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Entries tagged with: IEC 61508

Riken Keiki Co., Ltd. SD-1OX Galvanic cell method Gas Detector

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RIKEN KEIKI SD-1RI INFRARED GAS DETECTOR

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Seat-of-your-pants Software?
  • by John Yozallinas, CFSE
  • Wednesday, December 03, 2014
  • Software

Seat-of-your-pants Software?

I’ve had software development folks tell me that the “just do it” approach is a valid lifecycle model for SW development.  In their context, this means writing the code based on limited marketing and design information and then backfilling the requirements and design specifications to describe what was done. …

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Setting Goals for 2019: Are You Thinking About Functional Safety?

Setting Goals for 2019: Are You Thinking About Functional Safety?

When I went to set my goals for 2019, I set both personal and professional goals. One of my professional goals is to clean off my desk, but another is to get more people to think about functional safety before an accident occurs, instead of when they are normally…

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Setting the Pace

Going back in time to the turn of the century (remember 2000?), the amount and quality of failure data threatened to doom the whole probabilistic analysis approach.  I recall a letter in IEEE Spectrum magazine from Patrick D. O’Conner, a well known reliability engineering author, who expressed the…

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Site Safety Index™ (SSI) – A Simple Model for Site Variations in Safety
  • by Dr. William Goble, CFSE
  • Monday, April 11, 2016
  • Certification

Site Safety Index™ (SSI) – A Simple Model for Site Variations in Safety

In several of our technical papers over the years, we have noticed that failure rates for the manufacturer, model number are different at different sites, even when the processes were quite similar.  When I have mentioned this to end users and manufacturers, often the response is “Yes, I have…

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So what does Interference-Free mean?  And why do we care?

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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  • by John Yozallinas, CFSE
  • Wednesday, March 06, 2013
  • Software

So What’s an Impact Analysis?

It doesn’t take much to remember a time you wish you had “looked before you leaped.” The time you bought furniture that would not fit through the doorway, or the small tree you planted whose roots are now cracking through the sidewalk. Don’t you wish you had given more…

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Software Metrics

Software Metrics

Both IEC 61508 and ISO 26262 highly recommend a modular approach to software development. One question that comes up regularly asks if there are quantitative targets for determining whether sufficient progress has been achieved by software engineers.

IEC 61508-3 Table B.9 Modular approach

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  • by Dave Butler, CFSE
  • Thursday, August 29, 2013
  • Software

Software Modeling and Functional Safety: Part 2

Part 1 of this blog entry discussed software modeling, modeling notation, and modeling tools. But, what does this have to do with Functional Safety?  The IEC 61508 standard has requirements, for certain SIL levels, regarding the use of:

  • “Semi-formal methods”
  • Computer-aided specification and design tools
  • Design standards
  • Performance modeling
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  • by John Yozallinas, CFSE
  • Thursday, December 06, 2012
  • Software

Spaces and Braces and Comments – Oh My!

What constitutes a good coding guideline?

Serious software development for functional safety requires a coding standard or coding guideline. Most organizations have one, but how do you know if it’s good?

You need to look beyond the boilerplate and physical code layout that are often defined in a coding…

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Spend Your Product Development Time Wisely

Spend Your Product Development Time Wisely

Want to improve your safety lifecycle and be more compliant with IEC 61508?  Focus on the things that have the most benefit.  Like what?  What are some of these valuable things?  

One of the major deficiencies I see while doing certification assessments is…

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Stress vs. Strength… In My Process?

Stress vs. Strength… In My Process?

I consistently find that with companies who are new to functional safety development, the SW process is not as structured or mature as the HW process.  SW development is often more informal, and subject to the interpretation of one or more SW developers.  But when project delays occur, it’s…

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  • by Dr. William Goble, CFSE
  • Friday, March 04, 2011
  • Certification

Tales from the Certification Wars - Who certifies the certification agency?

I have often heard the question “Who says they can issue a certification?”  This is often accompanied by “Why can’t I certify my own product?”  “Who knows our design better than we do?” Good questions.

The IEC 61508 standard does not require certified products for Functional Safety. …

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The Architectural Constraint Blind Side
  • by Denise Chastain Knight, P.E., CFSE, CCPSC
  • Thursday, August 27, 2015
  • Certification

The Architectural Constraint Blind Side

I did my homework, purchased certified devices, and specified physical redundancy. I expected an uneventful SIL Verification but the assessor is telling me that I have functions failing Architectural Constraints in the sensor and final element groups. How can that be? 

Low demand mode Safety Instrumented Function (SIF)…

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The Evolution of Coding Standards

The Evolution of Coding Standards

Sometimes it seems that things change slowly in the world of functional safety.  If you look at many of the technical references in IEC 61508 you will find that most come from the 1980s and 1990s.  There is even one reference that dates back to 1950!  With the rate…

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The exida Certificate Explained

The exida Certificate Explained

A manufacturer whose product passes the exida IEC 61508 Assessment Scheme will receive a certificate based on IEC 61508 and perhaps other functional safety standards. There is a significant amount of information on a certificate that may not be always trivial for a novice. This document explains how one…

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The exida FMEDA Process - Accurate Failure Data for the Process Industries

In this blog, I will talk about the FMEDA method and how it can generate realistically accurate failure rate data.

The first question we have to ask is “why do you need failure rate data ?”

One of the fundamental concepts in today’s functional safety standard, IEC 61508 and…

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The exida Scheme

Today I was asked: “What is the exida Scheme?”  If one person had this question, it is likely that others may be interested as well.  Therefore, I decided to take a moment and explain the exida structure.  Any Certification Body operates each product certification per a “scheme,” which references…

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  • by Dr. William Goble, CFSE
  • Wednesday, February 27, 2013
  • Software

The Real PFDavg Variables

I was recently asked how the PFDavg value in an exida FMEDA report was calculated. Those PFDavg values are calculated using the exSILentiaTM program. The person who posed the question was using the equations from Part 6 of IEC 61508 and got a different value. Why?

exSILentia

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