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Sempers23499  
#1 Posted : 04 February 2014 10:41:34(UTC)
Rank: New forum user
Sempers23499

I am currently doing a pre-delivery inspection of a case erector and am wondering about the card feed area. When card is in place the moving parts are out of reach, but if the card is removed there is only a card detection photocell that prevents the machine from operating. This can be easily defeated by covering it with a piece of card, which then allow the machine to operate with numerous fast moving parts within easy reach. Anyone any ideas? The machine is CE marked and the French manufacturers attitude is "well, any guard can be defeated, the machine is designed to onl operate when the card is in place"...
leadbelly  
#2 Posted : 04 February 2014 11:03:32(UTC)
Rank: Super forum user
leadbelly

S You state that when the card is in place, the moving parts are out of reach but then appear to contradict yourself by stating that the moving parts are easily reached when the photocell is covered with a card. Have I misunderstood? LB
David Borland  
#3 Posted : 04 February 2014 11:32:48(UTC)
Rank: Forum user
David Borland

Pretty much impossible to asnwer without knowing the specifics of the machine. Any infeed magazines of the packaging machines I have had experience of basically have a chain drag system which is manually loaded by an operator who is protected by the hazardous parts of the machine - the bits that can really do some damage - by a tunnel of some sort which means the principle of safe distance guarding is used. Any blockages in the tunnel area can be reached via interlocked access hatches. The exact arrangement of guarding at the infeed may require to be bespoke to application so there may not be a one size fits all approach which can be applied by the supplier. There are various standards available for packaging machines to allow "compliance" to be benchmarked but standard risk assessment principles should apply.
David Borland  
#4 Posted : 04 February 2014 12:11:14(UTC)
Rank: Forum user
David Borland

You also need to determine the function of the photocell you mention, it is quite likely there principally for process control i.e. the machine will cycle when card is present in the infeed magazine. This will not comply with the requirements of ESPE which are specific to safety.
Sempers23499  
#5 Posted : 04 February 2014 12:33:40(UTC)
Rank: New forum user
Sempers23499

Sorry, didn't explain myself very well. The card stack is end-on on a belt conveyor magazine that moves into the machine opening. Under normal operation, the stack of card obstructs operator access to the moving parts (a moving arm with air suckers, which pick up the individual cards from the magazine). There are operational photo-electric cells which detect card level and stop the machine indeed when the card level becomes low, which is fine. My point was that if I remove all the card, then the machine will not run because the photo-cell sees the gap. The photocell, however, can be easily covered, thereby making the machine think the card is in place and this allows the machine to operate. But without any card actually in place the operate can easily reach the fast moving parts. So under the normal design function, the machine is safe and will not operate which the having parts exposed (which is, in the manufacturer's point of view, machinery directive/PUWER compliant). My concern is that this photocell can be easily defeated, plus could also be accidentally covered with card swarf or debris. The manufacturer's view is that their design is reasonable and actions taken to defeat their system would be "unreasonable". If this was a more dangerous machine, such as a palletiser, I would reject this without a second thought as a single cell so easily defeated would be too high risk. In this case, the machine would only run through 3 cycles (about 3 seconds) before realising no card had been picked and would stop. The risk in this case would also be lesser, in that the severity of possible injury would be bruising from being struck by a moving part (no drawing in, or entanglement risk), so absolute worst case would be a broken finger….
David Borland  
#6 Posted : 04 February 2014 12:58:23(UTC)
Rank: Forum user
David Borland

The additional explanation is welcomed but still doesn't really allow any real judgement on this forum. Given your response I am not telling you anything you don't know in that your photocells are there for process control. You can't rely on them for safety and your risk assessment needs to reflect this. I will go back to my first point - if you can pre-load your infeed magazine with enough cartons to create a sufficient buffer zone before you reach the hazardous parts of the machinery then you can fit interlocked guarding around this portion and conform to the principle of safe distance guarding. Basically fit an interlocked tunnel over the pre-loaded section of the infeed magazine which you can stick your arm down but won't allow you to reach any moving parts.
Dazzling Puddock  
#7 Posted : 04 February 2014 15:30:30(UTC)
Rank: Forum user
Dazzling Puddock

A practical solution to your "boxer" problem is to fit a steel plate to one of the magazine uprights which is of the same size as the flat cartons that fill the magazine. This steel plate slides down with the cartons as they are used then sits in the opening once all the cartons have been used up.
paul.skyrme  
#8 Posted : 04 February 2014 18:11:06(UTC)
Rank: Super forum user
paul.skyrme

Well whilst not knowing the details of the machine, foreseeable misuse comes in so that should be considered. Also IF the photocell is to form part of the safety system then it must be that, part of the safety system and rated so, along with the remainder of its circuit. David B, Whilst I can see exactly where you are coming from, why should it be necessary for the end user to have to modify a machine. It should be down to the manufacturer to ensure that the machine meets all the EHSR's before sale, and "IF" I read this one correctly it does not, ergo, manufacturer pick up the bill at your cost. However, I would hope that the purchase contract is watertight!
David Borland  
#9 Posted : 04 February 2014 19:02:39(UTC)
Rank: Forum user
David Borland

Paul, Principally because like you and everybody else on this forum bar the OP, I have as much idea about the conditions of supply, installation and commissioning as I have about the actual carton packer itself. What I would be pretty confident about is that treating process control photocells as a safety feature is probably the wrong way to head in terms of completion of a suitable and sufficient risk assessment and in the event of any broken fingers or mangling of hands for 3 seconds would not stand up to much scrutiny. Only my opinion mind. Davie
stillp  
#10 Posted : 07 February 2014 09:36:51(UTC)
Rank: Forum user
stillp

Does the photocell and its associated control circuit comply with EN 61496-1? If not, then it is not an ESPE and not suitable for a safety-related control function. The application does not comply with CLC/TS 62046 "Application of presence sensing protective equipment to machinery".
James Robinson  
#11 Posted : 07 February 2014 10:06:18(UTC)
Rank: Forum user
James Robinson

Is the card taken from the base of the in feed stack? If so a top plate can be added that slides down with the stack and when the last card item is removed it is sitting in place, as if it was the last piece of card "guarding" the moving parts. It can then be lifted up, a fresh stack of card put underneath, and away it goes again.
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