When my spray cans are low on pressure, I just re-charge them with my compressor using the air nozzle. This works great, except for the nagging voice inside which says those cans could bust.
I posted this question on another site, and got lots of responses, mostly that I was crazy. Anyone one out there know what is the busting or working pressure of a typical aerosol can? I can’t believe I’m the only one engaged in this non-OSHA approved practice.
Replies
Geoff,
I'm at a bit of a loss here. Could you explain what areosol cans you are refilling and more importantly, why? Thanks.
Don
Don, most lately it was a can of oil that had run out of pressure long before the oil ran at. I refilled by blasting air back down the tip, and feeling with my hand to see when the sides of the can couldn't be easily pushed in....somewhat like filling a soccer ball with air. I've done this with paint spray cans also.
Naturally I prefer not killing or maiming myself. But no one seems to know what the pressure limit of a typical can is. I'm sure the cans are controlled by government regulation, because the potential danger is high. My guess is that they are tested to greater than 100 psi. ---geoff
geoff,
I agree with you that the govt. probably has some regulation governing the amount of pressure in the cans. I don't know what the regulation states, but I honestly don't think the risk involved here is worth the gain. It's just my opinion, but I have never even considered what you are doing as an option to getting that last little bit.
Don
the nagging voice inside ......... Listen to that voice.
I hope you're kidding. If you're not, you must be the biggest stupehead who has ever visited this forum.
Edited 10/3/2002 6:47:30 AM ET by CHASSTANFORD
Charles-
Please satisfy my curiosity. What on earth did you edit in that message? Toned it down some?
Nothing but a typo.... although something phallic did come to mind.
Edited 10/3/2002 6:40:37 PM ET by CHASSTANFORD
Phallic????? I would have though anal! hahaha History is full of people with more guts then sense. Just the thought of trying this makes me uneasy.
Don
I don't think that I would worry about over pressurizing spray cans but adding oxygen to a flammable under pressure is.. well... do you suppose that, when it blows, nominations for the Darwin Award would be in order?
BJGardening, cooking and woodworking in Southern Maryland
Wow! The abuse I've had to put up just to get some replies to my email... Well, I'll take it all, and thank you all for your comments and concerns. While I do have doubts about repressurizing cans (hence my posting) I also have a suspician that your fears are exaggerated.
What is missing? Facts. Any facts. I don't have much time to research the subject---I was hoping that someone on this forum might know, some engineer or scientist among you or someone with prior related experience.
In the meantime I shall follow Don's advice to listen to that inner voice of caution. Thanks again to all of you. ---geoff
GFSARK,
You're probably right. 999,999,999 times out of a million nothing will happen. But that one time may mean a hand. I've had half of a finger severed and reattached because of someone else's carelessness. When I forget, cold days have an unpleasant way of reminding me of what happened 20 years ago. I promise you, whatever you're losing in the can ain't worth the risk of your hand(s).
Don
Edited 10/4/2002 1:31:33 AM ET by Don C.
Listen, No one on this message board is going to do the calculations to determine the bursting pressure of an aerosol can. There might be engineers here, but most people here rely on common sense and street smarts, unless we're talking building loads.
Like everyone else is saying. You're putting a catalyst (oxygen) in a flammable. That just sounds like you want trouble. I would say don't be cheap, the cost of having shrapnel removed from your body is much more than the cost of spray cans.
Do you really want the facts about this? It might be frightening and I hope you put safety first. Best just to not be curious in this case.When people 100 years from now see my work, they'll know I cared. --Matt Mulka
No one on this message board is going to do the calculations
I've already admitted to being retarded (i was in good company!) in the "clamps" thread, so why not push the boundaries further?
I googled and found that the graffiti artists who rrrrreally want to strut their stuff, do it this way. I'm thinking this kid is spraying the walls at Stanford...
If you'd like to deform some cans, make sure it's for a good cause, which brings us to another discussion group, that features a fellow named Geoff talking about pickled pig parts and fermentation, well-known to clause explosions of a certain nature.
Coincidence? I think not! Watch him closely, folks...
Edited 10/4/2002 2:37:16 AM ET by SPLINTIE
In a word, Geoff, the answer to your original question is "no."
Aside from the bursting pressure of the cans themselves, I would also suggest considering the ignition temperatures of the various substances you're pressurizing. Boyle's Law is relevant here (direct relationship of pressure to temperature a la diesel engines. Oxygen is required for diesel ignition, of course, but that's exactly what you're inputting, right? I mean, you're not repressurizing the cans with CO2 or some other inert gas, I assume). One of the problems is that you probably can't maintain strict conditions during the process of casually adding new pressure to a can, and temperatures may vary depending on season and time of day, so I would think that numbers are fluctuating all over the board. I would use google, inputting words like "aerosol," "bursting pressure," and "explosion"; I found a number of sites that discuss the issue in one way or another; maybe the following would be helpful.
http://www.diversifiedcpc.com/download/documents/safety.pdf
http://www.osh.dol.govt.nz/order/catalogue/pdf/aerosol.pdf
As an aside here, I worked in an anesthesia service for 6 months (navy, long ago), and we were warned that merely being a bit hasty in opening the valve on some tanks could result in a temperature rise sufficient to trigger an explosion (the substance involved was cyclopropane, not your common paint or whatever, but it shows how dangerous the pressure/temperature equation can be).
Whatever, the mere thought of repressurizing a can without any knowledge of the pressures going in and the withstand pressures of the cans involved leaves me with very sweaty palms.
". . .and only the stump or fishy part of him remained."
Green Gables: A Contemplative Companion to Fujino Township
Edited 10/4/2002 5:10:21 AM ET by Norm in Fujino
I have begun researching our can question. My results, thus far, are as follows:
Refilling can using only the pressure from one's mouth poses absolutely no danger of explosion. (However, I was left with a strange taste in my mouth, and color on my tongue. Attempts to re-pressurize can of starting fluid was very pleasurable experience.)
Refilling can using 500 psi resulted in sudden, violent explosion of can. Although I only tried this once, I think we may safely assume that repeated attempts at said pressure will attain similar results.
Exploding cans hurt. A lot.
Please bear in mind that all research data is preliminary, but, even so, I think we've established the upper and lower parameters for continued study.
Study will continue as soon as they let me out of this hospital and I can get my garage rebuilt.
Jeff
Edited 10/4/2002 1:20:15 PM ET by Jeff K
I's Witchya GFSTARK,
Seems like the crowd has turned protectionist. Interesting post. Never thought of it. If you are really motivated go to the custom autopaint store in your area.
My local guy is a funny little man from the 3rd world who has ugly fingernails from the solvent he uses. I suspect he doesn't use approved hand cleaners to remove the automotive finishes before dinner. They make custom aerosols there. There is generally no more than 1 or 2 stores like this in a metro area of 1 million. That guy would know how much pressure he recharges the paint cans with. They buy them empty load them with paint and charge them with some propellant.
Strange, he sells bondo, paint for Lexus', Fords, & yugo's right along side the greatest collection of velvet Elvis and other trash.
Or experiment. Put a 2 dollar pressure gauge on a can of WD40 when it is new.
One thought. Some materials oxidize Paints, etc. The normal air mix will/may harden some finishes in the can. if you charge it with air I'd use it soon before it hardens.
Hey thanks Booch, for the first words of support. I've been amazed at the very strong reactions....and have concluded from this (and posting on TheOak) that my habit (been doing it for about 10 years) could be a really dangerous addiction.
So, I'm temporarily suspending the practice of re-pressurizing cans... till I can satisfy myself that it can be done safely. Having said that, I already feel the craving to go do it again, tonight!!!
In the meantime, as you have suggested, anyone can purchase a fillable aerosol can for mixing his own spray paint. If memory serves me the commercially sold cans support working pressures of 50 and 80 lbs, depending on model. ---geoff
PS there must be some other hi-pressure abusers out there. I'm surprised that no one else has tried this.
Geoff, i hope you didn't take my tongue-in-cheek post for a slam. I dig folks who think outside the can!
As any student of science, I've put them in the burn barrel when the color or content didn't suit my needs. Some have a rolled collar that exposes itself like a toro lawn sprinkler as the internal pressure builds. Others just go kablooey. Sure it is dangerous. Noone in their right mind would stand anywhere near this nor do it as anything other than an experiment. I got a surprise when my 13 year old snuck a mostly used butane cylinder from my Paslode into a bonfires last year. No one hurt, no shrapnel, but I now count the empties and dispose of them like I do the full beer bottles in my home. With kids, there is no warning or precaution fully workable except those that would land a parent in jail for abuse ("why I oughta" or neglect ("step into these leg irons").
No harm no foul.
Hey even Madame Currie made a couple of mistakes. Maybe they'll name a rechargable aerosol can after you.
When I was a little kid, I remember finding a couple of old bullets in my Grandmother's rarely used spare room. And being a curious tyke, I snuck them downstairs and threw them into the fireplace---on Christmas eve. Well, apparently the powder was too old to ignite, and I can remember being dissapointed at not seeing any explosion. What kids will do! Now adults...that's another thing. ---geoff
Pop used to recall putting 10 penny nails on the RR track as a kid. They made nifty knives for kids. One thing lead to another - spikes yielded bigger knives, then the brainstorm... Put a rr spike on the track and make a really big knife.
Laying in the bushes he and his brother watched. Along came a team of gandy dancers with a gas powered handcar and 2 trucks of repair material. The car hit the spike, the mess derailed. The little brother jumped up and started running. Next was hot pursuit for a mile or so of woods. The little brother outdistanced my dad. Pop was pooped, so he flopped into a bathtub / water trough. He heard the men searching for him for quite a while as he lay in the 2 inches of muck.
No repurcussions, no one seriously hurt. If we didn't do dumb things who would read the paper.
When I read this, I probably thought the same thing Charles deleted. This can't be for real!
Jeff
One thing to worry about is charging a can of a flammable substance with air. You might be holding a bomb waiting for a spark or perhaps not even a spark.
When the can blows up, and the news of his lawsuit hits the papers, we can all go testify that we told him it was dumb! Sheesh. That last bit in the can can't be worth the risk. And if the can ran out of air well before the product was emptied, then take the can back to the store and ask for another one.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Having been a lawyer in a past life, I know a thing or two about the damage caused by exploding closed vessels. I can't tell you the burst pressure of a spray can, but I have seen firsthand the damage they can cause. I defended a company that sold an automotive product in a spray can, with very specific instructions on how to use the product. Of course these were immediately ignored. the individual using the product was holding the can in his right hand, about a foot from his face. The can exploded, resulting in the traumatic amputation of all the fingers (but not the thumb, go figure) of the right hand, and loss of sight in both eyes from shrapnel. He sued the manufacture claiming defect and insufficient warning (we won)
The second case involved a person doing something similar to what you are doing. He was pressurizing a small tank with liquid (water) and air at a winery in Napa, California. He was also using the best guesstimate method. He guessed wrong, the tank exploded and decapitated him.
Gross stories, I know, but they hopefully will get everyone to stop and think. I bet both of these folks would gladly throw away cases of full cans of anything to not have suffered the consequences of their actions.
Please be careful! You can't unring the bell!
Michael
! here, here!!!!! . Nice post. what is a can of spray paint.....from .99cents to 3.00. Geesh!!
Geoff
My porter cable air compresser's instructions say to use pressures of 120 lbs or less to operate a brad nailer, air wrench ect.. The tank on my unit is thick enough to tap and thread for hose fittings. I doubt if the aerosol can is more than 1/16 inch thick. Here are some numbers to start with if you want to do the math!!!!!
BT
I really am surprised to see new responses to your question. Indulge me for a moment while I try to put this in perspective.
Are the 10 cents worth of aerosol product you recover really worth the possible risks to your health or possibly your life? Good God man! Use some common sense and stop being a damned fool.
Jeff
Due to the huge number of intense & earnest messages (such as yours), I've sworn off the the 10 year old practice till I find out. I don't normally give in to mob rule, but the mob has made such eloquent arguments that I would be a total fool not to do more investigation.
Common sense suggests that repressurizing would be safe, at some pressure. No one has told me what that pressure is. What is unsafe, then, is not knowing the true pressure limit. Ignorance could be very dangerous in this situation.
Thank you all for your warnings. I take them seriously.
---geoff
PS I think aerosols are expensive, and some quite expensive, especially when adding up the time to drive into town to replace.
Geoff -
Many years ago (like 30?) I soldered an air valve in the bottom of a depleted aerosol can. I would use a small funnel to recharge it with thinned paint then pressurize it from my compressor. It worked great. Some time later I started buying the small detail spray guns. That workes better, faster, and more safely.
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