4 ms·

Too bad that the backup generator refuelling pumps have been submerged (while the generators themselves are running). That sounds like some really ... unfortun

by unwind 14y ago

Too bad that the backup generator refuelling pumps have been submerged (while the generators themselves are running). That sounds like some really ... unfortunate planning of the positioning of these machines, made me think of the Daiichi incident when backup assets failed to come online because parts of the backup infrastructure were destroyed. Not as serious, of course. Fog Creek's hosting isn't a nuclear power plant. :) Makes me glad I don't work with things that are as hard to test in the real world as these kinds of backup solutions must be. I hope they manage the refuelling, somehow.

mikeash 14y ago
That's the first thing I thought of too. Seems like there should be a new rule that your backup generator infrastructure should be on at least the second floor.
- smackfu 14y ago
  Most basements are already waterproof (since you don't want groundwater getting in). It's generally the first floor that is the weak point, when the water gets over the basement walls. So if you think about it, it's not that hard to make the basement waterproof to a flood... just make the walls higher.
- emeraldd 14y ago
  That means that the fuel tanks will have to be there as well or you're going to need some specialized lines/equipment to prime the pumps. How much would a 3" cylinder of diesel fuel about ten foot tall weigh? (What ever it is that would be a crap load of vacuum to produce/maintain). Then you have the weight of the tanks themselves and refilling logistics. All fun engineering problems. :)
  - barrkel 14y ago
    What if you pumped it up by having a hydrostatically balanced system: instead of sucking up the fuel, pump water down to drive a piston that pushes the fuel up.
    - emeraldd 14y ago
      Interesting idea, I'm not an engineer so I can't really speak to that. It sounds like you'd be adding more points of failure and still have the potential of a submerged pump being and issue. Maybe something other than a piston?
      - barrkel 14y ago
        A flooded piston would be more reliable than a flooded motor IMO. Lots of reliability critical things like vehicle brakes use pistons. All you would need is enclosed tubing sufficient to withstand the internal pressure. Submersion shouldn't be an issue because the system already needs to be sealed - the pressure would cause a leak if it wasn't already sealed, and in fact flooding would reduce the probability of a leak by reducing the pressure differential. If you keep sufficient water (up to the weight of the fuel) at the location where it's needed, the entire system needn't need a pump at all when called into action, just a tap - gravity would be sufficient. This is presuming that the fuel is kept at basement level for safety purposes, of course, otherwise you could just keep the fuel where you're storing the water. You can get by with less water and active pumping, since hydraulics are easy to turn into gearing (force multiplication) effects.
- trhtrsh 14y ago
  If water is leaking in, not a crushing tidal wave, all you need is a small elevation about drainage / pump to route leaking water to another location.
- tlrobinson 14y ago
  Or just make the generators work submerged?
- dredmorbius 14y ago
  Cuomo's suggesting steps such as that, given that major storms seem to be "the new reality" in New York (both city & state). http://saratogian.com/articles/2012/10/30/news/doc5090186b1e46c903794134.txt http://saratogian.com/articles/2012/10/30/news/doc5090186b1e...
hellmans 14y ago
New York has some of the strictest building codes going, and I wouldn't be surprised if that played a part. Note that the pumps were in the basement because that's where the refueling location was, which logically it would be for a variety of practical reasons (you can't drive a fuel truck up an escalator, etc.)
RandallBrown 14y ago
The pumps have to be on the bottom floor. How else will you be able to get the fuel to them? At least in this scenario people can carry fuel up stairs to fill the generators.
achille 14y ago
Note that its not as trivial as you might think. Pumps cannot pull fuel from the 17th floor, because even if they create vacuum in the tube, atmospheric pressure can't push the fuel to the 17 floor. So the pump has to be positioned at the base, thus subject to flooding.
- bduerst 14y ago
  You could siphon the fuel up the tube to the pump at the time of the pump's installation, right? Through a one-way valve?
  - s_kilk 14y ago
    that is not how a siphon works. The destination must be at a lower elevation than the supply reservoir.
    - bduerst 14y ago
      That's what I meant - siphon the fuel up to the pump at installation, so you don't have any gas and don't have to rely on a vaccuum. As the pump draws fuel through the one way valve, the fuel continues to draw more fuel from below.
      - stickfigure 14y ago
        There are two reasons why this won't work. The first is that the fluid will draw a vacuum at the top of the pump. A vacuum on earth can only sustain 14psi - atmospheric pressure. For water, this constitutes a 33.9' column - after that you could draw a perfect vacuum at the top of the pipe and wouldn't the water to rise higher. Since diesel is less dense than water you might go a little higher, but probably not much. The second problem is that as you create a low-pressure zone at the top of the pipe, the fluid will boil (cavitate). This gasified liquid will fill the space and drop your pressure. Oils like diesel should have a significantly higher boiling point (aka lower boiling pressure) than water, but it's still a limit.

by unwind 14y ago

mikeash 14y ago

That's the first thing I thought of too. Seems like there should be a new rule that your backup generator infrastructure should be on at least the second floor.

smackfu 14y ago
Most basements are already waterproof (since you don't want groundwater getting in). It's generally the first floor that is the weak point, when the water gets over the basement walls. So if you think about it, it's not that hard to make the basement waterproof to a flood... just make the walls higher.
emeraldd 14y ago
That means that the fuel tanks will have to be there as well or you're going to need some specialized lines/equipment to prime the pumps. How much would a 3" cylinder of diesel fuel about ten foot tall weigh? (What ever it is that would be a crap load of vacuum to produce/maintain). Then you have the weight of the tanks themselves and refilling logistics. All fun engineering problems. :)
- barrkel 14y ago
  What if you pumped it up by having a hydrostatically balanced system: instead of sucking up the fuel, pump water down to drive a piston that pushes the fuel up.
  - emeraldd 14y ago
    Interesting idea, I'm not an engineer so I can't really speak to that. It sounds like you'd be adding more points of failure and still have the potential of a submerged pump being and issue. Maybe something other than a piston?
    - barrkel 14y ago
      A flooded piston would be more reliable than a flooded motor IMO. Lots of reliability critical things like vehicle brakes use pistons. All you would need is enclosed tubing sufficient to withstand the internal pressure. Submersion shouldn't be an issue because the system already needs to be sealed - the pressure would cause a leak if it wasn't already sealed, and in fact flooding would reduce the probability of a leak by reducing the pressure differential. If you keep sufficient water (up to the weight of the fuel) at the location where it's needed, the entire system needn't need a pump at all when called into action, just a tap - gravity would be sufficient. This is presuming that the fuel is kept at basement level for safety purposes, of course, otherwise you could just keep the fuel where you're storing the water. You can get by with less water and active pumping, since hydraulics are easy to turn into gearing (force multiplication) effects.
trhtrsh 14y ago
If water is leaking in, not a crushing tidal wave, all you need is a small elevation about drainage / pump to route leaking water to another location.
tlrobinson 14y ago
Or just make the generators work submerged?
dredmorbius 14y ago
Cuomo's suggesting steps such as that, given that major storms seem to be "the new reality" in New York (both city & state). http://saratogian.com/articles/2012/10/30/news/doc5090186b1e46c903794134.txt http://saratogian.com/articles/2012/10/30/news/doc5090186b1e...

hellmans 14y ago

New York has some of the strictest building codes going, and I wouldn't be surprised if that played a part. Note that the pumps were in the basement because that's where the refueling location was, which logically it would be for a variety of practical reasons (you can't drive a fuel truck up an escalator, etc.)

RandallBrown 14y ago

The pumps have to be on the bottom floor. How else will you be able to get the fuel to them? At least in this scenario people can carry fuel up stairs to fill the generators.

achille 14y ago

Note that its not as trivial as you might think. Pumps cannot pull fuel from the 17th floor, because even if they create vacuum in the tube, atmospheric pressure can't push the fuel to the 17 floor. So the pump has to be positioned at the base, thus subject to flooding.

bduerst 14y ago
You could siphon the fuel up the tube to the pump at the time of the pump's installation, right? Through a one-way valve?
- s_kilk 14y ago
  that is not how a siphon works. The destination must be at a lower elevation than the supply reservoir.
  - bduerst 14y ago
    That's what I meant - siphon the fuel up to the pump at installation, so you don't have any gas and don't have to rely on a vaccuum. As the pump draws fuel through the one way valve, the fuel continues to draw more fuel from below.
    - stickfigure 14y ago
      There are two reasons why this won't work. The first is that the fluid will draw a vacuum at the top of the pump. A vacuum on earth can only sustain 14psi - atmospheric pressure. For water, this constitutes a 33.9' column - after that you could draw a perfect vacuum at the top of the pipe and wouldn't the water to rise higher. Since diesel is less dense than water you might go a little higher, but probably not much. The second problem is that as you create a low-pressure zone at the top of the pipe, the fluid will boil (cavitate). This gasified liquid will fill the space and drop your pressure. Oils like diesel should have a significantly higher boiling point (aka lower boiling pressure) than water, but it's still a limit.