- by Loren Stewart, CFSE
- Tuesday, January 14, 2020
- Functional Safety
Back to Basics 20 – Safe Failure Fraction, SFF
Safe Failure Fraction (SFF) is defined as the ratio of the average rate of safe failures plus dangerous detected failures of the subsystem to the total average failure rate of the subsystem. It is defined for a single channel (no redundancy, 1oo1).
It is a measurement of the likelihood of…
- by Iwan van Beurden, CFSE
- Thursday, March 21, 2013
Changing the PVST Interval. Hey, my Architectural Constraints changed!
Did you see my Changing the PVST Interval. Hey, my failure rates changed! post? There is more…
In addition to impacting the way the Partial Valve Stroke Test (PVST) is addressed in the SIL verification calculation, the PVST frequency…
- by Steve Close
- Thursday, October 04, 2012
How to Decode an exida IEC 61508 Certificate: Part 2
Click here to read Part 1
Now that you know the step-by-step process of product certification, now let’s take a look at the actual information on the certificate.
In the left panel (gray background) you will find an exida certification logo. …
- by Dave Butler, CFSE
- Friday, October 19, 2012
IEC 61508 Compliant Module Testing: Part 2
Last week you learned about what exactly a module is, and examples of different types of modules. Now we will move on to interfaces, the need for module testing, and code coverage requirements.
An interface, such as the 3D printer’s communication interface, or the format of the 3D data…
- by Michael Medoff , CFSE, CISA
- Thursday, July 12, 2018
- Industrial Cybersecurity
IEC 62443: Levels, Levels and More Levels
By now we’ve all become familiar with safety integrity levels (SIL), as they have become part of our everyday lives. However, with the recent release of several cybersecurity standards in the IEC 62443 series, things are getting more complicated. This series of standards introduces two more levels…
- by Steve Close
- Thursday, July 12, 2012
Why should I get my mechanical device certified per IEC 61508?
I was recently approached with a question regarding why it would be necessary to certify mechanical devices, such as valves, per IEC 61508 when it is not clearly stated in the standard that the standard is applicable to such devices. After looking through IEC 61511 and Read More...