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Entries tagged with: IEC 61511

A Year in Review: Functional Safety and Cybersecurity in 2015
  • by Dr. William Goble, CFSE
  • Tuesday, January 26, 2016
  • Certification

A Year in Review: Functional Safety and Cybersecurity in 2015

Good things happened in the fields of functional safety and control system cybersecurity in 2015.  I am not going to include the exciting new Star Wars movie as an event in the list as it does not really fit into the topic. But keeping focused, my highlights is 2015…

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Are You Building a Safer World?

Are You Building a Safer World?

Every man takes care that his neighbor shall not cheat him. But a day comes when he begins to care that he does not cheat his neighbor. Then all goes well.”  - Ralph Waldo Emerson

I like to think about functional safety in a similar way.  We all want…

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Are You Ready For What’s Coming?

Are You Ready For What’s Coming?

If you’re like me then you’ve been waiting for the new draft of IEC 61511 to be officially issued since its release has been delayed for some time.  However, a draft has been released and can help in preparing end users for what’s to come.  The question…

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Are You Undertaking Periodic Personnel Performance Assessments?

Are You Undertaking Periodic Personnel Performance Assessments?

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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Back to Basics 01 - Functional Safety

Back to Basics 01 - Functional Safety

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.

1. Functional Safety

Functional safety means the…

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Back to Basics 02 - Safety Integrity Level (SIL)

Back to Basics 02 - Safety Integrity Level (SIL)

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.

2. Safety Integrity Level (SIL)

Safety…
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Back to Basics 03 - Safety Instrumented Function (SIF)

Back to Basics 03 - Safety Instrumented Function (SIF)

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.

3. SIF

SIF – Safety Instrumented Function…

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Back to Basics 08 – IEC 61511

Back to Basics 08 – IEC 61511

IEC 61511: 2016 Process Industry Sector

IEC 61511 is a technical standard that sets out practices in the engineering of systems that ensure the safety of an industrial process through the use of instrumentation. It entails requirements for users of process control and instrumentation for component / element or sub-system safety.…

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Back to Basics 09 – Safety Lifecycle – IEC 61511

Back to Basics 09 – Safety Lifecycle – IEC 61511

The IEC 61511 standard recommends the use of a functional safety lifecycle. Any safety lifecycle can be used, but the standard lays out a process which can be divided into three main classifications as an example. 

The lifecycle is set up like this: 

  1. Analyze the situation and document…

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Back to Basics 11 – How is SIL Used by an End User?

Back to Basics 11 – How is SIL Used by an End User?

Back to Basics 16 - PFDavg

Back to Basics 16 - PFDavg

PFDavg (the average Probability of Failure on Demand) is the probability that a system will fail dangerously, and not be able to perform its safety function when required. PFDavg can be determined as an average probability or maximum probability over a time period. IEC 61508 and IEC…

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Back to Basics 17 - PFH (Probability of Failure on Demand per Hour)

Back to Basics 17 - PFH (Probability of Failure on Demand per Hour)

PFH (The Probability of Failure on Demand per Hour)  is the probability that a system will fail dangerously, and not be able to perform its safety function when required. PFH can be determined as a probability or maximum probability over a time period of an hour. IEC…

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Back to Basics: Failure Rates

Back to Basics: Failure Rates

Failure rates are the number of failures per unit time for a piece of equipment which are usually assumed to be a constant value. They can be broken down into several categories, such as safe and dangerous, detected and undetected, and independent/normal and common cause. Failure rates are often…

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Back to Basics: Failure Rates - FITS

Back to Basics: Failure Rates - FITS

Failures ITime or Failure UnIT

FITs is the number of failures per billion hours for a piece of equipment. 

It is mentioned in both IEC 61508 and IEC 61511 standards as a preferred unit of measurement expressed by 10-9 hours.

Example: 5 FITs is expressed as 5 failures every 10-9 hours (5x10-9). 

When you…

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Back to Basics: Failure Rates - λ

Back to Basics: Failure Rates - λ

The Greek symbol lambda, λ, represents failure rates in functional safety, usually expressed in the unit of measurement of FITS.

λ can be expressed as a total failure rate for a device (λT), or it can be broken down into more specific groupings:

  • Safe detected (λSD)
  • Safe undetected (λSU)
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Back to Basics: Failure Rates - λD

Back to Basics: Failure Rates - λD

The Greek symbol  λD represents dangerous failure rates in functional safety, usually expressed in the unit of measurement of FITs, and can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).

λD is the number of dangerous failures per…

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Back to Basics: Failure Rates - λDD

Back to Basics: Failure Rates - λDD

The Greek symbol  λDD is the detectable dangerous failure rate in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).

Lambda DD

λDD is the number of…

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Back to Basics: Failure Rates - λDU

Back to Basics: Failure Rates - λDU

The Greek symbol  λDU is the undetectable dangerous failure rate in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).

λDU is the number of dangerous undetected failures…

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Back to Basics: Failure Rates - λS

Back to Basics: Failure Rates - λS

The Greek symbol  λS represents safe or spurious failure rates in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).

λS is the number of safe…

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Best Practices in Achieving Functional Safety in Turbine Applications - Part 1

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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