Optimal spare parts management for vessel maintenance scheduling

Condition-based monitoring is used as part of predictive maintenance to collect real-time information on the healthy status of a vessel engine, which allows for a more accurate estimation of the remaining life of an engine or its parts, as well as providing a warning for a potential failure of an engine part. An engine failure results in delays and down-times in the voyage of a vessel, which translates into additional cost and penalties. This paper studies a spare part management problem for maintenance scheduling of a vessel operating on a given route that is defined by a sequence of port visits. When a warning on part failure is received, the problem decides when and to which port each part should be ordered, where the latter is also the location at which the maintenance operation would be performed. The paper describes a mathematical programming model of the problem, as well as a shortest path dynamic programming formulation for a single part which solves the problem in polynomial time complexity. Simulation results are presented in which the models are tested under different scenarios

Determining return on investment of maintenance projects using statistical cost modeling

This paper presents a methodology for quantifying the expected benefits of maintenance improvement initiatives using statistical techniques. Multivariable regression models are used to correlate monthly equipment maintenance costs with monthly planned and unplanned downtime. The models permit the expected cost savings for an equipment fleet to be quantified as a function of the percentage reduction in unplanned maintenance downtime likely to result from an improvement initiative. The models also make it possible to quantify expected increases in fleet availability and reliability and to calculate cost factors that indicate how much more expensive it is on average to apply unplanned as opposed to planned maintenance strategies. A case study is presented that demonstrates how the methodology was applied to the mobile equipment fleets in an openpit copper mine in Northern Chile

Les nouveaux materiaux piezoelectriques : Leurs possibilites en tant que capteurs

On passe en revue les différents matériaux piézoélectriques qui sont apparus depuis quelques années, tant en France qu'à l'étranger : polymères (PVF2), copolymères (tri et tetra fluoroéthylène - PVF2), céramiques composites (grains ou barreaux de céramiques dans une matrice viscoélastique), nouvelles céramiques anisotropes. Leurs propriétés mécaniques et piézoélectriques (en statique et en dynamique), mesurées en laboratoire, sont comparées avec celles de céramiques classiques type titanozirconate de plomb ou titanate de baryum. On examine les problèmes liés à ces nouveaux matériaux: polarisation, métallisation, reproductibilité, vieil-, lissement, comportement en fonction de la température et de la pression hydrostatique. Enfin, on présente leurs utilisations possibles dans des capteurs acoustiques, en gardant à l'esprit les contraintes auxquelles le capteur est lie : immersion maximale, chocs, vibrations, capteur élémentaire dans un réseau (ponctuel ou étendu) bande passante et préamplificateur associé. Cet article est la synthèse de travaux financés par la DRET, le GERDSM ou sur fonds propres

Business-oriented prioritization: A novel graphical technique

Traditionally, Pareto analysis has been used to select the most critical components and failure modes of a system. A clear disadvantage of this technique is that it requires preselecting a single criterion to establish priorities. More recently, a graphical log-scatter diagram technique has been proposed. It considers three key performance indicators simultaneously: reliability (MTBF), maintainability (MTTR), and unavailability (D). This technique considers only times and does not include economical effects explicitly. This article extends both techniques to explicitly consider both direct and indirect costs to prioritize from the point of view of an asset manager or from a maintenance decision-maker, as required. Due to the economic-based approach of this article, cost discounting is also considered inside financial costs such as—but not limited to—reliability-related investments. Also, the results are displayed on simple and accessible graphs which make them particularly useful for conveying results to non-technical managers. The methodology is illustrated by analyzing a shovel from the copper mine industry, and it clearly shows how the proposed technique facilitates business oriented decisions and how they should change under different market conditions

Optimal inspection intervals for safety systems with partial inspections

The introduction of International Standard IEC 61508 and its industry-specific derivatives sets demanding requirements for the definition and implementation of life-cycle strategies for safety systems. Compliance with the Standard is important for human safety and environmental perspectives as well as for potential adverse economic effects (eg, damage to critical downstream equipment or a clause for an insurance or warranty contract). This situation encourages the use of reliability models to attain the recommended safety integrity levels using credible assumptions. During the operation phase of the safety system life cycle, a key decision is the definition of an inspection programme, namely its frequency and the maintenance activities to be performed. These may vary from minimal checks to complete renewals. This work presents a model (which we called ρβ model) to find optimal inspection intervals for a safety system, considering that it degrades in time, even when it is inspected at regular intervals. Such situation occurs because most inspections are partial, that is, not all potential failure modes are observable through inspections. Possible reasons for this are the nature and the extent of the inspection, or potential risks generated by the inspection itself. The optimization criterion considered here is the mean overall availability Ao. We consider several conditions that ensure coherent modelling for these systems: sub-systems decomposition, k-out-of-n architectures, diagnostics coverage (observable/total amount of failure modes), dependent and independent failures, and non-negligible inspection times. The model requires an estimation for the coverage and dependent-failure ratios for each component, global failure rates, and inspection times. We illustrate its use through case studies and compare results with those obtained by applying previously published methodologies.

Impact of accommodating resistance in potentiating horizontal-jump performance in professional rugby league players

This study investigated the efficacy of deadlifts and box squats, with a combination of traditional and accommodating resistance, as a postactivation potentiating stimulus of standing broad jumps (SBJ) in a multiple-set contrast protocol. Twelve professional rugby league players (21.4 [2.5] y; 181.3 [8.3] cm, 91.9 [8.8] kg; 1-repetition-maximum [1RM] back squat/body mass 1.59 [0.21]; 1RM deadlift/body mass 2.11 [0.25]; ≥3-y resistance-training experience) performed baseline SBJ before a contrast postactivation potentiating protocol involving 2 repetitions of 85% 1RM box squat or deadlifts, loaded with a combination of traditional barbell weight (70% 1RM) and elastic-band resistance (∼15% 1RM), followed by 2 SBJs. Exercises were separated by 90 s, and 4 contrast pairs were performed in total. Using a repeated-measures design, all subjects performed the squat followed by the deadlift and finally the control (SBJ only) condition in the same order across consecutive weeks. Changes from baseline in SBJ distance were moderate for the box squat (effect size [ES] = 0.64-1.03) and deadlift (ES = 0.80-0.96) and trivial in the control condition (ES = 0.02-0.11). The magnitude of differences in postactivation potentiating effect were considered moderate (d = 0.61) for set 1, trivial for set 2 (d = 0.10) and set 3 (d = 0.05) in favor of box squats, and moderate for set 4 (d = 0.58) in favor of deadlifts. Accommodating resistance in either box squats or deadlifts is an effective means of potentiating SBJ performance across multiple sets of a contrast protocol with only 90-s rest

Effect of Spare Parts Policy on Equipment ProductionLoss in Mining

Spare parts inventory in a mine incorporates various mechanical to electrical equipment components that need to be available in case of any repair, preventive maintenance, and/or revision on equipment. These parts are generally stored at the mine sites under a specific policy in such a way that any equipment production delay due to unavailability of the spare part is mitigated or prevented. Scope of such a policy may consider i) frequencies of different failure modes, ii) their contributions to equipment downtime, iii) lead times and prices of spare parts, iv) administrative point of view, and v) risk appetite of the company. Since each part in an equipment holds changeable surviving and maintenance times with a random behavior, and lead times of spare parts variate according to their supplier service, it may be challenging to measure the effectiveness of an existing spare part policy and its effect on production loss. In this regard, this paper presents a simulation algorithm that is capable of measuring the negative addition of a spare part policy to the related mining production. A numeric example is also provided in the study for a quantitative verification