Emergency Stop required?

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Girl Engineer

Girl Engineer

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Portland, OR
I am installing a new controller for 2 100hp motors that are mounted on a winch (direct coupled). When the maintenance guys are winding the winch, they will run the winch from a pendant (similar to a crane pendant control) with a speed pot, "jog up" and "jog down". There is a emergency stop on the controller/breaker cabinet within 20' and line of sight of the winch. The pendant cord will be 25' long. Is there a requirement for an emergency stop on the pendant? This was brought up during a project meeting. I have checked Articles 430.102, 610 and 670.4(B) and have no idea where this is coming from. Does anyone else know anything about this?
 
I cannot answer your question as citing any requirement which would mandate an e-stop, but----If ever there were a situation where one would be a pretty darn good idea, this would be one of them. Even the most basic risk analysis of this machine would call for measures to protect the workers from harm in the event of various failures. Without at least a control reliable method of stopping these hoists, there is a pretty fair chance that some day a button or contactor will stick or weld, the pendant cord becoming damaged/worn and creating an unintentional run signal. Putting an e-stop on something does not make it safe and is no substitute for a thorough risk analysis which could result in several risk reduction steps not related to the controls aspect.
 
It is an engineering judgment call, on where to place E-Stops. You are required to design safe machinery for the operators. It sounds like a very good Idea to have an estop on the pendant.
 
Are emergency stop buttons ever required when the equipment is operated by a "constant attention" (jog) button?
 
Installed TWO 15 ton rail cranes in July. No e-stops on the pendants but OSHA required an E-STOP and sign 1/2 way betweem the ends of the track even though the panel was within sight at the end of the track.
 
Well I hate to disagree with these fine gentlemen, but though an E-stop is never a bad idea, I don't think one is necessary with a disconnect 20' away and only momentary switches to as controls. I don't see it covered by the NEC either.;)
 
Adopt NFPA79

Adopt NFPA79

Although the NEC is a great document it does not cover industrial machinery. This despite the fact it has a section "Article 670 Industrial Machinery". That article is highly incomplete and does not truly address the additional problems.

Since many (read: most) OSHA inspectors are unfamiliar with the industrial environment, they tend to wing it a great deal. I suggest your facility should adopt a fine publication by a well respected organization that publishes many fine books - NFPA79 "Electrical Standard for Industrial Machinery". Most of your answers can be found easily in this <100 page industrial standard. For example:

NFPA79: 2007: 10.7.1.2 Stop or emergency stop pushbuttons shall be located at each operator control station and at other locations where emergency stop is required.
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The below quote is not actually incomplete. It's the start of a section. I include it to emphasis that the pendant is considered an operator control station.

NFPA79: 2007: 10.1.5 Portable and Pendant Control Stations.
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So although the NEC is vague about the need; the NFPA79 clearly addresses your question by saying you must install the Estop on the pendant.
 
"e-stop" can be found using your favorite search engine, both NFPA79: 2007
and OSHA come up a lot.

From what I've read;

This is a total dead stop that has to be reset from another station, it can't be used as a jogging or as a braking means, except the emergency aspect of the button itself. There should not be any button function on the pendant or any potential once it's used!
 
These are very good references, I really appreciate the input. This is definately what I was looking for.

So this leads into the thought that was initially going through my head - Why do cranes and overhead doors that have momentary controls not have a emergency stop? Those controls are used much more often and have a larger chance for injury. Are the installations I have seen grandfathered in or just bad practice?
 
Girl Engineer said:
These are very good references, I really appreciate the input. This is definately what I was looking for.

So this leads into the thought that was initially going through my head - Why do cranes and overhead doors that have momentary controls not have a emergency stop? Those controls are used much more often and have a larger chance for injury. Are the installations I have seen grandfathered in or just bad practice?
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Steve's comment aside, I don't think I have even seen a system with constant attention (momentary) buttons that had an emergency stop at the location of the constant attention buttons. Given that the control buttons for cranes and overhead doors are often supplied by the manufacturer of the crane or door, there must not be a code or OSHA rule that requires the e-stop.
 
don_resqcapt19 said:
I don't think I have even seen a system with constant attention (momentary) buttons that had an emergency stop at the location of the constant attention buttons. Given that the control buttons for cranes and overhead doors are often supplied by the manufacturer of the crane or door, there must not be a code or OSHA rule that requires the e-stop.
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I agree it isn't common. Most system I see like this don't have an E-Stop. I have seen several lawsuits, injuries, and near misses. Standards have changed in the US just in the last couple years. It isn't lead by OSHA, but by liability. It up to the designer to design a safe system. Controls do and will fail. 99% of the time it may not cause an injury. Times are changing for machine safety standards.
 
Girl Engineer said:
These are very good references, I really appreciate the input. This is definately what I was looking for.

So this leads into the thought that was initially going through my head - Why do cranes and overhead doors that have momentary controls not have a emergency stop? Those controls are used much more often and have a larger chance for injury. Are the installations I have seen grandfathered in or just bad practice?
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A little of both. The NFPA79 is not required by law therefore Estops at all control stations are not mandatory. Just good practice. I have enough momentary controls at my facility to have seen several fail on.

Remember that the disconnecting means can be used as the Estop also. Location and marking are important.
 
dbuckley said:
Certainly in Europe there would always be an e-stop button on the pendant.

Control systems do fail...
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Something like this. In this case, the EM stop is is on the end of the pendant. Once operated, the button latches in and requires a key release.
This is quite a typical arrangement for much industrial electrical machinery controls.
 
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