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 Post subject: PPE for plugging in/unplugging 480-volt reefer units?
PostPosted: Tue Jan 30, 2018 11:43 am 
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Hello! I work at a cold storage warehouse where I am working on developing a documented training program for my coworkers who plug in and unplug reefer units on shipping containers to/from 480-volt outlets, and I need some help doing a JHA. I'll try to make this quick. :D

A quick overview of our current SOP:
(1) we tell employees to don their PPE (right now that consists of Class 2 rubber insulating gloves with leather protector gloves);
(2) make sure that both power supplies are shut off;
(3) remove the cap covering the outlet;
(4) inspect the plug, power cord, and outlet to ensure they are all clean, dry, and undamaged;
(5) plug the connector from the shipping container into the outlet until the locking device on the cord is secured to the outlet;
(6) turn on the power supply to the outlet; and
(7) turn on the reefer unit.
(Disconnecting is basically that process in reverse.)

The problems that we have observed, include:
(1) reefer units get unplugged without shutting off the power to the outlet first (this gets discovered when somebody else tries to plug in a different unit and finds the outlet is already turned on);
(2) the outlet caps are not always being put back in place after disconnection (outlets are all outside and uncovered);
(3) cotton gloves are sometimes used instead of the interior and exterior gloves that have been provided; and
(4) employees sometimes only put the interior and exterior gloves on one hand.

Also, I am concerned that we have not been inspecting or testing the rubber insulating gloves, even though we have a glove inflator kit. It seems to me that if we are going to issue the gloves, we need to comply with the inspection and testing requirements. I don’t want to give anyone the illusion that they are protected by gloves that may be damaged and therefore useless.

Before we implement new procedures and do any training, we want to be sure of what is necessary. In theory, employees will only be touching equipment after confirming that the power indicator is in the off position, so they should not need protection. However, there is a chance that the outlet box may be live when it does not appear to be because of reported/unreported damage from a truck backing into the loading dock. With all that in mind, do we do need to require interior and exterior gloves? If so, we need to comply with inspection and testing requirements, correct?

Is there anything else that they need to wear? It has been suggested that they might need to wear a 100 cal suit.

What about requiring that employees test the outlet boxes to confirm that they are not live, despite what the power indicators may say, before touching them?

Thank you in advance for your feedback. I greatly appreciate your time and expertise. It is important to me that we keep our employees safe, but the information that I have found online thus far has not provided the definitive answers that I need in order to justify to management making changes to our current policies, procedures, and PPE purchases.


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 Post subject: Re: PPE for plugging in/unplugging 480-volt reefer units?
PostPosted: Wed Jan 31, 2018 4:47 pm 
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Posts: 442
My first thought is that you need equipment that mechanically prevents plugging/unplugging when on. Here's a three pole 30 A device.


Last edited by wbd on Thu Feb 01, 2018 5:49 am, edited 1 time in total.
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 Post subject: Re: PPE for plugging in/unplugging 480-volt reefer units?
PostPosted: Wed Jan 31, 2018 5:09 pm 
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stevenal wrote:
My first thought is that you need equipment that mechanically prevents plugging/unplugging when on. Here's a three pole 30 A device.

That would definitely solve one of our problems. Thank you very much for the link, it's helpful to have an example of exactly what we need.

Unfortunately for those who pay the bills, we have 50+ 480v outlets that are used for reefer units. It's definitely worth pursuing though. Thanks again.


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 Post subject: Re: PPE for plugging in/unplugging 480-volt reefer units?
PostPosted: Thu Feb 01, 2018 5:58 am 
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Location: Rutland, VT
Do you have a picture of these outlets? They sound like regular welding outlets which are plugged into by welders all the time.

Have you done a risk analysis for this task? The receptacle and plug are being operated as designed so what is the risk?

Why Class 2 gloves that are rated for use at at max voltage of 17,000V being used? Class 0 gloves would be sufficient although I think is overkill as the receptacle is designed to minimize any accidental shock. Can't design against someone sticking a nail in it, though. There is probably more chance of getting shocked plugging into a 120V outlet. Are you going to require gloves for that?

Since you have gloves, I assume they are inspected and tested prior to each use and there is a testing program that insures they are sent out for electrical testing every 6 months?

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 Post subject: Re: PPE for plugging in/unplugging 480-volt reefer units?
PostPosted: Thu Feb 01, 2018 3:30 pm 
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wbd wrote:
Do you have a picture of these outlets? They sound like regular welding outlets which are plugged into by welders all the time.

I have attached some photos.

wbd wrote:
Have you done a risk analysis for this task? The receptacle and plug are being operated as designed so what is the risk?

We have not done a risk analysis. That’s why I am getting involved and doing this research. In theory, yes, the receptacle and plug should be operated as designed so no risk. However, we have had a box that was live when the power indicator said that it was turned off and someone got shocked. So, I have a hard time not taking that possibility into consideration.

wbd wrote:
Why Class 2 gloves that are rated for use at at max voltage of 17,000V being used? Class 0 gloves would be sufficient although I think is overkill as the receptacle is designed to minimize any accidental shock. Can't design against someone sticking a nail in it, though. There is probably more chance of getting shocked plugging into a 120V outlet. Are you going to require gloves for that?

I wondered the same thing about the Class 2 gloves. I’m not sure why they picked those for this task, especially since they cost about twice as much as the Class 0 gloves. I was going to address that with the team if we determined that we do need to be wearing gloves.

wbd wrote:
Since you have gloves, I assume they are inspected and tested prior to each use and there is a testing program that insures they are sent out for electrical testing every 6 months?

The gloves are not being inspected and air tested at all. No electrical testing either. That is what started this inquiry. I wondered why we had PPE that we were requiring that people use, but were not maintaining it as required.


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 Post subject: Re: PPE for plugging in/unplugging 480-volt reefer units?
PostPosted: Sat Feb 03, 2018 11:23 am 
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I understand the situation. One of my customers is the a major turkey producer in the U.S. They have quite literally huge fields full of reefer trucks. They have the same setup and problems you do. They are very proactive when it comes to safety. They insist on hi viz PPE everywhere and fortunately my FR shirts and jackets already have it so I don't have to wear a vest. I work on their large chillers where the class 2 gloves and arc flash PPE are a necessity. But I can also say that I've never seen them wearing rubber gloves or arc flash suits while handling reefers except to test for voltage before repairing one when a trailer gets backed into it.

emv wrote:
Hello! I work at a cold storage warehouse where I am working on developing a documented training program for my coworkers who plug in and unplug reefer units on shipping containers to/from 480-volt outlets, and I need some help doing a JHA. I'll try to make this quick. :D

A quick overview of our current SOP:
(1) we tell employees to don their PPE (right now that consists of Class 2 rubber insulating gloves with leather protector gloves);
(2) make sure that both power supplies are shut off;
(3) remove the cap covering the outlet;
(4) inspect the plug, power cord, and outlet to ensure they are all clean, dry, and undamaged;
(5) plug the connector from the shipping container into the outlet until the locking device on the cord is secured to the outlet;
(6) turn on the power supply to the outlet; and
(7) turn on the reefer unit.
(Disconnecting is basically that process in reverse.)

The problems that we have observed, include:
(1) reefer units get unplugged without shutting off the power to the outlet first (this gets discovered when somebody else tries to plug in a different unit and finds the outlet is already turned on);


I have seen MANY plugs like you describe quite literally explode in an employee's hands from not taking load off. I haven't seen one explode without a load on it. The issue is that you can get away with this on 120/240 V plugs and often with things like say dock lights and stand fans, there isn't actually a way to shut it off other than an external switch or pulling out the plug so the practice gets accepted without realizing the danger with more current and power. That being said I can't give you an exact number but suffice to say that you are dealing probably with 30 A plugs and wiring. As such the wiring should have circuit breakers in the neighborhood of 50 A. Even though it's 480 V when I've run the analysis before the incident energy usually ends up under 1.2 cal/cm2. So there is an injury hazard in terms of exploding plugs to the HANDS but not to the rest of the body. As of right now the standard is to protect against fatalities only. Currently NFPA 70E recommends wearing clean, dry leather gloves when handling plugs but obviously rubber gloves would be required if they are wet.

Quote:
(2) the outlet caps are not always being put back in place after disconnection (outlets are all outside and uncovered);


Current NEC regulation for outdoor locations generally requires a weatherproof while-in-use cover for many locations like this although the focus is on 120/240 VAC receptacles. The flat face ones that go in a 4x4 type box are only rated for indoor/dry locations not outdoor so it's basically not up to Code. There are however several designs where the receptacle has an outer shroud and points down out of the box which protects it against rain, even of the wind driven type. Meltrics makes a much fancier "dead front" style one where the plug slides a cover back as it is inserted eliminating this issue. Hubell makes an even more aggressive one that has the shroud and also has a pin that pokes into the mating plug that is also mechanically interlocked into the disconnect handle. With the handle in the open position you can freely remove or insert plugs. In the closed position you can't remove a plug that was inserted nor insert one if no plug was inserted. But they are very, very pricey compared to the Meltrics stuff.

Quote:

(3) cotton gloves are sometimes used instead of the interior and exterior gloves that have been provided; and


So? NFPA 70E requires clean, dry leather gloves for inserting and removing plugs and thats it as long as things are dry. If not, then the rubber comes out.

Quote:
(4) employees sometimes only put the interior and exterior gloves on one hand.


It's shock protection. There is an old work practice that says to put your other hand in your pocket and do everything one handed so that you are less likely to shock yourself arm-to-arm through your heart or to resist the temptation to accidentally put your off hand where you're not looking. I'm not a lineman so I'm not required to wear gloves "cradle to cradle" in a bucket truck. Often I find myself having to remove at least one glove to manipulate the controls on a meter while I use my gloved hand to hold the probes in a confined area where there is a potential shock hazard.

At 480 V the goal is to stay 12" away from exposed conductors for qualified employees without shock protection. Exposed means not insulated, guarded, or accessible. Guarded means not that it is totally covered but that it is recessed in some way to prevent inadvertent contact and that's what 480 V receptacles do. When you are inserting a plug into the receptacle, the housing of the plug keeps your body away from the "business end" of things. So there's not really any reason to wear gloves in the first place unless you have a whole bunch of dry indoor location-only receptacles mounted outdoors where the gloves become necessary to overcome the installation issue.

Quote:
Also, I am concerned that we have not been inspecting or testing the rubber insulating gloves, even though we have a glove inflator kit. It seems to me that if we are going to issue the gloves, we need to comply with the inspection and testing requirements. I don’t want to give anyone the illusion that they are protected by gloves that may be damaged and therefore useless.


A pinhole is all it takes. The electrical field WILL find that pinhole and open the glove up as well as the wearer very easily. That's why linemen take maintenance of their gloves dead seriously. But few line crews carry glove inflators. Most of us just do the roll test. It doesn't take any more time to do the inspection properly. If you're not going to inspect them daily never mind sending them out every 6 months for testing and cleaning, don't bother with them. The testing lab by the way is really interesting in how they test. They fill the glove up with water up to a certain number of inches of the cuff and then submerge the glove in water. The tank is grounded and then an electrode that dangles down in the water inside the glove is energized to high voltage. Technically the leakage current should be below a certain amount but in reality the glove rips apart if there is the slightest pinhole and fails spectacularly. When I toured a test lab they said they had NEVER had gloves fail by leakage alone...it was always a destructive test if one failed. So in practice the gloves can be completely soaked in water and still meet the rated voltage, not that I recommend working with energized equipment while soaked in water...even line workers don't really like it even if their PPE an equipment is designed for that duty.

Quote:
Before we implement new procedures and do any training, we want to be sure of what is necessary. In theory, employees will only be touching equipment after confirming that the power indicator is in the off position, so they should not need protection. However, there is a chance that the outlet box may be live when it does not appear to be because of reported/unreported damage from a truck backing into the loading dock. With all that in mind, do we do need to require interior and exterior gloves? If so, we need to comply with inspection and testing requirements, correct?


Again you shouldn't need it. But even if you did, what I'm not reading here is testing for absence of voltage. There is a device on the market made by Grace Engineering that has redundant indicator LED's per phase and phase-to-ground so you should see 2 lights on every phase or no lights...if you only have 1 light then the device needs to be replaced. Plus they are red LED's with typically have failure rates in the 10-20 year or better range.

Quote:
Is there anything else that they need to wear? It has been suggested that they might need to wear a 100 cal suit.


How big are these receptacles? If you have adequate fuse/circuit breaker protection I seriously doubt you are even going to get to 40 cal never mind 100 cal. First off it's open air so the arc flash dissipates quickly compared to in a panel. Second again in practice I have never seen one get above 1.2 cal/cm2 mostly because of the very small size of the breaker or fuse. It tends to trip almost instantaneously. It doesn't "prevent" an arc flash, just limits the time one exists down to a very short period of time, typically under 0.05 seconds. I haven't found any molded case breakers for panelboards with a 50 A or smaller rating that have a longer opening time than 1.5 cycles or around 0.025 seconds. The arc is short lived so the amount of heat you get from it won't be much.

Quote:
What about requiring that employees test the outlet boxes to confirm that they are not live, despite what the power indicators may say, before touching them?


Let's look at this. In terms of normal plugging/unplugging unless something is wrong (and it should be repaired or use a different receptacle if something is wrong), then there's nothing exposed so no shock protection needed. I think we can agree that there might be an arc flash hazard but given the extremely limited time that an arc can occur, it could cause an injury but not anything that the arc flash standard is attempting to protect against anyway. As I've said before there is no attempt being made at least intentionally to protect the hands and arms. It's all about preventing fatalities and minimizing injuries, not preventing injuries.

Quote:
Thank you in advance for your feedback. I greatly appreciate your time and expertise. It is important to me that we keep our employees safe, but the information that I have found online thus far has not provided the definitive answers that I need in order to justify to management making changes to our current policies, procedures, and PPE purchases.


Strongly suggest looking into the online courses from ESTS for a couple reasons. It's online so you don't have to leave the office. I believe Terry also let one person "audit" the course for free. Even if you do end up paying for it, the price is very reasonable and Terry's course is meant for craftsmen, not engineers. And it might give you a much better idea of what's going on since the things you are suggesting (class 2 gloves, 100 cal suits) are way, way beyond any hazard that might exist.

Here's the problem without understanding what you are doing. There was data collected from real arc flash incidents (a little over 50 of them) by some folks at Dupont about 10 years ago. The results showed that organizations that just "winged it" or did "nothing" without following any kind of standard or approach had a pretty dismal track record. About 90% of the cases resulted in serious injuries or fatalities. For those who didn't pay for an engineering study done I've heard quotes that this decreased to 50% but my own analysis of the same data shows it's much better than that, under 25% odds. And for those that pay for the engineering study and follow a standards based approach, the overwhelming evidence is almost no injuries. And having too much PPE is just as bad as too little because you lose dexterity, heat related injuries become an issue, visibility gets very poor, and it strongly encourages short cuts which you apparently said are already happening.


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 Post subject: Re: PPE for plugging in/unplugging 480-volt reefer units?
PostPosted: Fri Feb 09, 2018 6:23 pm 
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Thank you so much for taking the time to share all of this information with me. I feel like I just hit the jackpot with this response!


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