Berlin AquaDom explosion - what went wrong? - Page 1
Forum section: electronics / general

author: tom66
author_rank: Super Contributor
timestamp: December 16, 2022, 11:16:21 am
content: https://www.bbc.co.uk/news/world-europe-639969827https://www.dw.com/en/berlin-massive-aquarium-home-to-1500-fish-bursts/a-64119337It's no more. Quite a feat of engineering. For it to fail catastrophically, it seems like there must have been unseen damage. What isn't clear to me is what parts are acrylic and what are glass. The news report talks of people injured by flying glass but the construction was mostly plexiglass according to the 'net, though I suppose in the confusion being cut up by exploding plastic is probably more or less the same.What might cause such a catastrophic failure? I could see the tank leaking but for it to explode like that suggests some catastrophic stress failure.Also, the poor fish. I hope there were no endangered species there.

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 16, 2022, 11:51:50 am
content: There is, or better was, enough glass in the area around the aquarium that would have caused such injuries.I just read that an earthquake station 15km away from the Hotel recorded the event as an earthquake with a magnitude of 1.2 (https://mastodon.social/@erdbebennews)

author: rdl
author_rank: Super Contributor
timestamp: December 16, 2022, 12:34:52 pm
content: I doubt it "exploded" that sounds like the media just getting a bit carried away. Catastrophic failure I could believe. All that moving water probably blew out the hotel windows causing the glass shards. It's a crazy thing to happen no matter what.

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 16, 2022, 12:40:23 pm
content: I totally agree, Ii don‘t think that it was an explosion. The effect looks like one. But with that amount of water that‘s no surprise.

author: Ian.M
author_rank: Super Contributor
timestamp: December 16, 2022, 01:10:21 pm
content: It wasn't a bomb, it was a time bomb!Acrylic plastics are notorious for stress cracking and poor chemical compatibility, and its generally inadvisable to use them under significant tension. Simply drilling a hole near the edge of a sheet of acrylic with the wrong (or no) coolant can create micro-cracks that will grow under stress till critical failure. Using the wrong sealant, failing to deburr a hole so there's point loading on the hole to surface corner, or simply overtightening a fastener can also start it cracking.As the outer wall at the base was carrying a hoop stress of approx 620 KN per meter height and (presumably for aesthetic reasons), it didn't have any tensioned reinforcing bands supporting it, all it would take is one tiny mistake assembling it, maintaining it or cleaning it, and future failure became inevitable. It could have been as simple as using the wrong cleaning spray on its exterior!

author: tom66
author_rank: Super Contributor
timestamp: December 16, 2022, 01:25:19 pm
content: Reading some of the information about how it was constructed. Several large sheets glued together then brought into the lobby, with the remainder of the hotel constructed around it after completion. Seems very unlikely it will be replaced without at least partial demolition of the hotel, unless there's some way to go in via the roof. I don't know how much revenue the attraction brought in, it sounds like it was just an incentive to stay at the hotel, as the SeaLife aquarium was separate from it, so it might just be removed and the hotel remodelled. Apparently there's a similar construction in Bahrain.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 16, 2022, 02:55:49 pm
content: Quote from: Ian.M on December 16, 2022, 01:10:21 pmI think it is only the press reporting on the material being Acrylic Plastic.If that is true, it would be horrible.I would assume it was made of Poly-Carbonate Plastic instead, which is much stronger than Acrylic.But who knows....

author: ebastler
author_rank: Super Contributor
timestamp: December 16, 2022, 04:25:21 pm
content: I tried to find some more technical detail on the 'net -- there must be some engineering firms who were involved in the initial construction and proudly explain how they mastered that challenge, which materials were used etc. Didn't find much yet, except for this little gem -- a firm specializing in leak sealing, whose services were needed right after the initial construction:https://web.archive.org/web/20220807223255/https://www.webac-grouts.com/projects/aquadom-berlin/That's an archived copy of the page, since this section of their live site has just been deleted, now throwing a few pages of Typo3 errors. I wonder why...

author: HighVoltage
author_rank: Super Contributor
timestamp: December 16, 2022, 05:07:31 pm
content: Here is a small documentary (partially in English) of how this was built.Allegedly, based on this video, this AquaDom was built in the USA and the material is acrylic.

author: Ian.M
author_rank: Super Contributor
timestamp: December 16, 2022, 05:09:45 pm
content: @HighVoltage,The manufacturer knows for certain - it was Acrylic:https://www.reynoldspolymer.com/category/aquariums-zoos/(bottom right) which leads to:https://www.reynoldspolymer.com/projects/aquadom/Elsewhere you can find the common figures that the outer wall was 16cm thick at the top and 22cm at the bottom.Allegedly it was fully drained for maintenance two years ago. I wonder what was done then . . . It would only take one idiot using Loctite on a bolt in contact with the Acrylic shell to trigger this.

author: coppercone2
author_rank: Super Contributor
timestamp: December 16, 2022, 05:15:53 pm
content: I drilled a hole on the edge of a acrylic and tightened it with a screw, 1 month later it cracked. I used a acrylic drill bit too and drilled with coolant. Very sensitive material

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 16, 2022, 05:20:32 pm
content: And now you know why the other firm withdrew.At some point in the video the American spokes person of the firm states that there are only two companies in the world capable of doing this and that they got the job, and a very impressive one, I must say. With the elevator in the middle. One can only wonder what caused this failure.But like tom66 wrote, the poor fish indeed.

author: tooki
author_rank: Super Contributor
timestamp: December 16, 2022, 06:34:02 pm
content: Poor fish!!I also wouldn’t want to be their insurer: a million liters of water is already horrible for a building, but a million liters ofsaltwatercould mean much, much bigger problems.

author: tom66
author_rank: Super Contributor
timestamp: December 16, 2022, 06:39:45 pm
content: That's a good point. Also a lot of that water will have gone into sewers and underground. It could easily corrode parts of the structure for the hotel and adjacent buildings if it is not cleaned up promptly.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 16, 2022, 09:45:57 pm
content: That's unfortunate.

author: Zero999
author_rank: Super Contributor
timestamp: December 16, 2022, 10:18:37 pm
content: Quote from: tom66 on December 16, 2022, 06:39:45 pmI've heard too much sodium chloride can create other problems in the treatment plant, as the microbes used aren't the right type to deal with it.

author: The Soulman
author_rank: Super Contributor
timestamp: December 16, 2022, 11:54:59 pm
content: How it could have happened:https://www.dumpert.nl/?selectedId=100048979_8401a828

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2022, 12:03:08 am
content: I wonder if AvE will do an analysis?

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2022, 12:04:35 am
content: Quote from: tooki on December 16, 2022, 06:34:02 pmSalt water, yeah, that's extra bad.

author: magic
author_rank: Super Contributor
timestamp: December 17, 2022, 08:52:08 am
content: Quote from: tom66 on December 16, 2022, 11:16:21 amThe fish suffered for a while but they are in a better place now.Poor are the men who thought that they knew what they are doing, for them hell is just beginning right now

author: EPAIII
author_rank: Super Contributor
timestamp: December 17, 2022, 08:56:40 am
content: The coolant may have been the problem. I once sprayed a mechanical, multi-button switch assembly with a tuner cleaner because the contacts were dirty. It had clear plastic buttons on metal fingers and the spray apparently got up in those recesses. For the next several days almost every time someone pressed one of the buttons, it fell off in pieces. The tuner cleaner wicked into the stress cracks and lubricated them into progressing far faster than they were without it.I had to buy and replace all the buttons. After that I removed the buttons before spraying the switch assembly.So yes, some plastics can exhibit very rapid cracking when cleaners are used.Quote from: coppercone2 on December 16, 2022, 05:15:53 pm

author: HighVoltage
author_rank: Super Contributor
timestamp: December 17, 2022, 09:10:29 am
content: When studying at the Hamburg university, we had a little project, researching gases.For this project I built a small pressure chamberAcrylic tube, about 50mm in diameter and 50 mm long and 10mm wall thicknessThe ends were closed with aluminum platesAt about 10 bar pressure, this acrylic chamber bursted into many pieces, even killing a light tube, 2 m above the chamber!We were extremely lucky that nobody was near the chamber at the time.Afterwards we used polycarbonate tubing in the same dimensions, tested it to much higher pressure and never had a problem again.So, I learned early on, to never use acrylic plastic for critical applications.That is why I am so much surprised to read that they used acrylic plastic for this AquaDomBut maybe its is a special acrylic.The final investigation report will probably be very interesting.

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 17, 2022, 10:43:56 am
content: What surprised me was that the tank was constructed from separate parts of the curved acrylic, and that they managed to stick them together without visible seams.For the inner cylinder not to big a problem with a compressing force on it, but the outer cylinder must have had a lot of strain on these seams due to the outward pushing force. Can't but wonder how they did this bonding and make it so strong. It did hold for 19 years.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 17, 2022, 11:19:13 am
content: Quote from: pcprogrammer on December 17, 2022, 10:43:56 amWith a suitable glue with refractive index close to that of acrylic, the seams just disappear completely from sight.Acrylic enables visually stunning structures, clearly this is why they used it. I can confirm the chemical compatibility is total crap. Even just something like water with the usual contaminants in it can cause almost invisible micro cracking.But polycarbonate does not look as nice. It has that smoky or purple tint in it, and a little bit of haziness, too.

author: tom66
author_rank: Super Contributor
timestamp: December 17, 2022, 11:19:51 am
content: The bonding is claimed to be proprietary, but it's a reasonable guess that it's a case of polishing the mating surfaces and then using an adhesive of some kind, there are only so many ways to solve this problem. I wonder if it is possible that at the surface exposed to the water that adhesive could progressively allow water into the joint, which eventually forced two halves apart, especially if the low temperatures of the hotel lobby allowed for some kind of expansion-contraction against the 26C tank water.The problem with this explanation is this might lead to the tank bursting, but I'd expect to see some complete parts of the tank assembly either where the tank was, or at least on the floor adjacent. That would be even more dangerous than the situation we've seen, because a ten-tonne piece of acyrlic crashing through the adjacent hotel block would probably tear a hole in some of the residences. We didn't see that - the pieces of acrylic are, at most, the size of a large sofa in the lobby. Maybe that suggests that the bonding is not simply an adhesive but a plastic welding process, creating effectively a single continuous sheet of acrylic. In which case, the only failure mechanism available is catastrophic.I'm also surprised we don't see much of the central tube remaining, as I would have thought that would be safe from a failure of the outer walls. Imagine if someone had been in that elevator shaft when the main tank burst. That could have been deadly.

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 17, 2022, 11:43:29 am
content: Quote from: tom66 on December 17, 2022, 11:19:51 amOr what about a diver in the tank doing maintenance or the fish feeding.

author: Ian.M
author_rank: Super Contributor
timestamp: December 17, 2022, 11:51:16 am
content: All the shots I've seen so far show the inner tube is still intact. However its probably compromised as its most likely been exposed to the same chemicals the outer shell, and experienced the rapid removal of the inwards stress and a transient outwards pressure differential of up to one atmosphere over much of its length as the water fell out.Got any photos (or video + timestamp) showing significant damage to the inner tube?

author: AndyBeez
author_rank: Frequent Contributor
timestamp: December 17, 2022, 12:15:42 pm
content: The sheets were bonded in 2003. Did theyultrasoundthe material and the bond lines for micro fractures - as you need to do on an aircraft wing/body?So does anyone have access to a mechanical stress simulation package? Would be interesting to calculate the loading at the base of the inner and outer cyclinders; especially as they held 1000 tonne of water. The surface loading at the base would have been similar to that experienced by a nuclear submarine or an orbiting space capsule. And we don't make those from plexiglass. Other factors to model; temperature cycling, vibration from the lift, air pressure on the top surface... even ultraviolet and chemical ageing of the material.An fine example of, if engineers can, then maybe they shouldn't. Fail.

author: tom66
author_rank: Super Contributor
timestamp: December 17, 2022, 12:26:36 pm
content: You can see parts of the inner tube failed here, at least it appears to be part of that area:I'm not sure how much of the tube is damaged. It could have occurred post-collapse when the rest of the structure fell in towards it, perhaps.

author: tooki
author_rank: Super Contributor
timestamp: December 17, 2022, 12:51:51 pm
content: I saw one interviewee on a German news segment who suspected it wasnotfatigue, but mechanical damage. I assume the German authorities, the tank manufacturer, and all the involved insurance companies will be performing extensive analysis on the failure, so I expect we will eventually find out exactly what went wrong.

author: Ian.M
author_rank: Super Contributor
timestamp: December 17, 2022, 12:54:29 pm
content: @Tom66,The area below the aquarium base was a bar + access to the elevator. I don't believe the inner tube extended below the concrete aquarium base. However I think there were curved glazing panels above the bar to give the appearance it did.I agree that looks like a crack in the inner cylinder (right photo behind shard of outer shell). I did say "probably compromised" . . . IMHO the whole inner cylinder is scrap as its probably crazed with micro-cracks, and even if it isn't, the general public would never trust it unless it was completely replaced.@AndyBeez,The hoop stresses are easily calculable (without stress simulation software) if you take the known tank dimensions, and scale off them for the water level. However without knowing the details of the shell and inner cylinder to base joints, and also whether or not any of the weight of the two cylinders was supported from the top, its impossible to calculate the stresses there.Wikipedia claims the water column was 14 m. That's only about 1.4 atmospheres pressure, or about 5% of the typical operating depth for a nuclear submarine in deep water. It is 40% more than the internal atmosphere pressure the ISS runs at. However neither application requires a transparent hull so comparison with them is totally irrelevant except to get a 'human scale' feel for the forces involved.

author: MrMobodies
author_rank: Super Contributor
timestamp: December 17, 2022, 07:57:06 pm
content: According to this article there was there a power cut before the explosion.https://www.bbc.co.uk/news/world-europe-64010677QuoteI wonder could that be a contributing factor?I mean if there was any power used to maintain a set water temperature.Quote from: tom66 on December 17, 2022, 11:19:51 amhttps://abcnews.go.com/International/wireStory/huge-berlin-aquarium-bursts-housed-1500-tropical-fish-95405351QuoteSo it was -10c before the explosion but that is speculation.

author: langwadt
author_rank: Super Contributor
timestamp: December 17, 2022, 08:31:10 pm
content: Quote from: MrMobodies on December 17, 2022, 07:57:06 pmhow do you interpret "followed the incident" as being before it happened?if you spill 1 million liter of saltwater, you are probably going to lose power ...

author: ebastler
author_rank: Super Contributor
timestamp: December 17, 2022, 08:44:21 pm
content: Quote from: MrMobodies on December 17, 2022, 07:57:06 pmThe aquarium tank was located in a hotel lobby, i.e. a well-heated, temperature-controlled environment. And any source which uses the word "exploded" in this context can't be trusted with their speculation anyway.(Edit: typos...)

author: MrMobodies
author_rank: Super Contributor
timestamp: December 17, 2022, 08:49:48 pm
content: Quote from: langwadt on December 17, 2022, 08:31:10 pmI interpret the power cut before the explosion happened.For you to ask obviously my interpretation is wrong.*Aaah I see, the flood caused the powercut.Sorry about that.

author: tom66
author_rank: Super Contributor
timestamp: December 18, 2022, 12:04:41 am
content: Quote from: MrMobodies on December 17, 2022, 07:57:06 pmThis is speculation I think which originated from the police, but I am sure the lobby area was heated somewhat; to not do so would be greatly uncomfortable for anyone walking through. However, it *is* conceivable, due to the current price of energy, that the heating was reduced. So perhaps instead of 20C, with a 6C delta between the inside and outside, maybe the lobby was kept around 15C, and maybe colder overnight? I am not sure what the law is in Germany, but there was something about public buildings being restricted for heating in winter due to gas shortages, maybe this applied to hotels too?

author: Infraviolet
author_rank: Super Contributor
timestamp: December 18, 2022, 12:33:09 am
content: Does anyone know if any footage of the moment of the burst was captured? I heard it happened in the early morning hours, but was there CCTV? if there is it might be very revealing as to how the burst happened, also it would be facinating to truly see what the event looked like as it happened.

author: tom66
author_rank: Super Contributor
timestamp: December 18, 2022, 12:36:49 am
content: There is probably at least some CCTV, and assuming the DVR wasn't sitting right under the million litres of salt water, that footage will be analysed to see what happened. Whether it was pointing at the tank was another matter, it seems unlikely you'd need to film that unless you were expecting catastrophic failure. I think it's unlikely that such footage gets released unless the German state decides to conduct whatever their equivalent of a public enquiry is, given it's not a public building and no one is dead there is probably no scope for that. It is probably a matter for the insurers and lawyers at this point, so unless someone leaks the footage we'll just have what their report says (or maybe the Reynolds company or another construction firm will end up in court - if so it's likely the footage would make an appearance.)

author: AndyBeez
author_rank: Frequent Contributor
timestamp: December 18, 2022, 12:56:12 am
content: Quote from: Ian.M on December 17, 2022, 12:54:29 pmIn fresh water the depth pressure at 14 meters is 19.85 psi, but in salt water this rises to 20.38psi. The added 0.53 psi equates to an extra 35cm in depth. A million litres of salt water weighs in at 1,023 tonne, 26 tonne more than the 997 tonne for just fresh water.

author: Ian.M
author_rank: Super Contributor
timestamp: December 18, 2022, 01:18:06 am
content: Yes, and the density also varies with temperature, but the difference is even smaller. It really doesn't matter as we don't know the fill depth accurately enough for a density difference of under 3% between fresh and sea water to be significant.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: December 18, 2022, 01:37:54 am
content: As long as they did their sums using salzwasser

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 18, 2022, 06:33:48 am
content: Quote from: bigfoot22 on December 18, 2022, 02:47:24 amThe outside of the tank was over 8 meters of of the lobby floor, so no passing by to stick anything to it.

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 18, 2022, 07:06:45 am
content: True, but I doubt it to be fully open. To much of a liability on someone getting hurt. And then still the inner tube may have survived and not have been the cause of the whole ordeal.

author: tom66
author_rank: Super Contributor
timestamp: December 18, 2022, 08:42:30 am
content: If the inner tube broke first, the failure would have been to flood the lobby and lift with water and fish, but the tank itself would still look relatively intact. Instead, it looks like the outer wall failed first, and in the collapse, it may have damaged parts of the inner tube.

author: ebastler
author_rank: Super Contributor
timestamp: December 18, 2022, 09:03:46 am
content: Quote from: tom66 on December 18, 2022, 12:04:41 amMore speculation. There was a large bar and café in that lobby, right beneath the aquarium. People were meant to sit there, eat and drink and be comfortable. Rest assured that it was not at 15°C.Quote from: bigfoot22 on December 18, 2022, 06:54:05 amSheesh, of course the elevator cabin was fully enclosed, by transparent walls which were part of the moving cabin. You could, like, squeeze your fingers otherwise.The level of uninformed speculation in this thread is particularly bad. Why not use at least the publicly available information?

author: Barny
author_rank: Frequent Contributor
timestamp: December 18, 2022, 11:02:11 am
content: My guess is that some cleaning company used an alcohol based cleaning agent.Or some diligent person desinfected EVERY surface.The fumes of disinfectant could also added to the disaster to.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: December 18, 2022, 11:16:14 am
content: One assumption is the aquarium burst at the bottom of the tank. The break may have been higher up, causing the acrylic to unzip in a catastrophic failure. The 'nitch' that broke it may even have been on the very top edge. Going unnoticed for days/weeks, the near invisible crack propogated slowly downwards, until reaching the depth where load exceeded strength.Only the fish know the truth, and they ain't here to talk

author: amyk
author_rank: Super Contributor
timestamp: December 19, 2022, 12:40:19 am
content: Quote from: ebastler on December 18, 2022, 09:03:46 amI think what he's saying is that they could've adjusted the thermostats to a lower setpoint during the night in order to save heating costs when there might not be people in the lobby, leading to more thermal cycling.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 19, 2022, 03:36:16 am
content: This is a fish genocide.

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 07:48:11 am
content: Quote from: Barny on December 18, 2022, 11:02:11 amI think we can safely rule that out, since it was completely out of reach, and there’s no way they’d leave cleaning up to a regular maid service even if it had been in reach.

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 07:55:07 am
content: Quote from: ebastler on December 18, 2022, 09:03:46 amI’ve seen discussions elsewhere where people are claiming the atrium was barely heated above ambient, and that the “uninsulated”* glass roof would have led to the air at the top being colder than at the bottom…* more speculation by someone who apparently is unaware of the existence of double- and triple-glazed insulated windows.I looked at the hotel website. There is — well,was— a bar in the atrium. I agree with you: absolutely no chance that space was not heated to indoor temperatures.Besides, I’d think that the requirement for the water to be kept at its stable 26°C would have largely negated any advantage to heating the air less. They’d just have to put more energy into the water to stop it from cooling off too much.

author: AndyC_772
author_rank: Super Contributor
timestamp: December 19, 2022, 09:11:02 am
content: Quote from: tooki on December 19, 2022, 07:48:11 amI'm not so sure about that. During Covid, anything and everything got liberally sprayed with whatever product was to hand that said "anti-viral" on the label, and this was seen as a Good Thing (TM).

author: tom66
author_rank: Super Contributor
timestamp: December 19, 2022, 09:24:22 am
content: It is possible that the bar was using infrared heating to reduce costs, whilst the air was kept colder. But it does seem a bit odd for a 'premium' location to do that. But, after last orders, maybe they did reduce the air heating power to save money?Regardless it's clearly a terrible design flaw if colder air could lead to the failure of these structures. Heating systems fail sometimes!Though I do agree keeping an aquaria at 26C year round is surely a significant consumer of energy, probably the biggest single consumer in the building.

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 10:41:40 am
content: Quote from: AndyC_772 on December 19, 2022, 09:11:02 amNo, definitely not! The aquarium was not within reach of anyone’s hands, other than the divers who fed the fish and took care of the enclosure, and they’d know damned well not to use anything improper on the aquarium. (Nor would they use any toxic chemicals, since many cleaners are toxic to marine life.)Quote from: pcprogrammer on December 18, 2022, 06:33:48 amThere is literally no need to disinfect a surface that has no contact with people.

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 10:51:07 am
content: Quote from: tom66 on December 19, 2022, 09:24:22 amAm I literally the only person on the entire internet who simply went and looked for photos of the damned atrium?!? Everyone is just speculating speculating speculating, when the photos make it crystal clear: it’s an indoor space. No radiant IR heaters, no half-outdoor environment, nope, just plain indoors.https://www.domaquaree.de/en/See-and-Experience.htmlhttps://www.radissonhotels.com/en-us/hotels/radisson-collection-berlin/restaurant-barQuote from: tom66 on December 19, 2022, 09:24:22 amI doubt it would save any power anyway, since the huge thermal mass of the water column would stabilize the air temperature around it, and the water had to be maintained at a stable temperature.Quote from: tom66 on December 19, 2022, 09:24:22 amI haven’t seen any evidence that this explanation has any legitimacy whatsoever. Nobody really knows where it originated, but it wasn’t the result of an engineering analysis of the failure. My guess is that someone who walked into the lobby post-burst noticed that it’s cold inside, which it would be since all the doors to the outside were washed out, and started babbling.

author: Ian.M
author_rank: Super Contributor
timestamp: December 19, 2022, 10:54:30 am
content: With a big warm cylinder in the middle of the atrium, unless the whole space was actively conditioned to the tank temperature, there must have been a considerable convection effect in wintertime, with air round the tank rising, being chilled by the glass roof (even if it was fairly well insulated), and falling nearer the atrium walls, so it seems likely that there would have been a gradual build-up of urban particulates on the exterior of the tank. It would have needed regular cleaning to maintain the aesthetic effect, possibly at intervals of a few years or so, possibly more frequently. I'd bet it was cleaned when the tank was drained for maintenance back in summer 2020.- 2020 maintenance

author: tom66
author_rank: Super Contributor
timestamp: December 19, 2022, 10:56:39 am
content: Quote from: tooki on December 19, 2022, 10:51:07 amApparently. I didn't think to check the hotel website, I had assumed they would nuke everything whilst the hotel was still soaked in salt water.OK, so it doesn't seem that temperature is a likely cause.

author: ebastler
author_rank: Super Contributor
timestamp: December 19, 2022, 11:00:56 am
content: This thread is good for months of idle speculation, until the insurance experts release their actual assessment of the fault. Has anyone looked into the position of the planets yet, or the effect of 5G networks?

author: jonovid
author_rank: Super Contributor
timestamp: December 19, 2022, 11:03:24 am
content: explosion - maybe after nord stream 2, it was something dropped into it. accidents will happen like in a movie the Dam Busters

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 11:06:07 am
content: Quote from: Ian.M on December 19, 2022, 10:54:30 amI’m sure it got cleaned regularly, but almost certainly was done by specialists. They wouldn’t have just had hotel cleaning staff do it. It’s possible the aquarium staff itself did it (in which case we’d be talking about people within a highly specialized, expert team), or specialized outsiders.(People don’t realize there are specialty cleaning companies for any imaginable thing. For example, when I worked at the “fruit stand”, every few months we had a specialty company come in to clean all the stainless steel paneling. Other times, a different specialist company to deep-clean the sandstone floor. Both specialist companies, separate from the general facilities maintenance company that did the everyday cleaning.)

author: Ian.M
author_rank: Super Contributor
timestamp: December 19, 2022, 11:16:57 am
content: I agree. It wouldn't make sense for the hotel or even the aquarium to keep a cleaning team trained for high rope access, even if you also used them for exterior window cleaning. Contracting such occasional cleaning out to a specialist company would have been the only sane thing to do.However even the specialists can get it wrong, e.g. if they *think* they are using an acrylic safe cleaner, but its actually a container of counterfeit cleaner with the wrong formula.

author: ebastler
author_rank: Super Contributor
timestamp: December 19, 2022, 11:20:18 am
content: Quote from: tooki on December 19, 2022, 11:06:07 amWhile the AquaDom was located in a hotel lobby, and owned by the investment fund which owns the hotel building, it wasoperatedby the Sea Life aquarium -- a large commercial aquarium located next door. They operate their own facility with many tanks there, so it is safe to assume that they employ full-time experts for all aspects of aquarium maintenance.

author: tom66
author_rank: Super Contributor
timestamp: December 19, 2022, 11:33:32 am
content: Quote from: Ian.M on December 19, 2022, 10:54:30 amInteresting, the guy who was in the construction video was on site for the maintenance. So presumably they had Reynolds Polymer involved. You would expect that they would know what cleaning processes and adhesives to use!

author: themadhippy
author_rank: Super Contributor
timestamp: December 19, 2022, 11:56:04 am
content: regardless of how many specialists you employ mistakes still get made,

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 12:01:17 pm
content: Quote from: ebastler on December 19, 2022, 11:20:18 amIncorrect:QuoteSource:https://www.visitsealife.com/berlin/media/qk1lspla/pressemitteilung-sea-life-berlin.pdf(Also attached)While this leaves open whether care for the animals was done by sealife, maintenance clearly is not.

author: tom66
author_rank: Super Contributor
timestamp: December 19, 2022, 12:11:52 pm
content: Also worth a look (per a Wikipedia source):https://madisongroup.com/wp-content/uploads/2022/09/Investigating_Acrylic_Aquarium_Failures.pdfCurious that the failures seen so far are usually progressive though. You might expect to see an empty AquaDom with a crack running through the middle of it, not one that appeared to fail explosively, so I wonder if the failure method is different to that shown on slides 18, 19 and 21. Those failures seem to be almost universally at the adhesive joint, rather than of the actual acrylic. (Does this mean they do not use a plastic welding process to bond the sheets permanently? I know very little about acrylics to comment on whether this would be viable.)Slide 20 shows a crack that was on a tank built by none other than Reynolds... (not sure who repaired it, but apparently that tank is fine now)https://www.koreatimes.co.kr/www/news/nation/2014/12/116_169594.htmlSlide 27 is also quite interesting, I guess you really want to be approaching the 1010side of the time curve for a product like this, for a long term installation with a life of around 50-100 years. It did do over 19 years, or 6x108seconds. Maybe the warranty was 15 years.Anyone care to calculate the stress on the walls of the AquaDom given the weight of water?Side note - it's crazy to me that there's so much demand for over-sized aquariums that there are several companies in the USalonethat specialise in making them. I can't imagine how many they produce per year to make this viable, but it can't be a small number.

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 19, 2022, 12:17:58 pm
content: The video about the maintenance showed redoing of the joints, and I guess that Reynolds Polymer was called in for that job. Even though special material, it won't last, just as normal silicone in your bathroom.It looked like quite the undertaking that was carefully planed, and most likely also very costly.One can only wonder how often the outside of the tank needed to be cleaned, but with a many million euro investment and possible liability on the line, I doubt they would cut corners and outsource it to some no good cheap ass cleaning company.Think of the insurance claim if someone was killed by it and it turns out to be due to cutting corners.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: December 19, 2022, 01:39:33 pm
content: First rule of engineering fails ask, what has been changed? Countless times buildings and bridges have collapsed after maintenance, upgrade and improvement. I assumed the Aquadom had been in some steady state since it's construction. Nope, it was "modernized" in 2018/19, leaving a potential ticking time bomb: It's possible the update work used materials that were too rigid. The materials work fine in Florida, but this ain't the sub tropics.

author: ebastler
author_rank: Super Contributor
timestamp: December 19, 2022, 02:38:55 pm
content: Quote from: tooki on December 19, 2022, 12:01:17 pmThanks, tooki. It is not quite clear to me what is included in "Wartung und Instandhaltung": The major overhaul a couple of years ago would clearly be included in that term, and it makes sense that this was the responsibility of the owner rather than the operator. But daily maintenance like cleaning, which on the inside of the tank was apparently done by two divers employed full-time -- not sure whether that falls under "Wartung" or daily operation.There is probably a bit of spin-doctoring going on with that press release too. The "separate attraction" was not all that separate, it seems: You always bought a single ticket for both, access to the AquaDom elevator and the other aquairiums at Sea Life. "It wasn't us!" is obviously the message here...

author: Haenk
author_rank: Super Contributor
timestamp: December 19, 2022, 03:02:08 pm
content: I suspect cleaning, creating micro-scratches. Inside and outside. Acryl is not that tough and will scratch easily, even more so if being cleaned/wiped for many years.

author: Stray Electron
author_rank: Super Contributor
timestamp: December 19, 2022, 03:21:23 pm
content: The first question I would ask is what did they mean by "modernize"? And exactly what was done when they did?Given the amount of counterfeit materials (cleaners, adhesives, fasteners, etc) coming out of China and SE Asia today, I wouldn't be surprised to find that some of that was at fault.I talked to a friend of mine that used to do failure analysis for a US Gov military contractor about this incident and he told me that they had a big problem with people using a product call "Chloro-clean" and that it destroyed some plastics within days and also would creep in past the seals in diodes and other electronic devices and would destroy them as well.

author: tom66
author_rank: Super Contributor
timestamp: December 19, 2022, 03:30:21 pm
content: I wonder if "modernize" is a poor translation. I have heard other Europeans use that word when they mean "refurbish". As far as I know they didn't replace the actual panels themselves. That would require the roof structure to be removed (at the very least) and would be extremely disruptive.

author: ebastler
author_rank: Super Contributor
timestamp: December 19, 2022, 03:40:21 pm
content: Quote from: tom66 on December 19, 2022, 03:30:21 pmHere's a short interview which describes the scope of the works - unfortunately German only:https://www.domaquaree.de/de/Modernisierung-AquaDom.htmlIt is indeed "refurbishment" rather than modernization: They removed the old silicone seals, polished and re-sealed the acrylic, and overhauled the elevator. The interview stresses a couple of times that there was a risk of the 20 cm thick acrylic drying out if it is no longer in contact with water from the inside, which could cause cracks. They applied adhesivefoilsfilms to the acrylic to avoid this.(Edit: "Films" it is -- thanks tooki!)

author: iMo
author_rank: Super Contributor
timestamp: December 19, 2022, 04:17:03 pm
content: This kind of funny stuff like the AquaDom shall be designed and constructed such way that in case of a failure the water has the free way to escape without causing catastrophic damages or dead bodies. An assumption such that specific construction will last forever would be pretty naive one, imho..

author: rdl
author_rank: Super Contributor
timestamp: December 19, 2022, 04:23:35 pm
content: I'm not exactly sure why, but this seems a little odd to me.Quote from: ebastler on December 19, 2022, 03:40:21 pm

author: ebastler
author_rank: Super Contributor
timestamp: December 19, 2022, 05:20:41 pm
content: Quote from: rdl on December 19, 2022, 04:23:35 pmYes, that surprised me too, and is counterintuitive. But despite being hydrophobic, PMMA (= acrylic) can absorb water, up to 2% by weight:https://pubmed.ncbi.nlm.nih.gov/22799564/Surprising that thin adhesive foils should be enough to prevent the PMMA drying out. But the application of these foils was nicely visible in the refurbishment video someone share earlier in this thread. Maybe they only need to slow down the evaporation, so it happens slowly and without causing excessive stress in the material.

author: ebastler
author_rank: Super Contributor
timestamp: December 19, 2022, 05:26:55 pm
content: Quote from: imo on December 19, 2022, 04:17:03 pmRight. Just like it's good practice to design towers, bridges and cranes in a way where they gently sink down in case of a collapse, provide an emergency exit to the occupants, and sort the rubble into neat piles in the process.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: December 19, 2022, 05:27:38 pm
content: Quote from: tom66 on December 19, 2022, 03:30:21 pmDuring refurb, the panels were wrapped in plastic film and shrouded in a giant curtain; maybe to ensure the acrylic didn't dry out or go out out of geometry. Modernized; in the UK we say, "in need of updating", so what was updated? Someone clearly felt the need to rearrange the rocks on the bottom of the ocean, but was there a more fundamental motivation? Was the Aqaudom out of it's OEM guarantee? And was the 'modernizing contractor' the same firm as the OEM installer? Until someone puts the broken pieces together like an air crash investigation, no-one will know where the fail started.Either way, this spectacular fail will be a memorable case study for structural engineering students for decades to come.

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 05:54:49 pm
content: FYI to our German-speaking friends, in English, “folie” translates to “film” for plastics, while “foil” is for metals. We never say “plastic foil”, while “metal film” is possible, but then means a thin layer on some substrate (i.e. “Metallbeschichtung”).What I wondered from the start is whether they use scratch-resistant films on acrylic aquaria. Many of the public transit vehicles here in Switzerland are now having films applied to the windows to stop vandals from scratching the glass. The film is essentially sacrificial.

author: tom66
author_rank: Super Contributor
timestamp: December 19, 2022, 06:03:35 pm
content: Theslideslinked in a prior post indicate pedestrian scratches and impacts are just something that has to be accounted for in the design, but it's amazing how little damage is needed to weaken the structure. The indication (chart on slide 27) is that the entire material strength is reduced by around 5x for a 2.5mm deep scratch, which seems utterly mad to me, but material physics is weird. I am not sure whether this is just for the 'wet' side (with the greatest pressure) or if any part of the material could be susceptible.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 19, 2022, 06:06:04 pm
content: Quote from: tom66 on December 19, 2022, 06:03:35 pmThe dry side would be the critical one in this case, as it's under tension, while the wet side is under compression.

author: ebastler
author_rank: Super Contributor
timestamp: December 19, 2022, 06:57:17 pm
content: Quote from: tooki on December 19, 2022, 05:54:49 pmAha, thank you! I have used "foil" in various contexts, and it always felt wrong. But "film" didn't come to mind, although I must have read it many times -- and I never realized that English uses different words depending on the material. Learnt something new today!

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 19, 2022, 07:47:54 pm
content: Quote from: AndyBeez on December 19, 2022, 05:27:38 pmIn the article eblaster provided, they state that near the base it was leaking water and needed attention. They replaced the silicone seal between the concrete base and the acrylic cylinders.Quote

author: rf-messkopf
author_rank: Regular Contributor
timestamp: December 19, 2022, 10:31:34 pm
content: Quote from: tom66 on December 19, 2022, 06:03:35 pmOn German TV a guy from Deutsches Meeresmuseum Stralsund was interviewed who said that in large aquariums it is general practice to regularly check polymer panes for scratches from visitors, and to polish them out as soon as possible. Happens easily when people scrape their backpacks along the pane.

author: james_s
author_rank: Super Contributor
timestamp: December 19, 2022, 10:40:51 pm
content: Quote from: rf-messkopf on December 19, 2022, 10:31:34 pmI'm surprised there isn't a non-structural protective layer on the outside for that reason. Something similar to the adhesive film used to protect car headlights.

author: tom66
author_rank: Super Contributor
timestamp: December 19, 2022, 10:55:24 pm
content: Of course, in this case it's unlikely that the aquarium was scratched by a normal member of the public, except if someone climbed onto it... which is probably something you'd notice. But, could divers accidentally damage it during the routine feeding and cleaning that was performed? A heavy SCUBA tank hitting the walls of the tank accidentally could damage it - and if you weren't paying attention, maybe it would go unnoticed? I can't see how you could spot the kind of damage that leads to unexpected failure unless youvigorouslyinspect the tank regularly. The safety factor is around 11x for these types of tanks, so if the scratch/fracture damage is beyond about 5mm deep (out of a total of 200mm) it sounds like you lose that factor altogether and unzipping is all but guaranteed. How many acrylic aquaria are there out there where divers regularly have access to the interior space? I can think of larger ones, but they are only part acrylic, like around viewing windows and so on.

author: rf-messkopf
author_rank: Regular Contributor
timestamp: December 19, 2022, 10:56:12 pm
content: Quote from: james_s on December 19, 2022, 10:40:51 pmI can only guess but a protective layer would surely degrade the optical properties of the pane and distort. Maybe the visual impression is supposed to be particularly spectacular. However, scratches from visitors probably weren't a problem in the case of the AquaDom, because it seems that the public had no way to touch the panels.I have walked past that building countless times, but I never knew that tank inside even existed. From the pictures it does not look too aesthetically pleasing though, but more like a hydrodynamic test facility.

author: tooki
author_rank: Super Contributor
timestamp: December 19, 2022, 11:49:45 pm
content: Quote from: rf-messkopf on December 19, 2022, 10:31:34 pmSure. But in this case the aquarium was 8m off the ground, so no contact with visitors.

author: james_s
author_rank: Super Contributor
timestamp: December 20, 2022, 12:28:07 am
content: Quote from: bigfoot22 on December 19, 2022, 11:59:13 pmIn other words you either lack an understanding of math and statistics, or you are more driven by emotional feeling than by logic.Yes if a crash occurs you are more likely to survive in a car, however per mile driven you are many times more likely to get into a crash in a car. Per mile traveled, flying is much safer, that is not an opinion, it is an objectively true fact. Commercial aircraft are extremely safe, there are thousands of them in the air at any given time and crashes are so incredibly rare that they make front page news any time they happen. Fatal car accidents happen every single day, they are so common that they don't even make the local news most of the time.

author: EEVblog
author_rank: Unknown
timestamp: December 20, 2022, 02:30:44 am
content: Quote from: ebastler on December 19, 2022, 11:00:56 amWe cant rule out a directed beam energy weapon. Or aliens.

author: james_s
author_rank: Super Contributor
timestamp: December 20, 2022, 05:00:55 am
content: Quote from: EEVblog on December 20, 2022, 02:30:44 amThat might not be quite as absurd as it first sounds, well, the first part anyway. I have some small diode lasers that are capable of >1W of optical power output and can be run from batteries. I really doubt it is what happened here, but an invisible IR diode laser of a few watts might be enough to damage the acrylic, they certainly will set cardboard on fire from across the room. I'm not seriously suggesting that's what happened but it is technically plausible.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: December 20, 2022, 05:02:43 pm
content: Quote from: Zero999 on December 16, 2022, 10:18:37 pmI don't think that's too much of a problem. My water softener uses about 50 pounds of salt a week and all of that goes into a septic tank and it doesn't seem to have any effect on the bacteria that break down the waste.

author: tooki
author_rank: Super Contributor
timestamp: December 20, 2022, 05:25:14 pm
content: Quote from: bigfoot22 on December 19, 2022, 11:59:13 pmWell I’m sorry to be so blunt, but that attitude is just stupid.Quote from: bigfoot22 on December 19, 2022, 11:59:13 pmNope, absolutely incorrect. Most failure modes result in “the passengers didn’t even realize anything went wrong because the 3-4 layers of safety design completely prevented a failure from causing a catastrophe.” Commercial aviation is THE model of how to perform safety engineering, with every incident being thoroughly analyzed and effective countermeasures taken by actually doing skilled root cause analysis.I don’t know of any other industry that even comes close to commercial aviation’s level of safety engineering. (No, it’s not perfect in the Boolean sense. Do not list exceptions to “educate” me, folks, I am well versed in this industry.)And on the other hand, by design, airplaneswantto fly. Things have to go insanely wrong for a plane to literally fall (i.e. complete unrecoverable aerodynamic stall) from the sky. It’s possible to glide a jumbo jet to the ground unpowered, and it’s been done more than once.I highly urge you to deep dive into the YouTube channel called “Mentour Pilot”. He, a commercial airline pilot and trainer, goes into the hows and whys of aviation, including doing FAR more in-depth explanations of aviation incidents, but with the explanations of an aviation insider needed to give the proper context to what happened.Quote from: bigfoot22 on December 19, 2022, 11:59:13 pmAnd this is the root problem with skeptical flyers: loss of control. We know from research that a) people are insanely bad at weighing risk, and b) vastly underestimate risk when they’re in control (and overestimate it when they’re not). You need to be honest and recognize that this psychological bias is why you don’t fly, and not facts.Quote from: bigfoot22 on December 19, 2022, 11:59:13 pmWhat an obnoxiously arrogant thing to say.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 20, 2022, 09:09:28 pm
content: Quote from: EEVblog on December 20, 2022, 02:30:44 amOr maybe it's Elon's fault too. Who knows!

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 20, 2022, 11:07:28 pm
content: One detail that hasn't been mentioned is that while the water would keep most of the tank at basically the same temperature, the part above the water line would be closer to ambient and thus thermal stress is still a possibility.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 21, 2022, 09:58:00 am
content: Isn't the cross stress in a cylindrical shape always twice as high as the stress in direction of the axis?(This might only apply to closed systems like a pressurized tank)But in any case the cross stress should be higher.If so, one could easily measure the circumference of such cylinder and monitor it at the AquaDom bottom, where the static load is the highest. This way there would be an alarm system go off if the diameter gets too large.I wonder if there was any monitoring for mechanical stress in the cylinder.It could have easily be applied and the cost would be minimal compared to the overall construction cost.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 21, 2022, 11:38:28 pm
content: Interesting, especially about the responsibilities, but he says "nobody was hurt", and I beg to differ. Poor fish.#iamfish

author: Bud
author_rank: Super Contributor
timestamp: December 21, 2022, 11:49:30 pm
content: I am guessing the elevator went kaput as well ?

author: PlainName
author_rank: Super Contributor
timestamp: December 22, 2022, 12:01:59 am
content: Quote from: EEVblog on December 21, 2022, 11:15:50 pmWhat does this chappy know that everyone else in this thread hasn't already learned or postulated? This is "A Brit, curious about everything around him, lives in Germany and has a video camera", so appears to be just repeating whatever he's picked up from the likes of YouTube and news media. Just wondering why this one is picked vs the probably hundred or so others that weren't (many of which would have at least some engineering background to flaunt).

author: nctnico
author_rank: Super Contributor
timestamp: December 22, 2022, 12:35:40 am
content: Quote from: PlainName on December 22, 2022, 12:01:59 amAgreed. I just read an article in an online (reputable) newspaper about the accident but no real information about the cause. The article mentioned that the cylinder should have been heated to 80 deg. C to treat the material. Appearantly that has not been done during the recent maintenance cycle. But the article doesn't state whether not doing the heat treatment is part of the cause. Maybe it was deemed unnecessary and somebody who thinks otherwise has a huge 'I told them so' moment.

author: EEVblog
author_rank: Unknown
timestamp: December 22, 2022, 12:45:37 am
content: Quote from: PlainName on December 22, 2022, 12:01:59 amMeh, it just popped up on Youtube.

author: tom66
author_rank: Super Contributor
timestamp: December 22, 2022, 01:57:06 pm
content: The architect (in ~2003) reckoned that you could shoot a bullet hole in the aquarium, and nothing but some water would leak out. Catastrophic failure was "impossible".

author: MK14
author_rank: Super Contributor
timestamp: December 22, 2022, 02:26:42 pm
content: Quote from: tom66 on December 22, 2022, 01:57:06 pmIn the past, sometimes bridges have collapsed when there was wind of just the right frequency, so called unsinkable ships would sink (Titanic, although the true history, seems or might be that, that was not claimed). I used to have or came across (if I remember right), some C or D cells (possibly Ray-O-Vac), which said something like 'Absolutely 100% Guaranteed Totally Leak-proof', with huge amounts of horrible brown (glue like) goo, coming out of them, like crazy. Great pity I didn't photograph it!Engineering is full of learning by dramatic failure. Hindenburg Airship disaster, oops we shouldn't have used Hydrogen, it can burn/explode (the fuller details, with flammable outer coverings and war-regime NOT being allowed to purchase US Helium, Static electricity being able to set it on fire, via mooring ropes etc, are probably the real factors, especially).

author: ebastler
author_rank: Super Contributor
timestamp: December 22, 2022, 02:50:28 pm
content: You need to read the small print in that advert -- the claims clearly relate to "freshRay-O-Vac Flashlight Cells" only.

author: MK14
author_rank: Super Contributor
timestamp: December 22, 2022, 03:17:07 pm
content: Quote from: ebastler on December 22, 2022, 02:50:28 pmIt's like some of the crafty/tricky (slightly bordering on dishonest) datasheet techniques, that manufacture's sometimes use, to make semi-exaggerated claims, about their devices.

author: james_s
author_rank: Super Contributor
timestamp: December 22, 2022, 06:47:46 pm
content: Quote from: tom66 on December 22, 2022, 01:57:06 pmThere have been many cases of "impossible" things happening. The Titanic sank, Flight 231 lost all 3 hydraulic circuits, and so on. It's easy to overlook a failure mode that bypasses all of the redundancy you engineered into something.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 22, 2022, 07:16:41 pm
content: Quote from: james_s on December 22, 2022, 06:47:46 pmYeah, that "impossible" statement is hilarious.