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Product Certification

Over 60 new products received functional safety or cybersecurity certification this year. Those products and more…

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Please see the first entry of the Requirements Management blog series here.

The concepts of allocation and derivation are sometimes misunderstood when it comes to requirements management.  This can lead to confusion and even to safety problems.  The process of derivation involves the writing of a new requirement, …

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I was told by an end user engineer that he considers all field devices to be simple Type A devices.  In IEC 61508, Type A is defined as a device with well-defined failure modes, well known failure rates, and behavior under fault conditions that can be completely determined.  Type…

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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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Olympic athletes don’t wake up one day and decide to compete in the Olympics.  They don’t arrive at the games by chance or coincidence.  Their journey starts long before the games begin. They are often influenced and inspired by watching others or by their own interests.  They may begin…

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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.

1. Functional Safety

Functional safety means the…

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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.

2. Safety Integrity Level (SIL)

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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.

3. SIF

SIF – Safety Instrumented Function…

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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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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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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

Systematic Capability is achieved when the equipment…

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IEC 61508 and IEC 61511 functional safety standards allow Safety Integrity Levels (SIL) to be used four ways by end users:

1. To establish risk reduction requirements - How much risk needs/can be removed from the process to achieve a tolerable risk level? (For more…

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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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Systematic Capability is achieved when the equipment used to implement any safety function achieves two goals: the design process has used procedures intended to prevent systematic design errors (fault avoidance) and the design has systematic design control mechanisms such as a diagnostic for incorrect software execution (fault control).  The rigor…

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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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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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PFH (Probability of dangerous Failure 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 61508 and Read More...

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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Failures In Time or Failure UnIT

FIT 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 10⁹ hours.

Example: 5 FIT is expressed as 5 failures within 10⁹ hours . 

When you…

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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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