Need to incorporate a safety device for this equipment

[mark32]

Hey guys!

A friend does maintenance work for a machine shop of sorts. Recently, a worker was injured by the equipment shown, as it can be started while that hood/cover is in the up/open position. So, he was asked if he can fabricate something that would prevent the equipment from being started while the cover is open. I can't think of anything off the top of my head, but figured someone here would have an idea. My buddy tells me it's three phase, 208v

 

[tom baker]

many options that would wired to controller mounted on machine
Must not be able to override, which is why a limit switch is not advised

 

[jim dungar]

There are manufacturers of safety relays and limit switches, like Schneider, Eaton, Siemens, AB, Bannner,.
They make keyed devices where one part mounts on the machine and the key on the cover. The relay checks to make sure things have not been bypassed.
This is going to cost some money, but probably less than an OSHA fine or a personal injury lawsuit.

 

[scrubbin]

You could use a tamper resistant magnetic switch mounted to the machine base looking at the closed cover. like:

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Tie the switch into the E-stop circuit or motor start circuit if there isn't an E-stop.

 

[petersonra]

I would be very leary of calling anything you add to this thing "safety".

I don't mean to be obnoxious about it, but the fact that you are asking more or less random people on the Internet about it suggests you do not have the knowledge and/or experience to have anything to do with designing "safety" anything.

At the very least, to be "safe", the cover probably needs to have an interlock with the motor so the cover cannot be raised while the motor is still spinning and the motor cannot be started until the cover is down.

There are also safety issues associated with the design of the cover such as the gaps around the edges, and how hard the cover closes. Can't have the cover smashing fingers when it closes.

To be safe it may need some kind of mechanism to lock the cover open before the operator can reach inside.

There are probably a dozen other issues that might also need a look. This is called a risk assessment and is supposed to be done for every machine or process

 

[tom baker]

Agree with PetersonRA. By adding an interlock on your own, you recognize it’s a safety hazard, but if done incorrectly it’s a simple lawsuit for the injured party
Is it possible to purchase a new machine that has required safety fearures and labels?

 

[TwoBlocked]

Good points about being sued. That is what insurance is for. They are also for consulting about work place safety. If the owner gives them a call they will be GLAD to give advice.

 

[mark32]

Thank you all for taking the time to respond! I like those magnetic switches scrubbin brought up, and maybe use those in conjunction with an interlock that petersonra mentioned, hmm. And Tom and petersonra made some valid points about liability. My buddy has worked for this shop for many years, I gather if this was a concern, he would've discussed that initially with me, but I will bring this to his attention.

Additionally, for petersonra, your post is both informative and as you correctly described, obnoxious. First, I've been on this site over 20 years, so I don't view (A bulk) of the members here as random folks. Regardless, even if I joined yesterday, what difference does it make, this site exists purely for the purpose of asking/discussing electrically related questions. Here, your ill-chosen reply, would suggest I came on here asking you guys how to wire a 3 way.

 

[rambojoe]

I thought the same thing... some of these guys either help newbies do their job (or worse) and help young adults who can't even spell, or will not even try a skosh to buy a code book... and then be a bit hard on someone else... its the forum for ya.

A piece of dangerous equipment is serious business so it is a fair question on your part, even if the answer is easy for some...

Just to be fair, im sending you utbe vids on 3-ways. Jk! But dont take it personally, everybody comes wrong sometimes.
But you are right though, it is what this forum is for.

Without really seeing the unit and operation, or knowing type, model and function, there is generically 1000ways to do it and only one would be right. Im suprised there isnt a simple n/o switch (or n/c depending..) on the thing to begin with.

 

[petersonra]

Aditionally, for petersonra, your post is both informative and as you correctly described, obnoxious. First, I've been on this site over 20 years, so I don't view (A bulk) of the members here as random folks. Regardless, even if I joined yesterday, what difference does it make, this site exists purely for the purpose of asking/discussing electrically related questions. Here, your ill-chosen reply, would suggest I came on here asking you guys how to wire a 3 way.

The thing is that just because part of the solution might involve things that require wiring does not mean that an electrician is especially suited to be designing retrofit safety functions. It is a completely different kind of expertise.

You could be the greatest electrician ever, but that does not mean you have any expertise in safety.

Just out of curiosity, how do you go about doing a risk assessment on such a project.

 

[jim dungar]

The thing is that just because part of the solution might involve things that require wiring does not mean that an electrician is especially suited to be designing retrofit safety functions. It is a completely different kind of expertise.

You could be the greatest electrician ever, but that does not mean you have any expertise in safety.

Just out of curiosity, how do you go about doing a risk assessment on such a project.

To build on this.

Is the goal simply to prevent the device from starting.
Does the device need to be stopped when the door is opened, while it is running?
Does the door need to be prevented from bring open until the device has stopped moving?

Let's not even get into other aspects of safety such as if the existing cover provides the appropriate center safe spacing and if emergency stop devices, including motor brake, are required.

If lawyers are already involved do not exclude them from any modifications you plan to make.

 

[drcampbell]

... Just out of curiosity, how do you go about doing a risk as sessment on such a project.

As with anything else involving health or safety, you start by asking a registered professional engineer with expertise in this sort of thing.

Another thing you can do -- certainly not the only thing -- is to design the guard so that it can't easily be removed. Put it on hinges, weld them in place, and make it more of a nuisance (or impossible) to operate the machine with the guard out of place.

 

[petersonra]

As with anything else involving health or safety, you start by asking a registered professional engineer with expertise in this sort of thing.

Another thing you can do -- certainly not the only thing -- is to design the guard so that it can't easily be removed. Put it on hinges, weld them in place, and make it more of a nuisance (or impossible) to operate the machine with the guard out of place.

A registered professional engineer may not have any expertise in this area either. But a guy certified as having such expertise probably does.

The point is there is a lot more to making this thing "safe" than just wiring a switch into the motor starter circuit.

Personally, if a customer asked for an interlock switch to be wired into the motor starter circuit to prevent the motor from starting unless the cover is closed, I don't think I would object. But once they refer to it as safety anything, I would want to go thru the process the right way.

 

[gadfly56]

Is this a home-brew device, or is there a manufacturer behind it? If the later, you might start with them to see if they offer after-market safety devices for this equipment.

 

[mark32]

Thank you all again for your time! I spoke with my buddy yesterday, and he stated he has insurance when I brought up the liability issue, which he noted had already crossed his mind. He likes the idea of the magnets, and is able to fabricate bracketry to mount them to the machine, but is unsure if there are any viable spots on the machine to do so. I think the players involved (The shop foreman and my buddy) just want to do something to the machine so that it cannot be started with the cover open, and likewise, shut off if the cover is opened while running. Lots of in-depth thoughts and observations here, I don't imagine they would involve anyone else like a certified safety engineer, lawyers, etc. But, reaching out to the manufacturer of the equipment is a great idea gadfly56. I know a number of machines in this shop are from overseas, so that may complicate things, perhaps. I'm just a bystander at this point, but we sometimes work together, which is why he asked if I had any ideas how to make this happen.

Special thanks to rambojoe and petersonra xoxo

 

[jim dungar]

Take some time and read the application literature from companies like Banner Engineering or Schneider Electric as you are looking for solutions. Yeah, some of it is a push for really advanced safety stuff like light curtains for automated processes, but they usually have something about risk assessment and concepts you might not have thought of.

I remember when magnetic key switches first became wide spread, some 25 years ago, the workers simply ordered additional 'keys' and taped them in place to bypass the stupid 'makes my job harder' interlocks

 

[petersonra]

They make a switch you can mount to the hinge. Might be easier and more out of the way.

 

[Krusscher]

Im sure most magnet switches are but make sure you get a coded magnet device so it can't be defeated with just any magnet it needs to be one that matches the device