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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum ( )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Posted by: SPM
Date posted: Tue Sep 17 10:26:14 US/Eastern 2002
Subject: RCM / Condition Monitoring
What is the difference between Reliability Centred Maintenance and Condition Monitoring. I have come across varying definitions and would like something definitive. Thanks in advance.


Subject: RCM / Condition Monitiroing
Reply Posted by: Patrick Hetherington ( )
Organization: RAC
Date Posted: Mon Sep 23 5:44:10 US/Eastern 2002
There have been many debates on this topic, most of that is probably unnecessary. After all is debated the important issue is that equipment is being maintained through the use of preventive actions in the most economical manner. Reliability Centered Maintenance (RCM) is a disciplined approach that follows a logic structure to match an items failure modes with the most effective preventive maintenance tasks with emphasis on preserving safety. Any consideration for performing a preventive maintenance task must be based on economic grounds (i.e. it is less expensive to attempt to prevent the failure than have it occur unexpectedly). While there may be many methods to perform preventive maintenance, RCM favors the cheapest and most effective approach. Originally embraced by the aerospace industry, it has gained widespread acceptance. Another outcome of RCM is the justification that no preventive maintenance is effective and the item should be run to failure. Condition monitoring is the act of measuring the condition of a piece of equipment and taking some action based on the condition indicators. For example, placing an accelerometer on a hydraulic pump and measuring vibration levels may indicate when bearings are degrading or gears are wearing. Knowing this information will provide insight to when the equipment should be taken out of service for rework or repair. Many people think of condition monitoring as a continuous act of monitoring equipment remotely or with automated data collection devices, but it could also be performed on an interval such as checking the freezing point of the antifreeze in a car every six months. RCM is generally thought of as scheduled preventive maintenance tasks performed on a fixed interval, however comprehensive RCM programs should be considering the economic benefit of condition monitoring techniques as well as predictive maintenance and condition based maintenance actions.


Subject: RCM and condition monitoring
Reply Posted by: Larry George ( )
Organization: Problem Solving Tools
Date Posted: Sun Oct 6 15:04:01 US/Eastern 2002
This RCM definition is sure to generate protests, because it's so simple. Accretions have obscured this definition.
Replace a part when its operating time exceeds a life limit determined by reliability, P[Life>limit(p)] = 1-p, where the life limit is chosen to provide acceptably low risk from failure of that part. (Risk = p*cost per failure.) Use condition monitoring to make sure the part's reliability does not get worse than the reliability, P[Life>t], used in determining the life limit.

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