Sight glass separator

[AJB]

Hi all,

I've done a fair amount of sleuthing but come up short. I'm looking for stainless flanges to use as separators to expand my reflux still - 3" column. Has anyone managed to source these, or know of a supplier?

2026-08-06 21_07_21-3D Viewer.png

Here's a 3D mockup of what I'm after, it looks the same both bottom and top:

2026-08-06 21_09_21-Double_sided_110mm_PTFE_carrier_preview.stl ‎- 3D Viewer.png

I have a STEP file ready if anyone's able to machine a set in Australia.

[BigSwede]

I'd guess your best bet is to find a "Mom and Pop" machine shop to do them manually. Big shops with their gigadollar CNC machines might do it, but they like quantities in the dozens or hundreds.

The materials cost will not be low. If they source solid 304 SS or similar, everything in the middle is wastage. Perhaps thick-walled DOM stainless might serve, but even that will be pricey.

I don't want to be too discouraging - good luck, I hope you can find a way to make it happen. Hopefully others will perhaps have better ideas.

[tommysb]

Look into a 3" sight glass from Oakstills (or similar). It's not exactly what you've asked for, but should do roughly the same job. Just add a couple of those along with plates to extend and add more plates to the column.

I had a column I bought a few years ago from aliexpress which had a (silicone) rubber gasket between the glass sections. Do you already have the extra glass sections? Maybe the silicone gasket would work, also, and you could try to source that. Something like this:

image.png

[shadylane]

Here's a 4" column that used seals from StillDragon.
https://stilldragon.com/product/crystaldragon-gasket-4/

[AJB]

Thanks everyone — some useful suggestions here.

BigSwede, I think you have identified the wall I’m currently hitting. One-off machining, setup costs and the amount of wasted stainless make what appears to be a simple ring surprisingly expensive. You haven’t discouraged me, though; I’m still holding out hope that a small manual machine shop or starting with a suitable stainless tube or ring blank, might make it viable. I’m in Australia, so once international freight and delivery time are included, it may actually be easier and cheaper to have these made locally by a small corner shop machinist than to import finished parts from the US or elsewhere.

tommysb, the additional borosilicate glass sections are already on the way. I’m deliberately trying to keep silicone to an absolute minimum in the finished setup, particularly around the vapour path. That is why I’m pursuing stainless separator flanges with PTFE gaskets on either side, rather than silicone seals between every glass section. The complete stack will be compressed using long external retainers.

shadylane, thanks for the StillDragon gasket reference - I came across them through Tech Ingredients YouTube channel. Even if its gasket material isn’t what I ultimately want, the way the glass sections and plates are located may still give me some useful ideas.

If anyone knows a small Sydney-area shop willing to tackle one-off manual turning work, I’m still very interested.

[shadylane]

shadylane, thanks for the StillDragon gasket reference - I came across them through Tech Ingredients YouTube channel. Even if its gasket material isn’t what I ultimately want, the way the glass sections and plates are located may still give me some useful ideas.

The downside to making what you're thinking about is there will be 3 flat seals needed for each plate.
Finding ready-made seals that fit perfectly is going to be a futhermuker.

[tommysb]

Ok - so you could get this laser cut as 3 pieces which will be aligned by the rods passing through the holes. Could even work with just a single disk and ptfe seal between the disk and the glass, as this is the actual seal point. The vertical pressure will hold everything in place - the extra two retaining disks are just for security.

[GrumbleStill]

Just something to be aware of. In that design the glass carries all of the weight of the tower. Most of the commercial ones pictured use the rods to carry the weight.

[Salt Must Flow]

Just something to be aware of. In that design the glass carries all of the weight of the tower. Most of the commercial ones pictured use the rods to carry the weight.

Actually the rods still carry all of the weight of the tower in both designs. The rods travel through the stainless separator in ABJ's pics and hold the gaskets used to seal to the glass. The Still Dragon gaskets don't use a stainless separator, but the rods still hold it all together and carry the weight of the tower.

[LWTCS]

Just something to be aware of. In that design the glass carries all of the weight of the tower. Most of the commercial ones pictured use the rods to carry the weight.

Yep.
The truss rods should carry all of the weight from the top flange, dephlegmator, reducer, line arm and any cantileverd load needed to carry the PC.

[30xs]

Multiple glass sections and teflon gaskets are probably going to be a nightmare to get to seal up sandwiched into one set of truss rods. Zero margins for error.

[shadylane]

Multiple glass sections and teflon gaskets are probably going to be a nightmare to get to seal up sandwiched into one set of truss rods. Zero margins for error.