exploding plastic storage tanks

[Gregor]

Originally Posted by Tytus Gerrish

this makes me want to test one to failure just to see that it takes to bust em

Don't do it. It's seriously scary, especially when you're 4ft away from it. I couldn't hear from the ear facing the tank for about 15 minutes, and it hurt for the rest of the weekend. The shrapnel went flying into a pit about 30 ft. away, and killed our driver station computer.

Don't do it.

So it seems that this has happened at least four(?) times in the last two years. If FIRST was serious about safety these would be outlawed.

[thefro526]

Originally Posted by Jared Russell

In one case, the problem was a student over-tightening a fitting to the plastic threads. In another case, we believe that Loctite was used on the fitting threads.

Thankfully, the new (for 2014) Black Clippard Tanks that AM sells have a push to connect fitting that should (in theory) eliminate any failures that the connection point, or at the very least cause the hose to pop off before the tank fails. Otherwise, over tightening of threads, especially NPT threads into plastic is an issue that's difficult to make 100% fool proof.

Originally Posted by mman1506

1310 had an air tank explode in their pit and the pieces went right through the FRC Ball puncturing 2 layers of fabric and rubber without slowing it down. I doubt the bumper fabric would be able to contain it.

Assuming the proposed sleeves all are wrapped reasonably tightly around the tanks, it shouldn't take much to contain a tank failure pretty well. In the instance you mention, it sounds like the tank burst and the pieces of shrapnel were allowed to accelerate to some speed (becoming projectiles) and then they punctured the ball. Assuming you're containing the failure as it happens, the chances of getting projectile type shrapnel will be significantly lower (since they'll be slowed as they contact/break through the sleeve) and if anything does mention to get past the sleeve, it will be traveling significantly slower than if the sleeve were not there.

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We're actually running two of the black clippard tanks on our robot now, and haven't had any issues. Our mounting is fairly simple, we ran a strip of adhesive backed rubber down one of our metal structural members and then ziptied the tank to the member. The rubber does a pretty good job of holding the tank snug while also allowing it to have a bit of cushioning.

[Racer26]

Originally Posted by JamesCH95

No, no it wouldn't. See other posts in this thread about shrapnel puncturing ball covers without issue.

I think I posted something similar last year... but biaxial kevlar sleeve or similar would be required to provide even modest protection. Multiple layers would be required IMO, and a good way to keep the ends of the sleeve closed.

Edit: what velocity air flow is needed to exert a significant pressure on a fabric? Said fabric doesn't need to be air-tight to sustain significant loading in the event of a storage tank's catastrophic failure.

I realize what happened at GTR West and 1310's exploding tank puncturing their ball and killing a laptop.

I can't help but wonder, though, if even a bumper-fabric sleeve would eat a significant amount of the kinetic energy, when applied at the failure point (thereby partially inhibiting the extreme acceleration of the plastic shrapnel). Agreed that kevlar would be better, though.

[Steve W]

Originally Posted by donkehote

One of 1310's tanks blew at GTR west. One of the mentors was tightening a fitting into the tank with the tank inflated to 120 psi try to eliminate a leak. The tank exploded in the mentors hands, (thankfully no injury's) and destroyed the laptop that was below the tank, aswell as popping one of their balls. The shrapnel was sent flying all the way to the roof of the fieldhouse, and was quite a shock to those at the event.

I spoke to the mentor involved within a minute of the explosion. He told me that he had tightened the tank and was testing the tank when it exploded. I may be wrong but if he was tightening when it exploded he would have had shrapnel in his hands or body. There was enough force to blow the top off of a laptop and throw plastic everywhere and he had only a small minor cut on one of his hands. There are many "stories" going around about what happened. Please don't pass around hearsay.

That said, air pressure is nothing to play around with. As we have seen an many posts about exploding tanks this year, safety MUST be taken when using pneumatics. Many people are trying to find a way around the Safety Rules by saying they are not rules. In FIRST we do not want to see people injured. We want FIRST to be a positive experience for everyone. Losing a part of your body or an eye is NOT a positive experience. I know, it won't happen to you, but we don't want to take a chance. Some rules are maybe a bit overboard but I would rather have that than have someone hurt because of lack of rules.

[Ether]

Originally Posted by donkehote

The tank exploded in the mentors hands, (thankfully no injury's)

Maybe not visible ones. I am concerned about his hearing. Voice of experience, 43 years later...

[Tytus Gerrish]

as a person whom has had PVC explode in my hands I would like to testify that you won't necessarily get pvc shrapnel damage to your body

[cgmv123]

Not over tightening the fittings is important as well. The threads are tapered, so the tighter they get, the more force is exerted on the tank. Brass vs. Plastic, plastic tends to get stressed and deform more.

[JesseK]

As soon as someone gets seriously injured, I conjecture that FIRST will require metal tanks again. Those little tanks from Clippard are a pain in more ways than one, but FIRST HQ may have their hands bound by insurance should it happen.

I think the biggest mitigation moving forward is a pneumatic safety campaign. Perhaps we could come up with some standardized signage to post at events? Things like

• Don't over-tighten fittings
• Do not use Loctite on fittings
• DO release pressure before adjusting
• Unofficial Pneumatic Safety Consultants: ________
• Teams who are willing to help with any pneumatic situation: _______

Any takers?

[Tom Line]

Originally Posted by Gregor

Don't do it. It's seriously scary, especially when you're 4ft away from it. I couldn't hear from the ear facing the tank for about 15 minutes, and it hurt for the rest of the weekend. The shrapnel went flying into a pit about 30 ft. away, and killed our driver station computer.

Don't do it.

So it seems that this has happened at least four(?) times in the last two years. If FIRST was serious about safety these would be outlawed.

I STRONGLY disagree that the only avenue of improving the potential safety issues around plastic pneumatics tanks is outlawing them. I would much rather see a numbers-driven problem solving method applied.

However, I can see vendors stepping away from supplying a 'safety' item like a sleeve since it becomes a question of liability if someone gets injured.

[mman1506]

Whether a sleeve is an effective solution or not wrapping a piece of bumper fabric around a tank in a bad location and deeming it safe without any proper testing is ignorant.

[Lil' Lavery]

After observing a crack in one of our plastic tanks in our shop last year, 1712 straight up refuses to use them at this point. We'd much rather sacrifice the weight and continue to use Clippard's aluminum tanks. It's simply not worth the risk, imo. I'd hope FIRST's safety rules would follow suit, and either institute a ban on these tanks or a safety procedure to ensure that exploding tanks cannot cause injury.

[Mark Sheridan]

Looks like I am gonna have to relocate my air tanks.

Just a crazy idea that is not FIRST legal:
Could we make our own storage system with large OD high pressure tubing and barb fittings?
http://www.mcmaster.com/#5632K43

This stuff is ductile and could be snaked around, cut to length and should not explode when pierced. Has anyone used this stuff at 120 PSI, the most I ever used is 90 PSI, same with barbed fittings. I am not a fan of barbed fittings but I think this could be safer.

The rules would have to change in order for this to happen. Thought? I am not sure this is the ideal tubing, but this is something I used before that sort of works.

[Gregor]

Originally Posted by Tom Line

I STRONGLY disagree that the only avenue of improving the potential safety issues around plastic pneumatics tanks is outlawing them. I would much rather see a numbers-driven problem solving method applied.

However, I can see vendors stepping away from supplying a 'safety' item like a sleeve since it becomes a question of liability if someone gets injured.

In an ideal world every safety precaution should be taken using all the advice given by the manufacturer and of that said here on Chief Delphi, but that simply does not happen. This is MUCH more dangerous than a HP sticking their hand into the field for half of a quarter of an eighth of a second, yet there are no strict rules on these tanks.

As said earlier in this thread, tanks hose clamped down passed inspection! There was a team at GTRE this weekend with the black Clippard tanks (which are better in terms of not needing fittings) on the bottom of their intake arms which extended beyond frame perimeter and were the first point of contact in high speed crashes with other robots! They passed inspection too.

The black tanks have their place in FRC if mounted correctly in the appropriate location, but the white tanks need to go. They've a hazard to everyone within 30 ft. of them. When teams (including my own) use them incorrectly, it's just a recipe for injury, and it's only a matter of time before someone seriously gets injured.

I've been hit by moving robots, smacked by robot arms, and had my fingers pinched in more robot mechanisms than I care to count, but none of these are even close to the potential danger of these tanks.

[Gregor]

For anyone who doesn't know, these are the terrifying pieces flying through the air that we're dealing with.

[DanielPlotas]

Originally Posted by mman1506

1310 had an air tank explode in their pit and the pieces went right through the FRC Ball puncturing 2 layers of fabric and rubber without slowing it down. I doubt the bumper fabric would be able to contain it.

The ball was punctured by pieces already moving at considerable speeds, but the fabric would be able stop them before they get moving.