In this blog series, I will cover the emerging trends in the valve assembly market, how these trends relate to the IEC 61511 requirements, and what's in a final element. When you look at the different devices that go into some of these safety systems, the final element becomes…
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Entries tagged with: SIL Verification
- by Chris O'Brien, CFSE
- Thursday, March 29, 2018
- Certification
Functional Safety Assessment of Valve Assemblies (Part 1)
- by Steve Gandy, CFSP
- Thursday, September 26, 2024
- Functional Safety
How Does Mission Time Work with Proof Testing to Impact SIL Verification?
I have been asked this question many times by various clients over the years. This comes down to whether a perfect proof test is assumed or not. Let us remember that Mission Time is defined as the amount of time we expect a set of SIF equipment to run until a…
- by Steve Gandy, CFSP
- Monday, April 28, 2014
- Software
Still Using Excel to do PFD Calculations?
It’s very interesting to me to find that people are still using excel to do PFD calculations. Whereas this is probably okay for simple single element architectures (i.e. single sensor, single logic solver and single final element), it becomes extremely complicated when dealing with redundant architectures. Moreover, for performing…
- by Steve Gandy, CFSP
- Tuesday, November 26, 2019
- Functional Safety
The Site Safety Challenge – Do You Follow Good Site Practices?
The question of whether companies follow good site safety practices is an interesting one. Firstly, what do we mean by good site safety practices? I think most companies believe they follow good site safety practices but do they really? Are they really measuring and tracking this?
The basis of having good site…
- by Dr. William Goble, CFSE
- Thursday, September 03, 2015
- Software
To Spreadsheet…or NOT to Spreadsheet
I remember the first time I ever saw a spreadsheet program. It was called “VisiCalc" and ran on a Commodore PET computer. My first thought was, “What is that good for?” Then I tried it and was totally hooked. I conclude that the creation of the spreadsheet has changed…
- by Steve Gandy, CFSP
- Thursday, April 26, 2018
- Functional Safety
Which FSAs Do I Have to Perform?
The new release of IEC61511:2016 has caused some confusion when it comes to the Functional Safety Assessments (FSAs). Which ones are mandatory?
The confusion comes from the wording in the standard and the clarifications in the notes. The relevant clause in the standard 5.2.6.1.4 states:
A FSA team…
- by Steve Gandy, CFSP
- Thursday, June 22, 2017
- Functional Safety
Why Run-to-Fail Is Not A Good Maintenance Strategy For SIS
One of the fundamentals of the Probability of Failure on Demand (PFDavg) calculations in SIL verification analysis, is the concept of a constant failure-rate during useful life of the equipment. Probabilistic calculations assume that the failure rate of the devices used in a Safety Instrumented System (SIS)…