ajaykumar asked 15 years ago


Suppose your Doing MTBF Prediction for one System. you assume that the target of the system of the MTBF is 2000 hours.

1)My Question is to Set the Target of the system is it Environment factor is important or not ?
2)how to find the Reliability in Series System

Kindly please help for these Questions.

3 Answers
smorris answered 15 years ago

Yes, you should use/select the most appropriate environmental factor. For example, if the system is used in an airplane, then you should use an airborne environmental factor.

To calculate the series failure rate simply add up the failure rates of each item making up the system.

To calculate series reliability (probability of no failure for any item used in the system), multiply the individual reliabilities (probabilities) of each item.

scpleta answered 15 years ago

I am computing the reliability of a truck but doesn’t seem to get the figures right. The guy who made the model some years back assumed that all components are in series which is pulling down the over-all reliabilty of the vehicle. Being a vehicle system, I know there should be a combination of series and parallel networks but couldn’t decide which can be considered as parallel.

I hope I could ask for some help from gurus here.

Thanks, in advance.

smorris answered 15 years ago

If you have redundant items you should model them as such. Also, another approach is to make a list of “mission critical” components and calculate the failure rate for only these items to determine the “mission essential” failure rate. Say you have a truck radio, but this is not really required for the truck to go successfully from point A to point B, so you do not include the failure rate associated with the radio in with your mission essential failure rate, but do include it with the “series” failure rate, which represents the demand for maintenance.