Control Panel Power Cycle Safety / Power On/Off MCR

[L5KEdit]

Hi All,

I'm trying to find a rule in the NFPA, NEC, etc. that talks about safety with respect to power cycling a control panel. Guys, I've been designing industrial control panels for over 15 years but never had to find this rule because I've always designed panel power on/off circuits using 'good practice' putting safety first. I now work for an unusual company that has inexperienced Mechanical Engineers in 'higher positions' than EEs making controls decisions on products to save a few bucks.

For industrial control panel power I usually use a power on and power off pushbutton, which seals an Master Control Relay; the power off button breaks the seal and powers down the panel. We do this because 'it has always been done' and also we don't want the panel to power up live on a power cycle or initiate any motion without pushing a 'safety reset' or 'power on' first. Similar philosophy to clearing a hardwired E-stop condition with 'machine safety reset' using a safety relay.

We have this simple panel which plugs into 120VAC being sold into the Industrial market. It controls a Fluid spray process and I was just assigned to add features to the product and 'add to the base design'. Well, the base design was not put through a peer review process and it has one "power" button which is maintained (push on, push off). Therefore this panel could start a liquid spray process on power cycle or when powering up WITHOUT pressing any sort of buttons. Because this is the only hardwired button; it has a simple HMI but WILL come up 'barking' (spraying) under certain conditions on power up if the power button is left pressed in.

So I'm asking for help to find a standard, rule, or code that states this is unacceptable. I've been beaten down by the fact that Marketing and Mechanical Engineers "know best" in terms of product design and I'm not interested in an argument so I'd really like to find a rule...

Thank you so much for any input....

-Beaten down and discouraged Controls Engineer

 

[petersonra]

I don't have a problem with the way it works if they can show through some kind of hazard review that it does not create a hazard to humans.

Should not be especially hard to do for something like this.

I would prefer it take a hard reset to start it back up but if there is no harm involved I just do not see it as a problem.

 

[L5KEdit]

if they can show through some kind of hazard review

Thank you for your response. Yes, I agree if a Risk Analysis proves there is no danger it would be OK. The trouble is we are an OEM (Original Equipment Manufacturer) and each application and installation for this product will be different at the end user's manufacturing floor. There are all sorts of timing, regulation, and spray 'trigger' modes configurable on this product and each installation will be different, spraying different chemicals. So I'm not sure how we, as an OEM, could perform a hazard review... The company has this 'once size fits all' attitude, so my opinion is to make the product as safe as possible (well, considering there is no E-stop for this small panel) for 'all' conditions. Wouldn't the end user have to do a risk analysis once our little spray panel is integrated into their machine ? Sort of an interesting problem, isn't it ?

 

[Jraef]

I don't think you will find a code requirement that says a machine must or must not handle power cycling requirements in any certain way. What you may find is requirements for labeling and warnings indicating the fact that it will or will not behave in a certain way. Surely you have seen the labels that say something to the effect of "DANGER! Machine may start automatically without warning!"

Many of these requirements are called out for in NFPA 79, others in OSHA 29 CFR 1910, mostly in Subpart O, but both of those can sometimes be very specific to certain types of machines and if yours falls outside of those requirements it can be deemed inapplicable. Nothing beat good sound engineering practice though.

 

[petersonra]

A lot depends on exactly what it is the OP is selling. He has been very sparse with details.

If this is something sold to be integrated into someone else's machine I would probably want to take out the on/off switch as well. The machine it is part of should take care of that.

 

[L5KEdit]

He has been very sparse with details.

Thank you all for your thoughts... This product can be stand alone OR integrated into a machine. For example, spraying fluid can be triggered by a photoeye, OR the customer can choose to hardwire a 'spray trigger' signal which is basically just a permissive for our box to spray. If the customer is integrating our panel into their machine then yes they take on the safety responsibility, it would be super easy for anyone in our field to wire up this box to operate safely. What I'm worried about is the customer who plugs a photoeye into our panel... Photoeye gets flagged by a product they are spraying... Power goes down, power comes back up.... Photoeye is still flagged because conveyor requires a restart ... Our panel would immediately start spraying. I would not want to be the guy getting sprayed in the face ....

I'll dig into Subpart O of NFPA 79, OSHA 29 CFR 1910 as suggested. We might have the OSHA standard in house.

Thanks again guys... I'm thinking I'll push back on the product person and remove the maintained power switch and change it momentary 'power on' and 'power off'. I just know the guy is going to say "Do we really need to incur that cost"... We'll see how it goes.

 

[petersonra]

I'll dig into Subpart O of NFPA 79, OSHA 29 CFR 1910 as suggested. We might have the OSHA standard in house.

i don't see how something like this falls under NFPA79.

 

[Timbert]

i don't see how something like this falls under NFPA79.

NFPA 79 covers a lot of equipment. Specifically "Electrical/electronic equipment, apparatus, or system of industrial machines operating from a nominal voltage of 600 volts or less." Industrial machine is anything that is power-driven, non-portable, that is used to process material. I'm not sure why you think a fluid sprayer would not be an industrial machine (or at least part of one). Could you expand your reason?

 

[Timbert]

t has one "power" button which is maintained (push on, push off).

This could possibly violate NFPA 79 9.2.6 which states if a single push button is used it can only be used where no hazard arises. You can't guarantee that the sprayer will only spray a nice soft mist of warm water.

Yes, I agree if a Risk Analysis proves there is no danger it would be OK. The trouble is we are an OEM (Original Equipment Manufacturer) and each application and installation for this product will be different at the end user's manufacturing floor. [...] So I'm not sure how we, as an OEM, could perform a hazard review... Wouldn't the end user have to do a risk analysis once our little spray panel is integrated into their machine ?

The end user is ultimately responsible for safety under US law (so sayeth OSHA). However, that is no defense against product liability. Your company might very well win by arguing that the end user should have performed a risk analysis. How much will the lawsuit cost? What if you're found liable (even partially)? or settle out of court? How much then? Opposing counsel would love to get you on the stand to ask about this 'second button' that could have prevented a horrible disaster.

I just know the guy is going to say "Do we really need to incur that cost"... We'll see how it goes.

Buttons are cheap, lawyers not so much.

 

[petersonra]

NFPA 79 covers a lot of equipment. Specifically "Electrical/electronic equipment, apparatus, or system of industrial machines operating from a nominal voltage of 600 volts or less." Industrial machine is anything that is power-driven, non-portable, that is used to process material. I'm not sure why you think a fluid sprayer would not be an industrial machine (or at least part of one). Could you expand your reason?

If it is part of a system it is not by itself an industrial machine.

If it is standalone, it is hard to make the argument that it is an industrial machine anymore than a sump pump by itself is an industrial machine.

If there is some benefit to calling it an industrial machine for the purposes of NFPA79, feel free to do so. But it isn't.

Note carefully what the scope is.

1.1* Scope.
1.1.1 The provisions of this standard shall apply to the
electrical/electronic equipment, apparatus, or systems of industrial
machines operating from a nominal voltage of 600
volts or less, and commencing at the point of connection of
the supply to the electrical equipment of the machine.

Reading carefully, it applies to the pieces of the industrial machinery.

3.3.55 Industrial Machinery (Machine). A power-driven machine
(or a group of machines working together in a coordinated
manner), not portable by hand while working, that is
used to process material by cutting; forming; pressure; electrical,
thermal, or optical techniques; lamination; or a combination
of these processes. Machine can include associated equipment
used to transfer material or tooling, including fixtures,
to assemble/disassemble, to inspect or test, or to package.
[The associated electrical equipment, including the logic controller(
s) and associated software or logic together with the
machine actuators and sensors, are considered as part of the
industrial machine.] [70:670.2]

i see no way that a sprayer by itself meets the NFPA79 definition of an industrial machine.

Does your sprayer process material by cutting; forming; pressure; electrical, thermal, or optical techniques; lamination; or a combination of these processes? If not, than it is not an industrial machine for the purposes of NFPA79.

 

[Timbert]

Does your sprayer process material by cutting; forming; pressure; electrical, thermal, or optical techniques; lamination; or a combination of these processes? If not, than it is not an industrial machine for the purposes of NFPA79.

Thanks for the reply. I see what you are driving at. I don't know the extent of the OP's device, but I imagined it was a container with a pump and a nozzle. In which case I would argue the it does fit the definition of industrial machine. It takes material (a liquid), processes it (using pressure) into a mist. Granted this processing isn't all that useful in and of itself but does that make it less of an industrial machine. Usefulness is not part of the definition. The definition is vague enough that a argument can be made to include almost anything.

 

[petersonra]

Thanks for the reply. I see what you are driving at. I don't know the extent of the OP's device, but I imagined it was a container with a pump and a nozzle. In which case I would argue the it does fit the definition of industrial machine. It takes material (a liquid), processes it (using pressure) into a mist. Granted this processing isn't all that useful in and of itself but does that make it less of an industrial machine. Usefulness is not part of the definition. The definition is vague enough that a argument can be made to include almost anything.

I am not sure what benefit there is to the OP to stretch the definition of an industrial machine to cover a standalone sprayer other than to win an argument with co-workers.

 

[L5KEdit]

I'm going to 'show my cards'

I'm going to 'show my cards'

All,

Thank you again for your responses. I was out of town on a startup for 'real' industrial controls (ie project with multiple ControlLogix processors and panelview HMIs networked).

The trouble with this 'product' is that it can be stand alone OR integrated into a machine. Therefore I agree it IS industrial equipment. When I cornered the product person about the power switch issue he said he 'thought' there was a setting in a custom version of our gun driver firmware [din rail mounted module manufactured by AutoJet Belgium] that could prevent the machine from spraying from a power cycle. And *yes*, this product can be sold paired with a pump. But I have not heard back from the product guy. Also, he is not a controls person. I've been with this company for about 8 years and think I have been slowly falling behind in the industry and also beginning to think like a 'marketing' person which is of great concern to me both personally and professionally.

OK so now I'm going to share who I work for and more...

Below is a link to the product we are discussing. Notice how on THIS version there is NO power switch. This is the European version (we also design and manufacture our own controllers with touchscreen and a couple dozen I/O but that is another product with several product lines). They use the rotary disconnect for power on/off (220 VAC, 2 pole with ground). So we are told to 'make it like just like that for the american version', like several other countries where we do manufacturing for the local market.

http://www.spray.com/automated_systems/2008.aspx

So when I originally re-designed it I used two buttons "power on" "power off" with a MCR. No problem. Then another team (non-electrical) takes control of the product line. This happens over a time of a couple years. Then, when they need something new designed into it that they can't handle they kick it back to me. Thats when I discovered the power switch became maintained. Now I own it. Its my name on the electrical schematic, so I am liable! At least thats the way I see it. I know I can be called into a court of law if someone gets hurt, and yes, we are a big company BUT the ethics of doing something wrong in my profession is what really troubles me.

Thank you for the specifics on the rules, especially the poster who specified sections.... I will dive deeper into the NFPA.

We USED to do all sorts of custom turnkey systems, but now are only focusing on a few products.... I learned about this shift by studying our web site [I noticed that the the custom automation section of our webpage went away] and noted how many project proposals we were all in the sudden turning away. So it might be time for me to consider getting back on a manufacuring floor supporting large scale production equipment. I used to work for a fortune 50 manufacturer, and I STILL miss working on those big projects. Perhaps this is a wake up call to move on.... I'd appreciate any feedback on this paragraph as well. I just hope my company does not employ search spiders and discover what I am sharing here.... LOL

Thanks, I'll keep this thread up to date.... Hopefully sharing the product and who I work for will help see where I am coming from.

-Jason

 

[pfalcon]

Well, regardless of prior descriptions, this is advertised for control of pressure spraying of coatings, adhesives, lubricating, (and other uses). That's a pressure process not just a standalone sprayer. NFPA79 or one of its siblings will apply. It's no longer a stretch.

Combined Start and Stop Controls. A single pushbutton and other devices that alternately start and stop motion shall only be used for secondary functions where no hazardous condition arises when they are operated.

Power On/Off is a primary function. Inadvertant spraying of coatings would most likely constitute a hazardous condition. Frankly at most pressures that would be true of water spray let alone the variety of chemicals in the ad.

Understand (which it sounds like you do understand) that at industrial site that any decent safety officer will go into adrenaline shock over any device that starts processing on power up. He'll ask "What if the hood is open for troubleshooting?"

 

[L5KEdit]

Thank you!

Thank you!

Well, regardless of prior descriptions, this is advertised for control of pressure spraying of coatings, adhesives, lubricating, (and other uses). That's a pressure process not just a standalone sprayer. NFPA79 or one of its siblings will apply. It's no longer a stretch.



Power On/Off is a primary function. Inadvertant spraying of coatings would most likely constitute a hazardous condition. Frankly at most pressures that would be true of water spray let alone the variety of chemicals in the ad.

Understand (which it sounds like you do understand) that at industrial site that any decent safety officer will go into adrenaline shock over any device that starts processing on power up. He'll ask "What if the hood is open for troubleshooting?"

pfalcon,

Thank you very much for taking the time to site a specific standard and for explaining your thought process. I should have shared a link to the product immediately, so I apologize to *all* of you who took the time to help without having 100% of the information available to you.

Looks like this forum will be a major source of my 'continuing' education ....

Sincerely,
L5KEdit