What are the "windows" on factory stills?

[goinbroke2]

I've looked at several stills (online) at distilleries and their swans neck has a bunch of glass windows in the upright portion. 6 or 8 small round windows/portholes.

What are they? I thought maybe where the plates would go for a reflux type still but these are potstills.

Anyone?

[brewmaker1]

Here's one explanation:
Further up the neck can be seen a small glass porthole which allows inspection of the contents of the still to ensure it does not rise too far up the neck and boil over. Before the advent of the porthole a wooden ball was swung against the neck of the still and the resulting 'ding' used to determine the state within.

[rad14701]

Back in my automotive days we called them a "sight glass" in the air conditioning systems which allowed us to see whether there were gaseous bubbles where only liquid should reside... Haven't even checked my current vehicle to see if they still use them... With stills you wouldn't want to see all fluid as it would most likely mean a flooded column...

[Ayay]

I would like to see what's happening at my reflux outlet; in reflux mode to see how much reflux is going through and how it is behaving, and in pot still mode to see if any reflux is going through at all.

I think seeing would be great rather than flying blind and only using instruments or intuition.

[brewmaker1]

Ahh, but if you could see in, the Leprechauns would get pissed because they couldn't work they're magic. Then all your hooch would be tails

[goinbroke2]

hmmm, just to see huh?

Thanks

[snuffy]

The eau de vie stills made by Christian Carl and Holstein are plate stills. There are sight glasses so you can see how each plate is doing. With perforated plates, you have to watch for either flooding or too much vapor velocity. Bubble cap stills are more forgiving, but still need watching. When the still is starting up, you watch for each plate successively getting enough liquid and when the top plate fills, you turn down the power to let it equilibriate.

There's usually one sight glass for each plate and one sight glass below the bottom plate so you can check the amount of reflux coming off the bottom downcomer and returning to the boiler. #Plates = #Sightglasses -1.

[goinbroke2]

Excellent explanation Snuffy, thanks!