I’ve been mulling this around in my head after seeing the kids had been experimenting with pneumatics this past weekend. In the interim, if teams insist on using the plastic tanks rather than switching to metal, what about placing some sort of containment device around the tanks? I was thinking a heavy sock with tie wraps around where the pneumatic tube connects to the fitting. At the very least it should help contain any shrapnel or at least reduce its kinetic energy should one rupture.
I wonder whether mere tensile strength is sufficient, or whether the shearing action of those shards in motion is a consideration? And do small shards pose less of a risk due to their small mass (like birdshot compared to buckshot)?
Although your suggestion of a sock sounds pretty good, what about versions of the mesh bags used to contain onions and other similar vegetables? (Those might be easier to incorporate into existing designs.)
This is an opportunity for a good discussion on risk, and what drives prudent decision-making. How much of the hazard and the associated uncertainty are realistically transferable between the specific tank that failed, others in its lot, others of the same model, others in the product line, and other product lines of similar manufacture? Or is this strictly a matter of perception being everything—action is being taken, so outsiders will perceive it as the responsible course of action?
I’m curious about what specific factors are driving your decision—not particularly to criticize you, but to discuss the proposition that a drastic response often isn’t a methodologically valid way to approach a spectacular failure.
After all, you (and everyone else) obviously take plenty of risks with the students. It’s our responsibility to try to manage those risks in a sensible way.
2 tanks burst at the same time? What was the ‘leak checking’ procedure? (tightening fittings or spraying soap?)
Were the tanks connected together with a common brass fitting, or a flexible hose between them?
Guys,
The OP posted that further examination showed what appeared to be a manufacturing defect in the plastic. Please remember that these tanks have been used on FRC robots in the past without failures.
In addition to Al’s statement above: Clippard,* FIRST* and AndyMark take safety VERY seriously and all of those parties are currently evaluating the situation. I believe they will have a statement and course of action very soon.
Al, correct me if I’m wrong, but I was of the impression that these Clippard tanks were new, and not before tested in an FRC environment, but that they were an answer to similar model tanks from another manufacturer used in the last couple FRC seasons by some of the heavy hitters like 217 and 1114.
Yes the Clippard tanks are new and not what we used last year. We will be harvesting the tanks from last years bots until this is resolved.
Would it make it safer to put a wrapping of duct tape around them, at least for testing and until we are given an actual course of action? I realize this would likely render them illegal, but might help to contain any shards since dict tape usually splits on a seam.
The chemicals in the adhesive of duct tape could also potentially weaken the plastic, I would be wary of this as a solution.
Theoretically, same materials, similar specs. I would suspect we are going to have a response soon. Please be patient. Use the tanks from last year in the meantime.
Indeed they should, but all too often people who don’t understand the science behind a decision are the ones who make it, especially when the government is involved…
I’ll never forget teaching in California when a law was passed (unanimously by both houses and signed into law by Governor Davis) that outlawed “chemicals made from dangerous elements” in science classrooms… Further investigation indicated that “dangerous” included anything “toxic” or “flammable”.
Not withstanding the absurd misunderstanding that toxicology is a matter of dosage (and that even water ingested in sufficient amounts is toxic), the ignorance of even middle school level chemistry was quite astounding.
Among the things unintentionally outlawed in California science classrooms: matches, table salt, water, air, humans.
Although your suggestion of a sock sounds pretty good, what about versions of the mesh bags used to contain onions and other similar vegetables? (Those might be easier to incorporate into existing designs.)
My thoughts around using the sock was that they would be elastic and absorb the energy of an expanding tank while allowing the compressed air to permeate the fabric and release pressure. The onion bag idea could work as well but are they not a relatively non-elastic material?
Would it make it safer to put a wrapping of duct tape around them
I think since the duct tape would be wrapped around the tank tightly it would tear as the tank expanded. I feel it would also contain the compressed gas which could cause it in itself to burst like a balloon.
I’ll just leave this here…
I do not advocate teams reinforcing their plastic tanks.
Though the added weight a reinforcing a plastic tank might make metal tanks weight-effective again. They will certainly be safer.
From the Tristan
“I’m curious about what specific factors are driving your decision—not particularly to criticize you.”
No criticism taken. Here is the reasons for my actions. Another school had an accident a few years ago and we are under a microscope. A failure of one of our tanks after being the alerted to the problem would cause us serious trouble. Our students run our machine shop and welder. I do not want to risk that program. The type of tank is not critical for out prototype and the definitive answer should be out in time for the final robot. While we all manage risks all the time because of our situation this risk is not needed or worth taking.
FYI, here is an email I just received.
Dear FIRST Team Member,
Clippard has been made aware of an incident where the white
polypropylene air tank had burst. There are several factors that
could have led to this and Clippard is evaluating the issue. We have
yet to replicate the occurrence at a pressure below 700 psi, and
believe this to be an isolated occurrence. However, working with
tanks under pressure can lead to dangerous circumstances and
precautions must be taken.Until a full evaluation is complete and in the interest of safety,
Clippard recommends that your team dispose of their current tanks and
replace them with the SS-1154, the 32in3 metal version, at no charge.
To replace your tank, reply to this email and include your team name
and number of tanks to be replaced. We apologize for any
inconvenience and wish you all success in your upcoming competition.Sincerely,
Clippard Instrument Laboratory, Inc.
You really can’t beat that for customer service!
We have at least 8 of the Clippard Tanks…until we know for sure if they’re actually bad, I think that if anything we’ll just ask for the minimum number of replacements that we actually need on robots this season. If they are indeed safe, the weight savings are worth it.
Does someone have the email address to request replacement air tanks from Clippart?
Thanks!
One of our air tank’s was cracked on the “rim” right out of the box. We’re glad we spotted it before we put it on to our robot all thanks to this thread. Thank you, and were glad everyone’s okay!
Spencer,
I bet that the manufacturer will want to know or see that defect.