Hierarchy of Controls

Forces, people and injuries — How hard is too hard?

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ISO/TS 15066 body model
This entry is part 5 of 5 in the series Hier­archy of Con­trols

For any­one involved in risk assess­ment and con­trol, there are always ques­tions regard­ing the amount of force it takes to injure a per­son. As soon as we decided that hurt­ing people when they were work­ing or using our products was not OK, clev­er people wanted to know what the lim­its were on forces applied to people. […]

Control Functions

How to do a 13849 – 1 analysis: Complete Reference List

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This entry is part 8 of 9 in the series How to do a 13849 – 1 ana­lys­is

As prom­ised in pre­vi­ous posts, here is the com­plete ref­er­ence list for the series “How to do a 13849 – 1 ana­lys­is”! If you have any addi­tion­al resources you think read­ers would find help­ful, please add them in the com­ments. Book List Here are some books that I think you may find help­ful on this jour­ney: [0]     […]


ISO 13849 – 1 Analysis — Part 6: CCF — Common Cause Failures

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This entry is part 6 of 9 in the series How to do a 13849 – 1 ana­lys­is

What is a Com­mon Cause Fail­ure? There are two sim­il­ar-sound­ing terms that people often get con­fused: Com­mon Cause Fail­ure (CCF) and Com­mon Mode Fail­ure. While these two types of fail­ures sound sim­il­ar, they are dif­fer­ent. A Com­mon Cause Fail­ure is a fail­ure in a sys­tem where two or more por­tions of the sys­tem fail at the same time from a single […]


ISO 13849 – 1 Analysis — Part 5: Diagnostic Coverage (DC)

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A graph showing the theoretical "bathtub curve" for product failure rate over the lifetime of the product.
This entry is part 5 of 9 in the series How to do a 13849 – 1 ana­lys­is

What is Dia­gnost­ic Cov­er­age? Under­stand­ing Dia­gnost­ic Cov­er­age (DC) as it is used in ISO 13849 – 1 [1] is crit­ic­al to ana­lys­ing the design of any safety func­tion assessed using this stand­ard. In case you missed a pre­vi­ous part of the series, you can read it here. In the last instal­ment of this series dis­cuss­ing MTTFD, I brought up the […]


ISO 13849 – 1 Analysis — Part 4: MTTFD – Mean Time to Dangerous Failure

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This entry is part 4 of 9 in the series How to do a 13849 – 1 ana­lys­is

Func­tion­al safety is all about the like­li­hood of a safety sys­tem fail­ing to oper­ate when you need it. Under­stand­ing Mean Time to Dan­ger­ous Fail­ure, or MTTFD, is crit­ic­al. If you have been read­ing about this top­ic at all, you may notice that I am abbre­vi­at­ing Mean Time to Dan­ger­ous Fail­ure with all cap­it­al let­ters. Using MTTFD is […]