Related Topics and Links:

Failure Modes and Reliability Analysis


 Duty Cycle

Setting the Operation Properties for an FMRA

Before you perform analytical calculations or simulations in the FMRA, make sure you at least specify the operating time for the top-level item. If applicable, you can also specify other operation properties at the individual item level.

These properties are located under the Operation heading when you select an item in the FMRA in XFMEA/RCM++/RBI.

In these cases, continuous operation at the rated load is considered to be a duty cycle of 1. Any other level of usage is expressed as a percentage of the rated load value or operating time. For example, consider the DVD drive mentioned above; its duty cycle value would be 18 min / 60 min = 0.3. A duty cycle value higher than 1 indicates a load in excess of the rated value.

If a duty cycle is specified for a subsystem or item, it specifies the percentage of operation as relates to the parent item. That is, the effects of the duty cycle for a parent item and the duty cycle for a sub-item are compounded. For instance, if a system has a duty cycle of 2 and its subsystem has a duty cycle of 0.3, the effective duty cycle for the subsystem would be 2 x 0.3 = 0.6, or about 2/3 the rated load value or operating time.

The ReliaWiki resource portal has more information on duty cycles at: http://www.reliawiki.org/index.php/Time-Dependent_System_Reliability_(Analytical).

Note: Maintenance groups defined for top-level systems in RCM++/RBI will not transfer to FMRA diagrams in BlockSim if you use FMRA synchronization. Similarly, maintenance groups defined for FMEA records in BlockSim's diagrams will not transfer to RCM++/RBI. This is because the applications use different structures to represent the FMRA hierarchy.

 

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