BS-EN Standards for light guarding

Steve Kemp

Member
Join Date
Nov 2003
Posts
122
Hello All. I'm trying to fight my way through the maze that is health & safety legislation with regard to the automatic re-start of a machine's operation following a light guard breach. Does anyone know whether this depends on the category of the system, or is it universal? What I'm missing right now is the "connection" between the selected category and the type of guarding to be used. I've always used manual reset for such applications, but then, I always err on the side of caution. (One of our customers specifies that the first press of the start button resets the guard monitor(s) and only the rising edge of the second press starts the machine cycle). By contrast, there's no use discussing the matter with this customer, as his attitude regarding the safety of dozens of operators on the shop floor is -and I quote- "F**k 'em". Incredible... So, any pointers most welcome, thanks.
 
Sounds a bit of a dumb way to do it.
I really think there should be 2 buttons. One for reset and another for start cycle. It is not really a safety issue as the machine cannot start if someone is within the work area (the light curtain would prevent this) but it can be confusing to the operators for what the button is going to do.
We have a few around here with the same attitude but thankfully they are becoming less as the court cases and huge fines weed them out.
Some have even gone the other way to the extremes. I was called to a job the other day after someone was injured (same plant, different area) to install safety access points onto some just installed fencing around a machine. I couldnt believe it, they had just built a new fence around the machine including the a main switchboard for the whole plant area. To reset an overload or any other work required shutting down the whole plant to gain access to the board. As I left they were deciding where to reinstall the fence so the board was outside the lockout area.
Regards Alan Case
 
Steve Kemp said:
One of our customers specifies that the first press of the start button resets the guard monitor(s) and only the rising edge of the second press starts the machine cycle.

I think you'll find in your search that what happens after a hazardous condition is clear is not specified by any industry standards and is often spec'd by the customer.

Your customer's approach seem unusual and probably acceptable but not preferred. I like the 2 button approach too along with a Auto/None/Manual Mode Selector switch. Some customers specify mandatory manual reset, others say auto reset of the light curtain relay is okay (but not initiate a cycle of course) so your customer is somewhere in the middle.

But ultimately it depends on the safety strategy that has been designed to address the issues resulting from the risk assesment and that will be based on the individual machine. For instance, is the light curtain there to detect a condition that can cause a fatalility , non-reversible injury, reversible injury, etc, etc, etc?
 

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