Miami Beach, Champlain Towers South apartment building collapse, Part 16 24

[dik]

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Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[zebraso]

This building didn't even have a 240v/120v system

Wait, what? So there is no neutral in the building back to the wye? I think I see how that would work.

 

[Nukeman948]

So there is no neutral in the building back to the wye?

I didn't say that. Every 120v circuit in this building has a neutral that goes back to the wye.
Edit: here's a hint, 120/240 volt systems don't have a wye.

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[zebraso]

Ok I misunderstood 240/120. Errr.

edit: i.e. there is no dedicated 240/120 entrance. Slight vernacular problem on my end.

 

[spsalso]

Nukeman948,

Nowhere did I say THIS building had a 240/120V option.

In my last paragraph, you will notice I used the term "...typical industrial stuff,...". THAT would not apply to THIS building. "Typical industrial stuff" is usually 240V Delta (or 480V, etc), and DOES usually have 240/120V single phase available.

zebraso,

In THIS building, there are three hot wires and one neutral. Across any two hot wires is 208V single phase. Across any single hot wire and neutral is 120V single phase. Most of the heating devices in the building used the 208V single phase. These would be electric ranges and dryers, especially. There was also 3 phase power, integrally included, which needs to use ALL the hots (and no neutral). This could, and did, supply various motors throughout the building. It could also supply "non-residential" heating systems, but I don't think there were any.

What is neat about the above system is that, not only do you get three phase, but the supply is fully symmetrical. When you wire stacks of apartment units, or you alternate floors, you just keep going 123123123123...

What you DON'T get is 240V single phase. The OTHER style of three phase WILL give you 240V single phase, but on only two of the three wires.


Anyway. It ain't easy to get it all first time out. But it DOES make sense. Generally, 208V three phase is used in large apartment buildings, and 240V three phase is used in industrial buildings.


spsalso

 

[Nukeman948]

Nowhere did I say THIS building had a 240/120V option.

I apologize for misunderstanding you.

I'm also fully aware of "Typical industrial stuff" and their voltages.

We have a reactor cooling pump motor replacement coming up this outage and need more workers if you're interested. It's only 6000hp and 12.5kv. It might be too small of a project for you though.

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[spsalso]

I'm booked up for awhile, but it does sound interesting.

What happened to the old one, that it needs replacing?


spsalso

 

[zebraso]

It ain't easy to get it all first time out. But it DOES make sense.

Thanks, I wouldn't be asking stupid question if I had the prints in front of me. I know you guys have looked at it.
There used to be a small industrial manufacturing out building across the street from me. They had 3 phase 240 (a+b) going in there from the same lines that fed the residential blocks and same sized center tap pole transformers as residential. What I have to absorb is that is not 3 phase 208 (the difference). They had some equipment related to textile industries that go back to the mid 20th century. But then again it was an outbuilding. The main buildings had a different feed and was about 100 yards away. One of those transformers also fed the street lights. A lot of context. Anyway, thanks for the edumucation.

Edit: Other than that I understand there is no A/B until the center tap comes into it. So the single phase street lights were returned to neutral/center tap. and 240 three phase went into the building. That would have to be delta also. but I never looked that close.

Edit2: And funny I once worked in a coil/transformer shop in engineering. A long time ago. Not a lot of 3 phase but doesn't mean I recall all the theory either. Forgive my stupidity. Small shop = many hats.

 

[Nukeman948]

I'm booked up for awhile, but it does sound interesting.

It's fun work and a lot of interesting things to learn about. Each unit gets refueled around every 18 months, usually in the spring or fall when power demands are low.

DC Cook has two units with four pump motors each that are on a ten year replacement schedule. We keep a spare motor in the plant in case it's needed for a total of nine motors. We replace one motor each outage with the spare and send the old one out to be rebuilt. When it comes back it goes on the spare motor stand until the next outage. When they have all been changed we get a couple outages that we don't need to do it but then it starts all over again.

There is a lot of other work that needs to get done at each outage. A lot of testing of systems that can't be tested when it's running. They test the thickness of steam generator and condenser tubes and other safety related systems. That sort of thing. Usually six twelve hour days for four or five weeks. Some plants use only union workers and some use non-union. There is a background check and psych evaluation. Nothing too hard to get through. Search the web for your nearest plant or do some traveling. I've worked at five different plants from Iowa to Pennsylvania.

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[Nukeman948]

They had 3 phase 240 (a+b) going in there from the same lines that fed the residential blocks and same sized center tap pole transformers as residential.

I got no idea what you are trying to describe but it could be 120/240 open delta. It only needs two transformers on the pole and can be up-rated by adding another transformer. The power company can usually supply whatever type of power system the customer asks for depending on their needs. Not all industrial customers have the same needs. I've worked in General Motors plants that have their own sub-stations and 13,800 volts running through the plant.

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[spsalso]

Nukeman948,

Interesting for sure! It's fun to hear about other people's work.

I assume that there is only bearing wear on a motor. I suppose other things could be checked, of course, like insulation resistance. I asked because I've assumed that big stationary motors under relatively smooth or continuous loads don't have bearing wear. Bearing lubrication and its pressure can be nicely controlled, I would think.


spsalso

 

[zebraso]

Not that it matters. There were 3 transformers with three lines into the building. One transformer was doing duty simultaneously powering street lights with return to neutral. I'm pretty sure the transformers were in delta, which is where 240 comes in. When they tore down that building they left the transformer on the pole that was connected to the street lights, but removed the other two from the tri-mount. But I am sure all three fed the building.
I worked in a plant that had to test a switch tube that operated at 100kv at a pretty high current. I think that was used in a microwave grain dryer. Lot's of x-rays with that tube. There was a substation in that plant too. Luckily I did not have to work around that tube. That guy was pretty nervous most of the time.
IOW all 3 kv lines (ABC) transformed and feeding building. Nothing special other that they also took a 120 from one of the transformers.

Edit: so it was closed delta. I put out a lot of jibber jabber. The main thing I was coming to grips with is 208 comes from a Wye connected setup. I had no good reason to throw in the stuff about what is a standard delta 240.

 

[Nukeman948]

I assume that there is only bearing wear on a motor.

LOL. 20 years ago I heard that nuclear power plants make a million dollars a day for each unit. It's probably more now. They really don't like down time not to mention the safety concern if one fails unexpectedly. One developed an oil leak a few years ago and they had to pump in many gallons of oil while it was running. There is no comparison between the complexity of these motors and the operating conditions they run in with the typical exhaust fan motor. They have air coolers to cool the air that cools the motor because of the ambient heat inside containment. The standby motor needs power continuously running through the windings to keep them warm to keep them from absorbing moisture out of the air. So yeah, every component that could possibly fail and result in down time gets checked over and replaced if it will keep the lights on. It is an interesting place.

Link

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[Nukeman948]

The main thing I was coming to grips with is 208 comes from a Wye connected setup.

Just to derail things even more, a 120/240 delta is also called a wild leg system and has 208 volts from the wild leg to the neutral. But they don't make any equipment that uses it so...
A 120/240 three phase panel that is only feeding single phase loads will have two breakers and a space, then two breakers and a space etc, because the space is the wild leg and is useless.

Google "mercury arc rectifier" and see if anything looks familiar.

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[zebraso]

good stuff

Thanks man, Getting derailed is how I make progress.

As far as the mercury arc thing. I think it was more akin to a lighthouse tube. I know there was a large metal cage with a bank of very large capacitors that no one went into and a guy from the utility once was killed in there when he fell off a platform. That's where they got the 100 kv from. You had the tube and the cage. I wish I knew more. I don't know if the switch tube was for turning on and off power to the microwave tube or developing 100KV DC via a doubler etc. They made Klystrons also. But they were only testing the switch tube in this spot beside the cage. It was surrounded by a very thick lead shield for testing. It could have been a rectifier that got you to 100 KV but there was no mercury in it that I heard of. I had to calibrate the meter that measure 100kv (by divider) once in the active system. Strict procedure and the product engineer was nervous just doing that. I never had to get a probe close to the 100 KV that I can recall. But I could be wrong. I don't think the rig I had went up that high. That was a prior life.
Something akin to this: look up S94000E Power Tube 120kv at 90 amps. So megawatt range I would say, anyway. Probably higher than that.

entertainment: Link

That should be right up nukeman alley. They were doing neutral beam stuff where I worked too. I know I said grain dryer, whatever.

 

[MaudSTL]

From NBC: Surfside collapse exposes an overlooked threat: Saltwater rising from underground

 

[FJBnomics]

Will be interesting when this Beast starts showing up on elevated parking decks at Florida Condo's.

"The all-electric monster pickup weighs 9,063 pounds and, according to new documents filed with the EPA, nearly a third of that is thanks to its battery."

https://www.foxnews.com/auto/the-electric-gmc-hummer-evs-battery-weighs-more-than-some-cars

 

[zebraso]

I think there is another mechanism that accelerates the salt based breakdown of concrete. Ironically it involves the ventilation fans. The salt attracts more moisture from the soil as the water evaporates. That in turn increases the salt concentration which increases the absorption of more water drawing in more salt ad infinitum at a rate that is increased by evaporation rate. One of the articles I read which I am trying to track down again claims a study show this process can draw water from the soil from as far away as 10s of miles depending on the conditions. That is not a simple problem and I don't see how it can be ignored.

Edit: this concept seems to go beyond the basic idea of "rising damp" where the water will permeate to a height were the evaporation rate equals the ingress rate. That is true with or without salt. What I think the above theory is saying is that as salt concentration in the concrete increases the rate water coming in will increase as a result. The mechanism for increasing the salt concentration is compounded by evaporation rate. I would like to see the study that shows that. Still looking.

While I am looking I thought this article on capillarity goes a long way. Link It's not about sulfate corrosion/erosion. But it addresses the forces of osmosis, which I think are the basis for the effect I am trying to describe. Interesting quote from article: "The theoretical limit of capillary rise in concrete is about 10 kilometers". Ouch.

 

[spsalso]

It will be very interesting to examine the results of the concrete sampling done by NIST. We will be able to see gradients of ingredients and contaminants through the thickness in the basement walls and floors, as well as vertically, in the columns (using multiple sampling points).

We can then compare our theories with the facts.

It'll be fun!



spsalso

 

[FJBnomics]

I think there is another mechanism that accelerates the salt based breakdown of concrete. Ironically it involves the ventilation fans. The salt attracts more moisture from the soil as the water evaporates. That in turn increases the salt concentration which increases the absorption of more water drawing in more salt ad infinitum at a rate that is increased by evaporation rate…….

Interesting thoughts, analysis and link. The ventilaton and circulation fan drying effects on underside of elevated parking/patio structural deck accelerates salt accumulation into lowest layer, in addition to gravity, then salt attracts moisture more.

 

[zebraso]

fan drying effects on underside of elevated parking/patio structural deck

Thanks for adding that. There was a "but what about the pool deck" thought going on in my mind as well. But I thought I should focus on one concept at a time. I was following a thought process based on the article Maud posted for now. Please feel free to add any additional thoughts about the grade level drawing water based on the idea. The article I posted talks about damage going into wood flooring and members at or above grade level, but that's a different animal. The idea here was the membrane was supposed to do a certain amount of protection. But that seems to not have worked so well.