exida explains Blog

One of the changes that was made in 2016 to the IEC 61511 standard was the inclusion of periodic personnel assessments (clause 5.2.2.3), whereby a procedure is required to manage the competence of all those involved in the SIS lifecycle; “periodic” assessments are to be carried out to document…

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In the following series of blogs, we'll go back to basics and run down everything you need to know to get started in functional safety.  We'll start with some more general terms and descriptions and make our way to more advanced material.

4. SIS

A SIS – Safety Instrumented…

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Many of you who follow exida’s blogs and webinars will know that we often talk about the requirement for competency.  In fact, the 2016 edition of IEC61511 specifically addresses competency in more detail now than the 2003 version.  The strong emphasis on competency is because the IEC61511 committee recognized that…

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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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Those operating in the process world should be familiar with the concept of Functional Safety Management (FSM) and the need to have well defined processes and procedures in place.  Otherwise, how else will they be able to ensure that their Safety Instrumented System (SIS) and plant…

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As an end-user, do you know how reliable and safe your Safety Instrumented Systems (SIS) and Basic Process Control Systems (BPCS) are from potential cyber issues?  Do you rely on your vendor statements regarding the robustness of their products?  If the answer to these questions is “don’t know”…

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As the cybersecurity threats in the industrial world continue to rise, the automation world continues to grapple with how to address these issues.  As such, the newly released IEC61511-1: 2016 edition has included a new clause to address this (Clause 8.2.4).  In essence, End Users have to carry out…

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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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When we were doing safety system designs in the 1980s, there was no Windows, there was no TCP/IP, there was no in Ethernet. We had to write our own protocols to transmit data to our I/O and our controllers.

Fault-finding was always a challenge . What we ended up…

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Some of you reading this may not be aware or familiar with the terms “leading” and “lagging” indicators, when applied to Functional Safety.  The concept isn’t new but does provide significant benefit when applying this to Functional Safety because, if used correctly, these indicators can help significantly improve performance. …

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Part of the changes to the IEC61511 standard in 2016, some five (5) years ago now, was to emphasize the need to do a better job with regards to the Operations and Maintenance phase of the safety lifecycle.  One of the key aspects of the Operation and Maintenance phase…

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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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exida has launched the web site www.silsafedata.com. SILSafe Data is a web site listing a number of product categories used in process control and the expected range of failure rates for process industry applications. The use of realistic and application appropriate failure rate data has a significant…

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It’s hard to believe that the IEC61511 standard has been in existence since 2003, and most companies operating in the process, chemical, and refining industries (or any other hazardous process manufacturer) have adopted its practices.  It’s also significant that any plants that were built back then with a…

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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 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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Many products have options and features that are valuable to users.  But not all these features should be permitted while the product is performing a safety function.  For example, HART communications should not be permitted to write data to a transmitter while it’s performing the safety function.  If you…

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If you’re a manager in the process industries then you should be familiar with the concept of Functional Safety and the need to have well defined processes and procedures in place.  If not, then how else will you be able to ensure that your Safety Instrumented System and plant…

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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)…

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This is a topic which comes up time and again, especially when reviewing legacy systems.  Although IEC61511 doesn’t preclude the use of shared devices, it does however provide guidance under Clause 11 of what the constraints are.  Even though the Safety Instrumented System (SIS) and Basic Process Control System (BPCS)…

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