Maintenence management

It is well-known that maintenance planning affects, in general, the life of the structures, material wear, and quality of service. In particular, the maintenance of rail-tracks affects the traffic volume as well, and therefore it is an important issue for the management of a railway system: then, an accurate maintenance planning is necessary to optimize resources. The condition of railways is checked through special diagnostic trains. Because of the vast amount of data that these trains record, it is necessary to analyze this data through an appropriate Decision Support System (DSS). However, the most up-to-date DSS's, like Ecotrack, are based on a binary logic with rigid thresholds and complicated algorithms with a large number of rules that restrict their flexibility in use; in addition, they adopt considerable simplifications in the rail-track deterioration model. In this paper we have implemented a neuro-fuzzy inference engine for a DSS to overcome these drawbacks; based on the fuzzy logic, it is able to handle thresholds expressed as a range, an approximate number, or even a verbal value; moreover, through artificial neural networks it is possible to obtain more precise rail-track deterioration models. The results obtained with the proposed model have been clustered through a fuzzy procedure, in order to optimize the maintenance schedule, thus grouping the interventions in space and in time. 7 absolute terms, not greater than 23 over 131 days. In critical cases, in which the calculated dates could be later than the Time Limits for Maintenance (TLM), the model provides in both cases correct dates, earlier or equal to TLM.

The service lift of thick-walled power plant components exposed to creep, as is the case with pipelines of fresh- and reheated steam, depend on the exhaustion rate of the material Plant operation at elevated temperatures and at temperatures below designed temperatures all relates to the material exhaustion rate, thus complicating remaining life assessment, whereas the operating temperature variation is a most common cause in the mismatching of real service and design life. Apart from temperature, the tube wall stress is a significant variable for remaining life assessment, whose calculation depends on the selected procedure, due to the complex pipeline configuration. In this paper, a remaining life assessment is performed according to the Larson-Miller parametric relation for a phi 324 x 36 pipe bend element of afresh steam-pipeline, made of steel class ICr0.3Mo0.25V, after 160.000 hours of operation. The temperature history of the pipeline, altogether with the pipe bend, is determined based on continuous temperature monitoring records. Compared results of remaining life assessment are displayed for monitored temperature records and for designed operating temperature in the same time period. The stress calculation in the pipe bend wall is performed by three methods that are usually applied so to emphasize the differences in the obtained results of remaining life assessment.

Thick walled components such as high pressure (HP) steam turbine casings operating under high parameter conditions are subjected to a complex stress state. As a result of that stress state, some parts of HP turbine casing undergo to the creep fatigue caused by the combination of thermal fatigue resulted from repeated start/stop operation and the creep which occurs during long-term operation at high temperature and high-pressure. It is well known that domestic thermal power plants have been in use over 100000 h which means that significant cost is required not only for maintenance, but often for renewal of equipment. Based on comprehensive investigation, the results of residual life assessment of one high pressure steam turbine casing, which belongs to the older turbine generation, taking into account simultaneous action of thermal fatigue and creep, are presented in this paper. Also, the critical flaw crack size of HP turbine casing is determined because this parameter has a strong influence on casing integrity and residual life. The results of residual life assessment provide not only a basis for further maintenance, but also estimated time for reparation or renewal.

Maintenance of buildings is a crucial process that has a great impact on both buildings' performance and the efficiency of their embedded systems. However, the building maintenance industry in Egypt has long been an area of neglect, as most of buildings stakeholders restrict its role to the operation phase of the building. This attitude disregards the precautionary maintenance processes that could be achieved through the preliminary phases of the buildings. The main concern of this paper is suggesting specific guidelines that enable the integration of maintenance considerations into the whole life cycle of the buildings. The ultimate purpose is to achieve better performing buildings regarding maintenance aspects.The study sheds light on the major barriers of applying efficient maintenance, through the analysis of results extracted from focused interviews that targeted a number of general and maintenance managers in a number of selected buildings.Emphasis is made on the role and impact of maintenance considerations in guiding the decision- making process, as well as the lack of integrating maintenance into the whole building design process. This paper ends up with suggesting a framework that demonstrates the impact of integrating considerations of maintenance throughout the whole life cycle of the building.

Reliability centered maintenance (RCM) has a key role in the quality system of thermal power plants. Electricity production is definitely not only production of a product, but also becomes a customer service. Reliability is the top quality tier of this service. Incorporation in the Integrated energy system means fast transformations of organization on all levels. The reliability of modern generation components basically influences the efficiency and capacity of a power plant as a whole. This paper presents the results of RCM practice on Unit Two of The Thermal Power Plant ″Nikola Tesla -B″, 2x600 MW, Yugoslavia. RCM implementation on current problems during exploitation emphasized problems with the boiler tubing system. The methodological approach included outages analyses, marking of the most significant ones, determination of main causes of damage (determination of the material exhaustion state based on expert analyses), application of adequate remaining life assessment methodology and finally the recommendations. Based on these analyses, certain technical solutions were performed and as a result, the mean time between failures of the plant increased, as well as its reliability. According to cost efficiency, RCM methodology presented the most effective cost-benefit method for reliability upgrade.

Problem of boiler component erosion is a very complex and present in practically all fossil fuel power plants burning low heating value coals irrespective of their particular design and operating characteristics. Major fly coal erosion accelerating factors are large amounts of abrasive components in the air-coal mixture and its high velocity. In general terms, there is a trend of implementation of appropriate erosion protection in critical place of pulverized boiler coal preparation equipment. In this paper are presented results of erosion tests provided on samples with different erosion protection materials. Erosion damage profiles of different protection materials were investigated and analyzed on tested samples.

Reliability centered maintenance (RCM) has a key role in the quality system of thermal power plants. Electricity production is definitely not only production of a product, but also becomes a customer service. Reliability is the top quality tier of this service. Incorporation in the Integrated energy system means fast transformations of organization on all levels. The reliability of modern generation components basically influences the efficiency and capacity of a power plant as a whole. This paper presents the results of RCM practice of one 620 MW thermal power plant. RCM implementation on current problems during exploitation emphasized problems with the boiler tubing system. The methodological approach included outages analyses, marking of the most significant ones, determination of main causes of damage (determination of the material exhaustion state based on expert analyses), application of adequate remaining life assessment methodology and finally the recommendations. Based on these analyses, certain technical solutions were performed and as a result, the mean time between failures of the plant increased, as well as its reliability. According to cost efficiency, RCM methodology presented the most effective cost-benefit method for reliability upgrade.