Explosion Proof Motors?

[chase standifer]

I have the Graco Pro-Shot II sprayer. In the instructions it says not to spray flammable finished since the motor is not explosion proof. How big of a danger is this really? I spray single smaller pieces, at the most something book cased sized and that very rarely. I also have a well ventilated garage that I would be working in. I would like to be able to spray shellac etc.

[Bill White]

I'm no expert by any means, but "explosions" are mostly caused by concentrations of flammables and oxygen. If you have adequate air movement and exchange, open doors, etc., I wouldn't think that you would have a problem unless the atmosphere in the shop/garage gets saturated with the mixture.
Having said that, I don't know why water won't explode. After all, it is a mix of hydrogen and oxygen. Shows ya how much I really know.
Bill

[Curt Harms]

I'm no expert by any means, but "explosions" are mostly caused by concentrations of flammables and oxygen. If you have adequate air movement and exchange, open doors, etc., I wouldn't think that you would have a problem unless the atmosphere in the shop/garage gets saturated with the mixture.
Having said that, I don't know why water won't explode. After all, it is a mix of hydrogen and oxygen. Shows ya how much I really know.
Bill

Not a chemist but I think the hydrogen and oxygen DID explode. The product of the reaction was/is water. There must be certain concentrations of explosive compounds in the air in order to support rapid combustion. I'm under the impression that those concentrations are pretty high; decent ventilation should keep the concentration of explosive vapors well below the flash point. The risk I think about is heavy vapors settling in areas where there is no ventilation so becoming concentrated but there may be an ignition source.

[Mike Dowell]

DISCLAIMER - I'm NOT advising you to throw caution to the wind.

I don't have an explosion proof motor, nor do I have the air tight light fixture covers, or anything else that's recommended. In the winter, I spray a piece, turn on my fan to suck out the lacquer dust, then I turn on my bazillion btu propane space heater to replace the heat which was sucked out by the fan. If you want to hear something even crazier, my father-in-law has been doing this since 15 years old and he's 62. In his shop, he has literally sprayed lacquer in the same room as a wood burning stove - freshly stoked up.

I'm not telling you not to take any caution, and I'm also not saying that I'm not careless, or my father-in-law. I'm just throwing out some hard examples for your comparison.

Watch, next winter I'll blow my shop up.

[John TenEyck]

I would not spray NC lacquer with that gun if the manufacturer says it's not explosion proof. On the other hand, shellac is nearly impossible to get a concentration of air/alcohol where an explosion could occur. I think you need something like 11% alcohol in air to support combustion. That just isn't going to happen if you have any kind of exhaust/make-up air.

John

[chase standifer]

Thanks for the input guys. Someone over on woodtalk brought up that eclectric sprayers often run the finish via hose near the motor to warm water based finishes for easier spraying. He thought the greater danger was probably from running liquids with low flash points running near that heat source might ignite.

[Jim Becker]

I also believe you will be fine with shellac and water borne finishes. But as John mentions, stay away from the more flammable stuff...which you shouldn't spray without a proper environment anyway. It's not just the sprayer... ;)