Drain Plumbing As Compression Port?

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ian_krase
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Real name: Ian Krase

Drain Plumbing As Compression Port?

Post by ian_krase »

The Bell Jar suggested using a hardware store "slip joint" meant for assembly of sink drains and traps as a cheap compression port. They are not entirely unlike a 40 or 50 mm compression port. Has anybody else tried this?
John Futter
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Re: Drain Plumbing As Compression Port?

Post by John Futter »

Ian
Picture?
what are you talking about?
sanitary fitting?
car exhaust system slip joint?

Many of us do not live in Donald Trumphville
ian_krase
Posts: 636
Joined: Mon Nov 28, 2016 2:48 am
Real name: Ian Krase

Re: Drain Plumbing As Compression Port?

Post by ian_krase »

I'm talking about fittings made for kitchen and bathroom sink drain tubing.

This was proposed in Figure 3 of http://www.belljar.net/system.htm

The fittings are something like this:http://www.homedepot.com/p/Eastman-1-1- ... /205971685

As you can see, it compresses a rubber gasket which appears to be a square cross section onto the OD of a tube.
John Futter
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Re: Drain Plumbing As Compression Port?

Post by John Futter »

Ian
aha
In vacuum parlance a "Cajon" type fitting (slip joint o-ring seal) widely used in vaccum work as a metal to glass transition.
Also for others reading this
Go to Ian's post and go to the links
I notice that belljar are advocates of soft solder just as I am for vacuum joints
super easy on copper and brass but very doable on stainless if you have the right flux
( i make killed spirit of salts, excess zinc with a small amount of hydrochloric acid then a few percent of phosphoric acid. If you want to jazz it up a bit around 1% HF added)
this makes stainless as easy as copper to solder as long as you do not overheat the stainless -- I use an old electric 100W soldering iron as the flux eats bits for breakfast
ian_krase
Posts: 636
Joined: Mon Nov 28, 2016 2:48 am
Real name: Ian Krase

Re: Drain Plumbing As Compression Port?

Post by ian_krase »

Heh. And here I am just silver brazing everything. After my incrementally expensive series of attempts to braze or solder aluminum I have been turned off from trying to soft solder things that passivate.

Yeah -- "quick disconnect", Ultra-Torr, Cajon, "Compression port" -- with the exception of "ultra-torr" every one of those names means something else as well. It is very difficult to search for these things (the legitimate vacuum version) on Ebay with much success. Or even Google. (Also, Ultra-Torr types are usually smaller and not meant for tubing that goes all the way through.)

But they do get prohibitively expensive above around 3/4 inch ID, even from LDS vacuum -- and when you take into account the wall thickness of a "safe" glass or ceramic tube, you need rather more than 1 inch if you want lots of space for your ion-ish goodness.

As far as I can tell, there are two kinds of these plumbing slip joints. One has a small molded V-cross-section plastic gasket, and the other (the kind I am interested in) has a larger square-cross-section rubber gasket/ring. I suspect it would be made out of EPDM which is not AFAIK a good rubber for vacuums, but I could probably replace with Buna since it's a simple cross section, maybe even an O-ring plus appropriate backing rings.
ian_krase
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Joined: Mon Nov 28, 2016 2:48 am
Real name: Ian Krase

Re: Drain Plumbing As Compression Port?

Post by ian_krase »

Well, I got a 1.5 inch to 1.5 inch slip fit compression union. It's plated with either nickel or chrome-nickel but this was reasonably easily removed with an electric drill and one of those sorta mega-scotchbrite foamy abrasive wheels. (The base metal is brass). This may actually work.

You can buy bare brass slip-fittings but they are uncommon, expensive, and mostly only represent a few P-traps and the like; I had no luck finding useful tubes like this.

I also found some nice rimless 38mm test tubes on Ebay, suitable for a column for the B.O.T.T.L.E. if I can successfully drill the end for a feedthrough.

I don't have any KF40 flanges to braze on right now, so that will have to wait, hopefully only until tomorrow. The wall of the fitting is pretty thin, about 1mm and much less than standard vacuum hardware.

The fitting comes with two sizes of square cross section compression gaskets made of a somewhat thermoplasticky-feeling black rubber. One is meant for a 1.5 inch OD tube, and the other takes up the space between the 1.5 inch bore and a 1.25 inch OD tube. Neither of them really felt like they were actually compressing against a tube inserted into the fitting. On the other hand, an O-ring with a cross section of 1/8 inch seemed to fit entirely within the compressing chamfer of the fitting body, and when the fitting nut was tightened it seemed to grip the test tube pretty well. A nice addition would be a shim/washer to serve a bit like the "piston" in a real Ultratorr/Cajon fitting and eliminate the rubber-to-nut friction, but I don't see where such a thing would be provided. I almost certainly need grease.

(I'm not sure what this O-ring is made of. From the hardware store so it's probably either Buna-N or EPDM.)

These fittings are bellmouthed so that the fitting can accept a tube of the same OD as the tail end of the fitting. This means that the inserted tube is blocked from slipping into the fitting but I feel like it isn't blocked very well, might put undue pressure on the glass. I am not 100 percent sure how to solve this -- maybe cushion with a thin layer of kapton tape or appropriate Teflon ring. Maybe even pipe tape.

I kinda wish I could completely strip the plating since I don't think it's really helping much and probably is hurting, but I do not in any way have equipment to do that.
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