Author: Doug Nix

Doug Nix is Managing Director and Principal Consultant at Compliance InSight Consulting, Inc. (http://www.complianceinsight.ca) in Kitchener, Ontario, and is Lead Author and Senior Editor of the Machinery Safety 101 blog. Doug's work includes teaching machinery risk assessment techniques privately and through Conestoga College Institute of Technology and Advanced Learning in Kitchener, Ontario, as well as providing technical services and training programs to clients related to risk assessment, industrial machinery safety, safety-related control system integration and reliability, laser safety and regulatory conformity. For more see Doug's LinkedIn profile.

How to Apply a Safety Edge to a Machine Guard — Part 1: Pressure-sensitive devices

This entry is part 4 of 6 in the series Guards and Guard­ing

Safe­ty Edges are often for­got­ten as safe­guard­ing devices. Most machin­ery engi­neers and design­ers are famil­iar with inter­lock­ing devices and light cur­tains, but once we step away from the famil­iar, our under­stand­ing of how to apply safe­guard­ing devices like a safe­ty edge becomes a bit fog­gy.  Con­tin­ue read­ing “How to Apply a Safe­ty Edge to a Machine Guard — Part 1: Pres­sure-sen­si­tive devices”

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Acknowl­edge­ments: SafeInd, IEC, ISO, Rock­well Automa­tio more…
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Q & A: Category 2 and Testing Intervals

This entry is part 1 of 2 in the series Q & A

Dur­ing the Free Safe­ty Talks that we did with Schm­er­sal Cana­da and Franklin Empire, we had a “hot ques­tion” come up regard­ing Cat­e­go­ry 2 archi­tec­ture and the test­ing inter­val require­ment. In the short video below, Doug answers that ques­tion.

If you have more ques­tions or felt some­thing wasn’t clear in the video, leave us a com­ment and we will get back to you!

If you are hav­ing prob­lems with devel­op­ing your safe­ty func­tion, please get in touch with Doug direct­ly.

Notes

Email Doug direct­ly.

References

[1]     Safe­ty of machin­ery — Safe­ty-relat­ed parts of con­trol sys­tems — Part 1: Gen­er­al prin­ci­ples for design. ISO 13849–1. 2015.

[2]     “The Bath­tub Curve and Prod­uct Fail­ure Behav­ior (Part 2 of 2)”, Weibull.com, 2018. [Online]. Avail­able: http://www.weibull.com/hotwire/issue22/hottopics22.htm. [Accessed: 13- May- 2018].

[3]    Ger­man Social Acci­dent Insur­ance (DGUV) — Insti­tute for Occu­pa­tion­al Safe­ty and Health (BGIA), “Func­tion­al safe­ty of machine con­trols — Appli­ca­tion of ISO 13849–1 — Report 2/2008e”, Insti­tute for Occu­pa­tion­al Safe­ty and Health (BGIA), Sankt Augustin, DE, 2008.

[4]     “Safe­ty Cir­cuit Exam­ples of Safe­ty Com­po­nents | Tech­ni­cal Guide | Aus­tralia | Omron IA”, Omron.com.au, 2018. [Online]. Avail­able: http://www.omron.com.au/service_support/technical_guide/safety_component/safety_circuit_example.asp. [Accessed: 14- May- 2018].

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Acknowl­edge­ments: ISO, OMRON, oth­ers as cit­ed.
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Five reasons you should attend our Free Safety Talks

Reason #1 — Free Safety Talks

You can’t argue with Free Stuff! Last week we part­nered with Schm­er­sal Cana­da and Franklin Empire to put on three days of Free Safe­ty Talks. We had full hous­es in all three loca­tions, Wind­sor, Lon­don and Cam­bridge, with near­ly 60 peo­ple par­tic­i­pat­ing.

We had two great pre­sen­ters who helped peo­ple under­stand Pre-Start Health and Safe­ty Reviews (PSRs) [1], CSA Z432-2016 [2], Inter­lock­ing Devices [3] and Fault Mask­ing [4].

Mr Vashi at Franklin Empire Cambridge
Mr Vashi at Franklin Empire Cam­bridge

Franklin Empire pro­vid­ed us with some great facil­i­ties and break­fast to keep our minds work­ing. Thanks, Franklin Empire and Ben Reid who orga­nized all of the reg­is­tra­tions!

Mr Nix discussing injury rates in machine modes of operation
Mr Nix dis­cussing injury rates in machine modes of oper­a­tion

Reason #2 — Understanding Interlocking Devices

A portrait of Mr Kartik Vashi
Mr Kar­tik Vashi, CFSE

Mr Kar­tik Vashi, CFSE, dis­cussed the ISO Inter­lock­ing Device stan­dard, ISO 14119. This stan­dard pro­vides read­ers with guid­ance in the selec­tion and appli­ca­tion of inter­lock­ing devices, includ­ing the four types of inter­lock­ing devices and the var­i­ous cod­ing options for each type. Did you know that ISO 14119 is also direct­ly ref­er­enced in CSA Z432-16 [2]? That means this stan­dard is applic­a­ble to machin­ery built and used in Cana­da as of 2016. If you don’t know what I’m talk­ing about, you can con­tact Mr Vashi to get more infor­ma­tion.

ISO 14119 Fig 2 showing some aspects of different types of interlocking devices.
ISO 14119 Fig 2 show­ing some aspects of dif­fer­ent types of inter­lock­ing devices [3]

Reason #3 — Understanding Fault Masking

Mr Vashi also talked about fault mask­ing, an impor­tant and often mis­un­der­stood sit­u­a­tion that can occur when inter­lock­ing devices or oth­er electro­mechan­i­cal devices, like emer­gency stop but­tons, are daisy-chained into a sin­gle safe­ty relay or safe­ty input on a safe­ty PLC. Mr Vashi drew from ISO/TR 24119 to help explain this phe­nom­e­non. If you don’t under­stand the impact that daisy-chain­ing inter­lock­ing devices can have on the reli­a­bil­i­ty of your inter­lock­ing sys­tems, Mr Vashi can help you get a han­dle on this top­ic.

A part of ISO 24119 Fig 2 showing one method of daisy-chaining interlocking devices.
A part of ISO 24119 Fig 2 show­ing one com­mon method of daisy-chain­ing inter­lock­ing devices [4]

Reason # 4 — Pre-Start Health and Safety Reviews

Portrait of Doug Nix, C.E.T.
Mr Doug Nix, C.E.T.

Mr Nix opened his pre­sen­ta­tion with a dis­cus­sion of some com­mon­ly asked ques­tions about Pre-Start Health and Safe­ty Reviews (PSRs). There are many ways that peo­ple become con­fused about the WHY, WHAT, WHEN, WHERE, WHO and HOW of PSRs, and Mr Nix cov­ered them all. This unique-to-Ontario process requires an employ­er to have machines, equip­ment, rack­ing and process­es reviewed by a Pro­fes­sion­al Engi­neer or anoth­er Qual­i­fied Per­son when cer­tain cir­cum­stances exist (see O. Reg. 851, Sec­tion 7 Table). If you are con­fused by the PSR require­ments, con­tact Mr Nix for help with your ques­tions.

Reason #5 — Understanding the changes to CSA Z432

CSA Z432 [2] was updat­ed in 2016 with many changes. This much-need­ed update came after 12 years expe­ri­ence with the 2004 edi­tion and many changes in machin­ery safe­ty tech­nol­o­gy. Mr Nix briefly explored the many changes that were brought to Cana­di­an machine builders in the new edi­tion, includ­ing the many new ref­er­ences to ISO and IEC stan­dards. These new ref­er­ences will help Euro­pean machine builders get their prod­ucts accept­ed in Cana­di­an mar­kets. Both Mr Vashi and Mr Nix sit on the CSA Tech­ni­cal Com­mit­tee respon­si­ble for CSA Z432.

Reason #6 — Hot Questions

We like to over-deliv­er, so here’s the bonus rea­son!

We had some great ques­tions posed by our atten­dees, two of which we are answer­ing in video posts this week. If you have ever con­sid­ered using a pro­gram­ma­ble safe­ty sys­tem for lock­out, our first video explains why this is not yet a pos­si­bil­i­ty. Mr Nix gets into some of the reli­a­bil­i­ty con­sid­er­a­tions behind the O.Reg. 851 Sec­tions 75 and 76 and CSA Z460 require­ments.

Mr Nix post­ed a sec­ond video dis­cussing ISO 13849–1 [5] Cat­e­go­ry 2 archi­tec­ture require­ments and par­tic­u­lar­ly Test­ing Inter­vals. This video explains why it is not pos­si­ble to meet the test­ing require­ments using a pure­ly electro­mechan­i­cal design solu­tion.

Edit: 16-May-18

A case in the UK illus­trates the dan­gers of bypass­ing inter­lock­ing sys­tems. A work­er was killed by a con­vey­or sys­tem in a pre-cast con­crete plant when he was work­ing in an area nor­mal­ly pro­tect­ed by a key-exchange sys­tem. Here’s the link to the arti­cle on OHSOnline.com. Allow­ing work­ers into the dan­ger zone of a machine with­out oth­er effec­tive risk reduc­tion mea­sures may be a death sen­tence.

References

[1]     Ontario Reg­u­la­tion 851, Indus­tri­al Estab­lish­ments

[2]     Safe­guard­ing of Machin­ery. CSA Z432. 2016.

[3]     Safe­ty of machin­ery — Inter­lock­ing devices asso­ci­at­ed with guards — Prin­ci­ples for design and selec­tion. ISO 14119. 2013.

[4]     Safe­ty of machin­ery — Eval­u­a­tion of fault mask­ing ser­i­al con­nec­tion of inter­lock­ing devices asso­ci­at­ed with guards with poten­tial free con­tacts. ISO/TR 24119. 2015.

[5]     Con­trol of haz­ardous ener­gy — Lock­out and oth­er meth­ods. CSA Z460. 2013.

[6]     Safe­ty of machin­ery — Safe­ty-relat­ed parts of con­trol sys­tems — Part 1: Gen­er­al prin­ci­ples for design. ISO 13849–1. 2015.

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Acknowl­edge­ments: Kar­tik Vashi, ISO, Franklin Empire, S more…
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