Industrial strength "clapper" needed 3

[Floyvin]

I am needing to free up a man standing next to an e-stop watching a crew working inside a sanitary spray dryer that measures 25'W x 50'L x 14'H.

I would like to free up the "watcher" with a "clapper" so if any employee is in trouble he can clap (or scream if so motivated). The "clapper" only needs to make or break a relay that we will interlock with a motor starter.

The "danger is a very slow moving bar that traverses from end to end along the floor that "sweeps" powder out of the dryer.

The crew can easily step over these bars while sweeping down the walls and ceiling, but we are afraid one will manage to get hung up in it if we don't provide a means of killing it instantly. I can handle the basic motor control end of it, but where is my "clapper" device?

Any suggestions? My suppliers all tell me it doesn't exist (although I've seen them on TV built into a nightlight)

 

[IRstuff]

Speaking from personal experience, that's a horrid concept. I've done ONE dangerous thing on the job by myself and will NEVER repeat without a backup person. I got extremely lucky, but...

There are any number of possible failures in that system, particularly since it ought to be seldomly used.

The worker may faint or lose control of the "clapper" and be screwed.

TTFN

 

[bigbillnky]

It sure sounds like this is a "confined space" as defined by OSHA standards if you are in the USA. I would strongly advise you to research the appropriate standards for the practical safeguarding of workers in this space. The only clapping I would recommend is the clapping of the workers hands in applause to being properly protected.

Bigbillnky,C.E.F.....(Chief Electrical Flunky)

 

[Murphy625]

Why not just put the estop on an extension cord and bring it in with you?

 

[jraef]

Floyvin,
I think you will find that the majority of people in this forum are going to think this is a bad idea. Safety is not a place to get cheap, or rely upon a device not designed as a safety cutoff. Most safety regulatory agencies, like OSHA in the US, have very specific rules as to how personnel are to be protected from pinching, grabbing and obstructive exit hazzards. If the observer / E-Stop button was designed in, it was probably because that was the acceptable compromise already. You should not consider changing that without thorough consultation with safety experts. The details of a workable device are somewhat irrelevent until that issue is resolved.

IMHO, even if you made such a unit AND made it sensitive enough to be a reliable safety device, you would be at the same time plagued by nuisance trips.

There may still be viable alternatives however. Some types of pinch / grab hazzards such as that can be protected with cable pull switches, perhaps running around the inside perimeter of the enclosed space at a low enough height as to be accessable by a man laying down and stuck. Again, you would need to check this out with the proper agency first.


"Venditori de oleum-vipera non vigere excordis populi"

 

[IRstuff]

This particular example makes some gross assumptions about the ability of the person in trouble to actually execute the required actions to stop the machinery. This is a classic single-point fail model.

However, real-life is rife with multiple fail scenarios. That's why military helicopters are not allowed to fly with a single pilot at night. Situational awareness is greatly diminished with the workload is high. A second set of eyes is mandatory in those situations.

TTFN

 

[Floyvin]

Thank you Murphy625 for submitting an actual suggestion. (Now if I could just loose the cord . . .)

The term "crew" was meant to imply that there were two or more people working inside the room.

The spray dryer the crew has to regularly sweep out is essentially a large stainless steel room. It has a couple large doors and is well ventilated. It is not a confined space.

I am not trying to get "cheap". I just want a means of giving every crew member the ability to kill the sweep bar from inside without restricting them to corded e-stops or pull cords actuating an e-stop.

The existing "watcher" system can break down if, for example, one of the crew convinces the "watcher" to fetch him a drink of water. (You don't think that could happen . . .? More e-stops is more better).

Perhaps I should have entitled this "Where can I buy a wireless e-stop"?

 

[OperaHouse]

Maybe something that that detected someone screaming in pain would be more appropriate than clapping!

 

[eglaude]

Confined space, exposed equipment moving while people are working, dust, reduced visability, etc. That's the perfect environment for a wireless gadget. Make sure that you buy good batteries and since this device will be dragging on the floor while the workers are cleaning this dryer, you might want to get it in a bright color.
I think that QVC might have something.
Do the right thing, the only thing, safety first. Employees come to work employees go home to their families at night.

 

[Floyvin]

All right - I give !

The watcher & conventional e-stop stays !

(You guys are a tough crowd)

 

[jraef]

OK, now that we have your complete capitulation , lets get down to alternatives. FYI, your first post indicated that you wanted to replace the safety observer, not add to the safety options. That is something you can probably do, as an adjunct function to the primary safety procedure (as long as everyone understands that).

I remembered someone did invent one a while ago, but I couldn't find any more about it other than this.

http://www.abc.net.au/newinventors/txt/s1242434.htm

Radio control is probably bettrer for this anyway, and since it is already in use in a lot of places, safety authorities would be more likely to be accepting of it. Have the cleaners carry a belt-clip transmitter that can ALSO activate the E-stop in case the observer is too slow to act etc. check these out:

http://www.bwieagle.com/air-eagle lt.htm

http://www.remtron.com/pdf/estop1.pdf

"Venditori de oleum-vipera non vigere excordis populi"

 

[edison123]

How about those portable wireless calling bells ? I use them at remote sites where a telephone (even an internal) is not easy to get and I need to call up my people. May be you could parallel an e-stop (very low voltage) to the bell so that the watcher is also alerted. Of course, the watcher stays.

 

[tinfoil]

Not knowing how these radio things operate, I would ensure that the LOSS of radio signal would itself activate the E-stop.

That is, a radio signal should be continuously received to allow operations.

The stopping of the radio signal should be the trigger to stop the process.

That way, if the radio transmitter were to malfunction, or the observer moves out of range (goes for water?), or the observer presses the button (releases the button if you make it a dead-man switch, which would be even better)

 

[IRstuff]

"large metal drum"

You might want to get a demo first, in case there's too much attenuation of the RF signal from the room.

Additionally, I'd be leary of trying a signal loss activation, unless I could be sure of EXTREMELY low false alarm rates. Anything that triggers more than maybe once every 20 to 100 uses will be a nuisance and the crew will try to figure out ways of circumventing, such as leaving the darn thing outside, where it won't do any good.

Also, signal loss detection means that you cannot have more than one activator, unless you're running multiple frequencies or running encoded signals, which increase the complexity of the system.

TTFN

 

[sasice]

One question, why does the device have to run whilst the men are in there?

 

[skiier]

any e-stop than requires the interface of "software" or anything other than a hardwired button is extremely dangerous. I am not sure about radio control but I am sure that whatever device you use should be "redundant". Radio controls are out of the range of my experience but I am quite sure that you will have substantial trouble in trying to introduce such a system.
cutting corners will only get people hurt.