Emergency Stop Safety Circuit

[bobhudon]

I have a conveyor passing through a rotating machine. The customer does not want the conveyor to stop if the machine emergency stop button is pressed because it will impact other machines sharing the conveyor. But I currently have all machine motors including the conveyor motor tied to the emergency stop circuit. Power is removed from all motors when the emergency stop is pressed.

My question is, do I really need to have the conveyor motor tied into the emergency stop circuit? I see no real safety issue with leaving the conveyor operational. Do conveyor motors in general require emergency stop circuits?

 

[edamico11]

Are you saying

Are you saying

if I get caught up in the conveyor, and someone hits the emergency stop, I will have to wait until I get thrown into the rotating machine before I am saved? Assuming that the conveyor, (which just grabbed my shirt) does not rip my arm off first. IMO.. could be a hazard...

 

[templdl]

I would ask the question as to what one would were to see a emergency stop PB and why it needs to be pushed and what the operator would expect to happen it he/she need top push it. If the operator expected the conveyor to shut down in it didn't then what?
And what about liability?

 

[bobhudon]

Emergency Stop Safety Circuit

I would ask the question as to what one would were to see a emergency stop PB and why it needs to be pushed and what the operator would expect to happen it he/she need top push it. If the operator expected the conveyor to shut down in it didn't then what?
And what about liability?

A quick safety assessment shows very little conveyor safety risk. The conveyor is carrying small plastic containers. I am considering adding a separate, conveyor mounted, emergency stop. This emergency stop would just remove power to the conveyor motor.

Thanks for your opinion but what I really need is what code says about this issue.

 

[edamico11]

bobhudon,,,

bobhudon,,,

I do not think the NEC would have a problem with it but

what about OSHA "Division 2, General occupational safety and health rules, subdivision F- Powered Platforms...?"

I do think that having one, even if it is separate, is a good idea as long as it is clearly labeled.

but what the hell do I know,, drank clearly too much egg nog,, happy holidays all:grin:

 

[petersonra]

The NEC does not cover estop buttons, where they are located, or what they even do, other than possibly the wiring to and from them.

I think you will find that you generally need some way to stop any motion that might be dangerous. I don't recall any requirement that an estop pb stop all motions in its immediate area.

Personally, I would want some way to stop whatever motion was going on in case of emergency, and one pb is better than two in most emergency cases.

If you find you are using the estop on a regular basis, it may be that the design is just wrong to begin with. Estops should not be used as stop buttons. A stop button should be used for that.

NFPA79 covers some requirements for estops located on machinery. You might want to take a look at the minimal requirements there.

 

[tom baker]

I'll elaborate a bit.
The NEC covers the wiring to machine, but not necessarily the wiring of the machine. It may cover the external disconnects and controlers. But as far as Estops go, the NEC is silent.

 

[edamico11]

bobhudon,,,

bobhudon,,,

Check this out ...

http://www.nj.gov/health/eoh/survweb/95nj018.pdf



Just an FYI....

 

[e150club]

bob like you said in your second post. we had a conveyor sys. and st./stop stations independent of each other but large red buttons at every station mark emergency stop shut down every thing.

 

[FNCnca]

There should be e-stops for the conveyor even if it is seperate from the main equipment e-stop. If the conveyor is NOT guarded and protected enough to prevent someone from falling into it, it should have e-stop pull cords ran down it's length. OSHA will have something to say about this, just don't have my books here with me at home, so can't site anything specific.

From a pure safety standpoint, this just makes good sense.

 

[realolman]

I know of a guy who got his hand stuck under the tail pulley of a running belt conveyor. Had to throw his hard hat at a hi lift operator to get someone's attention while the belt rubbed the back of his hand off.
(I don't see an emoticon for shuddering).

I imagine this looked like a pretty harmless conveyor.

I doubt you could put too many E stops in. Maybe a cable along the conveyor.

 

[hockeyoligist2]

Quote "it should have e-stop pull cords ran down it's length"

Ditto An E-stop button may not be assessable to someone that is hung in the conveyor. Pull cords run the full length! Even though you only have small plastic containers, they are not the problem, it is the belt itself.

 

[iwire]

The customer does not want the conveyor to stop if the machine emergency stop button is pressed because it will impact other machines sharing the conveyor.

Yeah that makes sense, can't have someone slowing production down just cause they are getting injured. :roll:

As Bob P mentioned if they are using an e-stop as the control button that habit should be changed and a regular stop button should be installed for that particular process.

 

[hockeyoligist2]

Quote "Yeah that makes sense, can't have someone slowing production down just cause they are getting injured."

Or getting dead! A local man was crushed in a machine recently here. Due to improper safety switches. Because it could slow production..........

 

[George Stolz]

My middle finger looks a little funny from catching it in a conveyor, when I worked at the paper. My other middle finger matches, from catching it in a chain inside a machine when I worked at the paper. They grow back funny when you lose a nail.

My sister worked at the paper too, and a tyer caught her hand while she was working the line, and ground the backside off her hand, down close to the bone. That healed pretty nasty.

Don't skimp out on the e-stops, please.

 

[petersonra]

No offense George but an e-stop is not going to prevent injury due to to either operator carelessness or poor machine design.

 

[realolman]

Especially if it ain''t there or doesn't stop the machine you're stuck in.

Merry Christmas folks!

 

[Tori]

I did a job at a coal handling facility that fed a small power plant, I remember that the conveyer (it ran through a tunnel underground with a side walk next to it ) did have a cable that ran it's entire length and all the down hoppers and up hoppers had cables all around them that would dissengage the motor from the moving parts.
This was a federal facility

 

[bobhudon]

Emergency Stop Safety Circuit

Thanks for all of the feedback!

 

[George Stolz]

No offense George but an e-stop is not going to prevent injury due to to either operator carelessness or poor machine design.

None taken, I agree. But sometimes physical damage can be minimized by having an e-stop handy.

In the first incident, it was over with as soon as it started, I jerked my hand out of the end of the conveyor. If it had held me, it would have taken my hand and made hamburger. Not only was that conveyor unsafe mechanically, but there was no e-stop at the end of it where people routinely caught the bundles.

In the second incident, I was boneheadedly cleaning the goop off a chain with the stacker idling, and it caught the rag. In that case, I stood in agony with my finger in the sprocket for an eternity before I realized there was an e-stop right in front of me, I was thinking of the one that was out of reach that I commonly used, and forgot about the one on the back of the machine.

In my sister's incident, if my second incident is an indicator, then clarity of thought kicks in after about five seconds of pain. The machine ran for about twenty seconds on her, before someone noticed and shut it off for her. Had there been a handy e-stop, there would have still been an injury but it would have been far less severe.