• Journal of Korean Society of Industrial and Systems Engineering
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• v.13 no.21
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• pp.19-24
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• 1990

This paper deals with a problem of choosing an optimum inspection period for an equipment with two stages of failures. Stage I failure which can be detected only through inspection detenorates the equipment and causes critical stage II failure after a random period of time. The expected average cost function is obtained and an optimum inspection policy is discussed. A numerical example is also worked out.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.113-118
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• 2021

The guided weapon system should ensure economical operation and user safety. In particular, in the case of guided weapon systems developed in the form of a guaranteed bomb, the standards for maintaining reliability considering the long-term storage environment are presented during the development stage, and an optimized inspection cycle is required to maintain this. This study calculated the reliability through a trend test, fitness test, and distribution analysis using a mathematical model based on the maintenance status and shooting results during the inspection period for OO missiles currently in operation for a long time in the military. Through this, it was applied to the inspection period model (Martinez) set during the development stage to determine if the improved inspection period can be utilized. Finally, by synthesizing the data from these studies, a policy management plan was developed according to the extension of the inspection period. The One-Shot system was operated at the inspection period set when it was developed. The study analyzed the actual failure and maintenance data to reset the efficient inspection period.

• Journal of Applied Reliability
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• v.1 no.1
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• pp.35-46
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• 2001

Replacement policy of a degradation system is investigated by incorporating the loss function. Loss function is defined by the deviation of the value of quality characteristic from its target value, which determines the loss cost. Cost function is comprised of the inspection cost, replacement cost and loss cost. Two cost minimization problems are formulated : 1)determination of an optimal inspection period given the state for the replacement and 2)determination of an optimal state for replacement under fixed inspection period. Simulation analysis is performed to observe the variation of total cost with respect to the variation of the parameters of loss function and inspection cost, respectively As a result, parameters of loss function are seen to be the most sensitive to the total cost. On the contrary, inspection cost is observed to be insensitive. This study can be applied to the replacement policy of a degradation system which has to produce the quality critical product.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.4
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• pp.96-104
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• 2017

A one-shot system (device) refers to a system that is stored for a long period of time and is then disposed of after a single mission because it is accompanied by a chemical reaction or physical destruction when it operates, such as shells, munitions in a defense weapon system and automobile airbags. Because these systems are primarily related with safety and life, it is required to maintain a high level of storage reliability. Storage reliability is the probability that the system will operate at a particular point in time after storage. Since the stored one-shot system can be confirmed only through inspection, periodic inspection and maintenance should be performed to maintain a high level of storage reliability. Since the one-shot system is characterized by a large loss in the event of a failure, it is necessary to determine an appropriate inspection period to maintain the storage reliability above the reliability goal. In this study, we propose an optimal inspection policy that minimizes the total cost while exceeding the reliability goal that the storage reliability is set in advance for the one-shot system in which periodic inspections are performed. We assume that the failure time is the Weibull distribution. And the cost model is presented considering the existing storage reliability model by Martinez and Kim et al. The cost components to be included in the cost model are the cost of inspection $c_1$, the cost of loss per unit time between failure and detection $c_2$, the cost of minimum repair of the detected breakdown of units $c_3$, and the overhaul cost $c_4$ of $R_s{\leq}R_g$. And in this paper, we will determine the optimal inspection policy to find the inspection period and number of tests that minimize the expected cost per unit time from the finite lifetime to the overhaul. Compare them through numerical examples.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1249-1254
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• 2012

Pipe inspections conducted in nuclear power plants play an important role in ensuring the structural integrity of pipes. Because considerable manpower and expense is required for pipe inspections, it is very important to determine the optimum inspection period and the level of inspection. In this study, the effects of the period and the inspection quality on the failure probability of pipes are investigated using the P-PIE program, which has been developed to calculate the failure probability of pipes. The pipe data of an internal nuclear power plant is used in the study, and fatigue and stress corrosion crack growth are considered in the analysis.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.44
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• pp.263-271
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• 1997

This paper presents a preventive maintenance model for determining the preventive replacement period of a system in which a failure rate is affected by the cumulative damage of fault and inspection. Especially, the failure rate function is considered to be a function of the cumulative damage of the fault and inspection time. Types of replacement considered are preventive replacement and failure replacement. Failure rate and expected cost function between replacement are derived. An optimal policy is obtained that minimizes the average cost per unit time for preventive replacement, failure replacement, inspection and repair.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.243-248
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• 2008

Seoul subway is an safety, quick, and clean public transportation to secure citizens safety. One of the most important elements of train is optimizing railroad function and need to conform railroad inspection for function maintenance. Railroad is the most biggest part of the railroad facility and it is a structure which requires sustainable maintenance. The purpose of study is to improve domestic metropolitan railroad facility inspection method and period. For this, we refer documents about present roving method, roving members and period of railroad roving. In addition, analyzed problems of railroad roving investigation method and period by examining the type and standards of railroad investigation and interviewing experts. By this, we analyzed improving plan and expectations of railroad maintenance and repair operation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.592-598
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• 2017

The purpose of this study is to suggest a new inspection period of ${\triangle}{\triangle}$ guided missiles by analyzing their reliability using field data. The ${\triangle}{\triangle}$ guided missile has an inspection period of five years which was determined using prediction data during its development process. However, from the analysis of its field data, it was shown that the inspection period could be extended to more than 18 years. Based on this result, a policy is proposed to reevaluate the inspection period by means of practical reliability tests.

• Journal of Korean Society for Quality Management
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• v.23 no.4
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• pp.74-89
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• 1995

In recent years, the safety of customers and the demand for rights to be protected from the risk have become stronger than ever day by day, and the function concerning product liability(PL) and quality assurance(QA) has been emphasized. Basically these functions can be obtained by inspection and there is the single rectifying sampling inspection for attribute (KSA-3105) as an existing method. But we can not say this method is good enough because of limitations in the range of applications and the approximate design of inspection methods which can not meet the rapidity and accuracy of quality information transfer according to the maturity of information period. Therefore, in this paper, a new algorithm is developed which can design the accurate inspection method by using the linear cost function that has not been considered in the existing inspection methods. Also in addition to this, a optimal rectifying sampling inspection plan, contributing to minimize the total costs, can be developed by programming the algorithm developed in this study and it can be applied to any field having many processes almost limitlessly.

• Journal of the Korean Society of Marine Environment & Safety
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• v.11 no.2 s.23
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• pp.51-63
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• 2005

In relation with inspection systems of small fishing vessels, Government is drawing up revision of the law about ships safety act(Article 3) on the basis of supporting safe fishing activities to expand the application range of ships safety act for vessels under 2 tons(small fishing vessels) that are exempted from inspection systems. There are two opinions about inspection of small fishing vessels. Government's opinion is that inspection of small fishing vessels must be enforced to confirm small fishing vessels' safety but fishermen's opinion is that inspection systems keep on existing law because inspection systems spends a lot of time and money to the poor and the old. The alternatives for countered opinions is that the poor fishermen's vessels' for living or small vessels' inspection must be operated by themselves in principle and minimizing the limitation through policies is recommended. In addition, Government needs to develop various programs for inspection systems of small fishing vessels like the main fisheries countries. Particularly, in case of operating inspection systems of small fishing vessels, Government needs to consider some solutions for example supporting inspection fee, minimum inspection for confirming vessels' safety, inspecting when a vessel is building, expanding an inspection period.