exploding plastic storage tanks

[protoserge]

I haven't seen it yet, so I'll reiterate this point: NEVER WORK ON A PRESSURIZED SYSTEM.

Tightening brass fittings in a pressurized plastic tank has a higher probability of causing cracks, which ultimately leads to a rupture.

I don't know the details of the GTR tank rupture, but all of the evidence in past explosions points to user error, not a design flaw.

[JamesCH95]

Originally Posted by stinglikeabee

I haven't seen it yet, so I'll reiterate this point: NEVER WORK ON A PRESSURIZED SYSTEM.

Tightening brass fittings in a pressurized plastic tank has a higher probability of causing cracks, which ultimately leads to a rupture.

I don't know the details of the GTR tank rupture, but all of the evidence in past explosions points to user error, not a design flaw.

If any of the mentioned failure mechanisms had been applied to a metallic tank would there have been a failure? Or a brittle/catastrophic failure?

[Lil' Lavery]

Originally Posted by stinglikeabee

I don't know the details of the GTR tank rupture, but all of the evidence in past explosions points to user error, not a design flaw.

In a competition designed for high school students where safety is assessed by volunteers whos professional background may have no connection with pressurized gas systems, the barrier between "user error" and hazardous explosions should be pretty darn high. This isn't about getting a refund for busted tanks, it's about preventing injury. If the current scenario has resulted in repeated failures, it's obviously not adequate.

[Trent B]

Originally Posted by Lil' Lavery

In a competition designed for high school students where safety is assessed by volunteers whos professional background may have no connection with pressurized gas systems, the barrier between "user error" and hazardous explosions should be pretty darn high. This isn't about getting a refund for busted tanks, it's about preventing injury. If the current scenario has resulted in repeated failures, it's obviously not adequate.

Likely a PSA of some sort would be needed, or harsher restrictions in order to prevent future problems. Unfortunately, these tanks are probably perfectly adequate in the other environments where they see a static loading. I recollect Clippard testing tanks last year at several times their advertised maximum pressure without failure in a presumably static low load environment. The environment of FRC is typically anything but static and warrants more care.

I would argue that user error in play would be utilizing the tanks improperly in an environment that they aren't made for. The problem is, teams see other teams successfully doing it and don't take the time to fully educate themselves on the different protocols necessary to make them safe.

If you want to have tanks in an area that risks being hit or needs to be strapped down rigidly, go with metal tanks. Using plastic tanks necessitates finding a location where they will be under minimal load, mounting which will result in no damage, and ideally if one does explode shrapnel will be contained or redirected in a safer direction (i.e. at the ground).

Despite maintenance being a chore that is one of the reasons I now prefer putting plastic tanks in our 3x3 1/8" wall drive tubes. In the event of a fracture shrapnel would be stopped by the walls of the tubes and the drive modules at either end. Additionally I make a huge emphasis of informing any of our students who may work on our plastic storage tanks that if it is leaking you are better off removing the fitting and redoing the teflon tape than continuing to tighten it if it is leaking.

[Tom Line]

Originally Posted by 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.

Who suggested that someone should do that?

[fox46]

Take some heavy socks and make tank cozies! At the very least the fabric will help contain the fragments while allowing the air to escape.

[JamesCH95]

Originally Posted by Tom Line

Who suggested that someone should do that?

You, and someone on 3883 said they covered up their tanks with bumper fabric.

Originally Posted by Tom Line

A spandex sleeve (or even bumper material...) over each tank would be an elegant and easy way to safeguard folks from flying debris, and the porous nature of the fabric would prevent the air pressure from 'exploding' the sleeve.

Hey ANDYMARK! Are you listening?

Originally Posted by FRC3883FRC

Our team had our tanks on our intake a very vulnerable position. We were highly highly HIGHLY recommended by the inspectors (almost to the point of not passing) to cover our tanks. We simply added bumper material over both of the tanks. They still fit right in the same c claps they some with and they dont look all that bad. A couple zip ties and the bumper fabric and we were good to go. You can see in the video that our robot has two red tubes at the top of the intake and around 9 seconds in you can see why they highly recommended covering them up.
Here is the video.
http://www.youtube.com/watch?v=nvAFL...u8USGMhWY2qgkw
If you are using these tanks make some covers or make sure they are in a very safe location.

[Tom Line]

Does anyone happen to know if the Andy Mark white tank that is sold is Clippard, or Pneuaire?

Can someone confirm that the tanks that exploded are only the Clippard brand 'white' threaded version?

[Jim Wilks]

Is Clippard the only maker of plastic tanks? Are the ones from PneuAire also from Clippard, or does PneuAire make their own?. Anyone else?

Are all of the failures so far on Clippard tanks?

[thefro526]

Not to add another reason to not use (or be wary of) plastic air tanks but, has anyone paid attention to the temperatures they're being exposed to, either while in operation or storage?

The published temperature range for the New (2014) Black AVT-PP-35 Tank is 35* F - 100* F (1.5*C - 37.5*C), and I believe (but don't quote me) that the tanks from previous years have the same or at least similar temperature range.

I can think of a handful of different ways that tanks could be exposed to conditions outside of that window, which makes me wonder if environmental conditions play some role in the tank ruptures...

[Wren Hensgen]

Team 225 has managed to make one of the new black plastic tanks fail, but the failure actually occurred on the push-to-connect fitting, which snapped out under pressure. This might be an intentional design, as losing a hose is probably less dangerous than throwing shrapnel around

[JamesCH95]

Originally Posted by thefro526

Not to add another reason to not use (or be wary of) plastic air tanks but, has anyone paid attention to the temperatures they're being exposed to, either while in operation or storage?

The published temperature range for the New (2014) Black AVT-PP-35 Tank is 35* F - 100* F (1.5*C - 37.5*C), and I believe (but don't quote me) that the tanks from previous years have the same or at least similar temperature range.

I can think of a handful of different ways that tanks could be exposed to conditions outside of that window, which makes me wonder if environmental conditions play some role in the tank ruptures...

The compressor definitely outputs air warmer than 100F, evidenced by the compressor routinely getting "too hot to touch." I don't know if plastic tanks have ever gotten to that temperature, but the possibility is definitely there.

[Mr V]

Personally I'm for a ban of the plastic tanks. It is not that they are inherently unsafe, but that there are so many ways to unintentionally compromise their safety that are likely to occur when used in FRC.

[Racer26]

Originally Posted by thefro526

Not to add another reason to not use (or be wary of) plastic air tanks but, has anyone paid attention to the temperatures they're being exposed to, either while in operation or storage?

The published temperature range for the New (2014) Black AVT-PP-35 Tank is 35* F - 100* F (1.5*C - 37.5*C), and I believe (but don't quote me) that the tanks from previous years have the same or at least similar temperature range.

I can think of a handful of different ways that tanks could be exposed to conditions outside of that window, which makes me wonder if environmental conditions play some role in the tank ruptures...

1310s tank would have definitely seen temperatures (at least briefly) outside of that range, if only when transiting between their school and haul vehicle, and then into the venue. If the haul vehicle sat outside not running anywhere for a while, the tank could have conceivably seen temps in the neighborhood of -20C.

Originally Posted by Wren Hensgen

Team 225 has managed to make one of the new black plastic tanks fail, but the failure actually occurred on the push-to-connect fitting, which snapped out under pressure. This might be an intentional design, as losing a hose is probably less dangerous than throwing shrapnel around

Well, its a failure, but at least its not a catastrophic failure of the part, resulting in explosive decompression and flying shrapnel.

[Trent B]

Originally Posted by Jim Wilks

Is Clippard the only maker of plastic tanks? Are the ones from PneuAire also from Clippard, or does PneuAire make their own?. Anyone else?

Are all of the failures so far on Clippard tanks?

The PneuAire tanks are distinctly different in design from the Clippard tanks. Unfortunately I don't have a pair handy to take photos of, but I have handled both at the same time this past build season.