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Entries tagged with: Loren Stewart

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 04 - Safety Instrumented System (SIS)

Back to Basics 04 - Safety Instrumented System (SIS)

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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Back to Basics 05 – What is a Safety Function?

Back to Basics 05 – What is a Safety Function?

A Safety Function is the action of a collection of equipment to implement automatic mitigation of a particular hazard. It is the job of the Safety Instrumented Function (SIF).

Some examples of common Safety Functions: 

  • Car brake stop
  • ESD valve – Shutdown process
  • Sprinkler system 
  • High…

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Back to Basics 06 – IEC 61508

Back to Basics 06 – IEC 61508

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.

IEC 61508: 2010 International Performance-Based Standard 

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Back to Basics 07– Safety Lifecycle – IEC 61508

Back to Basics 07– Safety Lifecycle – IEC 61508

The IEC 61508 standard recommends the use of a functional safety lifecycle. Any safety lifecycle can be used, but the standard does lay out a nominal 16-step process which can be divided into three main classifications as an example. 

The Analysis phase of the lifecycle deals with gathering background…

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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 10 – How Does a Product Get a SIL?

Back to Basics 10 – How Does a Product Get a SIL?

IEC 61508 functional safety standard indicates Safety Integrity Levels (SIL) needs to be evaluated by three design barriers:

  • The Systematic Capability Rating
  • The Architectural Constraints for the Element
  • The Probability of Failure for the Product

What Makes a SIL?

Systematic Capability is achieved when the equipment…

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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 12 –  What is IEC 61508 Certification?

Back to Basics 12 –  What is IEC 61508 Certification?

IEC 61508 Certification is a Third-Party Validation against the standard’s requirements, comprising of:

  • Detailed Analysis of engineering processes to determine Systematic Capability and Cybersecurity Strength 
  • Detailed Analysis of hardware design / design margins resulting in Random Failure Rate in all failure modes
  • Analysis/Testing to show safe, correct operation and Cybersecurity Susceptibility

To achieve an…

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Back to Basics 13 - How Do I Start IEC 61508 Certification?

Back to Basics 13 - How Do I Start IEC 61508 Certification?

Do you want to know more about IEC 61508 certification, but you’re not sure if you are ready to jump in? Don’t worry, we will make this process as painless as possible.

Here is what to expect:

  1. Introduce Scope
  2. Kickoff Meeting
  3. Perform FMEDA on Product
  4. Creation of…

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Back to Basics 14 - Systematic Capability

Back to Basics 14 - Systematic Capability

Systematic Capability is achieved when the equipment used to implement any safety function is designed using procedures intended to prevent systematic design errors.  The rigor of the required procedure is a function of a Safety Integrity Level (SIL). This is evaluated through an assessment of the quality management system…

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Back to Basics 15 - Architectural Constraints

Back to Basics 15 - Architectural Constraints

Architectural constraints are limitations that are imposed on the hardware selected to implement a safety-instrumented function, regardless of the performance calculated for a subsystem. Architectural constraints are specified (in) according to the required of the subsystem, type of components used, and of the subsystem’s components. (Type A components are simple devices…

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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 18 – Route 1H

Back to Basics 18 – Route 1H

Route 1H is one of two Architectural constraints options made available in the standards IEC 61508-2 and IEC 61511. Route 1H . Both Route 1H and Route 2H are limitations that impose the hardware selected to implement a safety-instrumented function, regardless of the performance calculated for a subsystem. 

Route 1H  is…

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Back to Basics 19 – Route 2H

Back to Basics 19 – Route 2H

Route 2H is one of two Architectural constraints options made available in the standards IEC 61508-2 and IEC 61511. Route 1H . Both Route 1H and Route 2H are limitations that impose the hardware selected to implement a safety-instrumented function, regardless of the performance calculated for a subsystem. 

What exactly is Route 2H

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Back to Basics 20 – Safe Failure Fraction, SFF

Back to Basics 20 – Safe Failure Fraction, SFF

Safe Failure Fraction (SFF) is defined as the ratio of the average rate of safe failures plus dangerous detected failures of the subsystem to the total average failure rate of the subsystem. It is defined for a single channel (no redundancy, 1oo1).

It is a measurement of the likelihood of…

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