My PrincetonTec flashlight exploded! OUCH!

[fracmeister]

I mainly post here, but candlepowerforums seemed to be the right spot for this one. Those of you with dive lights or sealed flashlights shoudl definitely read this.

 

[Esav Benyamin]

Sheesh! I think I'm gonna go back to setting the neighbor's car on fire when I need to light up the night. Sounds safer than using a flashlight.

I hope you didn't sustain any permanent personal damage, though. Too bad about the pants.

 

[Cougar Allen]

I've been thinking about that incident, and the other reports in that thread of flashlights exploding. I think Fracmeister's experience was the worst case; a flashlight explosion can't get any worse than that. Flashlights explode because hydrogen leaks from a battery and forms a hydrogen-air mixture in the sealed case, and that is ignited somehow (it doesn't take much at all to set off the right mix; a tiny static electricity discharge would do it, or the tiny spark in the switch every time you turn a flashlight off -- the friction of unscrewing the cap might be enough). There's a limited amount of air in the case, though, and that limits the explosion, no matter how much hydrogen the battery emits.

I don't want to store all my water resistant flashlights with the cap partly unscrewed. I'm thinking from now on, though, whenever I unscrew the cap to change batteries I'll be expecting it to go off and I'll treat it like unloading a pistol. I'll point it in a safe direction and keep my hand out of line with the "muzzle" as I unscrew the cap, just like I avoid putting my hand in line with the muzzle of a pistol as I jack the slide back to clear it. I think that will be adequately safe. If it goes off the cap will tear out of my grip and no doubt sting my fingers a bit, and the flame coming out could burn me a little too, but I figure that can't do me any real injury. The danger is if the cap hits me, especially if it only travels an inch or two before striking my hand; then I'd get hit with the full muzzle velocity.

Thanks for posting that! I'd had no idea there was any danger in unscrewing a flashlight cap.

 

[fracmeister]

I think Cougar's suggestion would have decreased my brief pain. but my hands weren't in a very different position than what he described. The flashlight would still have been destroyed as the lens cap, bulb and PCB were all blown off. I didn't see any flame and the switch was off. I am wondering if the explosion was limited by the air in the light or the H2 generated. It exploded just as I started unscrewing it -- perhaps allowing air in? I subsequently have tried pulling the screwed on lens cap straight off the threads. No easy feat, confirming that it was a pretty strong explosion.

And the sound was almost exactly that of a Glock 34 firing a 9mm round. So much so that my I was thinking someone had shot my pistol rather than thinking the flashlight went off!

 

[Cougar Allen]

Seems to me it couldn't be letting air in; it had to be pressurized above atmospheric pressure. There are a lot of reports of them exploding just as the cap is unscrewed; that has to be igniting it. I can think of several ways that could happen -- the friction, and it's rubbing on a rubber O-ring; that could cause a static discharge. It doesn't take much. I have experience with acetylene-air mixes and they are very easily ignited -- basically you have to expect if the right mix is in a container it will go off. Hydrogen-air ignites at a lower temperature than acetylene-air if I recall correctly. A gas mix only needs the temperature to be at ignition point in a volume the size of the point of a pin and that sets off the whole volume of mix. Whenever there's friction there's heat, only in a tiny surface area one molecule thick, maybe, but that's enough.

The bigger the flashlight the more hydrogen-air mix it can hold. Small flashlights should be less dangerous.

Maybe the manufacturers should design to reduce the empty space inside.

Come to think of it, though ... my reasoning could be all wrong here. Maybe there's much more hydrogen than air in the flashlight and it's when the cap is opened and the hydrogen jets out and mixes with the ambient air that the correct mix for an explosion is formed. You didn't see any flash of flame, though ... well, it would be very brief ... I dunno. Were you in a bright place? The muzzle flash from a 9mm isn't conspicuous in bright sunlight; it's a blinding fireball in the dark, especially with a short barrel or a slow-burning powder....

If the explosion or part of it is in the open air outside the flashlight body that'll make flash and bang but it won't contribute to propelling the cap like a bullet. That's the danger, the cap and maybe fragments of the lens.

 

[grnamin]

Pelican Products used to have hydrogen gas absorbers in their Saberlite Submersible model at least. I'm not sure if they still have the absorbers now. That may help alleviate the volatile environment within waterlight flashlights.

 

[fracmeister]

The PrincetonTec models have them as well -- small platinum bits. But if you read the cpf comments there appears to be a mode in which the generation of H2 can be accelerated, particularly for a partially depleted bank of batteries.

 

[fracmeister]

Well, they replaced my Surge, no questions asked (other than how I was doing which is "no damage").

I did read the instructions this time.

IMPORTANT - remove batteries during long periods of storage. Remove exhausted batteries from light immediately.
The batteries were definitely running low... hey I was trying to replace them!

and NOTE - Some battery forumlations can emit hydrogen gas. This gas can create an explosion potential in sealed devices if not vented or removed. Your light is equipped with a platinum catalyst that will remove this gas. When replacing batteries, visually inspect reflector assembly for broken or missing catalyst. If catalyst appears to be damaged or the light has flooded, replace the catalyst assembly before using.

Not really relevant to my problem, but good to know.

So, PrincetonTec recommends a step in excess of loosening the cap -- they suggest battery removal.

Just thought I'd pass that on.