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Some problems on the selection of a condition based maintenance technique for mechanical systems
Linköpings univeristet. (Systemekonomi)
1990 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In the first paper we focused mainly on establishing a sequential method for the selection of a maintenance technique for mechanical systems. The selection problem is studied for the components having considerable consequences and a non-negligible failure intensity. Identification of these components based on their failure mechanisms and failure causes is discussed and a modified version of the usual Failure Modes, Effects and Criticality Analysis, FMECA is suggested. A cumulative sum chart is proposed to identify a replacement time. This is explained by way of two examples. In order to run cost per unit time is proposed. The selection of a maintenance technique based on the intrinsic information of monitoring parameters is introduced.

Ability of a monitoring parameter in predicting failures, can be described as a probability of failure in the future conditionally on the current value of a model monitoring parameter. Thus, the second paper is focused on introducing a model relating a condition dependent failure rate to a component condition. For the selection of a cost-effective technique a modified proportional hazards model, PHM, is proposed. The modified model is able to reveal the effect of observing monitoring parameters and operating conditions on failure rate function.

A graphical method, based on a Generalized Total Time on Test, a GTTT- plot, for the selection of a cost-effective technique is proposed in the third paper. Also, a graphical method to estimate the threshold level for a cost-effective technique based on the same concept is suggested. These methods are illustrated by way of an example.

Place, publisher, year, edition, pages
Linköping, sweden: University press, Linköping University , 1990. , 23 p.
Series
Linköping Studies in Science and Techology, 248
National Category
Engineering and Technology
Research subject
Technology (byts ev till Engineering), Terotechnology
Identifiers
URN: urn:nbn:se:lnu:diva-21361OAI: oai:DiVA.org:lnu-21361DiVA: diva2:548332
Supervisors
Available from: 2012-09-03 Created: 2012-08-30 Last updated: 2014-05-14Bibliographically approved
List of papers
1. Condition based maintenance for mechanical systems
Open this publication in new window or tab >>Condition based maintenance for mechanical systems
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper a sequential method for the selection of maintenance technique for mechanical systems is presented. It is based on technical knowledge concerning component failure mechanisms and failure causes. Classification of failures according to their consequences is stated. A modified version of failure modes, effects and criticality analysis is given and a way to identify significant components is discussed. Analysis of collected data is discussed and a method to identify a replacement level of a monitoring parameter is proposed. Criteria for the selection of a monitoring technique based on the intrinsic information of monitoring parameters are introduced. Finally, a decision rule for the selection of a suitable maintenance technique is suggested and a modified expression of the long run average cost per unit time is used as a distinguishing criterion between applicable strategies.

Keyword
Breakdown and preventive policies, condition based maintenance, component state, condition monitoring, decision-rule, failure, failure causes, failure consequences, failure mechanism, failure modes, long run average (expected) cost per unit time, monitoring parameter, significant component.
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:lnu:diva-21462 (URN)
Available from: 2012-09-03 Created: 2012-09-03 Last updated: 2016-02-01Bibliographically approved
2. On the modelling of condition dependent failure rates in mechanical systems
Open this publication in new window or tab >>On the modelling of condition dependent failure rates in mechanical systems
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The cycle between two replacements based on condition monitoring is discussed. Models representing a condition dependent failure rate function reflecting the information in a monitoring parameter are suggested. For the selection of a cost-effective technique, a modified version of the Proportional Hazards Model, PHM, is proposed. Utilizing this modified model, it is possible to reveal the effect of monitoring parameters and operating conditions on the failure rate function. General comments on the application of the cost equation are given.

Keyword
Condition dependent failure rate, cost-effective technique, cost equation, failure model, monitoring parameter, time to replacement.
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:lnu:diva-21465 (URN)
Available from: 2012-09-03 Created: 2012-09-03 Last updated: 2016-02-01Bibliographically approved
3. On a graphical method for the selection of a maintenance technique
Open this publication in new window or tab >>On a graphical method for the selection of a maintenance technique
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper a graphical method for the selection of a cost-effective monitoring technique is suggested. Also, a graphical method to estimate the level at which components should be replaced when using a cost-effective technique, i.e. threshold level, is proposed. These two methods are based on the concept of the Total Time on Test, TTT-plot on age and condition dependent replacement is discussed.

Keyword
Age replacement policy, condition dependent replacement policy, cost-effective technique, Generalized Total Time on Test, GTTT-plots, threshold level, total Time on Test, TTT-plot.
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:lnu:diva-21468 (URN)
Available from: 2012-09-03 Created: 2012-09-03 Last updated: 2016-02-01Bibliographically approved

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