14-Aug-2013 (Wed)
Wherein the new stair nosing's here, and we pump, pump it up.

Oooooh, pretty! This is so much better than the crappily-painted-yellow aluminum nosing we've been using before. It's powder-coated steel, so it should stay yellow for much longer than the couple-of-weeks that the paint used to last. (Please imagine this with the residual yellow paint on the stairs painted gray).

These are also going on the currently-noseless stairs leading from the street to Above DNA. Road cases get dragged up and down those stairs several times a week, so they really need some protection.

Check out the crazy curve in this last one, from the stage-right stairs. The corresponding stage-left stair doesn't look like this, because there's nothing even remotely symmetrical about our stage. The front edge of the stage is about 4" longer than the back edge, and the left stair landing is 6" or more higher than the right. Also either the pillars or the stairs aren't the same distance from the front wall and I'm not really sure which. It's the DNA Mystery House. The fact that he actually bent that piece of steel to fit around the pole shows that our contractor is almost as obsessive about these things as I am, which is why we keep him around!

He brought a laser level out today to take a look at the wavy, multi-layered mess that is our sidewalk, and figure out what we need to do to make the parklet's decking line up with it. It's... not simple. But it looks like construction on the parklet will begin off-site on Monday, and installation will probably begin the Monday after that! (We don't actually get the Kickstarter money for a few weeks, but we're gonna jump the gun a little.)

Segue involving the word gun!

We recently made a change to how our soda guns and beer pumps work, spurred into action by a de-obfuscated invoice. So, we've got this giant CO2 tank in back, that Airgas fills from the street, and all this time we thought we were just paying them for gas, but they made their invoices clearer recently and we realized that we're actually renting the tank from them too! Which is insane. So we're buying the tank, about ten years too late. But that caused us to also think a little more critically about how the whole Rube Goldberg system works and fix some stupidities in it.

I'll bet you're really curious how all that crap works, aren't you? Well I'll tell you.

So we've got two serieses of tubes, one set for beer and one set for soda. The beer starts in refrigerated kegs and is pumped up to the bars as-is; the soda starts in syrup bags, is pumped to the bars as warm syrup, where it is then mixed with water and CO2 and cooled just before the tap. (There's a big, flat aluminum thing that lives under the ice in the bar's ice well that does the mixing and chilling. Fun fact: the carbonation process requires low temperatures, so if there's no ice at the bar, soda comes out flat.)

Beer is forced out of the kegs by displacing it with CO2, and both systems are pumped along with pumps that work kind of like a single-chambered heart: pressurized gas is used to turn a little actuator that compress a bladder, forcing the delicious nectar through some valves. The gas going into the pump doesn't actually enter the line being pumped. The old way looked like this:

The glycol lines are a closed loop of antifreeze that run alongside the beer lines to keep them cold.

There are also some extra valves in there to prevent back-flow, so that if a keg is empty, the beer in the line is locked down so that it doesn't foam up.

(Fun Fact #2: when you have 2 kegs in series, the one on the outside always empties first. The beer from the outer keg is displaced into, and will fill, the inner keg before being pushed downstream.)

So, you may notice that it's kind of insane that we're paying for CO2 just to spin the actuators on the pumps, and then fart that perfectly good carbon dioxide right out into the room. So we stopped doing that, and bought an air compressor to run them instead:

We're still using CO2 to displace the beer in the kegs (if you use air, the yeast goes hog wild and the beer goes bad) and to mix with the soda (because the C is for carbonation) but this should cut our CO2 bill by a lot.

Now, I hope you're also thinking: "Wait, you're using electricity to compress air, and then squirting that air at a spinning wheel to move fluid... isn't that stupid? Why not just use electric pumps instead of going through this gaseous middle-man?" Because that's what I was thinking. And I couldn't really get a straight answer other than, "Nobody uses electric pumps for this because it would be crazy expensive." I still don't understand why that would be -- surely that would be a more efficient way of turning electrons into motion -- but apparently it's cheaper this way.

20 Responses:

  1. I'm confused. Were you asking the CO2 supplier why people use gas instead of electric pumps?

  2. bluknight says:

    I'm taking a wild potshot here, but I'm going to guess that electric (impeller) pumps, especially multiple pumps over significant distance, cause enough turbulence in the "beer stream" that it could cause said beer to lose its carbonation, sort of how shaking a soda bottle causes the CO2 to come out of solution and "fizz up".

    I know a couple of people who currently or used to work in the industry, maybe they'll have some insight nobody else does. (Yeah, right.)

    • cthulhu says:

      I suspect you're correct; same reason why IVs are regulated by a pump that squeezes the IV line - other kinds of pumps are too rough on the solutions / mixtures (like whole blood, for example). I would think it would be extremely easy to cavitate carbonated beverages by anything other than very gentle pumping.

    • bbot says:

      Yeah, but you wouldn't use an impeller pump. You'd use a peristaltic pump as usual, just electric drive instead of pneumatic drive.

      • Anthony says:

        Peristaltic pumps are usually slow, which is fine for pumping blood into people, but not for pumping beer into them. Faster peristaltic pumps are expensive.

  3. phuzz says:

    On a related note, does anywhere in the US use hand pumps (like this). Most pubs in the UK use them for beer.

    • nathan says:

      Yes, many places use hand pumps/beer engines, but only for cask-conditioned ("cask") beers. Here in the US, those are put into a totally different shaped container, and are carbonated only from the yeast inside the cask. The level of dissolved CO2 is much lower than "keg" beer (which frequently has additional CO2 dissolved into the beer as part of the brewing process), which is distributed with external CO2 or nitrogen as Jamie describes. The same beer delivered with each of the three methods actually tastes distinctly different.

      • phuzz says:

        Over here, we just call it beer.
        As opposed to something like budwiser, that we call "piss". ;)

        It just struck me that practically every pub in the UK has a beer engine with manual pumps, because basically everywhere will server at least one ale, usually two, and often more. In fact, a typical bar would have one or two lagers, a cider and one or two ales on tap, with regional variations (here in the south west at least two ciders on tap is normal). (Oh, and by cider, I mean the stuff with alcohol in).

        I've not been over to the States and I was just interested as to what sort of thing you'd find on sale at a typical bar.

        • nathan says:

          The variance of American bars is huge compared to what you're describing. Alcohol is regulated on a state level, which makes things interesting across particular state lines.

          But on sheer statistics and pure numbers across all the entirety of the USA, the joke is: A beer snob walks into a bar and asks the bartender, "What's on tap?" "We've got everything: Bud, Bud Light, Miller, Miller Light, Coors, Coors Light,..."

          That said, depending on the city, lots of places have other stuff on tap, or in bottles. The particulars of beer distribution beyond a local/regional level are complicated.

          What I've noticed as one of the newer trends is what we call "bottle shops", a shop that stocks bottles/six-packs of a wide range of craft/micro beers, like a hundred or two hundred different beers. Whether it's off-site and/or on-site sales gets back to the particular state and regional alcohol regulation.

          So there is no typical, really, especially as one tries to compare two different cities.

        • Owen W. says:

          This is by no means typical, but some bars in my area have a few more than three or four beers on tap:

          Most places I go to have 6-12 choices of tap, usually half of which are local.

          There are plenty of bars in the US that sell bud/budlight/etc, but it's not hard to find serious beer any more.

  4. Jeremy Wilson says:

    Compressing air with an electric pump is really cheap and runs on a cycle, so the compressor only kicks on below a certain pressure. It's not constantly using electricity like a fully electric pump would be.

    It makes logical sense to me, but obviously I have no conclusive proof for you. This link seems to imply that the type of pump makes the difference, in that an electric screw pump (like you'd find in a car for fuel) is far more efficient:


  5. Eric says:

    If liquid leaks past the pump seals, it's a lot safer if it contaminates the compressed-air system (hopefully it just gets vented out downstream). Leaking liquids into a live electric motor can get a lot more exciting.

    • Shasta McNasty says:

      Fair enough, but just about every car made in the last 3 decades uses an electric fuel pump, which is usually inside the gas tank! I'd rather leak beer into an electric motor than gasoline...

  6. Marcelo says:

    After my first encounter with the last night, I have to say. Those new nosings are incredibly slippery... that could become a problem with a bunch of drunk people walking up and down all night long, just saying. :-)

    • Jason P says:

      Strips of no-slip tape might help, or might result in abrasion injuries. Is an ounce of prevention on one end worth whatever amount of pain might result on the other? I'm sure an actuary could tell you.

  7. Douglas says:

    Would there be any way to dispense with the CO2 entirely, thus making the process more environmentally friendly?

  8. sneak says:

    Guinness is spelled with two "n"s.

  9. Philip Ngai says:

    The truetex site's analysis is as follows:

    "Using the CO2 as an energy source to run the syrup pumps might seem crazy, but the amount consumed is negligible. The volume is about equal to the syrup dispensed and the pressure is only about 1/3 that of the carbonation. Since the syrup volume is 1/5 of the water, and the water itself has about 4 volumes of CO2, the pumps are only using a proportion of about 1/20 extra CO2."