Control.com - Nerds in Control

We have a problem with operators using the emergency stop circuits to power down a line rather than doing the "right thing" and going through the sequence of pressing the individual stop PB. is there any international standards which states that emergency stop push button should be placed outside panel?

Why is it the "right" thing to use the stop pushbuttons in lieu of the e-stop? Does it harm anything to stop it with the e-stop?

Most places after the machine is stopped one would trip the estop anyway.

--
Bob

> We have a problem with operators using the emergency stop circuits to power
> down a line rather than doing the "right thing" and going through the sequence of
> pressing the individual stop PB.

Hmmmmm. The international standard for operators not following plant operating procedures and taking unauthorized shortcuts is to sack them.

Sounds more like the facility does not have any SOPs (Standard Operating Procedures) which dictate the processes and procedures to be followed to operate equipment at the plant. If there are no SOPs or similar documents/training, then it's pretty difficult to hold people accountable and expect them to follow "proper" operating processes and procedures for the equipment at the plant.

What say you about the existence of such documents (SOPS) and/or operator training? Do the proper documents exist for operators to refer to and to follow to operate the plant/equipment? Have the operators been properly trained to operate the equipment?

So, is the problem the operators or the lack of documentation/training for plant/equipment operation?

This is a very common complaint of technicians who have to deal with operators that have little or no training and no documentation (SOPs) to use to operate a plant or the equipment in a plant. To solve a problem like this requires commitment from operations management/supervision to produce proper documentation and to train the operators in the operation of the plant/equipment using the documentation, and then to hold the operators accountable for not following established processes and procedures.

> Hmmmmm. The international standard for operators not following plant operating
> procedures and taking unauthorized shortcuts is to sack them.

Unfortunately this is not possible in all countries.

Collective bargaining agreements and labour laws were (and still are) necessary in some parts of the world. There are many unscrupulous owners and their minions who ignore common sense and diplomacy when dealing with insubordinate employees, which has led to the proliferation of collective bargaining agreements and labour laws in many places in the world for good reason.

In these places, it's found that SOPs (Standard Operating Procedures) are necessary, and then once the personnel has been properly trained in the operation of the equipment per the procedures/documents that it's much easier to document violations of SOPs and documents, making it much easier to discipline, or even sack, the repeat offender(s).

Unless, of course, the FBI system is also in place at the plant.

Yes, E-Stops have to be readily accessible (what if there's an emergency?).

I'm sure the operators don't WANT to ruin product or leave the machine into an undesirable state, so just talk to them informally and explaining the reasons you don't want the E-Stop used as an auxiliary stop. Don't forget to ask them why they do it that way. Maybe the proper stop button is in a location inconvenient for them, and you can fix this just by adding some more stop buttons at more numerous and/or more convenient locations.

If that approach doesn't work, you may need to develop a written shutdown procedure, have some operator training in it, and an escalating list of consequences for operators who repeatedly refuse to follow the policy.

Ezer... start with:

http://control.com/thread/950636217

Regards, Phil Corso

Ezer... further to my earlier response, there is a rather simple logic-circuit to implement the correct shutdown sequence regardless of the operator's contrary procedure?

Contact me if you are interested!

Regards, Phil Corso

If you want the operators to do something, make it the easiest thing for them to do. It seems like hitting E-stop must be easier for them than pressing a "sequence" of multiple pushbuttons. Give them ONE "Line Stop" pushbutton and I'll bet they'll have no trouble using it.

-James Ingraham
Sage Automation, Inc.

I am just going to be blunt here. They are there for an emergency, therefor hiding them would be STUPID.....You have a management problem.....fix the real issue.

Dave Ferguson
Control Systems Engineer

In my experience if the operator is doing something wrong (or shortcut) like this it is because they don't know how to do it, or the procedure is too complex for them to remember or to do it in a timely fashion. I suspect your regular stop procedure is too complicated. Unless there is some kind of intelligent human interaction *needed* to stop the machine just have a stop button and program the shutdown sequence as mentioned earlier.

KEJR

The ESTOP must of course be easily reached. How about a nice shrill EMERGENCY horn that tells the world there has been Emergency Stop hit, this is serious, call out the medics?

I think all the talk about this is silly. Most times in a properly designed system, hitting the estop is going to hurt nothing. If the system is so poorly designed or so unusual that an estop trip harms the equipment or product, then worry about it. If it is just bad design fix the design and stop screwing with the operators.

The reality is that no one should ever have to use the estop to shut the process down in an emergency anyway. If they do, it is because of poor design that did not prevent or detect some out of the ordinary condition that caused the problem in the first place.

People like to talk about someone getting a coat caught in a machine and being dragged. That can never happen in a properly designed machine. if there is someplace an operator can be grabbed and dragged into the machine, that flaw in the machine needs to be dealt with. And adding estop buttons is not the answer. Maybe a safety light curtain is an answer, but not an estop.

--
Bob

Silly! Boy, talk about throwing fuel on the fire.

Talks about E-Stops are NEVER SILLY! These issues have to be dealt with to the satisfaction of everyone involved: Operators, Owners, OSHA, Designers, Manufacturers, etc.

Emergencies are by definition emergencies that are frequently unexpected and cannot necessarily be dealt with through 'proper programming'.

Within our industry, a hydraulic leak that is spraying fluid everywhere is constituted an emergency, but is undetectable by the equipment in enough time to react to it. ESD buttons will always be needed.

Please do not cloud the issue by even suggesting that an Emergency Shutdown button is not needed.

Who suggested they were unnecessary? I don't recall anyone suggesting that.

IMO, a run of the mill leak is not an emergency, but it is a good example of something unusual that might happen that it would be a good thing to trip the estop for.

The point about proper design was that if there is something you know is a problem, you need to deal with that problem and not rely solely on the estop to cover you.

BTW, if hydraulic leaks are a common problem on your equipment would it not make sense to fix that problem rather than relying on the estop?

--
Bob

> I think all the talk about this is silly. Most times in a properly designed
> system, hitting the estop is going to hurt nothing.

Sorry, but this isn't correct. An EStop immediately removes power from moving parts of the machine. If you have a "long" process - say extruding plastic, making paper, baking bread - the machine stops with product still inside it.

Using E-Stops can indeed be seriously detrimental to the machinery in some cases.

Apparently in this particular case, the operators are not aware that using the EStop can cause a problem (or maybe on this occasion it doesn't). As suggested by others there area number of ways to deal with this ...

- Flashing Lights and sirens make it obvious when someone hits an e-stop
- Training and potential disciplinary procedures.
- An easier to use Normal Shutdown Procedure.

Every country has slightly different regulations on how and where EStop buttons are placed - But the basic premise is they must be Obvious, Easy to reach and Always work. So the solution to this particular problem is never going to be "move the Estops" or "make them harder to use"

Rob
www[.]lymac.co.nz

> We have a problem with operators using the emergency stop circuits to power
> down a line rather than doing the "right thing" and going through the sequence of
> pressing the individual stop PB. is there any international standards which
> states that emergency stop push button should be placed outside panel?

E stop are designed to be use during emergency condition and should not be used under normal operating procedure this is very obvious. I suggest you should make a control circuit which is having one push button and will sequentially stop each and every equipment in proper order based on your requirement.

EZER... I suggest you contact Allen-Bradley (ABRockwell) for their 2011 document covering Emergency Stop Devices. Following is their conclusion:

"There are many global standards that govern emergency stop design and installation. And while there are some discrepancies, the global standards organizations are quickly moving to more uniform standards. This document briefly mentions some applicable standards from the US and Europe, but it is not all-inclusive. The standards mentioned are readily available and provide a detailed description. It is the responsibility of the designer and installer to know the applicable standards, safety requirements, laws, codes, and regulations."

Regards, Phil Corso

Good Luck with that. I have the same issue here. It is material handling equipment, conveyors and sorters. we have over 100 estops, not all tied into the hmi software. We spend at least one hour per shift E stop hunting. It all goes back to the people working on the line and supervision. It is easier to pull an estop then walk 20 feet and press a stop button.

One fix - make the Estop a lockout so they have to walk to a central location and get the key to restart.

If that doesn't work, invent a "Please Explain" form to be completed each time.

I completely disagree with Bruce Durdle's suggestion: make the Estop a lockout so they have to walk to a central location and get the key to restart.

Don't ever do ANYTHING to discourage use of the E-Stop. If hitting E-Stop is a big deal, they won't hit it. They may even start to circumvent automatic E-Stop devices like mats, light curtains, or gate switches just to avoid the hassle. If someone sneezes and it startles you, your reaction should be HIT THE E-STOP FIRST, ASK QUESTIONS LATER.

Granted, there are some processes where hitting E-Stop really is a big deal, and recovery is a nightmare. In that case, you've ALREADY got the disincentive, and there's no reason to add the hassle of the key switch.

-James Ingraham
Sage Automation, Inc.

James -

Fair comment - but I've seen some strange things in my time - would you believe an electrical supervisor who preferred to open a 3.3 kV MCC cubicle and use the trip button on the breaker housing rather than use the "open" button on the panel? Took us an age to retrain operators that that wasn't the right procedure once he left.

I think, like anything else, E-stop locations and procedures depend on the exact situation. My background is petrochemical/process control and it was common practice on at least one site to use a lockout/key reset. But an e-stop was a big deal - at least 24 hours down-time and a few thousand hours off the life of equipment because of thermal stresses. Any e-stop action (or other plant trip) usually resulted in a bit of an inquest. Key-switch was very useful in locating which of the many switches had activated - as much as insurance for fault-finding as anything else. It also confirmed that there wasn't a transient process condition that had escaped the relatively crude SEM system we had.

The best solution is to make it very easy to do the right thing in the circumstances - like locating a fire alarm call-button right alongside the exit door rather than in the middle of the stack of flammable material. The same sort of mindset as making sure that any essential routine maintenance on running plant can be done without using overrides or jumpers to get around protection. This means getting alongside operators and trying to look at the real problems they have to deal with and sorting out those issues, rather than just assuming they are all prats without a clue. Unfortunately, a lot of designers focus on the hardware and software and totally overlook the wet-ware.

Cheers,
Bruce

I worked on a system where the operators would hit the e-stop as they knew it would take 45 mins to get the line running again meaning they would get an extra tea-break. They installed lock-out switches but the operators discovered that if they gently pressed the push-button it would activate the e-stop but wouldn't lock-out the device so it didn't prevent the problem. In the end we replaced all the e-stop cabling with additional cores to send a digital input back to the PLC identifying which button had been activated and shift reports would state who was working in that area at that time. Funnily enough, it stopped the problem immediately.

Also, I have worked on many systems where problems were caused from shutting down via E-Stop instead of system stop. In many cases some improvements could be made by simple software/hardware changes but sometimes on larger existing systems this wasn't always feasible. Also I have to agree that in my opinion the e-stop should not be used unless it is an emergency condition.