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Topic Title: Do Pull cord Estops need to be tension type to meet Cat3 PL-D?
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Created On: 25 September 2017 09:19 AM
Status: Read Only
Linear : Threading : Single : Branch
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - Mal415 - 25 September 2017 09:19 AM  
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - Mal415 - 27 September 2017 07:36 AM  
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - paulskyrme - 27 September 2017 07:06 PM  
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - Mal415 - 28 September 2017 10:25 AM  
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - Mal415 - 28 September 2017 10:44 AM  
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - Mal415 - 28 September 2017 12:57 PM  
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - paulskyrme - 28 September 2017 05:32 PM  
 Do Pull cord Estops need to be tension type to meet Cat3 PL-D?   - Zoomup - 29 September 2017 03:38 PM  
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 25 September 2017 09:19 AM
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Mal415

Posts: 8
Joined: 20 September 2017

I have seen references to the below specific standards in datasheets for tension type safety (ESTOP) cables. Also sometimes I see that the same tension type safety cable systems say they meet CAT 3 PLD.

Formally - BS EN 418:1992
Now - BS EN ISO 13850:2015

I do not have access to fully read these standards through my company nor the personal money to buy them.

My main question revolves around the following example.

An old machine that is most likely built and operated pre Machinery Directive.
This machine is then not used for a few years and moved to another building on the same plant/premises.
This has an original design of Estop circuit that uses Safety Cable Estops that are not tension type but pull to break type i.e. if the estop cable went slack or was cut would not function correctly.
If the hazard on the machine can cause severe injury, the frequency of exposure (working close to the hazard) is high and there IS the ability to avoid the hazard under certain conditions (i.e. a trained worker can easily avoid the Hazard by Training but the Hazard is still possible then, from risk assessment, the system would now require a minimum of a Cat 3 Performance level d Circuit. Well that is my understanding. Feel free to correct me on that.

Q1) does an old machine as described require the safety circuit upgrading?
Q2) Can a "Cable Pull Switch without Broken Cable Detection" ever be used on machines which require Cat 3 Performance level D? i.e. if the machine is old and maintains original specifications.
Q3) Can a safety cable of any type ever meet Cat 4 Performance level E (I have never personally seen this)
Q4) I find it common to see safety cables used as inputs to an estop system that have both dual input redundancy and dual output redundancy in the reset loop, i.e. the safety relay is configured as CAT4, but if safety cables are only rated as CAT3 PL D, does that make the system in general as CAT 3 system and not a CAT 4, it is just a "more reliable" CAT 3 System?
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