Maintenance condition-based

Condition-based maintenance, 45 467 Conditioning, in cane sugar refining, 23 453... 

Maintenance is not merely called upon to repair failed equipment (breakdown maintenance). Over the course of time, maintenance workers have teamed with plant operations personnel to develop preventive maintenance (PM), predictive maintenance (PdM), and condition-based maintenance (CBM) programs, all in an effort to get ahead of problems occurring in plant operations, and to do so as efficiently as possible. 

The electric utility industry is today forced by the Market Directive to adopt condition-based maintenance to ensure steady supply. The method universally adopted to ensure proper installation of cable system accessories and to periodically determine the state of the insulation for decision making about repairing or replacing before failure occurs is partial discharge (PD). This method is based on the time-of-flight principle of induced PD signals a time variation is attributed to local faults. Calibration is needed to establish a correct relationship between the magnitude... 

Chadha, S., Poster-Miller s On-Line Oil Condition Monitor, A Cost-Effective Cross-Platform Tool for Condition-Based Maintenance , Lubr. Fluid Power J. 1, 26-30, Nov 2000. Jacobs, Kenneth S., Applying RCM Principles in the Selection of CBM-Enabhng Technologies , Lubr. Fluid Power J.1, 5-14, Nov 2000. 

Toms, A. M., Jordan, E. and Humphrey, G. R., The Success of Filter Debris Analysis for J52 Engine Condition Based Maintenance , Proceedings of the 41st AIAA, AIAA-2005-4338, Tucson, AZ, July 2005. 

This was based on the bathtub curve (Fig. 1) which depicts the increase in the failure rate of items in time. Time-based maintenance does not account for the fact that the condition of the items depends not only on elapsed time but also on operational and environmental conditions. Based on advances in diagnostic techniques in the 1970s, condition-based maintenance (or predictive maintenance) was introduced. Here, maintenance activities occur when symptoms of wear or failure are determined either by monitoring or diagnosis, i.e., maintenance effectiveness depends on the existence of appropriate diagnostic techniques. 

Condition-based maintenance is effective when prognostics are available but more cost intensive (Takata et al. 2004). 

The objective of preventive maintenance is to extend the life of an item and prevent all failures before they occur by detecting critical wear that leads to failure or breakdown. This can be accomplished by estimating a lifetime schedule for each item. The way this estimation takes place determines the type of preventive maintenance. In predetermined maintenance the estimation is static and results in static maintenance intervals. In condition-based maintenance, maintenance intervals are determined according to either the detection of a degradation mechanism by monitoring or a forecast derived from the analysis and evaluation of a number of parameters (i.e., vibration, imbalance, machine noises, power demand) of the degradation mechanism (thus, condition-based maintenance is often referred as predictive maintenance). 

Preventive maintenance activities include equipment checks, scheduled or craidition-based worn tool changes, cleaning, and partial or complete overhauls at specified periods, e.g., oil changes and lubrication. In addition, workers can record equipment deterioration so they know to replace or repair worn parts before they cause system failure. In the case of condition-based maintenance, sensors and software tools are used for the monitoring and analysis of the desired item parameters. 

Work sequence optimization through bundling of activities proof of fulfillment of safety standards extension of service intervals condition-based maintenance Consultation on dose rate reduction, in particular on highly contaminated plant items and on work procedures... 

Condition-based maintenance based on ADAM (Valve dia-gnosis and evaluation method)... 

By changing from preventive to condition-based maintenance - based on the Siemens Nuclear Power GmbH diagnostic and evaluation method ADAM (A maturen-Diagnose und Auswerte-Methode) — the number of valves to be maintained may be reduced considerably. The application of such sophisticated software tool will lead to cost reduction and can also extend the service intervals. 

FIG. 6. ADAA The way to condition-based maintenance of MOV s evaluation method of ADAM. 

Owing to the periodic monitoring of valves including actuators and the evaluation of the measured data by ADAM the actual conditions of the valve can be determined to ensure the readiness for function. Based on the information obtained from ADAM and operational experience over a longer time period a condition-based maintenance can be performed in order to extend the maintenance periods. That means, preventive measures as inspections and replacement of parts can be reduced. 

In addition, Mimir should be compliant with the ISO-13374 industry standard for moving information in condition-based maintenance systems. This will result in its own set of design and implementation requirements. 

ABSTRACT Condition based maintenance is an advanced maintenance strategy able to achieve both cost reduction and high availability and reliabihty performance. It is based on the system health monitoring whose issues are diagnostic and prognostic capabilities. 

One of the most advanced maintenance strategies that can be implemented is the Condition Based Maintenance (CBM). It is a very powerful approach but requires several technology devices as sensors, acquisition card, etc. and relevant knowledge in order to implement the diagnostic and prognostic intelligence. 

Moreover there are a lot of applications of BNs as support system for the maintenance strategies. An example of preventive maintenance is (Celeux et al. 2006) hut the greater part of the papers investigate the BNs as a diagnostic model for the condition based maintenance. 

These brief considerations highlight as Bayesian formahsm can be very useful to model decision support system for condition based maintenance. Indeed, the diagnostic and prognostic issue are implicit in the inference process. 

The learning process of the net has followed several steps. The first one was the definition of the system variables it meant to decide which variables described the system behavior from the diagnostic and prognostic point of view. So some field measures have been excluded from the model while only the sensors measures that can be considered the effects of a failure modes has been introduced. Moreover, the model has been enriched by a set of variables with prognostic and diagnostic issues. So the variables failure modes and system prognosis have been modeled by some nodes that represent the support elements for the condition based maintenance. 

Grail, A., C. Berenguer, and L. Dieulle (2002). A condition-based maintenance policy for a stochaslly deteriorating system. Reliability Engineering and System Safety 76, 167-180. 

Condition-based maintenance of engineering systems with periodic inspection... 

Weide, J.A.M. van der, M.D. Pandey and J.M. van Noortwijk, 2009. Discounted Cost Model for Condition-based Maintenance Optimization, submitted to Reliability Engineering and System Safety. 

Imperfect condition-based maintenance on a finite time span for a gradually deteriorating system... 

ABSTRACT This paper deals with a system which can be for example a large structure such as a bridge, a dike or a pipeline. A such system should be preventively maintained in order to avoid failures which would have disastrous consecpiences. An imperfect condition-based maintenance policy is then proposed considering a finite horizon. As preventive maintenance actions are imperfect their impact on the system is determined through a function called improvement function . The aim of this paper is to compare two types of improvement functions. An imperfect condition-based maintenance policy is then proposed and evaluated on a finite time span for each improvement function. 

As the considered system represents a large structure its lifetime can be considered as finite, but most of condition-based maintenance policies that exist consider an infinite time span. Few papers deal with maintenance policy on a finite time span, refer to Marquez Heguedas (2002), Nicolai et al. (2009), Nakagawa Mizutani (2009) and Jayabalan Chaudhuri (1992). 

If the deterioration level of the system, collected through perfect periodic inspections, exceeds a safety level the system is said to be failed and as the system is not repaired after a failure, it is unavailable imtil the finite horizon. Let us call the remaining time to the finite horizon, the residual time. In order to avoid failures and to stay in an operating state, the system should be preventively maintained. The strategy of the considered condition-based maintenance policy, in this paper, is a control hmit strategy as done in Wang (2002), Nicolai et al. (2009) and Moustafa et al. (2004). 

In de Smidt-Destombes et al. (2004) the tradeoff between repair capacity and spare part inventory control is investigated for a single k out of N system under condition based maintenance i.e. when the number of defect components exceeds some previously defined limit, maintenance is initiated. They propose exact and approximate methods to analyze the system availability. Continuing along these lines, de Smidt-Destombes et al. (2007) considerM identical k out of N systems under block replacement. For each system all defect components are replaced every fixed time interval. Two methods are proposed to analyze the system availability as a function of the number of spare parts stocked and the block replacement interval. The main difference between these studies and our contribution is that in our contribution we focus on applying a cost structure, while their focus is on estimating up-time. Furthermore, we consider multiple different systems, while de Smidt-Destombes et al. (2004, 2007) focus on either just one system, or on multiple identical systems. Finally, in our model maintenance is immediately initiated when equipment fails. 

In this paper we will present an improved methodology for the modelling and analysis of complex production systems by using a combination of extended coloured stochastic Petri net (ECSPN) and a reliability block diagram (RDB). This enables us to model condition based maintenance strategies as well as dynamically grouped maintenance actions. The models are analyzed by applying a Monte Carlo simulation. 

On line condition-based maintenance for time dependent deteriorating systems... 

Dieulle, L., C. Berenguer, A. Grail, and M. Roussignol (2003). Sequential condition-based maintenance scheduling for a deteriorating system. EJOR 150(2), 451—461. 

In this way, according to Jardine et al. (2006) more efficient maintenance approaches such as condition-based maintenance (CBM) may be implemented to handle this simation. CBM is a maintenance program that recommends maintenance actions based on the information collected through condition monitoring (OMS, for instance). CBM attempts to avoid systems being over or imder maintained by taking maintenance actions only when there is evidence of abnormal behaviors of a physical asset. 

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