and quality rate, i.e. overall equipment effectiveness of the manufacturing systems.

Practical models for condition monitoring inspection intervals

Markov models find optimum inspection intervals for phased deterioration of monitored complex components in a system with severe down time costs. The number of (pseudo)‐phases can be increased, but in most cases, simple models tracking actual states and their perception by the user will suffice, because of paucity of data and near‐constant rates. The matrix is cyclic; it includes renewal and regression to earlier states, simplifying solution and matching observation. An example involves roller bearings in paper mills with three phases, no defect, possible defect, and final deterioration towards failure. In the last phase, continuous monitoring is used.

Economic criteria to select a cost‐effective maintenance policy

The reputation of an organisation is often built through hard work on improving quality, reliability, delivery time and price. In this paper a graphical method for the selection of a cost‐effective monitoring technique is suggested. This graphical method is also used to select the most cost‐effective replacement vibration level, when a vibration‐based maintenance is implemented, i.e. when the available data are mainly condition‐based replacement. This method is based on the concept of the total time on test, TTT‐plot. The use of this method is explained by three examples.

A conceptual model for fault detection and decision making for rolling element bearings in paper mills

Rolling element bearing failures in paper mill machines are considered in relation to their critical role in the machine function. The use of expensive, sophisticated and highly automated equipment and machines and the intention to achieve higher quality products, longer machine life, higher machinery effectiveness and safer operating processes were the main driving force motivating efforts to improve the maintenance concept during the last 50 years. In this paper, a conceptual model that integrates the available condition information, the deterministic models used in condition monitoring based upon mechanical theory and the probabilistic models used in the area of operational research is developed and its applicability is discussed. This model covers fault detection of a mechanical component such as a rolling element bearing, prediction of its vibration level in the near future, assessment of the probability of failure of a component over a finite period of time of interest.

Impact of real‐time measurements of operating conditions on effectiveness and accuracy of vibration‐based maintenance policy ‐ A case study in paper mill

Relevant and reliable data from the surroundings in addition to the vibration measurements are required to achieve effective diagnosis and prognosis when a vibration‐based maintenance (VBM) policy is used. The main conclusion is that the variation in the machine load and speeds influences the amplitudes of rolling element bearing defect frequencies. Therefore, changes in the machine speed and load should be considered when interpreting vibration spectra. This will improve the effectiveness and accuracy of fault diagnosis and prediction of the time to maintenance action. The paper classifies stoppage times and highlights the reasons behind them. Also, it discusses the consequential economic losses incurred by unplanned stoppages. During the period covered by this study (58 days), the total stoppage time was about 76.6 days and caused appreciable economic losses of about 2.3 million SEK.

A concept for detecting quality deviation earlier than when using traditional diagram in automotive: a case study

The problem addressed in this paper is how to utilise the concept of TQMain to develop an integrated vibration‐based maintenance (VBM) for detecting deviations in the machine condition and product quality (technical specifications) before the machine starts manufacturing defective items. Concepts of TQMain and integrated VBM are discussed. A technical analysis is conducted to identify quality problem cause roots when manufacturing crankshafts in Volvo Motor, Sko¨vde, Sweden. A factorial experiment is conducted to assess the effect and significance of the suspected causes. Vibration measurements from seven points are collected. The major conclusion of this study is: when using an effective, e.g. on the basis of TQMain concept, integrated VBM, deviations in product quality can be detected at an earlier stage than when using usual quality control diagrams. Manufacturing defective items can be reduced dramatically (or prevented), which will eliminate bad quality‐related losses.

Improved effectiveness of vibration monitoring of rolling bearings in paper mills

Abstract Rolling element bearing failures in paper mill machines are considered in relation to their critical role in the machine function. The paper discusses these failures according to what becomes damaged and how, and relates them to the vibration spectra and their development over the lives of the bearings. Interpretations of some variations in the vibration signature, i.e. relating vibration amplitude changes and frequency shifts to the deterioration processes involved, are proposed and discussed. The literature was found mainly to confirm this analysis. A new approach to envelope alarming is presented and shown theoretically (logically) to offer later renewal with fewer failures, and therefore lower cost and higher productivity. Deficiencies in data coverage and quality, and the feedback of case study results, are discussed. A model to improve maintenance experience is proposed and discussed. Using vibration to monitor component conditions, the accurate prediction of remaining life requires (a) enough vibration measurements, (b) numerate records of operating conditions, (c) better discrimination between frequencies in the spectrum and (d) correlation of (b) and (c). This is because life prediction depends on the amplitudes of (and) the frequencies generated by the component damage. Much money could be saved because some of the present policies utilize as little as half of the useful life of a bearing.