Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Cylindrical aquarium housing 1,500 exotic fish bursts in Berlin

theguardian.com

Post reply on HN
Print view View original

151–160 of 265 posts

Re: Cylindrical aquarium housing 1,500 exotic fish bursts in Berlin

#151

Post by bombcar »

wyuenho wrote: post #14

From the guidelines: > Off-Topic: Most stories about politics, or crime, or sports, unless they're evidence of some interesting new phenomenon. Videos of pratfalls or disasters, or cute animal pictures. If they'd cover it on TV news, it's probably off-topic. HN really needs a European mod to maintain the quality of this board.

I mean as long as we're quoting (and breaking) the guidelines:

> Please don't complain that a submission is inappropriate. If a story is spam or off-topic, flag it. Don't feed egregious comments by replying; flag them instead. If you flag, please don't also comment that you did.

(someone flag me, I can't flag myself)

Re: Cylindrical aquarium housing 1,500 exotic fish bursts in Berlin

#152

Post by mardifoufs »

bombcar wrote: post #137
barbegal wrote: post #117

From an engineering perspective these sorts of acrylic tanks are a nightmare to ensure they are safe. The seams are impossible to inspect rigorously so the only real way of checking that they are safe is to load them with an excess pressure ( https://en.wikipedia.org/wiki/Hydrostatic_test ). This can't be done with a tank of this size so the engineers can only real fall back on giving the tank excessive safety margin…

Is there no way to detect cracks or is it just prohibitively expensive to do so? I know that metal fatigue is a known thing that airlines check for and when they went to carbon fiber they had to develop tools to detect fatigue/cracks.

From my limited knowledge[0], it does not seem like this would be an easy structure to scan for inspection. Acrylic can even used for the wedges that interface between the phased array (or single element) probe [1] because it's very good at not interfering with ultrasounds. Water is also a very good "coupling" material, which makes it even harder to get a useful scan since there would be no "backwall" reflecting back the ultrasounds on the other side of the acrylic.

There are other ways to scan for defects, but I'm mostly familiar with ultrasound phased arrays. Other NDT methods are also hard to use in the field after manufacturing.

[0] I work in NDT (non destructive testing), but I'm not a physics engineer and (work further up the stack from the actual probes/scanners). So this is an approximation, and I might be wrong.

[1] This random link is pretty useful to get an idea I think, but I'll also ask around our inhouse scientists if I get the occasion today!

https://www.olympus-ims.com/en/ndt-tutorials/transducers/pha...

Re: Cylindrical aquarium housing 1,500 exotic fish bursts in Berlin

#154

Post by matheusmoreira »

barbegal wrote: post #117

From an engineering perspective these sorts of acrylic tanks are a nightmare to ensure they are safe. The seams are impossible to inspect rigorously so the only real way of checking that they are safe is to load them with an excess pressure ( https://en.wikipedia.org/wiki/Hydrostatic_test ). This can't be done with a tank of this size so the engineers can only real fall back on giving the tank excessive safety margin…

What's the best material for a tank like this, if not acrylic? Normal glass? Not educated on this subject.

Re: Cylindrical aquarium housing 1,500 exotic fish bursts in Berlin

#156

Post by barbegal »

lqet wrote: post #121
barbegal wrote: post #117

From an engineering perspective these sorts of acrylic tanks are a nightmare to ensure they are safe. The seams are impossible to inspect rigorously so the only real way of checking that they are safe is to load them with an excess pressure ( https://en.wikipedia.org/wiki/Hydrostatic_test ). This can't be done with a tank of this size so the engineers can only real fall back on giving the tank excessive safety margin…

Would it be possible to construct a seamless acrylic tube, maybe on-site?

Not of this size. Certainly single pieces are used in other applications where safety is even more critical such as submersibles. But manufacturing a tube this big would be impossible.

Re: Cylindrical aquarium housing 1,500 exotic fish bursts in Berlin

#158

Post by usefulcat »

barbegal wrote: post #117

From an engineering perspective these sorts of acrylic tanks are a nightmare to ensure they are safe. The seams are impossible to inspect rigorously so the only real way of checking that they are safe is to load them with an excess pressure ( https://en.wikipedia.org/wiki/Hydrostatic_test ). This can't be done with a tank of this size so the engineers can only real fall back on giving the tank excessive safety margin…

The article specifically says that this particular aquarium was made of glass?

Re: Cylindrical aquarium housing 1,500 exotic fish bursts in Berlin

#159

Post by fwungy »

ChuckNorris89 wrote: post #46
feb wrote: post #33

According to a german news report [1], it could be due to material fatigue. [1] https://www.rbb24.de/panorama/beitrag/2022/12/berlin-karl-li...

Fatigue from what? It's a stationary object housed indoors, not a car or plane that goes through several climatical, temperature and environmental changes to cause fatigue. Unless they were subjecting the tank to draining and filling cycles often, it seems more like a design/build fault that was a ticking time bomb from the start.

Building temperatures were mandated reduced due to energy sanctions. This put stress on an already sensitive structure and caused it to fail.
Post reply on HN