Manufacturing Safety E-stop Challenge

I'd worry that you might discourage people from using an e-stop in borderline situations. Would a beacon be insufficient for your needs?

check out Federal Signal. I know they have a audible alarm that can use a pre-recorded message. You may have to contact a distributor for the exact part number. It could be triggered off a normally closed contact on the safety relay that your e-stops are hard-wired to and use the monitoring contacts that each e-stop PB has to select the message; assuming you have safety circuits that are of recent standards.

Try Mircom.

www.mircom.com, like Federal Signals their equipment is just as superior yet substantially cheaper.

Wheelock and Whelen both have some good equipment, but it can get pricey. But then again you get what you pay for!

I DONT KNOW ABOUT HAD WIREING IT IN. WHAT WE DID WAS PROGRAM THROUGH OUR P.L.C. THAT WHEN A E-STOP IS PULLED IT SOUNDS THE NEAREST START UP HORN IN THE AREA. WE EVEN HAVE IT PROGRAMED FOR A DIFFERENT SEQUENCE WHEN THIS HAPPENS.

You could wire a system that taps from the E stop switch or light. Set a relay that powers a signal to your phone system or switchboard for PA. Each machine will need to be wired individually and connected to a seperate channel. When the E-stop is pressed a signal is sent out to the relay. The relay closes a seperate circuit that could trigger a siren, (each machine could use a different tone)or, each channel could have a different message that plays on the trigger. Depending on how many machines, you may have to employ a PLC to execute the PA.

A while back, I came across some e-stop switches that were addressable individually.Can't remember the vendors, but I am sure there are more than one.Using these would save a lot of wiring and simplify your circuitry.

Are you sure you mean "E STOP" switch, not "INTERLOCK" switch? (such as door open).

Some equipment applies either friction or dynamic braking during an "Emergency" stop, versus a normal coast-down for interlock open or a programmed stop request.

Some machines are not meant to execute an "Emergency" stop on a frequent basis.

Perhaps this is why they want them monitored?

If you can clairfy your situation, perhaps I can be more helpful.

Good point, more background on situation. We compound rubber, the mixer, picture a bread maker, is located on the second floor and this takes raw components and mixes them. It then drops through the floor onto a mill, picture two huge, heated rolling pins spinning in opposite directions at slow speeds. These rollers are very close, inches apart and help disperse the polymers in the compound. It's then transfered to a second mill where the same applies. If anyone happens to get caught in the mills, this e-stop would shut down the mixer not allowing anymore batches to drop onto the mill. This e-stop would be tripped by a second operator as there is one at each mill, the mill would shut down due to safety interlocks built into the machine. We've thought about tying the two together but the interlocks are frequently tripped due to the nature of what we're doing. (leaning over to grab rubber as it sticks to the rolls) What I'm hearing is that the easiest way to do this may be a stand alone system with a simple audible alarm. Tying into the PA system or PLC sounds outside of our realm internally.

Thanks for the input!

It sounds to me like a very dangerous situation, having a person grab the sticky rubber from a moving roller, and I am sure it violates some OSHA rules regarding lockout/tagout proceedures.Relying on a second person to activate the E-Stop is also dangerous as well.

Perhaps a doctor blade on the rollers would be safer and more effective.I realize it has probably " Always been done that way" and changing a proceedure will not be easy. an "Exclusion Zone" should be incorporated into the system to detect if anything larger than the normal feed material enters it.

I am glad you posted this question, because it may save a life.By posting this question, you have made others aware of a known hazardous condition, and now the company is legally obligated to correct it, if it is as you described.

I would not want to be the AHJ over safety in that plant.

Or perhaps I misunderstood the conditions?

This situation is fairly common in the rubber industry. There are "belly bars" that the guys must lean over to grab the rubber and if caught, those bars will shut down the mill and stop the rotation within X amount of inches. The mills are moving very slow, the rolling pins are 3-4 ft in diameter and move at roughly 10rpm. In order to remove/package the rubber, it is cut into slits which are manually pulled off the roll and onto a conveyor. You are absolutely correct in the fact that if they bypass these bars, which they do, and if they get stuck, death will be very slow and very hot. I do appreciate the concern though and assure you that our safety team is working on correcting any poor practices that may have been utilized in the past. If you are unfamiliar with rubber processing and just happen to find yourself in southern WI for some odd reason, I'd be happy to give you a tour.

Thank you to everyone for there comments.

Glad you clarified your plan. A very loud audible warning is a good idea for rubber mills, and even your original plan of audibly identifying the machine itself might not be overkill. I don't envy your position. I worked in the tire industry for about 20 years, and have spent loads of time around mixers and mills. People get dragged into mills too often, and the result is too often death. Any money you spend on being certain your mill rescue team is really top notch and able to respond instantly is money well spent. I think frequent mill rescue drills in which the participants really go through all the steps, including spreading the rollers, is very valuable. Sometimes, problems are uncovered in these drills that point out the need for repair of items that would otherwise impede a rescue's progress (jammed gap adjust screws, etc.). Likewise, having multiple rescue kits, one very close to each mill, is a good idea, in my opinion. Mill accidents are grizzly events, and can be extremely expensive in many ways beyond the obvious. Loss of productivity throughout the plant, low worker morale, OSHA fines, lawsuits …

You mentioned people reaching into the mill and tripping interlocks. You probably have rules about using hooks, etc. rather than hands to pull on rubber. But where do you draw the line between what can be done with hands and what is too close to the bite of the mill? I've seen a lot of variation in interpretation; it is an area where you are better to be conservative, in my opinion.

There are areas in a typical tire plant that produce more injuries than the mills, but I can't think of another area that has higher potential for really grizzly stuff. (Although a close second might be the trenches below curing presses in old, poorly maintained plants, where people have been turned into soup as a result of bursting superheated water pipes.)

OK. Enough preaching.

Wow! You really know how to ruin a guy's appetite.