Reasonable Maintenance Research Articles

Assessment of the maintenance costs of electro-medical equipment in Spanish hospitals

ABSTRACT Objectives Electro-medical equipment generates a high impact on the sustainability of a hospital and require high availability at a reasonable maintenance cost. The aim of this paper is to analyze the sustainability and performance of the maintenance of electro-medical equipment, through several healthcare variables (hospital admissions, surgeries, consultations, etc.), infrastructure variables (surface area, number of beds, number of operating theaters, etc.), human resources and the acquisition value of the equipment, relating them to the labor, materials and total and operative maintenance costs. Methods 4,586 electro-medical equipments were analyzed (grouped into 16 categories) installed in 12 Spanish hospitals of between 20 and 200 beds during the 2016–2018 period. Results The results show that the maintenance costs of electro-medical equipment correlate with the number of beds and operating theaters, nursing staff, equipment acquisition value, number of admissions, surgeries and the total length of hospital stay. Conclusion Different equations are proposed to estimate maintenance costs based on the variables studied. They include indicators that give an overall view of maintenance operations.

Iodine-125 interstitial brachytherapy for malignant lacrimal sac tumours: an innovative technique

ObjectivesPrimary malignant tumours of the lacrimal sac are rare, surgery and radiotherapy may induce substantial side effects for patients. Here, this article reports an innovative technique of interstitial brachytherapy developed for the treatment of malignant lacrimal sac tumours.Patients and methodsFour patients (male 3, female 1), with an average age of 52.7 years (range 41–72 years), were individually diagnosed with squamous cell carcinoma, adenocarcinoma, adenoid cystic carcinoma and lymphoma. All patients received Iodine-125 interstitial brachytherapy after surgical resection for malignant lacrimal sac tumours. Visual function examination (vision, intraocular tension, fundus photography, fluorescein angiography, and optical coherence tomography) and CT/MRI/PET-MRI were performed to look for signs of recurrent tumours or metastasis.ResultsFour patients were followed for an average of 28 months (range, 23–37 months). All patients were free from local disease. Their visual function was normal, and CT/MRI did not reveal any tumour recurrence.ConclusionsIodine-125 interstitial brachytherapy can be used as an alternative to wide excision or exenteration of these tumours. There was good local control, reasonable maintenance of vision, and good cosmesis.

Long-Term Characteristics of Prestressing Force in Post-Tensioned Structures Measured Using Smart Strands

The proper distribution of prestressing force (PF) is the basis for the design of prestressed concrete (PSC) structures. However, the PF distribution obtained by predictive equations of prestress losses has not been sufficiently validated by comparison with measured data due to the poor reliability and durability of conventional sensing technologies. Therefore, the Smart Strand with embedded fiber optic sensors was developed and applied to PSC structures to investigate the long-term characteristics of PF distribution as affected by concrete creep and shrinkage. The data measured in a 20 m-long full-scale specimen and a 60 m-long PSC girder bridge were analyzed by comparing them with the theoretical estimation obtained from several design equations. Although the long-term decreasing trend of the PF distribution was similar in the measurement and theory, the equation of Eurocode 2 for estimating the long-term prestress losses showed better agreement with the measurement than ACI 209R and ACI 423.10R did. This can be attributed to the more refined form of the predictive equation of Eurocode 2 in dealing with the time-dependency of the PF. The study results also confirmed the need to compensate for the temperature variation in the long-term monitoring to derive the actual mechanical strain related to the PF. We expect our developed Smart Strand to be applied practically in PF measurement for the reasonable safety assessment and maintenance of PSC structures by improving several of the existing drawbacks of conventional sensors.

Crack localization in stepped rotors based on Bayesian fusion of multiscale superharmonic characteristic deflection shapes

AbstractA crack is one of the most dangerous faults in rotors of key rotating machinery. In order to make reasonable maintenance, crack localization for rotors under operational conditions is very important and full of challenges. Focusing on crack localization in rotating rotors, a new crack localization method for stepped rotors based on Bayesian fusion of multiscale superharmonic characteristic deflection shapes (SCDSs) is proposed. The non‐linearity induced by cracks is utilized to eliminate the interference of stiffness reduction by steps in the rotor, and the noise‐robustness issue is tackled by casting the SCDSs into multiscale SCDSs with multiscale space theory. Moreover, Bayesian fusion is applied to the multiscale SCDSs to derive a new damage index to localize cracks. Numerical and experimental investigations are conducted to validate the proposed method. The results indicate that the proposed method is effective, accurate and robust for single or multiple crack localization in stepped rotors, and thus, it has a great potential in practical applications.

Multi-State System Modeling and Reliability Assessment for Groups of High-speed Train Wheels

The polygonization of high-speed train wheels is commonly considered as a serious threat to reliability of high-speed trains all over the world. Traditional studies in polygonization of wheels focus on modeling its mechanism via physics-based models. However, to the knowledge of the authors, the polygonization process has not been fully explained by existing studies due to the complex degradation mechanism and varying operation environment which is difficult to monitor and measure. In this article, the data-driven multi-state system (MSS) models are developed for the reliability assessment of high-speed train wheels based on the analysis of actual operation data. The results can be used to support practical maintenance decision making. Another contribution of this paper is to prove that the environmental factors exert significant impacts on the reliability of Chinese high-speed train wheels. This finding has been included in the development of the MSS models. The results by these models are used to suggest a more reasonable maintenance schedule for Chinese high-speed train wheels. The obtained maintenance intervals are expected to assist the railway companies to reduce the operational risk as well as improve the maintenance efficiency.

Introduction of “Risk Based Maintenance” Method, and Usefulness and Problems in Case of Applying It to Ships and Offshore Facilities - Proposal for Optimized Ship Maintenance

"Risk Based maintenance (RBM)" is a method to perform reasonable maintenance. The maintenance procedures and their interval are optimized based on the "Risk" calculated by PoF (Probability of Failure) and CoF (Consequence of Failure).RBM can perform the maintenance optimized safely and economically by using the CoF factor. Also, this is suitable for the long term management of facilities because this method is based on probability theory. RBM has already been known as a general method in Oil Refinery and Chemical Industry, and has a potential to optimize a maintenance of ships or offshore facilities.

Proton Exchange Membrane Fuel Cell Prognostics Using Genetic Algorithm and Extreme Learning Machine

AbstractThe prognostics can predict the degradation of proton exchange membrane fuel cell (PEMFC) to formulate a reasonable maintenance plan for improving its lifetime and performance. In this paper, the voltage degradation for PEMFC at different conditions is predicted, by using a novel prognostics method based on genetic algorithm (GA) and extreme learning machine (ELM). The novel prognostics method considers the effects of the PEMFC load current, relative humidity, hydrogen pressure, and temperature on the degradation for PEMFC. Firstly, the voltage degradation prediction model for PEMFC is built by the ELM. Then, the GA is adopted to determine the optimal parameter of the proposed degradation prediction model. Finally, the voltage degradation prediction of the proposed prognostics method is validated, using data derived from the PEMFC in actual postal fuel cell electric vehicle (PFCEV) at real conditions and PEMFC at dynamic load current. The experimental results show that the proposed prognostics method can obtain good voltage degradation prediction for PEMFC in PFCEV at real conditions. The proposed method achieves better voltage degradation prediction for PEMFC at dynamic load current than other traditional data‐based prognostics methods.

Decision method on optimal time of preventive maintenance for metro shield tunnels in soft soils

Abstract A reasonable maintenance time is vital in the metro shield tunnel maintenance to keep good structural performance and reduce maintenance cost. Lacking predictability, the existing maintenance mode cannot effectively resolve the contradiction between the limited maintenance cost and the growing maintenance need in the future. In this study, the degradation model of metro shield tunnels in soft soils was studied to predict the long-term serviceability. Based on that, a method was proposed to decide the optimal time of preventive maintenance for metro shield tunnels. It was found that the tunnel decay process can be expressed by the inverse exponential function-based prediction model. The cost-benefit analysis method was adopted to determine the optimal preventive maintenance time, considering the maintenance time, the maintenance cost and the maintenance measures adopted. The flow chart of this method and an application example were presented. Results can help metro operation owners to develop more scientific and reasonable preventive maintenance plans for shield tunnels in soft soils.

Maintenance Decision Method for High Temperature Reactor Equipment Group with Expense Ratio Target

The equipment group of high-temperature gas-cooled reactors has a wide variety and a large number. Reasonable maintenance planning is especially important. An effective maintenance management strategy can reduce the number of shutdowns and reduce maintenance expense during equipment operation. The goal of maintenance strategy optimization is to improve the reliability of system, prevent system from failures, and reduce maintenance expense influenced by degradation, that is, to maintain or restore products to the appropriate system reliability, availability, and safety performance with the lowest possible maintenance expense.

A Survey of Internal Combustion Engine Condition Monitoring and Fault Detection Techniques

The internal combustion engine is the heart of cars, trucks, and many machines. It is the main source of movement and operation, and it consists of different mechanical sectors. Due to usage and aging, different faults can appear which affect engine operation and managing. Any small engine fault can turn into a major malfunction if it is not monitored and maintained at the proper time. Therefore, monitoring the performance of motors can save time and costs, improve their performance, and help them operate safely. Fault diagnosis, fault detection, and condition monitoring terms are used to describe similar concepts detection of any abnormality or deviation from the engines or machines normal condition. This paper describes a summary of the existing condition monitoring and fault detection techniques of the internal combustion engine, which are used for information collection to ensure operational safety, performance, reasonable maintenance, pollution prevention, and cost reduction.

IGBT Remaining Useful Life Prediction Based on Particle Filter With Fusing Precursor

The remaining useful life (RUL) prediction is essential for the IGBT module when setting a reasonable maintenance schedule and improving IGBT reliability by design. In this article, an RUL prediction method is proposed based on the particle filter (P.F.) algorithm with a multi-parameter precursor developed from the IGBT aging data. By fusing the junction temperature ( $T_{j}$ ) and collector-emitter on-voltage( $V_{CE(on)})$ , a new fault precursor is established to monitor IGBTs’ condition. A simplified aging model of the precursor is also developed based on a two-stage fitting. After input the historical aging data of the selected IGBT module, the RUL of IGBT can be predicted by the proposed fault precursor based on P.F. algorithm. According to the aging data collected from accelerated aging experiments, the performance of RUL prediction using the fusing precursor is superior to those with the single parameter precursor.

Applying Reliability Centered Maintenance (RCM) to Sampling Subsystem in Continuous Emission Monitoring System

Continuous emission monitoring system (CEMS) is widely used in the field of environmental protection, but the maintenance routines of it consist mostly of pre-defined activities. Reliability-centered maintenance (RCM) uses a systematic approach to develop maintenance strategies that take into account factors such as system life, operating efficiency, and maintenance cost-effectiveness. This paper is motivated to apply RCM to sampling subsystem in CEMS. Based on the failure mode and effect analysis (FMEA), the RCM logic decision used to identify the reasonable maintenance mode is implemented. Subsequently, an average availability model is proposed to determine the maintenance interval cycle. Finally, the maintenance outline is formed, which can be then further used as valuable information to improve equipment reliability and develop maintenance strategies.

Particle Swarm Optimization-Based SVM for Classification of Cable Surface Defects of the Cable-Stayed Bridges

The machine vision system was employed to inspect the surface defects of bridge cables of cable-stayed bridges. After the acquisition and preprocessing of the defect images, it is necessary to classify and identify the defects of the cables to meet the requirements of non-destructive testing and evaluation. In this paper, feature extraction for defect images was performed using mathematical statistical methods. After that, 10 feature parameters including shape features, grayscale features and texture features of the defect images were obtained and selected for a classification model of support vector machine (SVM). To improve the SVM classification performance, the particle swarm optimization algorithm (PSO) was adopted to obtain the punish factor c and the kernel parameter g of the SVM model, namely the PSO-SVM algorithm. Finally, our PSO-SVM classification model was employed to implement the classification of real surface defect images of the bridge cables. Longitudinal crack, transverse crack, surface corrosion, and pothole defect can be automatically identified and the classification accuracy reached 96.25%. The experimental results showed that the PSO-SVM model can improve the classification performance of the surface defects. Based on the effective classification, we can find the distribution characteristics of the surface defects of the cable. It is very important to analyze the relationship between the type of surface defects and the material of the protective layer, so as to adopt appropriate materials and reasonable maintenance measures. Thus, it has a great significance in the structural health monitoring of bridge cables.

State evaluation of relay protection system for state maintenance

Relay protection is the first line of defense for power systems. Its reliable operation is an important guarantee for the safety and stability of power system. At present, Chinese relay protection system has long been implemented with regular planned maintenance and repaired supplemented by after-accident maintenance. This maintenance system has greatly caused the loss and waste of manpower, material resources and financial resources. It is urgently necessary to adopt a reasonable maintenance strategy based on the actual operating state of relay protection. The state maintenance of the relay protection system can formulate the maintenance strategy based on the actual operating state of the relay protection system, which can effectively improve the reliability of the relay protection system. Therefore, this paper studies the state evaluation of the relay protection system for state maintenance. Develop maintenance strategy based on the evaluation results of the current operating state of the protection system. It is of great significance to strengthen the reliability and operation level of the relay protection system and ensure the safe operation of the power grid.

Research on Comprehensive Multi-Infrastructure Optimization in Transportation Asset Management: The Case of Roads and Bridges

Optimization is the core of transportation asset management, but current optimization approaches are still in the stage of single infrastructure management, which seriously hinders the development and application of transportation asset management. This paper establishes a comprehensive multi-infrastructure optimization model for transportation assets consisting of roads and bridges, which is aimed at achieving the goal of transportation asset comfort, integrity, and security, taking budget funds as constraint conditions, and applying the optimization technique of goal programming and integer programming. An interactive fuzzy linear-weighted optimum-order algorithm is presented to solve the comprehensive optimization model. Finally, the comprehensive multi-infrastructure optimization model and algorithm are verified to be effective by practical data in a case study. The results indicate that the model and algorithm can provide a satisfactory and reasonable maintenance and rehabilitation schedule for transportation asset management agencies.

Glucocorticoid, immunosuppressant, hydroxychloroquine monotherapy, or no therapy for maintenance treatment in systemic lupus erythematosus without major organ manifestations.

To study maintenance therapy after achievement of the lowest possible disease activity in systemic lupus erythematosus (SLE) without major organ manifestations. We retrospectively evaluated patients with SLE who visited our hospital from Jan 2015 to Feb 2018 and were taking prednisolone (PSL) < 10mg/day. After excluding those with neuropsychiatric SLE or severe lupus nephritis, patients were divided into four groups according to their maintenance monotherapy treatment, namely, prednisolone (PSL), immunosuppressant (IS), hydroxychloroquine (HCQ), and no drugs. The groups were then compared with regard to cumulative flare rate and changes in SLE Disease Activity Index (SLEDAI). There were 47 patients on PSL, 10 on IS, 5 on HCQ, and 11 on no drugs. Flare rate was higher in the no drug group, and no patients with the IS or HCQ group experienced a flare (p = 0.003). A reduction in SLEDAI was only seen in the IS and HCQ groups (p = 0.05 and p = 0.03, respectively). There were no differences in adverse events among groups during the study period. Our results suggest that the cessation of all drugs is associated with disease flare for SLE patients without major organ manifestations. IS or HCQ monotherapy might be a reasonable maintenance strategy comparing with steroid monotherapy. Key Point • Immunosuppressant or hydroxychloroquine monotherapy appears to be a reasonable maintenance strategy.

Electrodes for Beam Position Monitors for Fourth Generation Synchrotron Radiation Source

Fourth-generation synchrotron radiation sources demand new quality for the electron beam diagnostic systems. Some of diagnostic system elements have to be accurately developed or redeveloped due to match the new requirements. Beam position monitor (BPM) is a most used detector and tens (even hundreds) BPMs are installed in numerous positions along beam transfer lines, booster and storage rings. Modern approach to this device development assumes such features as short transient time, wide bandwidth, high sampling rate, low noise architecture and reasonable production and maintenance price. As a part of the system, the BPM electrodes should meet all those requirements. In this article we describe a development procedure for high quality capacitive electrodes for the BPM. 3D electromagnetic model allows estimation of the sensitivity, frequency response and tolerance requirements for the manufacturing of hundreds of monitors. Presented here equivalent scheme for the electrodes is a basis for the BPM electronics design.

Advanced maintenance cycle optimization of urban rail transit vehicles

With the development of the economy and the increase in passenger flow, the contradiction between urban rail transit demand and capacity is becoming more and more prominent. Increasing the number of on-line vehicles can ease this situation. Because of no increase in investment, the total number of subway vehicles is fixed. And the total vehicles include the maintenance vehicles and the on-line vehicles. Therefore, this article aims to optimize advanced maintenance cycle, so that the maintenance vehicles reduce and the on-line vehicles increase. First, the minimum value of the key components safe and reliable operating mileage is determined. Then, the Queuing Theory is used to obtain the optimized advanced maintenance cycle. Finally, reasonable maintenance plans are arranged based on the optimized maintenance cycle. The on-line vehicles increase by the optimized advanced maintenance cycle, which can relieve passenger flow pressure and meet urban rail transit demand. In addition, the reasonable maintenance plans can ensure that vehicles at the same level of reliability and within the specified mileage to complete the advanced maintenance and ensure the safe and reliable operation of vehicles.

Prognostics for an actuator with the combination of support vector regression and particle filter

The accurate prognostics for actuator malfunctions is a challenging task. Developing reliable prognostic methods is vital for providing reasonable preventive maintenance schedules and preventing unexpected failures. Particle filter has been proved to be a traditional approach to deal with actuator prognostic problems. However, the measurement function in the particle filter algorithm cannot be obtained in the prediction process, this paper presents a hybrid framework combining support vector regression (SVR) and particle filter (PF). The SVR output prediction results are employed as the “measurements” for the subsequent PF algorithm. To accomplish the accurate prognostics for actuator fault of civil aircraft, an improved PF based on Kendall correlation coefficient is put forward to solve the problem of particles’ degeneracy. The experimental results are presented, demonstrating that the SVR-PF hybrid approach has satisfactory performance with better prognostics accuracy and higher fault resolution than traditional approaches.

Evaluation of thermal crack propagation for low alloy steel brake disk

Very high-speed trains are usually equipped with railway brake disks. During braking, frictional heat is generated by rubbing on the disk surface. Because of non-uniform contact, the frictional heat is localized, and the disk surface temperature rapidly increases in that local area, which is known as the hot spot. This hot spot causes damage such as cracking, which affects the disk life. Therefore, to enhance the disk life or to optimize maintenance intervals, accurately predicting crack propagation behaviours is necessary. This study aims to clarify the relationship between the disk crack propagation rate and braking conditions. Braking tests were conducted by using a reduced-sized brake dynamometer under various braking conditions. The tests revealed that the crack propagation rate decreased under two higher braking energy conditions. Fewer crack propagations were considered because surface cracks were removed as a result of higher wear rates. Furthermore, wear rates could be described by equations as functions of the power with the braking energy. The crack propagation behaviour was predicted using a developed equation that includes the rates of both crack propagation and wear. The crack propagation rates were assessed based on the fracture mechanics using the residual and thermal stress distributions calculated by finite element analysis. The test and predicted results were in close agreement. Thus, the braking conditions that accelerate crack propagation were clarified. This method contributes to the development of long-life disks or provides reasonable maintenance intervals.