Atmospherics best practices?

[skatche]

I have a question about atmospherics. I finally got my first pressurized, temperature- and pressure-regulated room set up suitable for plants and humans. It's crude but effective: air gets pumped out through an active vent, through a succession of three filters that siphon out water, oxygen and CO2, in that order. These gases are sent to three tanks, and I branched pipes off from those tanks to feed hydroponics and a gas mixer. Following the gas mixer there's a pressure regulator, and then a passive vent inside the base.

The trouble I'm having is that the gas mixer seems to pump all available gas quite quickly into the pipe that follows, and as a result my O2 tank is empty, while that short pipe section between the mixer and the pressure regulator reads at a thousand kPa -- sometimes as much as ten thousand. The system still functions (more or less -- I seem to still be bleeding out some oxygen somehow, as the interior pressure isn't reaching the 100 kPa I set the regulator to). But it makes it more difficult to gauge how much oxygen I have, as I can't just read off the tank. It also increases the risk of blowouts. I could rig up a circuit to switch the mixer on or off depending on the pressure in the pipe, but that seems overly complicated. Is there a simpler solution?

Thanks very much!

[Chitoloco]

I had the same thing happen with my setup until I added another tank after the gas mixer and then made a T junction which goes to the pressure regulator and then the passive vent which feeds the greenhouse. As for the bleeding of air. Do you have a back pressure regulator on the vacuum passive vent?

[skatche]

I don't have a backpressure regulator -- the active vent feeds directly into the gas filters. How would I set that up?

I can see how your tank-based solution would reduce the pressure in the pipes, but it still leaves my O2 tank empty. Or is there some other effect I'm not considering?

[Chitoloco]

Originally posted by skatche:

I don't have a backpressure regulator -- the active vent feeds directly into the gas filters. How would I set that up?

I can see how your tank-based solution would reduce the pressure in the pipes, but it still leaves my O2 tank empty. Or is there some other effect I'm not considering?

Yeah you are right about the the O2 tank emptying out. Thing is, I use a 90/10 O2/CO2 mix and the space suit comes with a CO2 filter so I just refill my canisters with that mix and all seems well.

To setup the exhaust you want to have a passive vent connected to a pipe that circulates back into your filtration setup. You put a back pressure regulator (the alternate pressure regulator - just scroll when youre installing) on the pipe right after the passive exhaust vent. I set mine to 110 kpa and have my intake passive vent at 105kpa. I do have active vents on both sides but only use that to flush the base or when melting oxites in the base and the pressure climbs too fast for the passive exhaust to deal with. One thing though, you don't want to have the back pressure regulator after an active vent or the pipes could hyperpressurize.

[skatche]

Er, to be clear, are you saying the intake setup is

AV -> - - - - |
              |
              |---> Filters
              |
PV -> BPR - > |

with the active vent only used for quickly flushing the system, or

AV -> - - - - |
              |
              |---> Filters
              |
PV <- BPR < - |

with the passive vent used to prevent the active vent from overperforming?

[Chitoloco]

Ok So I tried illustrating it but failed horribly.

Both your intake and exhausts will have 1 active and one passive vent. The passive vent on the intake side will have a pressure regulator and the passive vent on the exhaust side will have a back pressure regulator.

[skatche]

Huh. Okay, so that makes sense, but why have two active vents apiece on exhaust and intake, rather than just one?

[skatche]

Naw, I got the idea. :) You can use [ code ] tags if you want it to be a nice fixed-pitch font, by the way.

[Chitoloco]

Originally posted by skatche:

Huh. Okay, so that makes sense, but why have two active vents apiece on exhaust and intake, rather than just one?

You can use one but I find that two really gets the air moving fast when you need it. And it's not like theyre expensive so eh.

[skatche]

Got it, thanks! I'll try this out when I'm playing later on.

[Chitoloco]

And yes, with this setup you shouldn't really need to turn on the active vents unless you need to flush the system or readjust the gast composition in the room. The passive vents and pressure regulators keep the pressure within 105-110 kpa.

[Weyland-Yutani HR]

I've actually used my gas mixer as the fill valve before. I had it hooked up to a passive vent. It works great. For automatic controls you just need 2 IO, one processor and one memory.

I set it up like this.

Read pressure -> compare less than 101 ->'turn on gas mixer.

That way you don't need to worry about storing mixed gasses or running your supply tanks dry.

I also use active vents to pull off excess pressure using the same automatic controls. Just change the compare to greater than 104 or whatever you like. Those vents feed back into my filtration loop.

Another thing you can do is use one mixer and pipe it everywhere using volume pumps to fill various rooms. Just use a pipe analyzer to only turn on the mixer if pressure drops below 6000