Trend Monitoring

Trend Monitoring is an essential part of a robust calibration system.  It involves the comparison of results from previous calibrations to try and estimate at that time in service the device may exceed its allowable errors.  Done properly, trend monitoring will pay off in a very short time.  There are 3 possible outcomes of trend monitoring:

  1. The current calibration period is too long and a possible out of tolerance event may occur before the next scheduled calibration check.  Finding this out before it happes will enable the device to be re-calibrated before the event ensuring no work needs to be recalled and preventing any unsafe jobs leaving the workshop.
  2. The current calibration period is correct.  This won't save any money or improve safety, but it does gove the operators and quality management a nice feeling of confidence.
  3. The current calibration period is too short.  If the trend analasys shows that it would be safe to extend the calibration period, then why not save some dollars?  Extending the period by just 50% will save on down time, logistics and calibration costs.  After a few years of regular calibration and trend monitoring it is possible to extend some items by over 100%

Now for the hard part - Nope, there is no hard part, we will take care of all that.  Talk to us today about how we can implement trend monitoring for your tooling.

For trend monitoring to work, there needs to be consistency in calibration.  In other words, you need to take the device to the same cal lab every time so that the results can be monitored and plotted.  It takes at least three consecutive calibrations before we can see a trend and the trend is better if we can plot results taken at the same test point each time.

Just stating that it didn't need adjustment last year, so I will give it 2 years next time is not trend monitoring.  

The only way to do it properly is to compare the results and plot a graph against the allowable errors.  Take a quick look at the following example.  The purple plot is the torque wrench under test, the yellow and blue plots are the allowable errors.  The torque wrench in question has been in service for 5 years without needing adjustment.  Some would say;  "No adjustments in 5 years, this must be a good one! lets give it 2 years till the next cal!"  It doesn't take a maths degree to project the purple line line on the current trend and see that it is likely the wrench will exceed its 4% maximum allowable error within a few months of the last cal.  Instead of extending the cal period, it should be reduced, or the wrench should be repaired.  

What are the likely outcomes of extending the cal period?  

  • The torque wrench will be way out of tolerance when it's calibrated.  
  • Do you bury your head in the sand, say nothing and hope no one gets hurt as a result?  
  • Do you recall your last 18 months work to re-check it?  
  • Or do you see the results/remains of your last job on the 6 Oclock news?

 Trend Graph

Come on guys, this is something we need to take seriously! It's a good way to improve safety and reduce costs at the same time.  Seriously,  How often does that happen?

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