- by Dr. William Goble, CFSE
- Thursday, January 12, 2012
- News
2011…A Year in Review
2011 was a good year in many ways for Functional Safety and Cyber Security. Several instrumentation products achieved IEC 61508 certification. exida Certification alone issued 64 product certifications (http://www.sael-onine.com). With most certification projects, improvements to the design and quality are made. Some manufacturers…
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- by Dr. Eric Scharpf, CFSE
- Thursday, February 16, 2012
- Functional Safety
Babies, Bathwater, and Australian Safety Laws
The old saying goes, “Don’t throw the baby out with the bathwater.” But it looks like a number of people in Australia may be in danger of doing just that with their response to the country’s newly harmonized health and safety laws.
Australia’s new Read More...
- by Chris O'Brien, CFSE
- Tuesday, October 20, 2015
- Certification
Best Practices in Achieving Functional Safety in Turbine Applications - Part 1
The adoption of the functional safety standards continues to gain momentum in turbine applications. Both industrial and power turbine sites are now requiring compliance to IEC 61511. This blog will review both technical requirements and market trends related to functional safety system design. Market trends will cover which standards…
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- by Chris O'Brien, CFSE
- Thursday, January 07, 2016
- Certification
Best Practices in Achieving Functional Safety in Turbine Applications - Part 3
The adoption of the functional safety standards continues to gain momentum in turbine applications. Both industrial and power turbine sites are now requiring compliance to IEC 61511. This blog will review both technical requirements and market trends related to functional safety system design. Market trends will cover which standards…
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- by Dr. William Goble, CFSE
- Thursday, May 12, 2011
- Certification
Buy Certified Equipment, Meet the Standard, Right? WRONG!
While correcting a CFSP exam, I read a question which went something like this:
If you purchase all IEC 61508 certified equipment for a low demand safety instrumented function, then to meet the requirements of IEC 61511:
A. No other design verification is needed
B.…
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- by Iwan van Beurden, CFSE
- Thursday, March 21, 2013
- Software
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…
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- by Denise Chastain Knight, P.E., CFSE, CCPSC
- Wednesday, May 27, 2015
- Functional Safety
Close Enough? Not so Much
Performing a SIL Verification calculation on preliminary design information can be a very useful tool to dial in the Safety Instrumented Function (SIF), Safety Requirements Specification (SRS) content , and define critical elements for the field component purchase specifications. Conceptual verification is typically performed quickly with general design information.…
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- by Dr. Eric Scharpf, CFSE
- Tuesday, October 25, 2011
- Functional Safety
Do you believe the numbers?
In a couple of recent projects and discussions, I have come across something extremely concerning. Engineers are very good at performing accurate calculations, and the PFDavg and PFH computations for SIL performance verification are improving in precision all the time. Unfortunately, there is often such a focus…
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- by Dr. William Goble, CFSE
- Friday, January 10, 2014
- Certification
Functional Safety, Cybersecurity, and Alarm Management in 2013
2013 was a good year for functional safety progress. exida Certification issued a record number of new product functional safety certifications in mostly every product category - valves, actuators, solenoid valves, PLCs, fire and gas sensors, process sensors, and components. The component category is one of the most…
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- by Dr. William Goble, CFSE
- Thursday, February 09, 2017
- Functional Safety
Getting Good Proof Test Coverage Numbers
Several years ago we recognized that proof test coverage was an important variable that must be considered when doing PFDavg calculations. We ran some models and discovered that the difference between “perfect” proof test coverage (100%) and a very good 90% could mean a whole SIL…
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- by Loren Stewart, CFSE
- Friday, September 25, 2015
- Functional Safety
How can I improve my SIL?
Click here to read the first entry in this blog series (What is SIL compliance?)
Click here to read the second entry in this blog series (How is SIL Used?)
As we now know, a Safety Integrity Level (SIL) can only be given to a…
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- by Loren Stewart, CFSE
- Tuesday, September 22, 2015
- Certification
How is SIL Used?
Click here to read the first entry in this blog series
Once the Safety Integrety Level (SIL) of a product is found, it will be used FOUR ways:
- To establish risk reduction requirements
- Probabilistic limits for hardware random failure
- Architectural constraints
…
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- by Steve Close
- Thursday, October 04, 2012
- Certification
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. …
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- 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…
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- by Steve Gandy, CFSP
- Thursday, September 13, 2018
- Functional Safety
Is It Possible to Extend Proof Test Intervals?
I am often asked whether extending proof test intervals will be a problem.
This is a tricky question. The design and engineering SIL calculations for the Safety Instrumented Functions (SIFs) are taking credit for a specific proof test interval with a defined level of coverage, as defined within the…
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- by Dr. Eric Scharpf, CFSE
- Monday, April 18, 2011
- Functional Safety
Lifecycle Analysis: It’s Worth the Effort
Performing a risk analysis as part of an IEC61508 / 61511 / ISA 84.01 safety lifecycle process can be quite challenging. How can you be sure you get what you need within budget and how can your team provide the best value for money?…
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- by Steve Gandy, CFSP
- Tuesday, October 29, 2013
- Certification
Obtaining My CFSE/CFSP Certification: Why Bother?
It’s an interesting question and one I asked myself. For any engineer and/or professional working in the controls business or process industries where safety-related equipment is required, it is essential (per IEC61511-1 Clause 5.2.2: Organization and Resources) to prove competency to carry out any safety-lifecycle activities. So what does…
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- by Hal Thomas, CFSE
- Tuesday, August 30, 2011
- Functional Safety
PHA to LOPA: Part II

In some cases the screening methods will indicate that a SIF is needed. These screening methods can be designed to determine how many orders of magnitude risk reduction is needed, allowing a required SIL to be documented for a particular SIF. The screening…
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- by Steve Gandy, CFSP
- Thursday, October 19, 2017
- Functional Safety
Random versus Systematic Faults: What’s the difference?
I saw and responded to a LinkedIn discussion on this very issue, where someone had asked “if I have a misaligned limit switch that fails dangerously, then is it random or systematic? “. This is an intriguing question because many view human error as being systematic and, whereas, this…
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- by John Yozallinas, CFSE
- Thursday, February 16, 2017
- Functional Safety
So what does Interference-Free mean? And why do we care?
An Interference-Free component, either as an interface or a defined functional area, is a system component that is neither safety critical (C3) nor safety relevant (C2), but interfaces with such subsystems.
If a component has been shown to be interference free (C1), then it has been demonstrated that no…
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