scholarly journals Preventive Maintenance Interval Optimization for Continuous Multistate Systems

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Ruiying Li ◽  
Xufeng Zhang
Keyword(s):  
Preventive Maintenance ◽  
Breakdown Rate ◽  
Computer Cluster ◽  
Optimization Framework ◽  
Performance Change ◽  
Cost System ◽  
Binary State ◽  
Multistate Systems ◽  
Complete Failure ◽  
System Breakdown

Preventive maintenance (PM), which is performed periodically on the system to lessen its failing probability, can effectively decrease the loss caused by the system breakdown or the performance degradation. The optimal PM interval has been well studied for both binary-state systems (BSSs) and discrete multistate systems (MSSs). However, in reality, the performance of many systems can change continuously, ranging from complete failure to perfect functioning. Considering such characteristics of systems, two types of performance-based measures, performance availability and probabilistic resilience, are addressed to quantify the system’s behaviour for continuous MSS. A Monte Carlo-based method is given to analyse the performance change process of the system, and an optimization framework is proposed to find the optimal PM interval with the considerations of per-unit-time cost, system breakdown rate, performance availability, and probabilistic resilience. A computer cluster is used as an example to illustrate the effectiveness of our proposed method.

scholarly journals Reliability Modeling for Multistate System with Preventive Maintenance under Customer Demand

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Jinlei Qin ◽  
Zheng Li
Keyword(s):  
Preventive Maintenance ◽  
Customer Demand ◽  
Reliability Modeling ◽  
Reliability Indices ◽  
Optimal Decisions ◽  
Multistate System ◽  
Proposed Model ◽  
Random Failure ◽  
Complete Failure ◽  
Markov Random Process

The performance level of a multistate system (MSS) can vary among different values rather than only two states (perfect functioning and complete failure). To improve the reliability of MSSs, a maintenance strategy has been adopted to satisfy customer demand, and reliability modeling of MSS with preventive maintenance and customer demand is proposed. According to the regular degradation and random failure at each state, based on the Markov random process, the proposed MSS with preventive maintenance can be modeled to satisfy the customer demand in a specific state. This model can also be adapted to compute other reliability indices. Based on this model, the effect of different preventive maintenance actions on the reliability indices can be analyzed and further compared. Two numerical examples have been illustrated to show the validity of the proposed model. The reliability model presented in this study can be used to assess the type of MSS and help reliability engineers to compare different maintenance actions quantitatively and make optimal decisions.

scholarly journals Cost -Benefit Analysis of a Single-Unit System with Preventive Maintenance and Weibull Distribution for Failure and Repair Activities

2014 ◽  
Vol 10 (2) ◽  
pp. 5-19 ◽  
Author(s):  
Ashish Kumar ◽  
Monika Saini
Keyword(s):  
Preventive Maintenance ◽  
Single Unit ◽  
Failure Time ◽  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Single Server ◽  
Scale Parameters ◽  
Unit System ◽  
Complete Failure ◽  
Replacement Time

Abstract This paper deals with a reliability model developed for a single-unit system which goes for preventive maintenance after a pre-specific time ‘t’ up to which no failure occurs. There is a single server who takes some time to arrive at the system for doing repair activities. The unit does not work as new after repair at complete failure and so called the degraded unit. The degraded unit is replaced by new one after its failure with some replacement time. The failure time, preventive maintenance time, replacement time and repair time of the unit are taken as Weibull distributed with common shape parameter and different scale parameters. The switching devices are perfect. The system is observed at suitable regenerative epochs to obtain various measures of system effectiveness of interest to system designers and operation managers.

An integrated optimization framework for multi-cycle environmental stress screening tests and preventive maintenance scheduling

2016 ◽  
Vol 231 (5) ◽  
pp. 1037-1044
Author(s):  
Ming-Yi You
Keyword(s):  
Environmental Stress ◽  
Preventive Maintenance ◽  
Screening Test ◽  
Maintenance Scheduling ◽  
Screening Tests ◽  
Product Reliability ◽  
Integrated Optimization ◽  
Optimization Framework ◽  
Screening Model ◽  
The Cost

An integrated optimization framework for multi-cycle environmental stress screening tests and preventive maintenance scheduling is proposed. The proposed framework considers the improvement of product reliability through environmental stress screening tests and the associated screening cost, and the effect of preventive maintenance schedule on the maintenance cost as well. The environmental stress screening model is extended first to be applicable for multi-cycle environmental stress screening tests. The extended environmental stress screening model characterizes the product reliability function which survives the environmental stress screening test in terms of both the number of environmental stress screening cycles and the severity of screening stress. Afterwards, an integrated cost model is established by considering the cost of preventive maintenance, the cost of corrective maintenance, the cost of environmental stress screening test, and the cost due to failure of products in the environmental stress screening test. The application case study demonstrates the implementation procedures and the application effectiveness of the proposed approach. The application results show that, considering the cost due to environmental stress screening and the cost due to maintenance separately could lead to suboptimal decisions. For enterprises responsible for both environmental stress screening and maintenance, it is suggested to optimize the environmental stress screening test and maintenance scheduling jointly to minimize the overall cost.

Design and Realization of Virtual Computer Cluster System

2011 ◽  
Vol 271-273 ◽  
pp. 1313-1317
Author(s):  
Li Xian Fan ◽  
Yong Zhao Xu ◽  
Hong Tao Li
Keyword(s):  
Lower Cost ◽  
Virtual Machines ◽  
Computer Cluster ◽  
Cost System ◽  
Front End ◽  
Virtualization Technology ◽  
Virtual Computer ◽  
Virtual Resources ◽  
And Control ◽  
Actual Computer

Virtualization technology has revolted the computer technology. In the paper, we present our virtual computer cluster. The components of computer cluster have been improved by virtualization technology from the actual computer server to virtual server instance. Virtual computer cluster includes front-end machine and the cluster nodes. The front-end machine can be physical machines or virtual machines; the cluster node can also be virtual or physical machine node. The front-end machine of the cluster communicates with the cluster nodes through physical or virtual network adapter. The front-end machine connects with the cluster management software in each node so as to monitor and control every physical or virtual node within the cluster. A single virtual computer cluster extends its resources with adding physical or virtual resources including computing resources, storage resources and etc. within secure and stabile occasions with special needs. The technology can be widely applied to cluster and parallel computing demand but with lower-cost system design scenarios.

Simulation Study on HST Distribution for ONAN Oil-Filled Transformer

2015 ◽  
Vol 785 ◽  
pp. 269-273 ◽  
Author(s):  
Nor Asiah Muhamad ◽  
Hanafiah Kamarden
Keyword(s):  
Temperature Distribution ◽  
Simulation Study ◽  
Preventive Maintenance ◽  
System Performance ◽  
Distribution Transformer ◽  
Insulation System ◽  
Breakdown Rate ◽  
Distribution Study ◽  
Transformer Insulation ◽  
Spot Temperature

Advanced monitoring system and preventive maintenance introduced on serviced transformer successfully reducing the equipment malfunction and breakdown rate. However, faults that occur and developed inside the transformer can be very unpredictable. One of the measures can be taken is to analyse the hottest spot temperature (HST) of the transformer, because high temperature will affect transformer insulation system performance and its life-span. HST distribution study on the transformer surface body can give better understanding on how HST will behave at inner and outer transformer surface tank, so that it can be correlated to the actual temperature inside the transformer. Therefore, this paper presents a simulation study on 100 KVA ONAN oil-filled type of distribution transformer with three types of HST intensity. Result shows that temperature distribution projectile is tending to go upwards in the insulation oil and inward into the winding. Moreover, location of HST can be identified by comparing the temperature distribution plot with and without HST.

scholarly journals Reliability Measures of Two Dissimilar Units Parallel System Using Gumbel-Hougaard Family Copula

2019 ◽  
Vol 4 (1) ◽  
pp. 116-130 ◽  
Author(s):  
Garima Chopra ◽  
Mangey Ram
Keyword(s):  
Laplace Transformation ◽  
Present System ◽  
Time To Failure ◽  
Supplementary Variable ◽  
Variable Technique ◽  
Common Cause Failure ◽  
Complete Failure ◽  
Parallel Network ◽  
System Breakdown ◽  
Mean Time

The goal of the present study is to investigate the availability and the reliability of the system, which has two dissimilar units in the parallel network under copula. Other key parameters, such as mean time to failure (MTTF) and expected profit are also evaluated. Simultaneous malfunctioning of units, common cause failure and human fault are the causes of system breakdown. The present mathematical model is examined under the assumption that each failure rate is constant and is exponentially distributed. The system undergoes repair in the completely failed state as well as in degraded state. In the case of complete failure, the system is repaired by two repair facilities and that are tackled by utilizing Gumbel-Hougaard family copula. The present system has been studied by applying the concepts of probability theory, supplementary variable technique and Laplace transformation.

Low-Cost System Handles Patient Phone Calls

2007 ◽  
Vol 40 (11) ◽  
pp. 53
Author(s):  
BRUCE K. DIXON
Keyword(s):  
Low Cost ◽  
Cost System ◽  
Phone Calls

Bipolar radiofrequency induced thermotherapy and 1064 nm Nd:Yag laser in endovenous occlusion of insufficient veins: short term follow up results

VASA ◽  
2011 ◽  
Vol 40 (3) ◽  
pp. 235-240 ◽  
Author(s):  
Krnic ◽  
Sucic
Keyword(s):  
Side Effects ◽  
Success Rate ◽  
Nd:Yag Laser ◽  
Main Stem ◽  
Short Term ◽  
Main Trunk ◽  
Bipolar Radiofrequency ◽  
Saphenous Veins ◽  
Skin Redness ◽  
Complete Failure

Background: The aim of this study is to report our results in main stem vein closure using the bipolar radiofrequency induced thermotherapy (RFITT) system and the 1064nm Nd:Yag laser. Patients and methods: 44 incompetent main stem veins (37 great saphenous veins, one lesser saphenous vein, and 6 anterior accessory saphenous veins) in 29 patients were treated using RFITT. 53 incompetent main stem veins (45 great saphenous veins, 4 lesser saphenous veins, and 4 anterior accessory saphenous veins) in 43 patients were treated endovenously with 1064 nm Nd:Yag laser. All patients underwent postoperative duplex scanning within a month after procedure, as well as a short interview regarding postoperative discomfort. Results: In main stem veins treated with RFITT, the success rate within the first month was 86,4 % (38 out of 44 veins). Complete failure rate was 13,6 % (6 out of 44 veins). In 53 main stem veins treated by 1064 nm Nd:Yag laser, the success rate was 100 %, consisting of 98,1 % complete success (52/53 veins), and 1,9 % partial success (1/53 veins). None of the patients treated with RFITT experienced postoperative adverse effects, whereas 13/43 (30,2 %) patients treated with laser had to use oral analgesics after the treatment, and 21/43 (48,8 %) patients reported transient skin changes, such as bruising or skin redness. Conclusions: RFITT system was fairly efficient in the short term for closure of main trunk veins, whereas longer term results are still scarce. Postoperative side effects of RFITT were minimal. 1064nm Nd:Yag laser, according to short term results, proved to be very effective for main stem vein closure. Postoperative side effects related to 1064 nm Nd:Yag endovenous laser treatment proved to be minor, transient, and acceptable.

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