exida explains Blog

Entries tagged with: SRS

Close Enough? Not so Much
  • 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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Do You Measure the Performance of Your SIS?

Do You Measure the Performance of Your SIS?

It always amazes me that when teaching our FSE 100 Functional Safety Engineering course, the number of times I find that end users in the class are not really measuring the performance of their SIS. In most cases, they are doing some measurements, but not thoroughly.

It…

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How the PHA and LOPA are going to affect your SIS

How the PHA and LOPA are going to affect your SIS

Both Process Safety Analysis (PHA) and Layer of Protection Analysis (LOPA) occur in the early stage of the Functional Safety Lifecycle, detailed in both IEC 61511 and IEC 61508. They both serve significant roles in the whole process safety management. Yet, as a facilitator…

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Is It Possible to Extend Proof Test Intervals?

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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Safety Requirements Specifications (SRS):  The Good and the Bad

Safety Requirements Specifications (SRS):  The Good and the Bad

The IEC 61511 Standard requires the user to create a Safety Requirements Specification (SRS) for a Safety Instrumented System (SIS) that incorporates all the analysis done during the Risk Assessment, HAZOP/PHA and LOPA reviews.  The SRS falls into two types: an initial conceptual SRS, often referred to as the…

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The Dos and Don’t of SIS Application Programming

The Dos and Don’t of SIS Application Programming

It’s interesting that the majority of the time when people talk about functional safety, they are usually thinking about hardware: what sensors to use, which logic solver, what actuator, solenoid or valve to select; what voting architecture, etc.  What often gets overlooked, initially, is the application program.

Essentially, when…

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The Site Safety Challenge – Do You Follow Good Site Practices?

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…

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Welcome to my world
  • by John Yozallinas, CFSE
  • Sunday, October 02, 2016
  • Certification

Welcome to my world

Sure, you might think I’ve got it made… sitting here on my perch telling you what you need to do to meet IEC 61508, while you sit there with all the work to do.  Well, it wasn’t always that way.  I was in your shoes, responsible for achieving functional…

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What do you need to know about traceability for IEC 61508?
  • by John Yozallinas, CFSE
  • Thursday, October 26, 2017

What do you need to know about traceability for IEC 61508?

Traceability is about connecting the dots to determine that the web of activities for a functional safety project have followed the proper paths.  Think of it like cheating at hide-n-seek; it provides a shortcut to find all those requirements and design parts that are hidden in your specification documents. …

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