International Journal of Quality Engineering and Technology (5 papers in press)

Regular Issues

• Applying Quality Function Deployment for Designing a Cryogenic Piping System  
  by Abid Hossain Khan, S.M. Tazim Ahmed, Md. Sumon Rahman, Md. Shafiqul Islam 
  Abstract: Cryogenic piping system is a delicate product. If it is not designed properly, i.e. without considering region specific weather condition, vaporization will occur at undesirable rate while cryogenic fluid flows through the pipeline. In this work, optimum design for a cryogenic piping system has been explored. To identify existing design limitations as well as customer priorities, quality function deployment has been employed. Data have been collected from local customers and experts through questionnaire-based survey. Double-concentric-pipes type construction with inner pipe diameter of 21.34-33.40mm and outer pipe diameter of 88.90-193.68mm has been considered. Four potential insulating mediums; Multilayer insulation, Vacuum, Polyethylene foam, and Perlite have been investigated. Multilayer insulation thickness and vacuum pressure have been varied from 6-30mm and 10e-5-5mbar respectively. Results reveal that use of multilayer insulation accompanied by vacuum pressure of 10e-4 mbar ensures optimum performance with optimum insulation thickness of 20mm.
  Keywords: Cryogenic liquid; heat transfer; house of quality; optimization; quality function deployment.
  
  
• Reliability assessment and veri?cation of safety instrumented systems with the application of LOPA and FTA in the isomerization unit of the Isfahan Oil Refinery  
  by Mahdi Ghasempour, Reza Gholamnia, Mousa Jabbari 
  Abstract: Investigating the reasons and points of accidents in industrial plants have played a pivotal role through risk assessment for preventing new accidents. Oil and gas refineries expose to different hazards like combustion, explosion, and toxic release and these accidents can have catastrophic and irreparable consequences. It is particularly important to conduct safety integrity level (SIL) studies in process industries to assess the safety and reliability of complex engineering systems. The purpose of this practical study is to evaluate the reliability and effectiveness of safety systems equipped with instrumentation in the isomerization unit of the Isfahan Refinery Complex. The research consists of two parts. In the first part, 22 hazardous scenarios were identified by using cause & effect tables and hazard and operability (HAZOP) studies. Subsequently, the semi-quantitative LOPA method was used to evaluate the protection layers and also determine of Safety integrity level required by the system (Target SIL). In the second part of the study, fault tree analysis (FTA) was performed to determine the safety integrity level of system (SIL verification). Based on the results of this study, out of the 22 selected hazardous scenarios, 4 scenarios have Safety Integrity Level 1 (SIL1), 17 scenarios have Safety Integrity Level 2 (SIL2) and 1 scenario has Safety Integrity Level 3 (SIL3). The scenario which is related to the cutoff the outflow of fluid from the pumps, with the consequent increase in reaction intensity and sudden rise in the temperature of the reactor isomerization and ultimately the reactor explosion and significant damage to the unit and the incidence of human losses, has the most critical points of the production process from the point considered safety in isomerization units and it has Safety Integrity Level 3 (SIL3). In all the selected scenarios, safety integrity level of the system accordance to the safety integrity level required (Target SIL). Also in all the scenarios, the final reduced event frequency, considering all the layers of protection, especially the safety instrument system, corresponded to the refinery's acceptable risk criteria. It was also determined from the results that intrinsically safe design and use of up-to-date and new equipment with high reliability resulted in an acceptable level of risk and acceptable safety in the process and the system is operating with good reliability.
  Keywords: Process industries; FTA; LOPA; SIL; Reliability.
  
  
• Proposal of a causal model to measure the impact of Quality management system on industrial performance: A case study of a multinational energy company located in Casablanca, Kingdom of Morocco  
  by MOHAMMED HADINI, MOHAMED Ben Ali, Said Rifai, Otmane Bouksour, Ahmed Adri 
  Abstract: The purpose of this article is to present a statistical approach using latent and manifest variables applied to measure the Quality management system performance of a multinational energy company located in Casablanca, Kingdom of Morocco. The principal idea is to measure the impact of Quality practices (which are divided into five segments: Leadership, Strategy & Policy, Human Resources, Partnerships & Resources, and Process Management) on the total performance (which is divided into four perspectives: Customer Result Perspective, Financial Result Perspective, Staff Result Perspective, Society Result Perspective). For this, we use the SEMs resolution based on the Partial Least squares (PLS) method via the XL-STAT software on a sample of 120 questionnaires administered face-to-face with managers, technicians, engineers and directors of this company. The obtained results should be examined in order to plan the improvements and develop an action plan. Of course, to further improve the total performance of this company and attain maturity, the leaders of such kind of companies must continually seek to improve the Quality practices and in particular those showing weak associations that may be direct or indirect (Leadership, Strategy & Policy, Human Resources, Partnerships & Resources). Our study also offers evidence to show that Quality practices generally have a positive impact on the total performance (financial and non-financial performance) of such kind of companies.
  Keywords: Quality Management System; Modeling approach; PLS; Company Performance; Modeling approach; SEM’s resolution.
  
  
• Many-objective x-bar control chart using hybrid NSGA-III and DEA  
  by Zahra Mohit-Ghiri, Ali Mohammadi, Seyed-Hadi Mirghaderi 
  Abstract: The present study aimed to find the optimal design of the x-bar control chart which optimises quadruple objectives. The objectives are the average run length, the detection power, the average time to signal, and the expected cost per hour. In this study, a many-objective mathematical model was developed to find the optimal design and solved it using three different variations of the third version of the non-dominated sorting genetic algorithm, named NSGA-III, ?-NSGA-III, and NSDGA-III. The third one is the contribution of this paper which hybridised the NSGA-III with data envelopment analysis (DEA) and technique for order of preference by similarity to ideal solution (TOPSIS). The performances of the three algorithms were tested using a numerical example. The results revealed that the developed NSDGA-III is well defined to explore the search area and in each generation, it is always the best one in choosing solutions that have higher efficiency. Therefore, it is superior in comparing with other algorithms to find better solutions. Hence, the new hybrid algorithm can outperform NSGA-III and ?-NSGA-III. It can be used in all processes with variation due to an assignable cause.
  Keywords: quality control; x-bar control chart; many-objective; multi-objective design; genetic algorithm; NSGA-III; ?-NSGA-III; NSDGA-III; data envelopment analysis.
  
  
• Steepest ascent improvement by response predictions implementation  
  by Vladimir B. Bokov 
  Abstract: For the exploratory runs of steepest ascent the use of response predictions is proposed. The factors for these runs are estimated on the data of initial experiment and by finding conditional extremum. Parameter estimates are employed to obtain estimated response functions on which the response of exploratory runs is predicted. Response prediction intervals for these runs are found by using the parameter estimates of linear models, factor estimates for exploratory runs, and linear models for response predictions. This allows to identify those response observations that go beyond the bounds of response prediction intervals and to find factor values under which exploratory run response at hand is still in its prediction interval. The comparison of two linear models reveals that the model with coded factors and response variables allows to obtain the smaller intervals of response predictions. This permits to identify more accurately the last run of steepest ascent and factor levels for design centre of the next initial experiment.
  Keywords: design of experiment; linear model; prediction interval.