Rant about Safety

[JHarris]

you have 2 guidelines to consider (there may be others)

NFPA70 - national electric code requires that all motors not within sight of the main control panel disconnect have a disconnect. see the definition in the code book "in sight from" all motors must be within 50 ft from the main control panel and be within sight of the panel disconnect.

nfpa 79 - electrical standard for industrial machinery.
this also applies.

you also may want to goto www.mikeholt.com and ask your question there. this is an electrical code forum.

regards,
james.

James,

Please note there is an exception that allows the lockable disconnect to NOT be within sight of the motor. The stipulation is that the disconnect is lockable AND the facility has a written Lock Out - Tag Out procedure.

For example, some facilities build enclosed MCC rooms. I am not saying it doesn't make sense to have a disconnecting means within sight, but in some instances it is not practical nor is it worth the extra cost.

Justin

 

[leitmotif]

Bruce

It has been commented that whoever is responsible goes to jail. In USA OSHA has no ability to send anyone to jail. Only a prosecuting attorney fed state or city can do that. The bottom line is to my knowledge there has been only one -- yes ONE -- criminal prosecution for workplace death. That was I believe in Chicago in 1980 or so in an outfit salvaging silver from film using cyanide.

OSHA is amazingly ineffective and in my opinion nearly useless. They only give a penalty. 10,000 for a life or worse yet life sentance in a cripple ward is pretty cheap and is not much incentive for management.

I believe you also said you have a separate source of control power. you need to ensure this gets locked out also. you are also required to label panels with more than one power supply.

The bad thing is that most safety people even with all that college know very little about electrical systems and motor control. That is your problem in this case. Even with a masters in industrial hygiene and safety I find that as old as it is and out of date that my Navy training as an electrician far outweighs my college education for anything to do with electrical.

Advice
1. Set up an electrician safety committee to address this problem. Your safety plans should at minimum be submitted to you for review and you have final buyoff. Better yet write em yourselves - they will make more sense.
2. Be patient with this safety guy -- he does not understand
3. Have safety guy send me airplane ticket round trip of course and I will help out.

Dan Bentler

 

[Gilbert W]

I believe you also said you have a separate source of control power. you need to ensure this gets locked out also. you are also required to label panels with more than one power supply.

Bruce,

I think Dan is right with this statement. I have seen installations where this type of inline disconnect was used. I was extremely surprised when I turned the disconnect on again that the motor started without having to push the start button. There was no control interlock sensing the disconnect was turned off to drop out the motor starter in the MCC. I don’t know how your system is designed, but it’s my guess that your safety guy is trying to avoid that possible situation.


Regards,
Gilbert

 

[leitmotif]

Bruce
what I was referring to is a separate source of control power. For example large circuit breakers at Trojan Nuc Plant control power was supplied by 125 VDC batteries. I cannot recall any instances where motor controller control power was supplied independent of the line supply right now -- maybe later on.
Oh yeah the cooling fan motors installed on large motors - often good for a surprise.

I can remember in sevaral cases
-- most commonly redundant equipment --
where interlock circuits could be hot -
something else to keep in mind.

What Gilbert is referring to is an additional disconnect near a motor which has a power supply and disonnecting means back at the MCC.
These are a mixed blessing and in my mind CANNOT be relied on as sole of LOTO.
REASON they are not designed or intended to shut on starting current and the knives inside can burn out.

Controller and main disconnect must be turned off and LOTO in my mind in this case.

Dan Bentler

 

[brucechase]

Bruce

It has been commented that whoever is responsible goes to jail. In USA OSHA has no ability to send anyone to jail. Only a prosecuting attorney fed state or city can do that.

I believe you also said you have a separate source of control power. you need to ensure this gets locked out also. you are also required to label panels with more than one power supply.

Advice
1. Set up an electrician safety committee to address this problem. Your safety plans should at minimum be submitted to you for review and you have final buyoff. Better yet write em yourselves - they will make more sense.
2. Be patient with this safety guy -- he does not understand
3. Have safety guy send me airplane ticket round trip of course and I will help out.

Dan Bentler

Bruce,

I think Dan is right with this statement.
Gilbert

Bruce

Controller and main disconnect must be turned off and LOTO in my mind in this case.

Dan Bentler

I am now real curious as to these statements. I do understand OSHA and actually, the driving force behind what I do is the need to do it right without anyone getting hurt. As for the electrical review committee, I actually teach the electrical safety course here for all electricians - I've been teaching here and local tech school for 12+ years. There really is no time for a demonstration or much other things. We installed this system over a 7 day shutdown and it had to make product the day we started. The problem was the safety man wouldn't let it start and everyone was looking at me. Working 16 hours days for several weeks tends to put my mouth ahead of my brain.

As for the other statements about control power needing to be locked out, I am curious as to why you think that. The local disconnect is a SquareD heavy-duty style with motor and current ratings at or above the connected load. It is labeled as suitable for service disconnect. I'm not sure why the control power would need to be off. I understand that opening the disconnect under load will create some arcing. Using an auxiliary mounted contact in the disconnect (which I do only on all VFDS) will not prevent the arcing when opening the disconnect (this should be the worst part of the arcing). The motor will start immediately upon closing the disconnect and that is expected and understood.

The reason the system is locked out at the disconnect is when someone has to work on the conveyor system, like replace a drive band (or replace the motor or gearbox). The other part of the system continues to run.

I've looked at our disconnects that have been used to open the motor under load hundreds (if not thousands) of times in the past 10 years and I don't see any problems with the blades. I can take pictures if you are interested in seeing what they look like. I just took out about 15 of them when I installed this new system.

Help me understand what I am missing on why you think the control power needs to be locked out.

 

[JesperMP]

I think Dan is right with this statement. I have seen installations where this type of inline disconnect was used. I was extremely surprised when I turned the disconnect on again that the motor started without having to push the start button. There was no control interlock sensing the disconnect was turned off to drop out the motor starter in the MCC. I don’t know how your system is designed, but it’s my guess that your safety guy is trying to avoid that possible situation.

This may be a problem from a proces point of view, but is irrelevant for the safety point of view. From a proces point of view, then every actuator, pump, drive etc. should have some kind of feedback into the control system. Either directly, or indirectly via for example the proces variable that is being controlled.

What Gilbert is referring to is an additional disconnect near a motor which has a power supply and disonnecting means back at the MCC.
These are a mixed blessing and in my mind CANNOT be relied on as sole of LOTO. REASON they are not designed or intended to shut on starting current and the knives inside can burn out.

That is irrelevant from a safety point of view. The only 'problem' is if the system is not designed to take an open disconnect into account, then maybe it will cost a burnt disconnect every now and then. It may also cost indirectly because an entire plant has to be shutdown in order to exchange a damaged disconnect.
I think that the problem with welding contacts only pertains to the very largest motors. And in that case I do not understand why someone would save a minimal amount of money for the auxiliary contact.

When the correct disconnect has been identified, opened, padlocked, and tagged - THEN it is allowed to start working on the machine.
If a disconnect cannot be opened because the contacts are welded in the closed position, then it is not allowed to work on the machine.

 

[PeterW]

Disconnect's should be rated to switch off under load, but not switch onto load.

The company I left recently installed a lot of equipment in the US and quite often with no feedback from contactors, we worked on older equipment as well and seeing no feedback from contactors was quite common.

I raised the question on this as I thought it was wrong and was told that with these old NEMA contactors the auxiarly often fell off and caused problems so they fitted them without and had no feedback.

I was and still am, horrified by this.

I am now shocked to hear that there is no legal comeback over here, I believe across Europe and definately in the UK you can be had for manslaughter if you do something insafe and someone dies.

I was told a story when I was on a safety assessment course some years back, about a warehouse in London. They had a problem because of the bumps in their roads, where the driver would bounce up causing the dead man switch to open and stop the truck, this annoyed them so they ended up shorting the dead man switches, this with the knowledge and support from the management.

One day when one of these trucks were being maintained, one cruched someone under the truck when it started.

At least one senior person went to jail for some time on a manslaughter charge.

The Health and Safety will go for the most senior personb they can, they will get someone if the death was due to unsafe practice.




Removing and locking off the source of motive power is the only safe method.

 

[leitmotif]

I am now real curious as to these statements. I do understand OSHA and actually, the driving force behind what I do is the need to do it right without anyone getting hurt.

REPLY I think your installation is a good one. I really like the local disconnects.

As for the electrical review committee, I actually teach the electrical safety course here for all electricians - I've been teaching here and local tech school for 12+ years. There really is no time for a demonstration or much other things. We installed this system over a 7 day shutdown and it had to make product the day we started. The problem was the safety man wouldn't let it start and everyone was looking at me. Working 16 hours days for several weeks tends to put my mouth ahead of my brain.
REPLY Well it is up to him to prove you wrong. I get a little tired of Safety guys who do not know anything and will not allow something to run because of their ignorance. I did not know everything about everything but the good engineers were able to explain to me and get me to understand what they were doing so I felt right about sign off.


As for the other statements about control power needing to be locked out, I am curious as to why you think that.
REPLY I believe you said control power was fed from somewhere else and was independent of motor controlller main power supply - for instance it could be 125 VDC.
Last place I worked they used 440 for a relay control power because they were too lazy or in too much of a rush to do it right - and that was a "professional" contractor installation.

I think if you were in a cabinet with energized 125 VDC or whatever (and NOT low volt ie 24) you would want it turned off.
The local disconnect is a SquareD heavy-duty style with motor and current ratings at or above the connected load. It is labeled as suitable for service disconnect. I'm not sure why the control power would need to be off. I understand that opening the disconnect under load will create some arcing. Using an auxiliary mounted contact in the disconnect (which I do only on all VFDS) will not prevent the arcing when opening the disconnect (this should be the worst part of the arcing). The motor will start immediately upon closing the disconnect and that is expected and understood.
REPLY These local disconnects are a newfangled luxury to me - in most places I worked they did not exist. But I sure like em.

The reason the system is locked out at the disconnect is when someone has to work on the conveyor system, like replace a drive band (or replace the motor or gearbox). The other part of the system continues to run.
REPLY I would always have the local disconnect locked out.

I've looked at our disconnects that have been used to open the motor under load hundreds (if not thousands) of times in the past 10 years and I don't see any problems with the blades. I can take pictures if you are interested in seeing what they look like. I just took out about 15 of them when I installed this new system.
REPLY I dont like using knife type disconnects to start motors. In part that is because I work on a lot of old stuff and in some cases undersized. Maybe you can get away with it with new stuff and on conveyers with only two or so HP motors but I think on larger equipment it would be better to use the starter which is designed for starting current.

Help me understand what I am missing on why you think the control power needs to be locked out.
REPLY discussed above.

Dan Bentler

 

[russrmartin]

Common battle

Bruce,

I don't know what your employer situation is, but if I were you, I would stick to my guns. The application you described is very common, and has been discussed and I am sure you are well aware, there are codes and standards that apply perfectly. It sounds to me like you've done everything right. I would explain that you will refuse to accept any responsibility for any LOTO plan that does not require the locking and tagging of the local disconnect when servicing any motor. If they still want to go with locking out the panel and not the local disconnects, give OSHA a call, refer specifically to the installation, and request their immediate investigation. The referral is anonymous, and there is no way your safety person's command of respect from management will trump an OSHA verdict. Basically, you can just have OSHA come in and win the battle for you. That's my advise. BTW, I feel bad for you, because it sounds like you have the worst kind of safety personnel possible, the kind that don't understand the risks, but think that they do. Tough situation, and it's bound to reoccur until they become competent.

Russ

 

[James Mcquade]

thanks for your remarks in regards to my posting.

my point is this, the main control panel is 500 ft away, you are 30 ft in the air, the plant is running and noisey. some smart know it all supervisor is tired of waiting for the line to get fixed and cuts the lock off the enclosure, starts the line and you are now hung up in the machinery. you yell at the top of your lungs and someone finally hears you. they hit the e-stop and the drive keeps going because the vfd controller is not wired into a motor contactor and the drive has shorted out. in the meantime, your arm is now swiss cheese.

don't laugh at what i'm saying. it happened several years ago for a company i worked for. that's the reason for wanting disconnect at motors.

regards,
james

 

[leitmotif]

thanks for your remarks in regards to my posting.

my point is this, the main control panel is 500 ft away, you are 30 ft in the air, the plant is running and noisey. some smart know it all supervisor is tired of waiting for the line to get fixed and cuts the lock off the enclosure, starts the line and you are now hung up in the machinery. you yell at the top of your lungs and someone finally hears you. they hit the e-stop and the drive keeps going because the vfd controller is not wired into a motor contactor and the drive has shorted out. in the meantime, your arm is now swiss cheese.

don't laugh at what i'm saying. it happened several years ago for a company i worked for. that's the reason for wanting disconnect at motors.

regards, james

I have had my lock cut off when I was not there just to satisfy the Production God. If it had happened while I was working I would walk out go home (mostly to keep me from beating him severely with a piece of pipe) and call the cops and have charges filed right then and there. I would not waste my time with state safety or OSHA - this is clearly an assault.

If I worked at that place I would be placing shorts and a ground on the disconnect output. That saved my life at Trojan. Blew the breaker right out of the MCC. County Sheriff and State Patrol did not find the guy who shut the breaker on me but not for lack of trying because they were nearly as ****ed off as me.

I maintain that I get to use any means I want to ensure I go home at the end of the day in one big piece. I think my 2nd Amendment rights allow me to defend myself from workpace idiots. If the Production God does not like it he can go see the complaint department.

Dan Bentler