exida explains Blog

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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I’ve been receiving several inquiries lately regarding the impact of the Partial Valve Stroke Test (PVST) interval on the failure rates of a final element. Specifically asking how does exSILentia® deal with this? exSILentia® allows users to specify if partial stroke testing is performed on their final…

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I was talking to a customer the other day regarding failure rate data and I brought up our Safety Equipment Reliability Handbook (SERH): 4th Edition.   Through the years, along with our comprehensive safety lifecycle tool exSILentia, the book set has become one of exida's flagship products. If you…

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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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Over the course of several blogs , I will talk about getting realistic failure rate data, where this failure data comes from, and how different methods of failure data analysis compare. I think if you understand this, you will begin to get a very good feel of what it…

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Many times in the design of a safety instrumented system it is necessary to utilize an interposing relay. Typically there is not a certified relay available. Since no certified product is being used it is important to follow the requirements to justify prior use and also to design…

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You will probably not hear me sing the LEGO® Movie’s “Everything is Awesome” song, I’ll keep that private (and you should be thankful to me for that). However as we just released the LOPAx™ module of the new exSILentia® v4 platform, I have come to…

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IEC 61508 and IEC 61511 are known as “performance” based standards.  Specific design rules, as found in “prescriptive” standards, are not included, allowing for innovation and new technology, as well as creativity and advancement.  However, it does imply that a certain level of competency is required.

Others would strongly…

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A question was posed to me this week about why the OREDA failure rate for a solenoid valve was greater than the Failure Modes, Effects, and Diagnostic Analysis (FMEDA) results from exida for a specific manufacturer’s solenoid valve.  The person asking the question was clearly challenging the exida…

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Each month at exida, we strive to spotlight one of our products that makes the job easier for today's industry professional.  In this blog, I wanted to talk about the PHAx module as part of our exSIlentia Safety Lifecycle Suite.

Process Hazards Analysis (PHA)

Process…

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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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The international functional safety standard IEC 61511 provides the safety lifecycle as a steadfast guideline to assess and mitigate risk for manufacturing processes including refineries, chemical, petrochemical, pulp and paper, and power plants. To achieve a functionally safe system, it is essential to follow each…

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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…

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I am working on a SIL verification project and just had to share some observations.

For this project, the customer decided to choose a logic solver for which no data is listed in the exida Safety Equipment Reliability Handbook (SERH). One could…

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Site Specific vs. Product Specific

During a field failure analysis study, it was discovered that the calculated failure rate of a specific device varied by more than 4X depending on installation site.  Particularly, it was one specific site with a high failure rate.  While any reliability engineer…

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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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Common Cause is one of those variables that is not always considered important when it comes to SIL compliance.  And yet, for redundant systems, it can have a significant impact on the PFDavg and Risk Reduction achieved (in Low Demand mode) or PFH (in high or continuous mode).  Most of the…

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What does tool integration mean? One can argue it is the ability for different tools to talk to each other and exchange data. Though this may be true from a typical software tool integration, a common definition of integrate, i.e. to bring together or incorporate (parts) into a whole…

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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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Conducting a Process Hazard Analysis (PHA) can be quite laborious. In a HAZOP, you will systematically evaluate the applicable deviations for each node, within each unit, within each plant. The exSILentia® v4 PHAx™ module is setup to use…

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