Arc flash PPE

I've had a read over the topics on here that sound similar or related. Most were from some time ago and none really get to what I'm aking about.

I've been down the arc flash and arc flash ppe rabbit hole on and off for several years now and never really got to grips with it and never really come to any final conculasions.

I work on ships (mostly, for now) and because I've often worked though agencies I end up on a variey of different ships with a veriety of differnt standards when it comes to procedures and equipment (ranging as far as on ship I joined not even having any Lock out/Tag out equipment).

While I understand and totally agree with the 'don't work live iunless absolutely unavoidable' Electrical Safety at Work directive etc. unfortunately there are times when it is not practicable to do this and maintenance is done when there is live conductors within the same enclosure.

Based on that, and the 'never knowing what you'll find when you arrive' scenario, is there any recomendations on arc rated ppe that would be good to carry, or if in doubt, it wouldn't be a bad start to wear this?

I know this is far from ideal, and realystically these hazards should either be designed out or an arc flash studdy carried out to know exacely what is what with a risk assessment based on known hazards to reduce the risks before PPE comes into play. On new ships nowadays (as I'm sure it is on land based installations) this is being done, but I've been on a lot of older ships that were built before this was probably even thought about. We risk assess the job before doing it, and reduce whatever we possibly can.

I'm also looking to pick up some more contracting work, at which point the provision of PPE and risk assesments/method statelments falls to me. So I want to make sure that I'm doing the best I can and not taking any unnecissary risks.

My current list of research to follow up on is:

The IET Arc Flash Risk Management paper

The European Arc Flash Safety Guide book

and the ea-guide.com website.

(Note - I hope this hasn't come across as though I take working live lightly and/or that its done or PPE is uesd as a first resort. I'd just like to have ensible conversation about this topic to help improve my safety standards in the right way)

Parents
  • Thanks for the replys. sounding like I've got the right idea at least in planning ahead and trying to learn as mich as possibel. Its just a very deep and winding rabbit hole that I'm in!

    Now just neet to get to grips with some of the finer points in estimating the likely hazards etc.

    My thinking on PPE at the minute is to have some Arc rated trousers and polo/tee shirt for day to day working with a boilersuit that I can put on over the top if the hazards are higher.

    Has anyone any experience with gloves such as these: https://gsworkwear.com/products/portwest-arcgrip-gloves-a780?variant=15698900156459 I was thinking somthing like this for day to day working but wondered if they are really offering any worthwhile protecation?Then with gauntles if needed.

    Plus the helmet, ear defenders, glasses, virsor as and when needed.

    Out of interest, how much of an arc flash risk exisitis on an average domestic/light commercial installation when carrying out things like external earth loop impedance tests? I figured this is probably the highest risk as its at the cutout/main DB, live and with some exposed live parts. Obviously it varies with the exact installations but for something around 2kA prospective fault current with the standard DNO 80amp fuses for example, would you be looking at a a full gaultlets and visor set up to carry out that test, or would glasses, basic gloves and long sleves be reasonable protection.

    Thanks

Reply
  • Thanks for the replys. sounding like I've got the right idea at least in planning ahead and trying to learn as mich as possibel. Its just a very deep and winding rabbit hole that I'm in!

    Now just neet to get to grips with some of the finer points in estimating the likely hazards etc.

    My thinking on PPE at the minute is to have some Arc rated trousers and polo/tee shirt for day to day working with a boilersuit that I can put on over the top if the hazards are higher.

    Has anyone any experience with gloves such as these: https://gsworkwear.com/products/portwest-arcgrip-gloves-a780?variant=15698900156459 I was thinking somthing like this for day to day working but wondered if they are really offering any worthwhile protecation?Then with gauntles if needed.

    Plus the helmet, ear defenders, glasses, virsor as and when needed.

    Out of interest, how much of an arc flash risk exisitis on an average domestic/light commercial installation when carrying out things like external earth loop impedance tests? I figured this is probably the highest risk as its at the cutout/main DB, live and with some exposed live parts. Obviously it varies with the exact installations but for something around 2kA prospective fault current with the standard DNO 80amp fuses for example, would you be looking at a a full gaultlets and visor set up to carry out that test, or would glasses, basic gloves and long sleves be reasonable protection.

    Thanks

Children
  • A crude worked example !

    80A BS1361 fuse perhaps the ferraz shawmmut BME42V80

    shows a total energy to open is 30,000 Amp2 seconds.
    We have to have a figure for the Zs of the supply, lets take a fairly bosky supply capable of a 230V open circuit and 20kA PSSC, so for the worst case, the energy into the fault and drop on the supply is equal, and 10,000A flows and 115V is dropped creating approx 1Megawatt of energy, but for how long before that fuse pops.
    so the time is 30,000 divided by 10000A squared,(which is 100,000,000 A 2) so the equivalent energy rectangular pulse duration would be ~ 1/3000 second (but course as the fuse 'blows' the current is not constant, but then neither is the switch off time a true knife edge). So worst case arc energy is the same as that megawatt for 1/3000 second , so about 3000 joules. Now if that was in free space, we would have to spread that over at least 600 square cm to get down to the "safe" (burnt bare skin, not that safe) limit, and that is actually not that large a sphere, about half a metre diameter or 25 cm ~ 10 inch radius. Redo the calc for 10 times the power density - about the "12 calorie" level for the overalls or thick gloves, divides the dangerous sphere diameter by about 3 (where 3 squared is almost 10) to  less that 10cm/ 4 inches But as above, the enclosure either saves you or could makes it 3 times worse depending where you are in relation to any focusing action.
    This sort of wet finger sum only should be used to give a feel for how far back to stand ! There are a lot of approximations, and the 'formal standards grade' formulea are quite a bit more complex and nuanced...
    Mike.