Over-Powered Oxygen Module -- OPOM

[sorrymybad]

Presenting the Over-Powered Oxygen Module (OPOM), a modified SPOM design that generates large amounts of excess hydrogen in exchange for less oxygen. It relies on the matter conversion bug, so unfortunately it won't work for purists, and may also stop working if Klei nukes the bug. Caveat emptor.

It's best used in liquid oxygen & hydrogen generation systems for powering rockets, but can also be used in mid-game to reliably generate power if there's an abundance of water.

Here's how it looks:

 

OPOM performance comparison

In order to understand OPOM's performance let's outline some landmark SPOM designs:

SPOM MKII by QuQuasar (This version sometimes over-pressurizes, limiting its throughput. Nevertheless, it's a great representation of all "standard" SPOM designs that do not attempt to make more hydrogen than the default of 112g H2 per kg of water)

PASSPOM by u/yiyas

SPHM by u/yiyas

 

Here's a table showing OPOM's performance vs other SPOMs. 1 kg/s of water is processed in these comparisons.

The OPOM converts water into 55% hydrogen by mass, creating 334 kg/cycle of hydrogen (and 267 kg/cycle of oxygen) if all its machines are powered by an external power source. This ratio is almost perfect for powering hydrogen rockets, which require a 1:1 ratio of liquid hydrogen to liquid oxygen. Compared to a standard SPOM with an 11% conversion ratio, the OPOM produces 5x more hydrogen, and allows you to launch rockets 5x more frequently (hydrogen production is usually the bottleneck in launching hydrogen rockets).

If run as a self-powered module, it creates 251kg/cycle of excess hydrogen, or a steady-state output of 3344 W. Below illustrates how that might look like:

Four excess power hydrogen generators will run full-time, and the fifth one will turn on occasionally. This is equivalent to 5.5 coal generators running full-time, or 1.65 petroleum generators running full time. It's a lot of power!

This power does not come free -- it only produces 267 kg/cycle of oxygen, which supports only 4.45 regular dupes per OPOM compared to the 8 dupes of the PASSPOM. In the early game, water tends to be scarce and power/hydrogen are usually not needed in large quantities, so I wouldn't recommend building the OPOM as your primary SPOM. It would deplete your water supply very quickly and force you to either store large quantities of hydrogen or waste power.

 

How it works

The OPOM relies on the matter conversion bug. Specifically, when a vacuum tile is exposed to a gas tile directly on top and another to the right, a new gas tile will be formed at the vacuum that takes its mass from the right-side tile, but its element from the top tile.

OPOM's design creates a permanent ideal gas arrangement that continually promotes oxygen-to-hydrogen matter conversion, illustrated below.

The liquid valve for each chamber is set to 333g/s, resulting in in 333g/s of gas being created, less than the 500g/s capacity of the gas pump. This excess pumping capacity allows the vacuum tile to permanently exist, and for maximum matter conversion to take place.

 

Construction notes

A loop is recommended for liquid input line

Looping the liquid input line ensures that water does not accumulate in large packets at the electrolyzer input when the gas outflow is blocked (which tends to happen often). If large packets of water have accumulated when the gas outflow is restored, the electrolyzer would temporarily output 1 kg/s of gas, causing the vacuum tile to disappear while also destabilizing the ideal gas arrangement. This causes hydrogen output to drop drastically, and if hydrogen were relied on to self-power the module, the system could completely drain the backup batteries and require an external power source to restart itself. Not fun. Looping the liquid input line solves this problem.

 

The hydrogen mechanical filter needs 3 gas valves

u/yiyas has created an excellent tutorial on how to set up a mechanical gas filter in their PASSPOM construction guide, so I won't repeat their work here. The basic idea is to set all gas valves to 1g/s, capture a hydrogen packet, then completely fill the filter loop with at least 1g packets of hydrogen.

OPOM uses three gas valves (instead of one in PASSPOM) because it has a much larger hydrogen output. If only one gas valve is used there would be a big risk that new hydrogen packets cannot enter the filter loop because that particular loop spot already holds 1kg of hydrogen, causing hydrogen to end up in the oxygen line. Not fun. Using three gas valves solves this problem.

 

Create two-tile liquid column using a bottle emptier then deconstructing

Two-tile liquid columns can be created by stacking two different liquids. They are a pain to set up.

I've found that the easiest way to make two-tile liquid columns is by setting up two layers of liquids using a bottle emptier, then deconstructing the bottom tiles.

 

 

Final notes and credits

A save file on QoL MK3 is attached if you'd like to try the build out quickly. Comments are welcome!

Big credit to u/yiyas for their work on PASSPOM and SPHM. They really pushed the envelope on electrolyzer hydrogen generation, and came up with the idea of using valves and liquid tiles to increase hydrogen output. The OPOM is a shameless adaption of PASSPOM and SPHM. Thanks u/yiyas!

OPOM test bench.sav

[mathmanican]

Would you like a 100% H2 version?  Or alternately a 100% O2 version? 

[Denisetwin]

2 hours ago, sorrymybad said:

 

Create two-tile liquid column using a bottle emptier then deconstructing

Thank you for posting, I love it, and I really like this two tile column building idea, this is great!  Thank you so much for posting all the overlays and how-tos as well!

 

4 minutes ago, mathmanican said:

Would you like a 100% H2 version?  Or alternately a 100% O2 version? 

of course!!!  I'm revising my five electrolizer get rid of this water some way build because I realized that it was generating very little hydrogen which is WHY I built the thing in the first place - well and to get rid of some of this water......  Love that this thread is so timely!

[Neotuck]

This looks useful for hydrogen rockets

[mathmanican]

47 minutes ago, Denisetwin said:

of course!!!

I think you'll have fun engineering the smallest possible version, and then sharing. Combine these two ideas (no need for the air pumps though, as you can let the gases recombine after the conversion), and make it small, compact, and easy to build. 

    

I'll work on it later today if you don't have a prototype up by then.

[Saturnus]

Here you go. Minimum required for making 1kg/s hydrogen ouput (unless you use a minipump for vacuum water loop).

Including everything you need to get it started which is oxygen primer vent, hydrogen primer vent, and priming separator door.

Note the hydro sensor opens the separator door and turns on the the electrolyzer at the same time. This ensures that you don't accidentally run the electrolyzer before the system is primed correctly.

Water consumed: 1kg/s
Hydrogen produced: 1kg/s
Power consumed: 601.68W(avg)
Power potential: 8000W
Surplus power potential: 7398.32W

[mathmanican]

3 hours ago, Saturnus said:

Here you go.

I didn't think you'd jump on this one, but I hope you had fun.  

This is pretty close to what I had in mind. A few comments.

• Be careful with using the door above for shutting it off. That setup can fail, by causing the H2 to get lodged in the vacuum spot (doesn't happen often, but can). When the door shuts, it is possible for the H2 to get stuck below the door, and then everything gets gross from there. I'm not sure how much you've played with this one @Saturnus.
• You can safely shut the thing off with 100% reliability by using a second valve supplying another 70g/s liquid, attached to a liquid shutoff. 
• I'd add space for a pressure sensor on both sides to shut the matter contraption off if the oxygen or hydrogen pressure gets close to vacuum. This is done by (1) turning on more liquid, and then (2) closing the door AFTER the extra liquid stops the matter conversion. The whole thing will break once either side reaches vacuum.  If the electrolyzer shuts off, the O2 side will reach vacuum quite rapidly.

[Saturnus]

21 minutes ago, mathmanican said:

I didn't think you'd jump on this one, but I hope you had fun.  

To tell the truth. I built it a long time ago. Just needed to find the save it was in.

I disagree though. You can shut it down safely using the door/electrolyzer switch. Even if hydrogen does become lodged in the vacuum spot it'll quickly disappear once you restart it as the oxygen pressure hovers around 13-15kg per tile under normal operation, and the hydrogen pressure is set to 2kg per tile by the atmo sensor that turns the pumps on.

[mathmanican]

25 minutes ago, Saturnus said:

Even if hydrogen does become lodged in the vacuum spot it'll quickly disappear once you restart it as the oxygen pressure hovers around 13-15kg per tile under normal operation, and the hydrogen pressure is set to 2kg per tile by the atmo sensor that turns the pumps on.

The danger is the following scenario.

1. Door closes, trapping hydrogen under the door.
2. The hydrogen can swap left/right with the oxygen, and I'm guessing there is a random number generator that decides what happens.
3. The door opens when the hydrogen has moved right, leaving oxygen under the door. 
4. The oxygen moves upwards (as it's 13-15kg and pushed the hydrogen upwards). The first tick of the game when the door opens will convert any upward moving oxygen to hydrogen (matter conversion), but after that there is a chance the oxygen will push upwards more (as the pressure is much higher than the hydrogen). 
5. Of course, if the hydrogen is blocking the O2 port for the electrolyzer, then the O2 could get shoved upwards as well on the right side, creating another problem in itself. 

I'll play with it tonight and try to break it.  I'm guessing you've stressed tested it already for 50+ cycles (as you posted an average), but this would be continuous operation. Have you stress tested toggling it on/off every 10 seconds for 50 cycles? If you've stress tested the last part, and haven't seen any problems, then it's probably fine.  Or it might be like that time with liquid duplication where after 50 cycles of stress testing, you saved the file for upload, and then the one time the aquatuner loop failed was upon reload.   Fun times.

[Saturnus]

I haven't stress tested it. It's a minimum build. I've shut it down with the door a few times, and haven't seen an issue but I suppose there could be one.

Regardless, I didn't build it to shut it down. I build it to keep running, on and on. And it certainly does that.

[Mr.Trueba]

@sorrymybad I really like your building. As soon as I have a chance I will try it and see if there is any contribution I can make. As mentioned before, this can be a shared and friendly solution to have an SPOM AND keep over for late game liquid hydrogen, which is a problem when you get to the part of the space but for hundreds of cycles you did not accumulate any hydrogen, hahaha.
Thanks for sharing and well done!

[Saturnus]

15 minutes ago, Mr.Trueba said:

@sorrymybad I really like your building. As soon as I have a chance I will try it and see if there is any contribution I can make. As mentioned before, this can be a shared and friendly solution to have an SPOM AND keep over for late game liquid hydrogen, which is a problem when you get to the part of the space but for hundreds of cycles you did not accumulate any hydrogen, hahaha.
Thanks for sharing and well done!

If you seriously want to use rockets you most certainly do not need to stock pile hydrogen.

Hydrogen is only useful in the inefficient hydrogen rockets to reach the farthest away planets, and you will do that very rarely.

Most rockets you will use are the more efficient petroleum rockets with liquid oxygen for farming the midrange planets.

Typically you'll need about 6 times more oxygen produced than hydrogen.

[sorrymybad]

Is there a reason you wouldn't transition all your rockets to hydrogen if you can generate enough LH2 to support them? Some reasons why hydrogen rockets are better -- (1) Water is renewable in much larger quantities than petroleum; (2) Hydrogen engines use less weight for the same distance, which is significant because the weight penalty increases exponentially with increasing weight; (3) Petroleum used in a sour gas boiler creates an insane amount of power, whereas as a fuel it's only so-so; finally (4) with the OPOM or your hydrogen generator you can recycle hydrogen engine exhaust 1:1 to fuel -- you can't do the same with petroleum engine exhaust.

3 hours ago, Saturnus said:

If you seriously want to use rockets you moydrogen is only useful in the inefficient hydrogen rockets to reach the farthest away planets, and you will do that very rarely.

Most rockets you will use are the more efficient petroleum rockets with liquid oxygen for farming the midrange planets.

Typically you'll need about 6 times more oxygen produced than hydrogen.

 

[Saturnus]

1 hour ago, sorrymybad said:

 (1) Water is renewable in much larger quantities than petroleum; 

Is it? Oil wells output 3.333 times the amount of water you put into them.

That point alone moots the rest of your points really.

Not to mention, I can create infinite amount of both water or petroleum, or any gas I like with relatively easy set ups. It's just a matter of defining for yourself where you draw the line.

 

 

[miauly]

On a side note, this post is a perfectly worded bug report.

[sorrymybad]

33 minutes ago, Saturnus said:

Is it? Oil wells output 3.333 times the amount of water you put into them.

That point alone moots the rest of your points really.

Not to mention, I can create infinite amount of both water or petroleum, or any gas I like with relatively easy set ups. It's just a matter of defining for yourself where you draw the line.

I'm not sure I follow your logic.

You say that hydrogen rockets are less efficient than petroleum rockets. Help me understand how that is true.

It's not true on a mass-per-trip basis.

A rocket travelling 60,000km to a midrange planet carrying 2 cargo bays will require 2122kg of petroleum and 2122k of oxygen. The same set up will only require 1071kg of hydrogen and 1071kg of oxygen.

It's not true on a loadout-per-trip basis.

A petroleum rocket can never reach 60,000km with 3 cargo bays, whereas a hydrogen rocket can. For any given number of launching pads, hydrogen rockets can always bring back material at a faster (if not equal) rate than petroleum rockets.

It's not true on a per-kg-of-water basis.

You mentioned that oil wells output 3.333 times the amount of water put into them. I've tried playing this out.

If we were to use a petroleum rocket to send two cargo bays to a 60,000km planet, we would need 2122kg of petroleum, pumped from 637kg of water, and 2122kg of oxygen, presumably from 100% water. That's 2759kg of water.

Using a hydrogen rocket instead, we can take that 2759kg of water, use 637kg of it to pump 2122kg of petroleum out from an oil well, convert that into 1413kg of natural gas, and put that natural gas through generators to give us 1061kg of water. We now have 3183kg of water. To power our hydrogen rocket we'd use 1071kg for hydrogen and 1071kg for oxygen, and have 1041kg of water left over.

On top of that, our petroleum to natural gas process would have also produced:

707kg of sulfur (can be used in more gas conversion)
354kg of CO2 (can be converted to petroleum at 50% efficiency)
212kg of dirt (at the cost of 1T of renewable regolith)
and ~9,000kJ of surplus power in 637 seconds, equivalent to 18 natural gas generators running full-time (assuming ~70% energy efficiency)

It seems to me that hydrogen engines are always more efficient than petroleum engines from an input/output perspective. Would love to hear how you're thinking about this.

--

Separately, I'm curious to know how you are able to create infinite amounts of water or petroleum using relatively easy set-ups. I am only aware of gaseous matter conversion, which (1) is unable to create new mass, and (2) is unable to create certain types of liquids, e.g., petroleum, because vaporized petroleum (sour gas) does not condense back into petroleum. Please share if you have the time!

[Prince Mandor]

22 minutes ago, sorrymybad said:

...

We now have 3183kg of water. To power our hydrogen rocket we'd use 1071kg for hydrogen and 1071kg for oxygen, and have 1041kg of water left over.

...

If we are not abusing a bug and not magically convert one gas to another, 3183 kg of water is just 354 kg of hydrogen.

9 to 1 water to hydrogen conversion - this is source of hydrogen inefficiency.

Of course, we can abuse bugs. Then all this cosmic thing became unneeded. Just bring some material and use mass-duplication bugs to produce more, without any hassle with rockets

[sorrymybad]

13 minutes ago, Prince Mandor said:

9 to 1 water to hydrogen conversion - this is source of hydrogen inefficiency.

Good point. In a world where we refuse to use any gaseous matter conversion, I agree that hydrogen engines are less efficient on a water-used-per-trip basis. Hydrogen rockets are still competitive if we want to keep the petroleum for energy + dirt + CO2, but you're right that we wouldn't be spamming hydrogen rockets across the map because water is scarce.

At the same time, in a world where we don't mind *some* gaseous matter conversion, it's hydrogen rockets all the way, baby! I live in this world, so hydrogen rockets will be my go-to.

Arbitrarily, I am okay with hydrogen conversion from SPOMs, but I draw my line at using vents to create matter conversion -- once you allow vents, any (gaseous) matter conversion becomes trivially easy to do. To each their own.

[Saturnus]

2 hours ago, sorrymybad said:

You say that hydrogen rockets are less efficient than petroleum rockets. Help me understand how that is true.

Without any exploits 1kg of water is 112g of hydrogen and 888g of oxygen. However, you have to throw the 776g of oxygen away because rockets are 1:1. So mass conversion efficiency of water to hydrogen plus oxygen for rocket fuel is fixed at just 22.4%.

However, with the same 1kg of water you can also make 558g of oxygen and 558g of petroleum by running 372g of the water in an oil reservoir and then through an oil refinery (note, not even using an oil cooker), and running the remaining 628g of water through an electrolyzer. That gives you a total rocket fuel mass of 1116g. And a mass conversion efficiency of 111.6%. Not counting the 70g of hydrogen plus the natural gas generated by the oil well and oil refinery you then throw away.

So for the same amount of resources used we can create 5 times as much petroleum rocket fuel as hydrogen rocket fuel. At least, because we are even using an oil refinery and not an oil cooker with this calculation.

And that is why petroleum rockets are, without any doubt, more efficient than hydrogen rockets.

Fortunately, it's not a question of either or. And you don't have to either throw oxygen or hydrogen away. If you instead used 682g of water to make hydrogen and oxygen you'd get 605.6g of oxygen and 76.4g of hydrogen. That's 529.2g surplus oxygen. And if we take the remaining 318g of water and use it in an oil well/oil refinery that gives us 529.8g of petroleum. Close enough to say it's about even. That means the total rocket fuel mass is 1211g per 1000g water spent. With a ratio of hydrogen to petroleum rocket fuel of 1 to (about) 7.

[mathmanican]

7 hours ago, sorrymybad said:

I'm curious to know how you are able to create infinite amounts of water

You'll find simplified versions, as well as a petroleum one, deep in the thread.  Have fun.

[erso]

On 6/11/2019 at 10:23 AM, sorrymybad said:

Separately, I'm curious to know how you are able to create infinite amounts of water ...

Prision cells with mesh tile floor and ugly crier&small bladder duplicants generate quite a lot of water.

[badgamer123]

would that be ok if I just use 1 opom and make a 332g/s of water input? seem too much to have 3.....

[sorrymybad]

Sure that would work as well if you don't need that much oxygen/hydrogen.

I provided a 3-stack as the reference build because (1) it's comparable to a regular SPOM, and (2) it's the biggest stack you can make in practice without needing additional oxygen and hydrogen lines.

[KittenIsAGeek]

On 6/10/2019 at 11:23 AM, Saturnus said:

Water consumed: 1kg/s
Hydrogen produced: 1kg/s
Power consumed: 601.68W(avg)
Power potential: 8000W
Surplus power potential: 7398.32W

OK, so.. I took your idea and ran with it.  As I've mentioned before, my current map has a HUGE number of water geysers.  Here's an example of one that I've tapped.

Spoiler

Basically I set it up so that the pump will turn off when all the reservoirs are full -- until the liquid sensor turns on.  Figured I'd save power, but.. the pump uses so little power in the long run, that the rest just run the pump.  The reservoirs are there as a buffer to last through dormancy.

Basically I set it up so that the pump will turn off when all the reservoirs are full -- until the liquid sensor turns on.  Figured I'd save power, but.. the pump uses so little power in the long run, that the rest just run the pump.  The reservoirs are there as a buffer to last through dormancy.  If my math is right, the geyser produces 2091.6g/s averaged through its dormancy.  

So, lets use that 95c water for something useful.  First, we need oxygen.

Spoiler

Including using an aquatuner in a pool of water to cool the oxygen, this powers itself and has a little hydrogen left over.  I haven't done any specific calculations, but its enough that my hydrogen overflow room was around 5kg before I started building Saturnus' system.

At maximum, this will produce exactly 1000g/s of oxygen (and the appropriate amount of hydrogen) and will use 1126g/s of water.  Its set up so that when there's a backup of oxygen in the pipes, it turns itself off safely.  Right now I only have 8 dupes, and one has diver's lungs, so it only ran full time long enough to pressurize my base and atmo suits.  Not it only runs sporadically.   

But.. I still have LOTs of water from that one geyser... So, lets produce hydrogen for power!

Spoiler

 Yes, I stole this straight from @Saturnus.  Thanks!

I replaced the liquid sensor shutoff with a gas pipe element sensor set to hydrogen connected to a NOT gate and a buffer.  Basically if the tank is full, it shuts itself off.  Currently the buffer is set to 200 seconds, since I'm not using a lot of hydrogen yet.

If both my oxygen production and hydrogen max out, the system will need a little over 2126g/s of water.  Which means that under normal use, the one geyser will pretty much fuel these two systems.  I have 3 more geysers just like it on this map.

Here's my full system, with overlays.  Yes, I need to do some re-designing yet, but...

Spoiler

Rooms on the left are for storing large quantities of gas for later use. 

Part of what I need to redesign is the power from the top hydrogen generator.  It currently powers both the oxygen production, the cooling loop, and the fan in the hydrogen overflow room.  It works, but on extremely rare occasions it'll burn out a wire.

There's another hydrogen generator that is dedicated only to powering the hydrogen production room.  I shouldn't ever have to jump-start anything from here on out.

The oxygen goes out to the base at about 16c.  When oxygen system is running at full capacity, it'll be about 16.4c as it leaves the cooling chamber.  The main part of my base is at about 23c, but after another 100 cycles or so I'll re-evaluate the temperature of my cooling room.

You can see the pipe that ran from my base's water reserves before I tapped the geyser on the upper left.  As well as some pipes I haven't deconstructed from  priming various systems.  Meh. Whatever.

 

My gas pipes are a bit of a mess.  BTW, I found that running my radiator up and down got my oxygen to the proper temperature.  Running it back and forth did not. Anyway, there's a bit of an extended hydrogen pipe feeding the generator for the oxygen supply.  That is specifically so that the fan in the hydrogen overflow room won't turn on during normal operation.  

Nothing special about the automation.  The cooling chamber is set up so that if the water in the pipes ever drops below 14c, it turns the valve off so pipes won't break.

As you can see, I haven't actually built my power station yet.  In the SS above, the room is running and the gas reservoir isn't quite full. It filled up really quickly.    Here's a SS after the reservoir filled up:

Spoiler

The liquid pump does not shut off, because when it did, the oxygen displaces the water and causes problems at restart.  This creates a potential long-term problem that I haven't bothered to fix.  My current hydrogen piping loop will run out past where the hydrogen generator for powering the system is located -- IF the system remains in standby for an extremely long time period (1000+ cycles).  Which means that if I don't use the system, eventually I'll have to jump-start it.  A better solution would be to have the feedback loop re-join the primary loop above the generator instead of right at the top of the gas reservoir.

Anyway, thanks @mathmanican and @Saturnus.  Also, thanks to @sorrymybad for starting this thread.  =^.^=

[KittenIsAGeek]

Update: @Saturnus "Minimum for 1kg/s hydrogen production" has a slight problem.

On 6/10/2019 at 3:14 PM, mathmanican said:

The danger is the following scenario.

1. Door closes, trapping hydrogen under the door.
2. The hydrogen can swap left/right with the oxygen, and I'm guessing there is a random number generator that decides what happens.
3. The door opens when the hydrogen has moved right, leaving oxygen under the door. 
4. The oxygen moves upwards (as it's 13-15kg and pushed the hydrogen upwards). The first tick of the game when the door opens will convert any upward moving oxygen to hydrogen (matter conversion), but after that there is a chance the oxygen will push upwards more (as the pressure is much higher than the hydrogen). 
5. Of course, if the hydrogen is blocking the O2 port for the electrolyzer, then the O2 could get shoved upwards as well on the right side, creating another problem in itself. 

I'll play with it tonight and try to break it.  I'm guessing you've stressed tested it already for 50+ cycles (as you posted an average), but this would be continuous operation. Have you stress tested toggling it on/off every 10 seconds for 50 cycles? If you've stress tested the last part, and haven't seen any problems, then it's probably fine.  Or it might be like that time with liquid duplication where after 50 cycles of stress testing, you saved the file for upload, and then the one time the aquatuner loop failed was upon reload.   Fun times.

This wasn't the problem I encountered.  Turning the machine on and off was just fine with no problems.  Instead, the oxygen vent/airflow tile weren't converting to hydrogen fast enough.  Maybe.  I'm still not entirely sure.  Anyway, here's what I observed:

1. Doors open, pumps going continuously.
2. Hydrogen pressure around 2500g/s in production room.  Oxygen around 14kg/s over priming vent and under airflow tile.
3. For one tick, hydrogen appears in upper-left corner of electrolyzer, pushing the water to the right.
4. Electrolyzer 'over-pressurizes' and doesn't operate for following tick.
5. Hydrogen might swap left-right with oxygen in airflow tile. Happened about once every 15 or so 'burps.'
6. Oxygen could swap left-right with water over electrolyzer.  Again, it took multiple times before I saw it happen.  I couldn't count the frequency since entire 'burp' process takes less than a quarter second -- however, I did get it to reproduce twice while i was watching.
7. Water settles back into place, pushing oxygen up into hydrogen room.
8. Electrolyzer continues to operate, but now oxygen/hydrogen production locations are swapped. 
9. Now producing 1kg/s oxygen.

I tried several things using the sandbox: Changing the liquids, adding more liquid, using less liquid, etc.  Changing the valve rate to 80g/s made the problem worse.  Setting the valve to 60g/s worked better, but didn't completely solve the problem.  Setting the valve at 50g/s let oxygen leak out into the hydrogen room.  

Anyway, it was really tough to diagnose because most of the time, at 60 FPS, the 'burp' would happen without getting drawn to the screen.  Twitching on the spacebar was the only way I could see what was happening.