Papers by Keyword: SPC

Abstract: The electric arc is one of the most unstable parts of the electrical circuit of submerged-arc furnaces in the ferrosilicon smelting process. In the carbothermal silica reduction electric arc has an important role as a high temperature heat source, and its presence is essential for the proper ferrosilicon process flow. Presence of the of electric arc and temperature conditions of the ferrosilicon process have a direct relationship with position of the electrodes tip and electrodes slipping. In the ferroalloy industry position of electrodes tip as similar as metallurgical parameters of the process are not directly measured. Most often these assessments are still based to a large extent on intuition and experience operating staff of the furnaces, and have qualitative and subjective character. In order to check the existing algorithm of electrodes slipping was carried out statistical studies of the FeSi75 ferrosilicon smelting process. The study was conducted at discrete intervals ∆t = 8h using data recorded by the furnace computer measuring system and methods of statistical data processing. It was found that the size of the electrodes slipping, and C_fix ratio in the feed are correlated and are among the most important parameters which have an impact on the technical and economic indicators of the process.

Abstract: Single-sided nuclear magnetic resonance (NMR) is a powerful tool to evaluate building-material properties such as layer thickness, moisture content, and ageing. Due to its simple setup, it is potentially applicable on site. It is non-invasive with a high depth resolution and makes a number of parameters for planning and executing the rehabilitation of buildings as well as for quality assurance easy accessible. In this paper, we focus on the quality assurance of a sprayed polymer-concrete (SPC), which was recently developed by Massenberg GmbH and the Institute of Building Materials Research (ibac) for the repair of sewage systems. Single-sided NMR was used to access curing time of the epoxy binder, binder content, layer thickness, and diffusion of acids through the SPC. However, single-sided NMR measurements only give relative values, so calibrations are given where required. While single-sided NMR shows great potential and can be used in various further applications, limitations of resolution, depth and measurement time need to be considered.

Abstract: In view of the appearance of instability and malfunction problem for level control system in the steam drum of boiler, a new method to use statistical process control (SPC) was proposed, which analyzed the level data by the SPC. It can extract the main features of the level variable, and set up the upper and lower monitoring limits for the level control system in the steam drum of boiler. The decision-making basis for the operator can be provided by monitoring control accuracy of the level control system. With this method, it can improve the control accuracy of the level variable and provide the information quickly and efficiently for the fault diagnosis of the level control system, prevent the malfunction occurs, ensure safety and stable operation for the boiler control system.

Abstract: The T² statistic is one important indicator of statistical process control theory to identify anomalies of the multivariate industrial process. In the research field of the coal gas pre-drainage process control, previous achievements mainly based on the univariate control chart, which leaded to huge workload and facilitated some human errors. Against these problems, a more comprehensive and easy-to-use method based on the T² statistic was proposed. First at all, the basic thought and the principle of T² control chart was elaborated. Secondly, the data structure and data samples were provided after their principle component analysis. Finally, the multivariate control chart of coal gas pre-drainage process was established. Results show that the proposed anomaly identification method can integrate dozen of univariate control charts into one. Then technicians needn’t deal with many control charts in the same time and many human errors can be avoided.

Abstract: According to the characteristics of quality management and control in mold manufacturing process, this paper adopts SPC technology to solve the problem of mold production quality control. First of all, it expounded the mechanism of SPC to control the quality and take the machining process of the stamping die mold as an example, using statistical techniques to control the production process quality effectively; Secondly, by using control chart, whether the production process in a state of statistical control could be quickly determined, and the fixture loosening caused by abnormal production would be found and eliminated timely; Finally, through the process capability analysis, the level of process ability could be timely understood, and then two effective measures of improving production processes were put forward in order to reduce the feed rate and improve the process ability of workers.

Abstract: Tapping by cutting is one of the most common operations in manufacturing. It consists of cutting internal threads on the wall of a previously drilled hole by means of a tool called a tap that has cutting edges on its chamfered periphery. When tap wear is slight the process and geometry are usually in control and correct, respectively. However, when tap wear level is high the geometry is not correct and the process is out of control. This is an unacceptable industrial cost. The aim of this paper consists on an industrial monitoring application to data coming from the current/torque signal of the tap spindle for assessing thread quality. It operates in real time and indicates when the tap wear is so critical that, if the process were continued, it would result in unacceptable screw threads. Then the system shows a red light so that the operator could replace the worn-out tap. The system would be very cost-effective since the tapping process could be run without any operator intervention.

Abstract: Control charts are made to identify assignable causes of difference that could exist in production processes. It is usually believed the probability distribution which represents the actual observations includes a known functional form and it is constant as time passes. However, in reality, observations obtained through continuous and discrete procedures in many cases are serially correlated. Autocorrelation not just breaks the actual independence assumption of conventional control charts, but also can impact the efficiency associated with control charts negatively. In this article, we are going to investigate the impact of autocorrelation to the performance of Hotelling T² control chart in which autocorrelated data were utilized to construct the Hotelling’s T² chart with induced autocorrelation from various levels of correlation at different sample sizes. Simulations had been done to generate the data set used to construct the Hotelling’s T² control chart and the outcomes implies that all of the control charts constructed had their points outside the designed control limits, that confirmed the effect of autocorrelation to the performance of the Hotelling’s T² control chart. Suggestions on how to tackle the problem was proposed.

Abstract: In todays highly competitive market, the demand for quality is a critical factor for organization to survive in the ever-expanding global marketplace. The concept of total quality management (TQM) has been developed as a result of intense global competition. Japanese companies have had superior achievement, and left their counterparts, non-Japanese far behind. One of the TQM strength practices in Japanese companies is technical aspects; tools and techniques namely statistical process control (SPC), total productive maintenance (TPM) and lean production. The purpose of this paper is to compare TQM practices between Japanese and non-Japanese companies, and develop the conceptual framework based on extensive review of the literature. Three theories; institutional theory, system theory and contingency theory have been identified and applied in this study for developing conceptual framework. Based on literature review, Japanese companies have higher TQM practices compared to non-Japanese companies. Furthermore, this study proposes that SPC, TPM and lean production are mediators for TQM in Japanese companies. This proposed research will help the academicians and industry players to have better understanding of TQM implementation in order to improve business performance effectively in the future.

Abstract: t is a big challenge faced by the enterprises that how to trace and manage the quality information of complex products effectively in the overall life circle. In this paper, two-dimensional code is regarded as a carrier of quality information,and statistical process control (SPC) is used to evaluate the production process and control the on-line quality.Quality tracing and management model is established which consists of three parts:the identification of parts by two-dimensional code,the real-time acquisition of process information and the quality management.The proposed model is validated and successfully implemented in a typical complex products manufacturer for quality tracing and management.

Abstract: The sulfonated Petroleum coke is used to synthesize n-propyl alcohol(N-PROPYL ALCOHOL) by hydration of ethylene oxide(EO) in chemical engineering and the catalyst of sulfonated Petroleum coke (SPC) is studied. The effect of reactive temperature on the activity of SPC is greatest when reactive temperature goes up，the activity of SPC is quickly enhanced，but when temperature exceeds a certain range, the activity of SPC will reduce; And the activity of SPC will become stronger along with reactive pressure rise，when pressure exceeds a certain value，selectivity of N-PROPYL ALCOHOL will decrease; Also，increasing airspeed will weaken the activity of SPC. The conversion rate of EO reaches 98-100%