Samir Khan

No Fault Found events in maintenance engineering Part 1: Current trends, implications and organizational practices

This paper presents the first part of a state of the art review on the No Fault Found (NFF) phenomenon. The aim has been to compile a systematic reference point for burgeoning NFF literature, and to provide a comprehensive overview for gaining an understanding of NFF knowledge and concepts. Increasing systems complexities have seen a rise in the number of unknown failures that are being reported during operational service. Units tagged as ‘NFF’ are evidence that a serviceable component was removed, and attempts to troubleshoot the root cause have been unsuccessful. There are many reasons on how these failures manifest themselves and these papers describe the prominent issues that have persisted across a variety of industrial applications and processes for decades. This article, in particular, deals with the impact of NFF from an organizational culture and human factors point of view. It also highlights recent developments in NFF standards, its financial implications and safety concerns.

No Fault Found events in maintenance engineering Part 2: Root causes, technical developments and future research

This is the second half of a two paper series covering aspects of the no fault found (NFF) phenomenon, which is highly challenging and is becoming even more important due to increasing complexity and criticality of technical systems. Part 1 introduced the fundamental concept of unknown failures from an organizational, behavioral and cultural stand point. It also reported an industrial outlook to the problem, recent procedural standards, whilst discussing the financial implications and safety concerns. In this issue, the authors examine the technical aspects, reviewing the common causes of NFF failures in electronic, software and mechanical systems. This is followed by a survey on technological techniques actively being used to reduce the consequence of such instances. After discussing improvements in testability, the article identifies gaps in literature and points out the core areas that should be focused in the future. Special attention is paid to the recent trends on knowledge sharing and troubleshooting tools; with potential research on technical diagnosis being enumerated.

Autonomous Maintenance for Through-Life Engineering

This chapter looks at the overall theme of automating maintenance practices with a particular focus upon the application of robotics within this field. Covering the current state of the art in automating maintenance processes this chapter also looks at the current challenges to moving beyond simple inspection and diagnosis to the design and construction of fully automated platforms for undertaking maintenance. This includes methodologies for capturing and classifying maintenance task processes so that they can be automated in some way and how to link this task classification with some level of automation. The chapter ends with a discussion on how the design process can be adapted to aid automated maintenance, self-healing and no fault found applications.

Research study from industry-university collaboration on “No Fault Found” events

Purpose – The purpose of this paper is to present the successes and barriers from an industry-university partnership on studying the impact of No Fault Found (NFF) events. As a consequence, various opportunities are explored to engage with industry to investigate the problem. A comprehensive training is also outlined to ensure that experience and troubleshooting techniques can be disseminated as guidelines across businesses. Design/methodology/approach – The study was performed by Cranfield University in collaboration with industrial partners on identifying the impact of the NFF problem within engineering services. This includes discussions with maintenance engineers, outcomes from a symposium organised specifically on NFF and the authors’ own experiences with the issue. Findings – The paper discusses the continuing serious problem with NFF events found at various maintenance echelons, and suggests a need for formal postgraduate training to be taught within the field of maintenance management. This includ...

Perspectives on trading cost and availability for corrective maintenance at the equipment type level

Characterising maintenance costs has always been challenging due to a lack of accurate prior cost data and the uncertainties around equipment usage and reliability. Since preventive maintenance does not completely prevent corrective repairs in demanding environments, any unscheduled maintenance can have a large impact on the overall maintenance costs. This introduces the requirement to set up support contracts with minimum baseline solutions that warrant the target demand within certain costs and risks. This article investigates a process that has been developed to estimate performance based support contract costs attributed to corrective maintenance. These can play a dominant role in the through-life support of high values assets. The case context for the paper is the UK Ministry of Defence. The developed approach allows benchmarking support contract solutions, and enabling efficient planning decisions. Emphasis is placed on learning from feedback, testing and validating current methodologies for estimating corrective maintenance costs and availability at the Equipment Type level. These are interacting sub-equipments that have unique availability requirements and hence have a much larger impact on the capital maintenance expenditure. The presented case studies demonstrate the applicability of the approach towards adequate savings and improved availability estimates.

Design for Zero-Maintenance

This chapter looks at the concept of zero-maintenance, in particular how it relates to design. It begins by defining what constitutes zero-maintenance, presenting current research on the themes of autonomous maintenance and self-healing and repair. A wider context of how zero-maintenance affects through-life engineering services is also discussed with a focus on the no-fault found phenomenon. Case studies are then presented for design strategies in self-healing electronics and no-fault found and the failure of design. Finally, a design for zero-maintenance process is outlined and discussed.

Zero-maintenance of electronic systems: Perspectives, challenges, and opportunities

Self-engineering systems that are capable of repairing themselves in-situ without the need for human decision (or intervention) could be used to achieve zero-maintenance. This philosophy is synonymous to the way in which the human body heals and repairs itself up to a point. This article synthesises issues related to an emerging area of self-healing technologies that links software and hardware mitigations strategies. Efforts are concentrated on built-in detection, masking and active mitigation that comprises self-recovery or self-repair capability, and has a focus on system resilience and recovering from fault events. Design techniques are critically reviewed to clarify the role of fault coverage, resource allocation and fault awareness, set in the context of existing and emerging printable/nanoscale manufacturing processes. The qualitative analysis presents new opportunities to form a view on the research required for a successful integration of zero-maintenance. Finally, the potential cost benefits and future trends are enumerated.

Supporting data for "A framework to estimate the cost of No-Fault Found events"

The article investigates a generic framework to estimate maintenance costs attributed to the No Fault Found (NFF) phenomenon. Such overhead costs are particularly difficult to quantify due to potentially serviceable equipment being returned for repair. Other factors, such as a reduction in the availability of the system, compromising reliability of high value assets, and logistical factors, can all contribute to the cost of resolving an unknown fault. Here we apply the soft systems methodology to capture the critical cost drivers of NFF across the supply chain and build a framework to estimate the cost of NFF. We use a multi-method design including an online survey, workshops and semi-structured interviews to study NFF related cost practices based on information from 12 key participants across 7 UK organisations. The study identifies the major NFF cost drivers across the supply chain (e.g. transportation), the OEM (e.g. inventory) and the customer (e.g. lost man hours). An agent based model is used to evaluate the impact of these cost drivers on the overall NFF cost. The analysis shows how the most appropriate drivers can be selected to represent the cumulative costs due to NFF events and their impacts across the supply network. From the academic perspective, the generic framework for NFF cost estimation demonstrates how qualitative and quantitative information can be used together to achieve maintenance objectives. From a practical perspective, by applying the framework on one component, an organisation has the liberty to analyse the cost of NFF for that particular unit only. & 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Modelling the Positional and Orientation Sensitivity of Proximity Sensors for Industrial IoT

This paper presents an analysis of robust proximity sensor interfaces for Industrial Internet of Things applications. A Model is presented with the aim of maximizing the range and freedom of orientation of passive sensing and communications devices in comparison to traditional source-sensor technologies. A matrix transformation approach is used to model the quality of mutual coupling between triaxial source and sensor coil arrangements for arbitrary relative position and angular rotation. Particular attention is paid to the recombination of triaxial sensor outputs and optimal rotation for maximal coverage given a specified coupling threshold. The model is useful for determining practical source-sensor configurations that achieve optimal coverage when the sensor position and rotation is restricted by the industrial application.