Reliability Improvement Strategies Research Articles

Reliability Analysis and Life Cycle Cost Optimization of Hydraulic Excavator

This study focuses on conducting a reliability analysis of an excavator from its field failure data and improve its reliability cost effectively. The aim of the research is to perform reliability estimation of systems and identify the critical subsystem with significant contributions to system unreliability. The reliability analysis was performed using repairable system data analysis approaches. Life cycle cost (LCC) was estimated for critical subsystems, and it was optimized to select cost effective reliability improvement strategy. The results of the study provide valuable insights into the performance and cost-effectiveness of the excavator and its subsystems, which can assist manufacturers and operators in optimizing their equipment’s reliability, availability while considering the cost implications over the life cycle of the equipment. The results show that the undercarriage has critical contributions to system unreliability. This study attempts deep down reliability analysis of critical undercarriage components for optimal selection of improvement method among feasible alternatives. LCC analysis and its optimization performed on the critical sub-system is expected to help OEM save approx. 15% of LCC. The empirical data used in the paper is based on field data gathered during the operational life of the hydraulic excavator over approx. six years in its Indian operations.

Reliability Analysis and Improvement Strategies of Microcomputer Relay Protection Devices

Reliability Analysis and Improvement Strategies of Microcomputer Relay Protection Devices

Research on reliability assessment and multi-time scale improvement strategy of electricity-gas integrated energy system under cyber attack

While the coupling between various energy systems is deepening as integrated energy develops quickly, security risks in the information network system will be introduced into the physical system, and the interaction between the systems causes the security risks to increase. It is essential to maintain the multi-energy coupling integrated energy system’s safe and reliable operation. Therefore, this paper first constructs the cyber physics system (CPS) model based on the electricity-gas integrated energy system (EGIES), the fault propagation mechanism of the system caused by the cyber attack is analyzed, and the cyber attack scenario simulation method based on the N-n predicted fault set is proposed. Secondly, based on the optimal load shedding model and the reliability assessment index, the reliability assessment method of the electricity-gas integrated system under cyber attack is proposed. Then, on the basis of system reliability assessment, a multi-time scale reliability improvement strategy based on branch power and pipeline flow optimization of EGIES under cyber attack is proposed. Finally, the simulation results of the IEEE57-NGS20 electricity-gas integrated system verified the effectiveness of the proposed method. The proposed optimization strategy reduces the out-of-limit range of power transmission lines and natural gas pipelines, reduces the probability of cascading failure in the system under information attacks, and improves the resistance and energy supply reliability of the system against cyber attacks.

Method for integrating classical and network reliability: A time varying network reliability evaluation

AbstractMany capacitated flow network papers treat reliability as a time‐invariant property. However, network components degrade over time suggesting that methods to quantify the time‐varying reliability of a network are appropriate. This paper proposes a method to compute the reliability of a multistate capacitated flow network in terms of multistate components characterized by a life distribution. The approach enables the calculation of the probability that demand can be satisfied over period of time despite component degradation. Examples are provided to clarify the steps required and to illustrate the assessments enabled. Based on the classical reliability theory, the Weibull reliability function is employed to characterize the degradation of network components. However, the approach is general and other distributions are also possible. The results indicate that the approach can assist a network supervisor determine reasonable demand rate and time constraint to satisfy demand as well as reason about alternative reliability improvement strategies.

Fault analysis of CNC equipment based on DEMATEL/ISM/ANP

To make a reasonable reliability improvement strategy for CNC equipment, it is necessary to clearly understand the fault relation characteristics and the weak links of reliability. While the fault complexity of CNC equipment makes the fault relation characteristics unclear, it is very difficult to determine the weak link of reliability. Therefore, a fault analysis method for CNC equipment based on decision-making and trial evaluation laboratory (DEMATEL)/interpretive structure modeling (ISM)/analytic network process (ANP) is proposed in this study to describe the relationship between CNC equipment faults accurately and identify reliability weaknesses. First, the fault mechanism was analyzed by the fault phenomenon, and the fault factors of the CNC equipment were identified in view of the system. Second, DEMATEL/ISM/ANP method was adopted to integrate the interaction direction and intensity between the failure factors, hierarchical structure of the factors, and their relative importance, and a hierarchical network structure model for CNC equipment fault factors was built. Finally, according to the analysis results of the aforementioned model, the fault factors of the CNC equipment were divided into drive, link, dependence, and independent fault factors, and the identification of the weak link of reliability was completed. Results show that the proposed method can quantify the fault factors of the CNC equipment and clearly identify the main direction of its reliability improvement.

The Reliability Improvement Strategy of Medium Voltage Distribution Network Based on Network Frame Optimization

The Reliability Improvement Strategy of Medium Voltage Distribution Network Based on Network Frame Optimization

Backup or Reliability Improvement Strategy for a Manufacturer Facing Heterogeneous Consumers in a Dynamic Supply Chain

This paper examines a manufacturer's supply management strategies for mitigating yield risk in a complex dynamic supply chain. Two strategies can be adopted for the manufacturer: backup and reliability improvement. Consumers may select to leave (instant consumers) or wait (delaying consumers) when they confront the manufacturer's insufficient inventory. Utilizing the method of multi-agent modeling, a manufacturer and a supplier are modeled as the intelligent agents with the reinforcement learning behavior. The study shows that: 1) when the number of instant consumers is small, reliability improvement strategy should be selected; otherwise, the manufacturer should adopt a backup strategy; 2) only when mean yield is large enough, reliability improvement strategy is the optimal choice; and 3) if yield uncertainty is small, the manufacturer should choose reliability improvement strategy; otherwise, it is suitable to use a backup strategy. In addition, when the main supplier can determine its own wholesale price, it is found that: 1) when the mean yield is small, a lower wholesale price should be designed for the main supplier, to induce higher order quantity under backup strategy; and 2) the impact of yield uncertainty on the manufacturer's supply management strategy can be changed by the main supplier's adaptive pricing behavior.

On optimal upgrade strategy for second-hand multi-component systems sold with warranty

Reliability improvement strategies such as upgrade, reconditioning and remanufacturing have been extensively adopted by dealers of second-hand systems to improve the system reliability and reduce the warranty servicing cost. However, most existing studies on this topic do not consider the multi-component structures of complex second-hand systems, and either treat them as black-box systems by ignoring their internal structures or simply deal with individual components. In this paper, a new upgrade model is developed for complex second-hand systems sold with a non-renewing free repair/replacement warranty, by explicitly considering their multi-component configurations. Two types of components, i.e. repairable and non-repairable components, are taken into account. During the upgrade process, non-repairable components can be upgraded only by replacement (if necessary), while repairable ones may be imperfectly upgraded with various degrees. The main objective of the dealer is to determine which components to upgrade and the corresponding upgrade degrees, to minimise the total expected servicing cost. In view of the problem structure, a marginal analysis based algorithm is presented. It is shown that the proposed upgrade strategy contains the ‘no upgrade’ strategy and the ‘component-level perfect upgrade/replacement’ strategy as special cases, and outperforms them. Finally, several extensions of the proposed upgrade model are discussed.

Transit Delay Estimation Using Stop-Level Automated Passenger Count Data

AbstractDespite the potential use of global positioning system (GPS) based automatic vehicle location (AVL) data in the development of reliability improvement strategies for transit systems, issues...

Optimal reliability improvement strategy in radial distribution networks with island operation of distributed generation

This study presents a mixed integer linear programming-based approach for determining the optimal strategy for reliability improvement in radial distribution networks where island operation of distributed generators (DGs) is allowed. The proposed approach simultaneously defines the optimal number, type, and location of new automation devices (ADs) to be installed in a network, the optimal relocation of the existing ADs and the optimal creation of DG islands. The load curtailment possibility in creating islands is considered along with the multi-level load model. The presented numerical results indicate the effectiveness of the proposed approach and the importance of simultaneous consideration of the aforementioned individual strategies in determining the best reliability improvement strategy in radial distribution networks with DGs.

Reliability improvement of transistor clamped H‐bridge‐based cascaded multilevel inverter

Reduced voltage stress and low-total harmonic distortion are the main causes for such widespread application of multilevel inverters (MLIs) in various industrial sectors. However, reliability is one of the major concerns of MLIs as it uses a large number of switches as compared with two-level inverters. Therefore, a newly developed transistor clamped H-bridge inverter is proposed in the literature which uses a relatively less number of switches and DC sources as compared with cascaded H-bridge but lacks in reliability due to the absence of redundant states. Hence, in this study, the reliability improvement strategy for newly developed five-level transistor clamped H-bridge-based cascaded inverter is proposed which can be generalised for any number of levels. In the proposed fault tolerant strategy, the fault can be broadly classified based on the two main legs of the proposed inverter. Moreover, the proposed fault tolerant strategy does not require any kind of external circuit for maintaining its capacitor voltage in the balanced state. Finally, to validate the concept, a laboratory prototype of the five-level inverter is developed and results are obtained successfully.

A game theory approach for the measurement of transport network vulnerability from the system prospective

Measuring the transport network vulnerability has become an important research issue recently. With the increase in the road user's value of time, users are now not only concerned about taking the shortest route to save travel times, but also decrease the variances by choosing a route that is more reliable to arrive at the destination within an acceptable time frame. Ensuring a reliable network and providing alternative options under network breakdowns are very important to reduce the network vulnerability. This paper proposed a potentially computationally efficient approach to measure system-level network vulnerability through a game theory approach. The most vulnerable link is indicated by link failure probabilities and the overall vulnerability measure of the network is represented by the expected total travel time. The performances are compared and discussed through the numerical results from several reliability improvement strategies.

Reliability Improvement Strategies for HVDC Transmission System

This paper analyses reliability data of HVDC systems of Southern China Power Grid. The weak links of HVDC systems’ operational reliability are DC control and protection, valve hall and valve cooling system and transmission lines. Some improvement measures and HVDC system reliability technology are proposed in this paper.

Modeling and analysis of effective ways for improving the reliability of second-hand products sold with warranty

Often, customers are uncertain about the performance and durability of the used/second-hand products. The warranties play an important role in reassuring the buyer. Offering the warranty implies that the dealer incurs additional costs to service any claims made by the customers. Reducing warranty costs is an issue of great interest to dealers. One way of improving the reliability and reducing the warranty servicing cost for second-hand items is through actions such as overhaul and upgrade which are carried out by the dealer or a third party. Improving actions allow the dealer to offer better warranty terms and to sell the item at a higher price. This paper deals with two effective approaches (virtual age approach and screening test approach) to decide on the reliability improvement strategies for second-hand products sold under various warranty policies (failure-free, rebate warranty, and a combination of free replacement and lump sum). A numerical example illustrates that from a dealer’s point of view, it is beneficial to carry out an improvement action only if the reduction in the warranty servicing cost is greater than the extra cost incurred due to this improvement action.

A quality and reliability improvement strategy for a small- and medium-sized manufacturing enterprise: a case study

The aim of this paper is to demonstrate how a Small- and Medium-sized Manufacturing Enterprise (SME) in New Zealand strives to improve its product Quality and Reliability (Q&R) through a proposed Q&R improvement programme. This was based on the work conducted for an electronic company in Auckland, New Zealand. The approach taken was to design a Q&R improvement programme based on reviews of its historical data, available facilities, future goals and benchmarking. To maintain confidentiality, the name of the company is omitted in this paper. Most SMEs are low volume manufacturers and it is unrealistic to generate Q&R data from large sample sizes. Despite this, Q&R has become an important factor for them to compete in the global market. A strategy has to be developed to produce products of high Q&R level. This strategy has been proven effective and has been integrated into the company's continuous Quality Improvement Program (QIP).

An electric power purchase strategy for bilateral contracts focusing on reliability of customers

AbstractWith the introduction of the competitive electrical power market, large‐scale customers can select electric power suppliers. Customers need to consider not only the economical efficiency but also reliability, to decide the amount of electrical power to purchase. This paper develops an economic electric power purchase strategy for customers focusing on reliability. A bilateral contract model expressing electric power suppliers as generators with a forced outage rate is proposed and introduced to assess potential outage risks of the bilateral contract between an electric power supplier and a customer. The outage‐related cost, consisting of potential outage risks and the estimated outage cost, is also proposed and introduced as an index of the reliability on the customer side, and an optimal reliability level of a customer is obtained by using the index. Several numerical examples demonstrate the availability of the proposed electric power purchase decision method and reliability improvement strategies for customers are discussed. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 9–21, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20345

View Through the Door of the SOFIA Project

The National Aeronautics and Space Administration (NASA), and Deutsches Zentrum Mir Luft- und Raumfahrt e.V. (DLR) are working together to create a Stratospheric Observatory for Infrared Astronomy (SOFIA) based on a modified Boeing 747-SP aircraft. One of the key elements of the modification is a new door system that protects the 2.5 meter infrared telescope during flight by covering the aircraft cavity within which the telescope resides. The door system follows the telescope's motion to provide an unvignetted view of the sky, while reducing turbulence inside the cavity. This paper describes the value added by a productive interaction of reliability engineering with the integrated product design team at NASA Ames Research Center that was responsible for the design of this "cavity door" system. The intent of this paper is to describe the interaction with the design team, to point out key reliability improvement strategies applied to the cavity door system, and to offer a few principles to guide interaction of reliability engineers with a design team. It is shown, for example, that significant assistance to improve reliability is achievable with a thorough, detailed understanding of the system's intent, and an organized approach to how it might fail to carry-out its intent. The specifics of the analyses performed are briefly summarized, but the paper emphasizes the key insights that were gained into the reliability of the system.

An Electric Power Purchase Strategy for Bilateral Contracts Focusing on Reliability of Customers

With the introduction of the competitive electrical power market, large-scale customers can select electric power suppliers. Customers need to consider not only the economical efficiency but also reliability, to decide the amount of electrical power to purchase. This paper develops an economic electric power purchase strategy for customers focusing on reliability. A bilateral contract model expressing electric power suppliers as generators with a forced outage rate is proposed and introduced to assess potential outage risks of the bilateral contract between an electric power supplier and a customer. The outage-related cost, consisting of potential outage risks and the estimated outage cost, is also proposed and introduced as an index of the reliability on the customer side, and an optimal reliability level of a customer is obtained by using the index. Several numerical examples demonstrate the availability of the proposed electric power purchase decision method and reliability improvement strategies for customers are discussed. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 9–21, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20345

Reliability Capability Evaluation and Improvement Strategies For Subsea Equipment Suppliers

Reliability Capability Evaluation and Improvement Strategies For Subsea Equipment Suppliers