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M_Gargantua
Oct 16, 2006

STOMP'N ON INTO THE POWERLINES

Exciting Lemon

helno posted:


The reheat/preheat system is pretty cool. Basically it boils down to the fact that nuclear reactors make a shitload of really crappy steam. The steam is not superheated coming out of the boilers and goes into the high pressure turbine pretty wet.
...

I'd hate to imagine the impingement damage to the turbine blading. I'd have thought it would have been the other way around with high quality high pressure steam that gets reused as low pressure wet steam. I've only heard wet steam go down our headers once when one of the moisture traps failed and it sounded like the rumble of death.

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Captain Foo
May 11, 2004

we vibin'
we slidin'
we breathin'
we dyin'

I didn't even know "dry steam" was a thing :stare:

Noctone
Oct 25, 2005

XO til we overdose..

Captain Foo posted:

I didn't even know "dry steam" was a thing :stare:

It's more jargon than a "scientific" term. "Wet" and "dry" steam are referring to the relative amount of condensate in the line.

John McCain
Jan 29, 2009

Captain Foo posted:

I didn't even know "dry steam" was a thing :stare:

Dry steam is superheated steam, i.e. water above the boiling point. Water at its saturation point is actually a mixture of liquid water and steam, which is called wet steam, and referred to using a parameter Χ, "quality", which is the mass fraction of the water that is in the gaseous state.

babyeatingpsychopath
Oct 28, 2000
Forum Veteran


Captain Foo posted:

I didn't even know "dry steam" was a thing :stare:

Also hot steam and cold steam. Also the temperatures of the water at various points, and whether it's expected to be boiling there or not. You can have 600C water in one point, and everything's OK, and 25C water somewhere else that really should be boiling there.

Comrade Blyatlov
Aug 4, 2007


should have picked four fingers





helno posted:

GE EHC mark II for large steam turbines. Hope you really like op-amp's.

The reheat/preheat system is pretty cool. Basically it boils down to the fact that nuclear reactors make a shitload of really crappy steam. The steam is not superheated coming out of the boilers and goes into the high pressure turbine pretty wet.

:stare:

I'm sure they've done the maths and all, but holy poo poo.

Captain Foo posted:

I didn't even know "dry steam" was a thing :stare:

Not only is it a thing, but it's an invisible thing that will kill you dead very loving quickly. Get a pinhole leak in a pipe, and it'll basically do this to anything that passes through it:
https://www.youtube.com/watch?v=iXgsCPFhSgc

Steam scares the living poo poo out of me for good reason.

TyroneGoldstein
Mar 30, 2005

Two Finger posted:

:stare:

I'm sure they've done the maths and all, but holy poo poo.


Not only is it a thing, but it's an invisible thing that will kill you dead very loving quickly. Get a pinhole leak in a pipe, and it'll basically do this to anything that passes through it:
https://www.youtube.com/watch?v=iXgsCPFhSgc

Steam scares the living poo poo out of me for good reason.

And this is what happens when you get cold water accidentally dripping on super heated steam pipes causing steam hammer:

https://www.youtube.com/watch?v=SImhkapRuIs

There was a tow truck right over when it erupted, you don't want to know what happened. Steam is fantastic in its uses, but when it goes wrong..

helno
Jun 19, 2003

hmm now were did I leave that plane

M_Gargantua posted:

I'd hate to imagine the impingement damage to the turbine blading. I'd have thought it would have been the other way around with high quality high pressure steam that gets reused as low pressure wet steam. I've only heard wet steam go down our headers once when one of the moisture traps failed and it sounded like the rumble of death.

The steam is 4.4 MPa but only around 250 degree celsius because it is being boiled by 305 degree water at 9.8 Mpa. I don't know the math or have the exact numbers but I have heard that it is about 0.1% moisture when it gets to the valve chest. At full power we boil about 1200 kg per second per unit (we have 8 units).

The older LP turbines look like a sandblaster have been taken to the last few stages due to impingement damage. We only turn at 1800 rpm so it is not as bad as the plants that run 3600.

John McCain
Jan 29, 2009
Expanding saturated steam from a quality of 1 down to about 0.9 (or in some cases down to 0.85 or so) is actually a pretty common cycle, or at least it was. Superheat is a newer addition to the cycle, because it's a bitch and a half to add heat to dry steam (heat transfer coefficient similar to that of air).

Comrade Blyatlov
Aug 4, 2007


should have picked four fingers





TyroneGoldstein posted:

And this is what happens when you get cold water accidentally dripping on super heated steam pipes causing steam hammer:

https://www.youtube.com/watch?v=SImhkapRuIs

There was a tow truck right over when it erupted, you don't want to know what happened. Steam is fantastic in its uses, but when it goes wrong..

As I've stated before, steam scares the living hell out of me for good reason.

I can't remember the exact figure, but I think water will expand up to like 1400 times its original volume when it becomes steam.

Groda
Mar 17, 2005

Hair Elf

FrozenVent posted:

Wait, H2 as in hydrogen?

Isn't that kind of... Flammable?

I worked at a plant that had a significant hydrogen leak, and the main concern was running out.

I heart bacon
Nov 18, 2007

:burger: It's burgin' time! :burger:


This is an example of a boiler explosion.
https://www.youtube.com/watch?v=fCej2OQSKnY

There's write up with better pictures here.

Another boiler explosion here.
https://www.youtube.com/watch?v=PsSVfAg1kRg

Crankit
Feb 7, 2011

HE WATCHES
I live in the UK and in our fuse box the first set of fuses says 415V 80A/100A, should I be frightened of arc flashes from them when they fail? What's the difference between the neutral and ground pins in a plug? I was told by a school physics teacher (some years ago) that a shaver socket is safer than a regular power outlet because if I came into contact with a wire I wouldn't be completing the circuit and so wouldn't receive a shock, is that true?

babyeatingpsychopath
Oct 28, 2000
Forum Veteran


Crankit posted:

I live in the UK and in our fuse box the first set of fuses says 415V 80A/100A, should I be frightened of arc flashes from them when they fail? What's the difference between the neutral and ground pins in a plug? I was told by a school physics teacher (some years ago) that a shaver socket is safer than a regular power outlet because if I came into contact with a wire I wouldn't be completing the circuit and so wouldn't receive a shock, is that true?

Fuses are designed to keep arcs in, so no problem there.

The neutral pin goes back to the source of your power, typically the transformer on the pole. The ground pin goes to the earth at your panel. Usually there's a bond between the two there. The fundamental difference is that the neutral pin is designed to carry current under normal circumstances (it's the second wire of a complete circuit) where the ground pin should only have current/voltage on it in a fault condition.

Going from memory here, but shaver sockets in the UK are usually powered by isolation transformers and are therefore ungrounded. So accidentally touching one wire doesn't give a complete circuit to anything, as the transformer isn't connected to ground. Touching both wires will still shock you, but maybe not kill you because the transformer is power limited (I think). Other parts of the world use a GFCI (ground fault circuit interruptor). If you touch one wire and complete a circuit to ground, the outlet senses the ground fault current and shuts the power off.

Three-Phase
Aug 5, 2006

by zen death robot

babyeatingpsychopath posted:

Fuses are designed to keep arcs in, so no problem there.

Pretty much this. But you would absolutely not want to do something like pull them with the power (I think you call that "mains") turned on. Is there a switch, and underneath that three fuses?

Both circuit breakers and fuses have a maximum current rating in kiloamps. So the fuse may have a label like this:

600V
50A
100kAIC

The 100kAIC indicates it can interrupt up to 100,000 amps. For fuses it isn't difficult to get fuses rated at 100,000 or even 200,000 amps of fault. Circuit breakers are much more expensive. We have some breakers at work (HFDs and HKDs from Eaton, fairly common industrial three-pole breakers) that are rated at 65kAIC at 480V, and they aren't cheap. I think the idea for sticking with higher capacities is so that if we change or salvage equipment later in its life, there's a better chance we can reuse the equipment rather than saying "Crap, this is rated too small for other places in the plant. Chuck it."

The fault level is limited mainly by the impedance of the source (the transformer feeding the system) and the impedance of the cable from the transformer to where the fault is) as well as if there are current-limiting devices in between.

If you have a fault that exceeds the rated capacity of the interrupting device, it may violently fail to interrupt the fault. I've seen pictures of circuit breakers exploding like a bomb when their capacity is interrupted.

Medium and large circuit breakers (thousands of volts and thousands of amps and up) have their fault rating in MVA. A breaker may have a 500MVA fault rating (500 million volt-amps).

Three-Phase fucked around with this message at 00:04 on May 8, 2013

ncumbered_by_idgits
Sep 20, 2008

babyeatingpsychopath posted:

Fuses are designed to keep arcs in, so no problem there.


And hopefully they are not exposed. I mean, they have some kind of cover them, right?

Three-Phase
Aug 5, 2006

by zen death robot
I think I've found a video showing the most spectacularly dangerous way to test a high-resistance grounded system. :psyduck:

If there was an undetected fault on another phase to ground, it would have probably blown up in this guy's face. Even more dangerous he could have accidentally gotten that cable between the phases leading to a potentially serious arc flash.

What I would have done if I had to test it this way: get a current-limiting fuse and fuseblock rated higher than the maximum short circuit current, and a contactor. Shutdown the system, LO/TO and cordon off the testing area, and rig the device to fault to ground via the contactor and the fuse. Then I could power the contactor from a safe distance away, and if for whatever reason there was a second undetected phase to ground fault, the fuse would open. (And even if the fuse failed the area would be cordoned and everyone would be a safe distance away.

In my opinion this is an absolutely Looney-Tunes test. A lot of people in the comments section seem to agree with me.

It looks like he's wearing garden/workshop gloves too. :psyduck::hf::science:

We really need a psyduck/science combined GIF.

Three-Phase fucked around with this message at 20:31 on May 18, 2013

Knitting Beetles
Feb 4, 2006

Fallen Rib
I once explained how arc flash works near generators to an ex- generator commissioning engineer (in Asia, so no recognition of the hazard in the first place). Basically everything this guy this did in his normal day to day work would be completely off limits if he had to follow arc flash policy of any kind. His PPE on hot days: shorts.

The general approach to electrical safety in Asia is pretty relaxed. In Taiwan there's no regulation whatsoever, but I was told it wasn't a problem because accidents only happen when you make mistakes.

Noctone
Oct 25, 2005

XO til we overdose..

Three-Phase posted:

I think I've found a video showing the most spectacularly dangerous way to test a high-resistance grounded system. :psyduck:

If there was an undetected fault on another phase to ground, it would have probably blown up in this guy's face. Even more dangerous he could have accidentally gotten that cable between the phases leading to a potentially serious arc flash.

What I would have done if I had to test it this way: get a current-limiting fuse and fuseblock rated higher than the maximum short circuit current, and a contactor. Shutdown the system, LO/TO and cordon off the testing area, and rig the device to fault to ground via the contactor and the fuse. Then I could power the contactor from a safe distance away, and if for whatever reason there was a second undetected phase to ground fault, the fuse would open. (And even if the fuse failed the area would be cordoned and everyone would be a safe distance away.

In my opinion this is an absolutely Looney-Tunes test. A lot of people in the comments section seem to agree with me.

It looks like he's wearing garden/workshop gloves too. :psyduck::hf::science:

We really need a psyduck/science combined GIF.

The entirety of that video my face was a combination of :psyduck:, :stare: and :ohdear:.

afen
Sep 23, 2003

nemo saltat sobrius
Hello! If it's cool with the OP I can answer your questions about marine electricity. I'm not familiar with marine HV, but we have 690V 60Hz onboard. We also have 5 gensets and 2 main engines for a total of approx. 18MW of electrical power.

All of this is controlled with our Integrated Automation System, which automatically(or manually if necessary) controls frequency, number of generators and load sharing.

Heres a picture of our main switchboard:


Engine control room:

GWBBQ
Jan 2, 2005


Three-Phase posted:

I think I've found a video showing the most spectacularly dangerous way to test a high-resistance grounded system. :psyduck:
Just to confirm, is he holding a ground wire in his hand and shorting a hot terminal to ground? I don't want to jump to conclusions since that seems monumentally stupid, but the reactions here seen to confirm that what he's doing is, in fact, monumentally stupid.

Three-Phase
Aug 5, 2006

by zen death robot

afen posted:

Hello! If it's cool with the OP I can answer your questions about marine electricity. I'm not familiar with marine HV, but we have 690V 60Hz onboard. We also have 5 gensets and 2 main engines for a total of approx. 18MW of electrical power.

All of this is controlled with our Integrated Automation System, which automatically(or manually if necessary) controls frequency, number of generators and load sharing.

Heres a picture of our main switchboard:


Engine control room:


Is that 690/400 or 1200/690?

I also heard somewhere, but wasn't sure about this, that some marine systems utilized 69/120V instead of 120/208V, so if you plugged in a 120V load, it was really line-to-line. The idea is that the line to ground voltage is much lower and a little safer. (Lots of potential transformers are wired 120V line to line, but I'm talking about for power.)

GWBBQ posted:

Just to confirm, is he holding a ground wire in his hand and shorting a hot terminal to ground? I don't want to jump to conclusions since that seems monumentally stupid, but the reactions here seen to confirm that what he's doing is, in fact, monumentally stupid.

It sure looks like that. It's a high-resistance ground, so there's no violent explosion that kills/seriously burns him.

Problems I can see:
1. If there was a fault in the high-resistance ground or an undetected fault on another phase, that would have blown up
2. He's wearing work gloves, not electrically rated gloves
3. No apparent PPE in a live cabinet
4. Risk of shorting phases together if he slipped
5. He didn't even turn away when tapping the wire to the phase

I'm not trying to insult the guy, I just don't want to see someone get killed in a fireball or worse surviving with debilitating injuries.

Even if he was wearing Level 3 or Level 4 PPE, I'd still think this procedure was absolutely nuts. I have to show the guys at work this; their jaws will drop. If we ever attempted anything close to this we'd be seriously risking termination.

Three-Phase fucked around with this message at 17:40 on May 19, 2013

Guy Axlerod
Dec 29, 2008
But:

quote:

See how the arc flash is minimum, as the ground fault current is just 5 A

Basically, it's cool bro, don't worry about it.

babyeatingpsychopath
Oct 28, 2000
Forum Veteran


Three-Phase posted:

Is that 690/400 or 1200/690?

I also heard somewhere, but wasn't sure about this, that some marine systems utilized 69/120V instead of 120/208V, so if you plugged in a 120V load, it was really line-to-line. The idea is that the line to ground voltage is much lower and a little safer. (Lots of potential transformers are wired 120V line to line, but I'm talking about for power.)


The US Navy's ships use a 69/120 ungrounded Y power system. Each circuit is 120V and has a fuse in each leg. A single ground fault opens the leg, turns on a light in the fuse panel, and the system faulted keeps running at 70V. It's very fail-safe and battle hardened, and takes multiple faults to totally fail.

The generators are also rated down to 18% power factor. 1800MW at 95% pf, 600MW at 18%. Impressive movers.

Three-Phase
Aug 5, 2006

by zen death robot
I was also reading about military systems with "battle short" circuit breakers. I am not sure if that overrides just 51 (inverse time overcurrent) or 51 and 50 (instantaneous overcurrent) protection. Basically if you're in the middle of a battle, you don't the circuit breaker controlling the motor that does something like rotate your turret tripping on an overload - electrical system damage is acceptable to save the ship. Sort of like a fire pump system.

afen
Sep 23, 2003

nemo saltat sobrius

Three-Phase posted:

Is that 690/400 or 1200/690?

I also heard somewhere, but wasn't sure about this, that some marine systems utilized 69/120V instead of 120/208V, so if you plugged in a 120V load, it was really line-to-line. The idea is that the line to ground voltage is much lower and a little safer. (Lots of potential transformers are wired 120V line to line, but I'm talking about for power.)

The generators are 690V-60Hz, and we have transformers for 440V and 230V.

Never heard of those systems before, but I've only been on Norwegian ships.

grover
Jan 23, 2002

PEW PEW PEW
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:

Three-Phase posted:

I was also reading about military systems with "battle short" circuit breakers. I am not sure if that overrides just 51 (inverse time overcurrent) or 51 and 50 (instantaneous overcurrent) protection. Basically if you're in the middle of a battle, you don't the circuit breaker controlling the motor that does something like rotate your turret tripping on an overload - electrical system damage is acceptable to save the ship. Sort of like a fire pump system.
I'm not sure the exact mechanism either, but I've seen the switches. There are many cases where it's preferable for your equipment to melt and burn than than for a fuse to blow and protect the equipment but result in the loss of the ship. It's an alien concept to most engineers, but common thinking on warships- like the power system that will keep going even after a ground fault. It's only used for the most critical systems.



e: some technical documentation on the implementation for one system here: http://firecontrolman.tpub.com/14100/css/14100_23.htm The NTDS computers this article is talking about battle-shorting are ancient water-cooled monsters that serve as the heart of the ship's combat system. They took up entire rooms in the 50s/60s, but shrunk in the 80s/90s to still-massive refrigerator-sized units.

grover fucked around with this message at 12:59 on May 20, 2013

Frozen Horse
Aug 6, 2007
Just a humble wandering street philosopher.

Three-Phase posted:

Even if he was wearing Level 3 or Level 4 PPE, I'd still think this procedure was absolutely nuts. I have to show the guys at work this; their jaws will drop. If we ever attempted anything close to this we'd be seriously risking termination.

A very low-impedance termination to ground, I presume?

Three-Phase
Aug 5, 2006

by zen death robot

Frozen Horse posted:

A very low-impedance termination to ground, I presume?

It's a high-impedance grounded source, so if a ground fault occurs the current is limited to a very low but detectable level. I've only seen high-impedance grounds on voltages much higher than 480V.

The issue is how the test was carried out.

Noctone
Oct 25, 2005

XO til we overdose..
Pretty sure he was making a joke there and not asking a real question. :D

Vaporware
May 22, 2004

Still not here yet.

penneydude posted:

So I have kind of a general question, and I'm not sure if this is the place to ask it but it seems like a good starting point.

I'm doing an art project about a local power plant, and it would be really awesome to have some sort of map or diagram that describes how the plant is connected to the grid, where the electricity it produces goes, who is using most of the power, fuel sources, demand over time...that kind of information. Does anything like this exist as an industry standard kind of document? If so, what is it called? And if not, what should I ask the power company if that's the kind of information that I'm looking for so they know what I'm talking about?

Are you talking about process flow diagrams? I used to make these. You are going to have a very hard time getting a specific layout of the plant, but a general concept process flow diagram isn't that hard to come by if you use the right terminology. For instance, if you find out your local coal plant has 4 units, then you likely have 4 identical or nearly identical parallel systems that make up that plant.

The other parts of the equation like fuel, etc. will take more research, but it's attainable. for instance, coal is normally sourced from just a few places. For instance, Powder River Basin supplies a lot of the low sulfur coal. Who uses the power is more likely to be given to you by the power company if they're in a good mood.

http://lmgtfy.com/?q=combined+cycle+power+plant
http://lmgtfy.com/?q=coal+fired+power+plant
http://lmgtfy.com/?q=simple+cycle+power+plant
http://lmgtfy.com/?q=integrated+gasification+combined+cycle+power+plant
http://lmgtfy.com/?q=LM6000

longview
Dec 25, 2006

heh.
I figure this is the place to ask: anyone know when the Carnival poo poo Cruises accident report will be published? I'm curious to read about what happened to the electrical system there.

FrozenVent
May 1, 2009

The Boeing 737-200QC is the undisputed workhorse of the skies.

longview posted:

I figure this is the place to ask: anyone know when the Carnival poo poo Cruises accident report will be published? I'm curious to read about what happened to the electrical system there.

These usually take at least a year; Costa Concordia's just got published last week. (And that was with the entire international maritime community pressuring the poo poo out of Italy to hurry up; there isn't that level of interest over the Triumph since nobody died.)

Three-Phase
Aug 5, 2006

by zen death robot
Two interesting power line videos I recently found on Youtube:

http://www.youtube.com/watch?v=56-va8jPbAo

http://www.youtube.com/watch?v=qnIe4mm6CTg

I'm not sure if the people flying the kite understand how dangerous and destructive that is. :psyduck:

schmuckfeatures
Oct 27, 2003
Hair Elf
And this one only got posted today, apparently - pretty goddamn spectacular:

https://www.youtube.com/watch?v=hAoP20mL_a4

How come the 60hz hum seems to drop an octave? I haven't seen an electrical mayhem video that sounded quite like this before.

Comrade Blyatlov
Aug 4, 2007


should have picked four fingers





longview posted:

I figure this is the place to ask: anyone know when the Carnival poo poo Cruises accident report will be published? I'm curious to read about what happened to the electrical system there.

I think we discussed this earlier in the thread with my thoughts on it as a marine engineer? I'll see if I can dig up the posts.


Here's my post:

Two Finger posted:

That article is not very precise - it should be noted those will be diesel generator sets, not just generators. If the ignition marks were on the wall, my money would be on a high pressure fuel line leak spraying fuel onto hot exhaust. My second guess would be a massive arcing of the actual generator windings themselves causing a fire.

Whatever the actual cause, the fixed fire fighting equipment (sprinklers and hifog) was unable to stop the fire raging out of control, and if the last-ditch C02 system was used, enough damage had already been done that they were unable to restore power.


As FrozenVent said it is VERY rare to have ALL generators paralleled at once. The switchboard itself is split into two, either half of it can power the ship in 'limp mode.' I have heard of a case where a massive fire spread upwards into the exhaust gas boilers, rupturing them and dumping tons and tons of freshwater all over everything below them including the electrical distribution gear. It is possible something like this occurred. Please note, I am guessing from previous experience and have no knowledge of what happened on here.
To answer your question about the two busses, the breaker is normally kept CLOSED so they function as one board. It can be split for maintenance, or for emergencies where one side of the bus may be damaged. The ship can move without the whole board, but it can't move without any of it.


It pretty much is. You may say 'well that's dumb as gently caress' but at the end of the day, at some point you have to stop redundancy-ing things or you're going to have two ships. Having the switchboard divided in half is, I think, a reasonable alternative, given that you have an emergency switchboard with life support systems. That did its job perfectly well, given that although the conditions weren't great, I don't think there have been any reported deaths.

It is also worth noting that the case I mentioned above, with the exhaust boilers dumping all over everything, is as close as you can come to 'get the gently caress off right now everyone' without actually being to it. At that point in time, you have way more serious problems than powering the ship - you're trying to save the lives of everyone involved.


Yeah, this is pretty much what I said above.

I want to stress here, I am not an employee of that company, but I do have engineering experience on cruise ships. This is all conjecture based on my knowledge of diesel electric ships, and should not in any way be taken as gospel.

I also want to stress that to my knowledge, no one died, and despite the terrible conditions all lives were preserved. This could have been so, so much worse if that fire had not been stopped.

http://forums.somethingawful.com/showthread.php?threadid=3533525&userid=122000#post412639555

Comrade Blyatlov fucked around with this message at 00:06 on Jun 27, 2013

Three-Phase
Aug 5, 2006

by zen death robot

schmuckfeatures posted:

And this one only got posted today, apparently - pretty goddamn spectacular:

https://www.youtube.com/watch?v=hAoP20mL_a4

How come the 60hz hum seems to drop an octave? I haven't seen an electrical mayhem video that sounded quite like this before.

I'm wondering if it's so loud that the microphone is having trouble picking it up. I'll ask some people with PE's on Monday.

This Liveleak Video is pretty impressive.

:phoneb: "I need the biggest fuse you have... no, that's too big."

Three-Phase fucked around with this message at 23:46 on Jun 28, 2013

Guy Axlerod
Dec 29, 2008
Sir, I can't hear you over the explosions and fire alarm. Could you please repeat the nature of your emergency?

FrozenVent
May 1, 2009

The Boeing 737-200QC is the undisputed workhorse of the skies.

Two Finger posted:

I think we discussed this earlier in the thread with my thoughts on it as a marine engineer? I'll see if I can dig up the posts.


Here's my post:


http://forums.somethingawful.com/showthread.php?threadid=3533525&userid=122000#post412639555

Did you see the electrical parts of the Concordia report? Some weird stuff about the interlock between the main switchboard and the emergency not tripping correctly... But the main blackout had a pretty straightforward cause.

The drat generators were under water.

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Comrade Blyatlov
Aug 4, 2007


should have picked four fingers





I haven't read it yet. It's on my to do list.

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