RMQSI Answers ForumCategory: Non-Electrical Component ReliabilityConversion from cycles to hours (NPRD)
louis DEQUIDT asked 8 years ago

Is there a standard method for converting failures per million cycles to failures per million hours in order to integrate a known value (i.e MCBF = 1 000 000 cycles) into a system level prediction (MTBF) ?

1 Answers
Best Answer
rwisniewski Staff answered 8 years ago

Failure rates in NPRD-2016 are presented in terms of failures per million hours, failures per million miles or failures per million cycles. If the failure rate has no suffix, the unit is hours.  A suffix ‘M’ indicates that the unit is miles, and a suffix ‘C’ indicates that the unit is cycles.  The same convention holds true for the operating hours/miles/cycles column, which contains the total operating time in millions of life units (hours, miles or cycles as indicated by the suffix described above).  Therefore, 0.224 represents 0.224E6 or .224 x 1000000 = 224,000 hours.  Similarly, 5.6000M would represent 5.6×1000000 = 5,600,000 miles.  The information contained in the operating hours/miles/cycles column are as provided to Quanterion by the data source – without any conversion or manipulation. Therefore, there is no uniform factor that can be applied to the data in order to convert between hours, miles and cycles. However, if your application provides a cycles per hour or miles per hour utilization rate, then you may be able to generate a conversion factor that is specific to your calculation.