lamp heat

[duke]

i have made a blasting cabinet which is 4ft H, 4ft W, 2ft D.
i will be using black beauty (coal slag). my question is, will a flood light connected inside the cabinet, get to hot & cause fire or explosion hazard from coal slag dust created by blasting ?
cheers

[non-stick]

generally speaking I'd say no as I've had those types of lamps in blasting rooms before but yours is a little smaller of a volume. Is it an option to cut a cole in the top or such and put a piece of plexi or lexan there and have the light on the outside? I think you'll find you get longer life out of the bulb that way as well.

[duke]

hmmm, back to the drawing board . or should i just use normal 60 watt bulb work light?
cheers

[non-stick]

no drawing board.... just "adjust" to suit your needs. Most commercial blasters use a hole in the top and shield it with either safety glass or plexi and have a small fluorescent tube light so they can see with. It serves two purposes.... first of all it take the risk of having anything in the way while you are flipping the part around and possibly breaking. Second.... if it's up and out of the way and a fluorescent tube, no heat is generated and therefore... you won't be sweating while you're already laboring moving grit and steel around.

Nope... a hole in the top with a small fluorescent is probably the easiest/cheapest way to go in this case I'd guess. Of course... if anybody else has a better idea, I'm all for it,natrually...... Russ

[duke]

thanks again russ, that makes a lot of sense.
cheers

[Fireblade]

Actually you can use the bulb inside the cabinet with no problems. If you look around at some other places that sell the cabinets, alot of them come this way, and these are commercial duty. I for instance, have 2 cabinets, one 8' long, the other 4' both have light assemblies in them in which I bought at Lowes for outdoor floodlights. The larger cabinet I designed mine after also has floodlight assembly in them, the smaller one which I bought, did not build myself, had a flourescent light tube, which really did a lousy job, and the tube themselves are not cheap. You can pick up a new halogen flood for $5.00, much better, cuts through dust, and cheap and easy to replace for nearly anywhere. You could however do as Non-stick said with hole and plexiglass, just you would have to either replace the plexiglass or buy film protectors to protect it. Either way will work fine.

[duke]

thanks fireblade, my main concern was if floodlight gets to hot while blasting with coal slag. as we know, coal burns.
you have used them. do you think coal dust would ignite in 4FTX4FTX2FT
cabinet?
cheers

[edclark]

I'm going to throw in my two cents, duke, 'cause I think you're getting ready to do something fairly questionable. From a safety standpoint, if the dust isn't combustible, it doesn't make a hoot whether the bulb is inside or outside the cabinet. However, I'm not familiar with coal dust slag, but if it's combustible and it sounds like it is, do not put an electrical source within that cabinet - particularly a bulb - unless it's very specially designed.

Combustible dust such as coal dust has a little property associated with it called the LEL (Lower Explosive Limit). You don't have to worry about it catching fire, you have to worry about it blowing your head off like a stick of dynamite.

I'm no expert, but it sounds to me like the dust concentrations in a blast cabinet could easily get above the LEL for coal dust. One spark and blooey!

If you were using sand or glass, no problem. Coal dust? Keep the lamp outside of the cabinet OR read up on the National Electrical Code for "Classified" areas which is what you are dealing with. Not trying to be a doomsayer, just trying to save your life here.

Good luck,
Ed

[non-stick]

thanks Ed! Always helpful and informative. Well said, bud.

[tomg552001]

I blast with coal slag all the time, and have a internal light, no explosions yet. I think you'll be fine, but if in doubt, cut a hole in the top, buy some lexan, and keep the lamp external. Good luck Duke.

[non-stick]

now would be a good time to remind everybody that we have a thread reserved just for these occassions. Better to show than tell. I say there's two methods and both are acceptable. But I've also whacked a bulb or two in my time slinging hose and what not... so to each thier own.

[duke]

thanks to all for your input. i guess it's best to be safe than sorry eh?
looks like the light goes on the outside.
cheers

[Fireblade]

If you have any doubts I would place it on the outside as Non-stick said to start with, I just think it will not be a problem. Think about this for a second, would a company allow the light to be mounted inside on all there cabinets if they could be held liable for something like that? I think their lawyers would step in and say something about that first. I could be wrong, but hey everybody is one time or another, this being my first time in my life! lol No really, the LEL threshold is right on, and coal does burn, most of our electricity comes from it. The question is, how low is the LEL limit for coal dust, I know from my job that a hydrocarbon vapor in any of our vessels, such as distillation columns, crude oil storage tanks, drums etc..are a limit of 20ppm, that is 20 parts hydrocarbon vapor to 1 million parts of air. Not a whole lot, this isn't the actual explosive limit, this is just the safe point of operating in the vessel and able to strike a spark. I really think the explosive limit is closer to 100, but better safe than sorry. Coal dust I would assume is much higher, but think about it this way. Do you use an intrisically safe dust collector? Or a shopvac to pull the dust out of the cabinet? The shopvac has an open source of spark, so if the light doesn't get ya the shopvac may! lol Ahhh so fun to instill fear in people! lol Good luck

[duke]

DECISION TIME.
i went to lowes & bought a hand held lamp with 4 fluro tubes, about 5" long 3/8 wide each tube. i turned it on & left it on for around 1/2 hour.
i picked it up by front clear plastic cover & held it with my hand wrapped around it & it was barely luke warm.
so, i have decided to hang it inside cabinet because it would never get hot enough to cause a problem. it also has a plastic hanging hook each end.
i want to thank all who took part in this objective discussion, & hope it will benefit others as it has helped me
cheers