Latent Failures Research Articles

Environmental stress screening modelling, analysis and optimization

Environmental stress screening (ESS) is widely used in industry to eliminate early or latent failures. However, the appropriate stochastic modeling for ESS has not been yet suggested in the literature. In this paper, we develop the corresponding stochastic model and analyze the effect of the ESS in terms of population characteristics. In our model, during the ESS, the manufactured items are exposed to a stress with the relatively large magnitude, which can result either in immediate failures of items or in the increased susceptibility to future failures. The corresponding optimization problems for obtaining the optimal level of the stress magnitude are also formulated and discussed. An illustrative example is considered.

Understanding the causes of intravenous medication administration errors in hospitals: a qualitative critical incident study

ObjectivesTo investigate the underlying causes of intravenous medication administration errors (MAEs) in National Health Service (NHS) hospitals.SettingTwo NHS teaching hospitals in the North West of England.ParticipantsTwenty nurses working in a...

The Strategic Assessment Model (Stratam) Studying and Preventing Strategic Failure

Abstract The purpose of this study is to introduce the Strategic Assessment Model (STRATAM), a model designed to assist in the prevention of strategic failure. STRATAM aids firstly in the assessment of a strategy, as well as its crafting and evolution; secondly, it aims to enable and possibly streamline civil-military strategic debates on military operations. It is argued that strategic blunders in many cases result from latent organizational failures on one’s own side. Therefore, STRATAM combines Clausewitz’ theory of war and strategy with organizational failure theory. To demonstrate the use of this model, this paper uses Operation Cast Lead (or the Gaza War) of 2008-2009 as a case study. The paper’s findings include that the ultimate reasons for strategic failure were on one hand Clausewitzian; on the other hand, the Israeli Defense Force’s failure in organizational learning from a previous war two years earlier. The timely, strategic assessment and an effective civil-military debate about the effects of ongoing military operations might have prevented this failure. STRATAM would have provided the necessary language, structure, and relevance to identify actual and potential strategic failures with the goal to evolve the strategy.

A Systems Approach to Diagnosing and Measuring Teamwork in Complex Sociotechnical Organizations

This paper presents a novel approach to diagnosing and measuring teamwork in complex sociotechnical systems. First, the underlying theoretical constructs that have inspired the development and use of a multi-level model to study team phenomena from a general systems perspective are presented. Next, in an attempt to theoretically ground the construct, “flow state” will be presented as an isomorphic variable in a multi-level model, meaning it is represented similarly at the system, team, and individual level. Approaching processes embedded in organizations from this perspective allows diagnosis of the systemic influences that contribute most to the variance in performance, identification of pervasive latent systemic failures, and the development of a tailored taxonomy of behavioral teamwork dimensions, which can then be translated into metrics to measure teamwork within any observable complex process.

Chromatographic Analysis of Oil-Based Electrical Equipment Discharge Failure

Discharge of failure was the fault type are likely to occur in transformers, bushings, transformers, and the extent of damage to the equipment is a serious and direct impact on the stable operation of the system, first introduced the principle and gas chromatographic analysis its test methods, then gas chromatography equipment discharge failure is how to judge the conduct described. Through the analysis of transformer oil chromatographic method can be found as early as possible transformers and other equipment inside the existence of latent failures, thus chromatography is to oversee and guarantee the safe operation of an important means of transformer.

KBE development for criticality classification of mechanical equipment: A fuzzy expert system

Recent research reveals that a significant number of unwanted events have occurred due to latent failures which route back to human errors linked to maintenance engineering applications. To assure systems safety at different technical levels, it is vital that human errors linked to the maintenance regime are mitigated. Frequent knowledge migration from one industrial organization to another has deteriorated maintenance engineering related assessments, evaluations and recommendations, especially as a result of inexperienced personnel and the lack of expert advice when it is needed. Hence, it is important to develop methodologies to recycle the knowledge accrued in an industrial organization. The knowledge based engineering (KBE) approaches, along with expert systems related analysis, provide a foundation for knowledge recycling. This paper presents an approach to perform functional failure criticality (FFC) based on the guidelines specified in a standard for prioritizing maintenance work orders for mechanical equipment and instrumentation. Use of the ranges and linguistic variables tend to occur suboptimal classifications in FFC assessments due to the lack of a consistent approach. This inhibits incorporating actual circumstances at the boundary of the input ranges or at the levels of linguistic data and criticality levels. This has further been exacerbated by the lack of experienced personnel. Hence, this paper suggests KBE development via a fuzzy logic system (FLS) to overcome the aforementioned challenge and minimize the variations present in the analysis. Membership functions and a rule base have been developed based on the experts’ knowledge, data, information and guidelines specified in the selected standard. An illustrative case has been performed with the help of two engineering contractor companies which provide maintenance support services. FFC assessments using the suggested KBE development have been presented to verify the applicability of the approach.

Sector-Disk (SD) Erasure Codes for Mixed Failure Modes in RAID Systems

Traditionally, when storage systems employ erasure codes, they are designed to tolerate the failures of entire disks. However, the most common types of failures are latent sector failures, which only affect individual disk sectors, and block failures which arise through wear on SSD’s. This article introduces SD codes, which are designed to tolerate combinations of disk and sector failures. As such, they consume far less storage resources than traditional erasure codes. We specify the codes with enough detail for the storage practitioner to employ them, discuss their practical properties, and detail an open-source implementation.

A Multiphase Decision Model for System Reliability Growth With Latent Failures

Reliability growth testing becomes difficult to implement as the product development cycle continues to shrink. As a result, the new design is prone to latent failures due to design immaturity and uncertain operating condition. Reliability growth planning emerged as a new methodology to drive the reliability across the product lifetime. We propose a multiphase reliability growth model that sequentially determines and implements corrective actions (CAs) against surfaced and latent failure modes. Such a holistic approach enables the manufacturer to attain the reliability goal while ensuring the product time to market. We devise a CA effectiveness function to assess the tradeoff between the failure removal rate and the required resources. Rosen's gradient projection algorithm is used to determine the optimal resource allocation in each phase. The applicability and performance of the reliability growth model are demonstrated on a fleet of semiconductor testing equipment.

Application of Dormant Reliability Analysis to Spillways

AbstractDams are essential infrastructures for water supply, flood control, energy production, and irrigation. A critical component for the safety of a dam is the spillway system which, by controlling releases, prevents overtopping of the dam. This in turn reduces impacts associated with excessive downstream flows and upstream water levels on infrastructures, the population, and the environment. This paper addresses reliability issues related to emergency spillways and specifically the estimation of their reliability level after prolonged periods of dormancy. During dormancy, spillway components are exposed to the environment and sustain cumulative damage that may trigger latent failures or failures on demand. Regular inspections and tests are used to detect and remediate latent failures and to assess the level of deterioration of components. The purpose of this study is to develop procedures to account for dormancy in the reliability analysis of spillways. It also demonstrates how these procedures can be...

GRP-165 Root Cause Analysis as an Opportunity to Improve the Safety of Paediatric Care

BackgroundPatient safety is a serious global public health issue. Causal analysis with a systematic and participatory approach is a useful tool for improving safety.PurposeTo perform a root cause analysis (RCA)...

Introducing transapical aortic valve implantation (part 2): Institutional structured training program

Introduction of a new procedure has a typical learning curve with the "learning phase" at the beginning, characterized by an increased mortality or complication rate. We developed our institutional structured training program for transcatheter aortic valve implantation (TAVI) with the aim of eliminating these negative effects. The program regulated the introduction of TAVI and building and training of the team. It combines cumulative knowledge from the field with the institutional and individual background experience. It includes stepwise acquisition of the tools necessary for the preoperative strategic planning, perioperative team communication, technical aspects of the procedure, and postoperative management. The program establishes a basis for interaction and feedback between the members of the team ("teach and learn"; "be proctor and proctored"). The program consists of 4 main parts: general principles, team building, team education and training, and the institutional clinical and procedural policies. The program possesses several control mechanisms, eg, occasional external proctoring. Additionally, a chain of steps spontaneously generates further procedural improvements and optimizes the overall outcome. The program has also had a global positive effect on the local institutional environment, awaking awareness of existing latent conditions and active failures, identifying them and inducing their correction, which has led to general clinical improvement. A structured educational training program enables implementation of a new procedure (TAVI) into clinical practice without increased morbidity and mortality rate during the learning curve. The program may also be used as a basis for any new device introduction into clinical practice.

Identifying the latent failures underpinning medication administration errors: an exploratory study.

The primary aim of this article was to identify the latent failures that are perceived to underpin medication errors. The study was conducted within three medical wards in a hospital in the United Kingdom. The study employed a cross-sectional qualitative design. Interviews were conducted with 12 nurses and eight managers. Interviews were transcribed and subject to thematic content analysis. A two-step inter-rater comparison tested the reliability of the themes. Ten latent failures were identified based on the analysis of the interviews. These were ward climate, local working environment, workload, human resources, team communication, routine procedures, bed management, written policies and procedures, supervision and leadership, and training. The discussion focuses on ward climate, the most prevalent theme, which is conceptualized here as interacting with failures in the nine other organizational structures and processes. This study is the first of its kind to identify the latent failures perceived to underpin medication errors in a systematic way. The findings can be used as a platform for researchers to test the impact of organization-level patient safety interventions and to design proactive error management tools and incident reporting systems in hospitals.

Human Factors and Maritime Safety

This paper presents key models and concepts developed in psychology which help to understand the role of human factors in complex systems. It aims to explain their significance for anyone who wants to analyze the role of human factors in maritime accidents. Reason (1990, 1997, 2000) makes a crucial distinction between “active failures” that are made by first-line operators (captain, officers or members of a crew) and “latent failures” that are deeper causes and upstream factors concerning people who are at a distance from the accident. In agreement with this theoretical framework, this paper proposes examining the role of human factors in maritime accidents at three different levels:i) the level of individual – and namely cognitive – factors of first-line operators,ii) the level of social – and namely interpersonal – factors andiii) the level of systemic or organizational factors which correspond to “latent failures”. For each level, the main and recent contributions of the human and social sciences are presented and then used to analyze an emblematic accident.

Optimal Burn-In Policy for Highly Reliable Products Using Gamma Degradation Process

Burn-in test is a manufacturing process applied to products to eliminate latent failures or weak components in the factory before the products reach customers. The traditional burn-in test over a short period of time to collect time-to-failure or go/no-go data is rather inefficient. This decision problem can be solved if there exists a suitable quality characteristic (QC) whose degradation over time can be related to the lifetime of the product. Recently, optimal burn-in policies have been discussed in the literature assuming that the underlying degradation path follows a Wiener process. However, the degradation model of many materials (especially in the case of fatigue data) may be more appropriately modeled by a gamma process that exhibits a monotone-increasing pattern. Here, motivated by laser data, we first -propose a mixed gamma process to describe the degradation path of the product. Next, we present a decision rule for classifying a unit as typical or weak. A cost model is used to determine the optimal termination time of a burn-in test, and a motivating example is then presented to illustrate the proposed procedure. Finally, a simulation study is carried out to examine the effect of wrongly treating a mixed gamma process as a mixed Wiener process, and the obtained results reveal that the effect on the probabilities of misclassification is not negligible.

Stochastic analysis of shock process and modeling of condition-based maintenance

The paper presents an analytical formulation for evaluating the maintenance cost of engineering systems that are damaged by shocks arriving randomly in time. The damage process is nonlinear in a sense that damage increments form an increasing sequence (i.e., accelerated damage) or a decreasing sequence (saturated damage) of random increments. Such processes are motivated from damage data collected from nuclear reactor components. To model the nonlinear nature of damage process, the paper proposes the use of non-homogeneous Poisson process for damage increments, which is in contrast with the common use of a renewal process for modeling the damage. The paper presents a conceptually clear and comprehensive derivation of formulas for computing the expected cost rate associated with a periodic inspection and preventive maintenance policy. Distinctions between the analysis of self-announced and latent failures are highlighted. The analytical model presented in this paper is quite generic and versatile, and it can be applied to optimize other types of maintenance policies.

Semi-Markovian Model of Control of Restorable System with Latent Failures

Mathematical model of control of restorable system with latent failures has been built. Failures are assumed to be detected after control execution only. Stationary characteristics of system operation reliability and efficiency have been defined. The problem of control execution periodicity optimization has been solved. The model of control has been built by means of apparatus of semi-Markovian processes with a discrete-contin- uous field of states.

Semi-Markovian Model of Unreliable Control of Restorable System with Latent Failures

Semi-Markovian model of control of restorable system with latent failures has been built with regard to control errors. Stationary reliability and efficiency characteristics of its operation have been found. The problem of control execution periodicity optimization has been solved.

Aplicación del análisis modal de fallos y sus efectos a la fase preanalítica de un laboratorio clínico

Introduction Safety dynamics should be the philosophy that supports improved quality in the healthcare environment. Strategies to reduce incidents have been undertaken for long-term solutions, to identify that errors occur (culture) are highlighted and the causal factors are pro-actively, preventively and systematically analysed. Material and methods In 2006 the Clinical Laboratory of Antequera Hospital proposed to carry out a descriptive analytical model to address the risk assessment for the safety of the high-risk patient, as this is the group in which the majority of errors is generated and study how this affects the professionals working in the laboratory, whose contribution to the final results is decisive, by applying the failure mode and effect analysis (FMEA). Results Considering the number of risk priorities, improvement actions were proposed, processes re-designed and indicators, procedures and instructions were implemented to measure the results in order to evaluate and establish methods for continuous improvement within the laboratory. Conclusions When looking at safety in the laboratory, the most important factors are the absence of adverse events (errors), reliability of the methods and the use of the information generated. As a result, the FMAE's findings are an important source of information in detecting active and latent failures of the system. In addition, the participation and dissemination of this type of knowledge promotes the commitment and responsibility of the professionals in safety issues.

A Multicenter Trial of Aviation-Style Training for Surgical Teams

This study measured the effect of aviation-style team training on 3 surgical teams from different specialties. It focused on team working and communication, particularly briefing, time-out, and debriefing, and sought to understand how improvements in team skills could be implemented in a broad range of naturalistic surgical environments to improve safety, quality, and efficiency. Surgical teams performing maxillofacial, vascular, and neurosurgery were studied during 112 operations: 51 before and 61 after intervention. Human factors experts delivered the training of up to 2 days in the classroom followed by 6 days of coaching in theater for each team. Trained observers measured teamwork using the Oxford NOTECHS and the frequency of preoperative briefings, pre-incision time-outs, and postoperative debriefings. The Safety Attitudes Questionnaire and ethnographic observations were used to provide contextual details. There were significantly more time-outs (chi = 18.17, P < 0.001), briefings (chi = 8.62, P = 0.004), and debriefings (chi = 8.58, P = 0.004) after the intervention. The NOTECHS scores showed an interaction between site and intervention (F2,106 = 7.57, P = 0.001). The Safety Attitudes Questionnaire and ethnographic observations helped understand these differences. Aviation-style teamwork training can increase compliance and team performance, but this was influenced by the attitude and collaboration of key individuals, and the effect was reduced by significant latent failures. This study demonstrates the need to improve organizational and personal management factors in the National Health Service if training in patient safety is to be effective and sustained. It also shows the influence of working conditions on clinical studies of quality improvement.

Unavailability equations for k-out-of- n systems

This paper updates and extends earlier published analytical results for the unavailabilities (probabilities of failure on random demand) of redundant standby systems with k-out-of- n logic. Such systems are mostly used in safety and protection systems and are subject to latent and detectable failures. Latent failures are detected by periodic tests and repaired immediately after discovery. Many potential failure and error modes are included in the formalism. Interesting relations between two approaches are pointed out. Both consecutive and staggered testing schemes are evaluated, and methods for including certain common cause failures in the analyses are pointed out.