Jump to content

Calculate the MTBF


Recommended Posts

Hi,

I would like to calculate the MTBF (Mean Time Between Failures) of a compressor. I have the running hours signal and captured capsules for failures. I want to create a trend showing the MTBF over time (MTBF= [current running hour - running hours at the beginning of the year]/the number of failures during the running year).

Q1: I used $Capsule.aggregate(count(),years(),startkey()).toStep() to display failures trend (it should be increasing over a year with the new failures) but this gives me the total over that year without showing step change against the next failure capsule.

Q2: how can I implement the MTBF formula in my calculation?

Thanks

Capture2.JPG

Link to comment
Share on other sites

  • Seeq Team

Hi Yassine - Below is one way to approach this problem:

Q1:  Refer to the below linked article on how to create a running count of capsules. 

For your use case, start by creating a Yearly Periodic Condition in your time zone of choice.

image.png

Next, create a signal with a set sample rate (I picked 1 day in this case, but you can make it shorter):

image.png

 

Then create a signal from condition to count each Maintenance Interval using the average of the signal during the maintenance capsule (which will be 1, so effectively, you're counting a single instance for each maintenance interval):

image.png

 

Finally, create a running sum of the capsules over the yearly period w/ max interpolation of 1 year:

image.png

 

This will result in a step signal with a continuing count of maintenance intervention capsules:

 

image.png

 

 

Q2: To perform your yearly MTBF calculation, you can create a signal for your current running hours and start of year running hours by using the Max and Min Aggregation in Signal to condition:

image.pngimage.png

 

With those signals available, Yearly MTBF can be calculated using Formula:

image.png

 

image.png

 

 

Edited by Patrick
fixed images
  • Like 1
  • Thanks 1
Link to comment
Share on other sites

Perfect.. it works.. the only thing I changed from your approach is that I used for Current_hours as the running run-hours from the compressor itself and not the created signal max_run_hours so the MTBF 1 trend looks sloped compared to the  MTBF you proposed. That works pretty fine.

Thanks Patrick

capture3.JPG

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...