Home made spraybooth lights

H

HIG

I have a wooden studded spraybooth with plastic covering the walls. When I built it I used a thicker clear plastic that was milky not nice and clear but I'm losing a lot of the light thru it (plus it's time to redo the plastic from overspray). I have about 7 - 8' florecent lights on the outside of the plastic.

The booth is vented thru an 18" explosion proof fan.



How important is "explosion proof" lights. I usually have some halogen lights plugged it inside of the booth - is this safe, could I safely install some florecent lights inside? I guess the issue would be a spark?

Any help would be great.

Thanks, Steve
 
The issue is an electrical malfunction occurring just at the time when the air/vapor mix is explosive. For the two to happen at the same time is like a million to one shot, but it can happen, and has happened, so if you want to have exposed electrical devices in the spray area, just say a prayer and have lots of life insurance. You'll probably beat the odds, but you never know...

P.S. Even Mythbusters had trouble reliably igniting gas mixtures that were intentionally made explosive, so it really is a very rare and unlucky event if it ever happens. But if it does, heaven help you.
 
crashtech;37316 said:
The issue is an electrical malfunction occurring just at the time when the air/vapor mix is explosive. For the two to happen at the same time is like a million to one shot, but it can happen, and has happened, so if you want to have exposed electrical devices in the spray area, just say a prayer and have lots of life insurance. You'll probably beat the odds, but you never know...

P.S. Even Mythbusters had trouble reliably igniting gas mixtures that were intentionally made explosive, so it really is a very rare and unlucky event if it ever happens. But if it does, heaven help you.
Click to expand...

Thanks for the sound advice, I understand it's highly unlikely but....

I guess with the lights I was thinking what could go wrong to cause a spark unlike with a fans motor it seems more likely but you never know.

Are some vapors more combustible than others, primers (2K & epoxy), base, clears (universal)?

Thanks again, Steve
 
I believe that most homemade booths do not move enough air to keep the air/fuel mixture below the UEL. I think the atmosphere is far richer and as such isn't as likely to go boom until the spraying is stopped - fans continue to run, overspray is reduced, then a light switch or fan switch is operated and makes the magic spark. That is why I do not connect or disconnect any electrical items inside of my home made "booths", Easy enough to run a cord to an outside source for the fan(s) and plug unplug it in nice clean air. The lights can be left on and turned off at the circuit breaker box which should not be in the same room as the booth. This is like knowing a person that has had a pvc pipe explosion, it happens, just don't hear of it to often.

Another item I have recently made, I no longer use steel couplers on my air hoses. Just another way to make a spark, disconnect the gun and drop the hose and the coupler makes a spark - booom. I should have done this decades ago, I knew better. Whenever we worked in the paint room of a coil coater we had to use beryllium tools to avoid making any sparks. Although the painting process there is a roll on application the air is heavy with vapors, mostly mek. Ventilation is extreme, explosion monitors all over, but still we used beryllium tools. The atmosphere that was evacuated from the paint room was routed into an afterburner to get rid of all the bad stuff. Really a waste, there was no heat exchanger on the afterburner to use any of that heat, which there was a lot of, 24/7/365.
 
Yeah, the contacts spark. Better to have the compressor out of the spray area for that reason, and also to prevent it from clogging its air filters by ingesting overspray.
 
Senile Old Fart;37351 said:
I believe that most homemade booths do not move enough air to keep the air/fuel mixture below the UEL. I think the atmosphere is far richer and as such isn't as likely to go boom until the spraying is stopped - fans continue to run, overspray is reduced, then a light switch or fan switch is operated and makes the magic spark. That is why I do not connect or disconnect any electrical items inside of my home made "booths", Easy enough to run a cord to an outside source for the fan(s) and plug unplug it in nice clean air. The lights can be left on and turned off at the circuit breaker box which should not be in the same room as the booth. This is like knowing a person that has had a pvc pipe explosion, it happens, just don't hear of it to often.

Another item I have recently made, I no longer use steel couplers on my air hoses. Just another way to make a spark, disconnect the gun and drop the hose and the coupler makes a spark - booom. I should have done this decades ago, I knew better. Whenever we worked in the paint room of a coil coater we had to use beryllium tools to avoid making any sparks. Although the painting process there is a roll on application the air is heavy with vapors, mostly mek. Ventilation is extreme, explosion monitors all over, but still we used beryllium tools. The atmosphere that was evacuated from the paint room was routed into an afterburner to get rid of all the bad stuff. Really a waste, there was no heat exchanger on the afterburner to use any of that heat, which there was a lot of, 24/7/365.
Click to expand...

There is a lot of good information posted there, thank you!!

I would never have thought about the quick disconnects.

I have no knowledge on this subject so sorry for the basic questions. I would assume the greatest chance for a explosion would be when there's the most overspray in the air, is this not true, is it after it's starting to clear out?

What is a pvc pipe explosion - Yeah, I've never heard of one. :)

Thanks for sharing!!
Steve
 
Atmospheres have both an lel and uel. They are the lower explosive limit and the upper explosive limit. The ration of air to the vapor has to be within a range, which varies with each volatile.
Think of it this way, put just a tiny bit of gas in a motor and it wont even fire ( to lean), dump a lot of fuel into the engine and it wont fire (flooded) At the point there is enough vapor to ignite is the lel, at the point there is so much vapor it will not ignite is the uel. Anything in between goes boom. Like an old carb fed car, to much choke and the engine will barely run or maybe even die, open the choke up and the engine cleans up and runs. Turn the idle mixture screws into far and the engine dies. lel and uel are what happened.

PVC pipe explosion is when PVC is used as compressed air piping.
The oils in the compressed air attack the plastics for one , making the pipe too brittle and it bursts sending shards of lethal plastic all over heck.
While pvc is safe for some fluids, that is due to the fact that fluids don't compress so when the pipe does fracture the pressure drop is instantaneous and since there is no compressed materials in the pipe all you have is a wet mess to clean up, but no boom like compressed gases will do.
Some don't believe it is a risk, I do. Never seen it in person, but seen plenty of training films with pictures.
Also I remember 40 years ago laying in a hospital bed , the guy in the other bed had his legs dam near blown off. He figured a hot water tank holds hot water it should hold air. He made it into a storage tank for his air system, failing to realize that it needed its own pressure relief valve, thinking the one on the compressor was sufficient.
It wasn't.
 
Senile Old Fart;37389 said:
Atmospheres have both an lel and uel. They are the lower explosive limit and the upper explosive limit. The ration of air to the vapor has to be within a range, which varies with each volatile.
Think of it this way, put just a tiny bit of gas in a motor and it wont even fire ( to lean), dump a lot of fuel into the engine and it wont fire (flooded) At the point there is enough vapor to ignite is the lel, at the point there is so much vapor it will not ignite is the uel. Anything in between goes boom. Like an old carb fed car, to much choke and the engine will barely run or maybe even die, open the choke up and the engine cleans up and runs. Turn the idle mixture screws into far and the engine dies. lel and uel are what happened.

PVC pipe explosion is when PVC is used as compressed air piping.
The oils in the compressed air attack the plastics for one , making the pipe too brittle and it bursts sending shards of lethal plastic all over heck.
While pvc is safe for some fluids, that is due to the fact that fluids don't compress so when the pipe does fracture the pressure drop is instantaneous and since there is no compressed materials in the pipe all you have is a wet mess to clean up, but no boom like compressed gases will do.
Some don't believe it is a risk, I do. Never seen it in person, but seen plenty of training films with pictures.
Also I remember 40 years ago laying in a hospital bed , the guy in the other bed had his legs dam near blown off. He figured a hot water tank holds hot water it should hold air. He made it into a storage tank for his air system, failing to realize that it needed its own pressure relief valve, thinking the one on the compressor was sufficient.
It wasn't.
Click to expand...

Thank you for another great explaination. The lel and uel when compaired to a motor makes a lot of sense, that is a great analogy.

Steve
 
I've seen garages with clouds so heavy you could hardly see the other side,
like that on a routine basis, and never a problem from all the normal spark devices
it came in contact with. As long as you have ventilation while spraying, it's not a problem.
 
jcclark;37394 said:
I've seen garages with clouds so heavy you could hardly see the other side,
like that on a routine basis, and never a problem from all the normal spark devices
it came in contact with. As long as you have ventilation while spraying, it's not a problem.
Click to expand...

Garage with clouds is definitely above the uel
 
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