nfpa79 safety devices

[S'mise]

I came across a safety problem on a large trash compactor machine in our shop. There are photoeyes that will disable the autocycle portion of machine operation if someone was to walk into the hazardous loading area. No problem there.
But if someone walked into this area (beyond photoeye boundry), someone else at a nearby control panel can manually jog a hydraulic arm that could strike an operator in the danger zone. I believe this safety device should disable all machine movement in the restricted area, including manual functions. Perhaps a reset button for the operator to clear (acknowledge) the safety photoeyes when he exits the restricted area.

Safety people seem to be ok with it. What do you think?

Can anyone cite a nfpa79 or maybe osha code for this situation?

 

[petersonra]

Generic photoeyes are not safety components and thus cannot be used for that purpose.

I would want to look at the actual setup before I commented on it any further.

In any case, you probably need to conduct a comprehensive review of the machine with respect to safety and look at all the hazards and how you might mitigate those hazards rather than going after the hazards one at a time.

 

[S'mise]

What I was hoping for was a general code reference pertaining to the requirement for controls to be inhibited when someone enters a restricted area. In this instance, a hydraulic arm can by manually jogged to dump a garbage hopper, but control panel button still moves hopper arm even after someone walks thru it.
Can we at least agree this is not right?

 

[petersonra]

What I was hoping for was a general code reference pertaining to the requirement for controls to be inhibited when someone enters a restricted area. In this instance, a hydraulic arm can by manually jogged to dump a garbage hopper, but control panel button still moves hopper arm even after someone walks thru it.
Can we at least agree this is not right?

As far as I know, there is no code that requires what you want to do.

The requirement (for the most part) is to remove the hazard(s). For instance, if there is a hazard presented by the situation you described, you might be able to remove the hazard by appropriate guarding.

My personal opinion is that if the ability to move the ram remotely while someone is in a position where they could be harmed by that movement is a hazard, than you will likely require some kind of safety rated controls to mitigate the hazard, if you try to do it from the control side. that could well require you to replace the ram's hydraulic valve with a safety rated valve, along with whatever else you might need to do.

 

[S'mise]

As far as I know, there is no code that requires what your trying to do.

How about a machine that requires an operator to load parts into a dangerous area? The operator reaches thru a light curtain which electrically inhibits any machine movement. Same with a gantry conveyor system picking up parts from a conveyor line. Photo eyes or light curtains and used to inhibit movement if someone enters the restricted area.

In this instance a forklift loads machine and the cycle can be reinitiated when it backs out of the way.
I'm just saying that someone entering the area breaking the photoeyes should be safeguarded against the machine cycling, be it automatic or manual jogging.

 

[Timbert]

What I was hoping for was a general code reference pertaining to the requirement for controls to be inhibited when someone enters a restricted area. In this instance, a hydraulic arm can by manually jogged to dump a garbage hopper, but control panel button still moves hopper arm even after someone walks thru it.
Can we at least agree this is not right?

I will say I don't like it, but I think that NFPA79 is not on your side. NFPA79 (9.2.4) allows the overriding of safeguards using a hold-to-run control device. OSHA also allows it provided that some other method is employed that gives workers an equivalent degree of protection. There are times you may need to do this so most of the codes I've seen give you an out.

So, the tack you have to take is that it is reasonably foreseeable that this button could be misused and you need to provide protection when it is misused. What gives the workers equivalent protection to the light curtain? Does the operator panel have a clear and unobstructed view of the danger area? Are there specific policies and training in place? Are there warning signs? Is the hazard avoidable? Is entering the area routine, repetitive, and integral to the operation of the machine?

Bottom line: you need a complete hazard analysis to see if the current safeguards are truly sufficient.

 

[S'mise]

I will say I don't like it, but I think that NFPA79 is not on your side. NFPA79 (9.2.4) allows the overriding of safeguards using a hold-to-run control device. OSHA also allows it provided that some other method is employed that gives workers an equivalent degree of protection. There are times you may need to do this so most of the codes I've seen give you an out.

So, the tack you have to take is that it is reasonably foreseeable that this button could be misused and you need to provide protection when it is misused. What gives the workers equivalent protection to the light curtain? Does the operator panel have a clear and unobstructed view of the danger area? Are there specific policies and training in place? Are there warning signs? Is the hazard avoidable? Is entering the area routine, repetitive, and integral to the operation of the machine?

Bottom line: you need a complete hazard analysis to see if the current safeguards are truly sufficient.

I understand what your saying, but this is plain poor design. If the photoeyes are blocked, it stops motion, but if you continue walking past the photoeyes the circuit is re-energized.
The way I usually see a set-up like this, is the light curtain or photoeye disables active modes (manual, automatic) and movement is not restored until a reset button near the LC is pressed to acknowledge the area is clear.

 

[petersonra]

I understand what your saying, but this is plain poor design. If the photoeyes are blocked, it stops motion, but if you continue walking past the photoeyes the circuit is re-energized.
The way I usually see a set-up like this, is the light curtain or photoeye disables active modes (manual, automatic) and movement is not restored until a reset button near the LC is pressed to acknowledge the area is clear.

It might well be poor design. It might also present some kind of safety hazard.

However, it is all but impossible to give you much in the way of solid advice about what you could do to fix it (assuming it needs fixing) without a detailed hazard analysis being done first.

You mixed the terms photoeye and light curtain together. They are completely different animals.

My personal opinion is that a mere photoeye (or multiple ones) may not be an adequate safety precaution if there actually is a hazard, regardless of whether the rest is automatic or manual.

What does the hazard analysis that was done when the equipment was installed say?

 

[S'mise]

What does the hazard analysis that was done when the equipment was installed say?

I have no idea. The likelihood is one was never done.
This arm for dumping garbage hoppers was retrofitted after the fact. All I'm trying to do is make the safety department aware rhat this is indeed a hazard. I was told this situation was allowable because it is a manual function.
If I can't cite a code to substantiate my claim, I'll let it go.
Just hope no one gets hurt.
Thanks for your advice on rhe matter.