Sciencemadness Discussion Board

Flat Flange lid not grounded o-ring

pneumatician - 16-9-2020 at 10:26

hi, I purchased a Flat Flange lid (schott-duran o-ring system) and the contact surface with the vessel is not grounded. My old is grounded.

I put the seal with my old and the new in the vessels and really the 2 glass part they do not touch.

When the vessel is heated the 2 parts, lid + vessel enter in contact? I doubt... I write to schott-duran but untill now no reply...

I have 2 types of seals, one of a hard brown material and some of silicone, white, soft, elastic...

So if no contact for what reason one is grounded and the other no?? ok, with the grounded you can use only grease and with the other only the seal??

[Edited on 16-9-2020 by pneumatician]

PTDC0002.JPG - 341kB

pneumatician - 17-9-2020 at 07:03

ok, I received a reply, this:

[It looks like you have bought a blank (one-neck lid). We sell these blanks to manipulators, who then grind the flange themselves.
Actually, you cannot use this cover without further additionals, as it does not seal tightly with the lower part.]

So you can use the plastic or silicone ring or only greased glass if both parts are grounded of course. But the problem is in using the ring: is necessary a big pressure to put in contact both glass parts, so I asked if any especial clam is necessary, because with which I have and use it is impossible for them to make contact, always remain around 3mm of separation between the lid and the veseel.

PTDC0004.JPG - 233kB

[Edited on 17-9-2020 by pneumatician]

PTDC0002.JPG - 221kB

Heptylene - 17-9-2020 at 07:06

Maybe you can grind the glass yourself? With some abrasive compound and water on a flat surface I'm sure you can achieve good results.

pneumatician - 17-9-2020 at 07:11

well I are waiting a reply from the seller. I prefer to use the ring but I see a chaos in all this. In reality is better a surface not grounded if is in use the ring??? but I think is good to have the system a bit more clear for customers...

[Edited on 17-9-2020 by pneumatician]

draculic acid69 - 18-9-2020 at 01:47

Quote: Originally posted by Heptylene  
Maybe you can grind the glass yourself? With some abrasive compound and water on a flat surface I'm sure you can achieve good results.

Unless you invest some serious money into proper and big enough equipment (more than the cost of buying a new one) I doubt a Dremel and some paste will get you a precise enough (for airtight fit) finish

Dr.Bob - 18-9-2020 at 10:41

I would return the item to the seller for being not a finished product. They likely got it and did not know what it was so they sold it. But if it does not work for what it was sold as, then I would return it.

Fyndium - 19-9-2020 at 00:31

Quote: Originally posted by draculic acid69  
Unless you invest some serious money into proper and big enough equipment (more than the cost of buying a new one) I doubt a Dremel and some paste will get you a precise enough (for airtight fit) finish

You will need a surface plate or other decently parallel surface, abrasive fabric or some paste and grind it against it with a rotating motion. Using any hand grinding tools or handheld grinding equipment, unless larger than the entire surface is absolutely no-go.

pneumatician - 30-9-2020 at 20:23

well after some time whitout more replies, or the builder or the seller not have idea about this item. Can you guys if one at hand tell me if is grounded or not? and with the seal the two pieces of the reactor, do they touch each other? TIA

OldNubbins - 30-9-2020 at 23:11

Based on the response you posted it probably needs to be ground. If you cannot return it, it can be ground by hand but it can be tedious.

I have hand-scraped flat laps before, you don't need any special tools, just three pieces of 25mm or so mild steel or cast iron plate. I won't go into detail here as there are plenty of tutorials out there for hand scraping but you basically scrape all three plates to each other using layout dye or Prussian blue to mark the high spots. The scraping tool can be hand-made with a sharpened piece of tool steel attached to a handle. Make sure your lap plates are larger than the face you need to grind.

Once all three of your plates are sufficiently flat (they will ring together and the high spots will be evenly distributed across the surface) you can use them to grind the glass face. I have used silicon carbide and aluminum oxide powders, moving up in grit and just move the surface you wish to grind in a figure-8 pattern so you don't spend any extra time moving in one particular direction. Glass grinds very fast so work slowly.

This is just my experience, I have never ground anything for deep vacuum (medium vacuum I have) but I am fairly confident in the procedure having done it in a precision machining environment.

wg48temp9 - 1-10-2020 at 01:24

I have cut the bottom of a one gallon demijohn/carboy by the the score, tap and crack method to make a bell jar. That method left a very uneven base and that had to be ground flat.

I attempted the grinding by hand using the side of a large grinding wheel that was only an inch or so larger than the base. That did not work very well so I switched to a large sheet of coarse emery paper on a aluminum plate. . I used a circular motion of the jar rotating it a quarter of a turn every two minutes. It was very laborious and time consuming. It took days to get it mostly flat. A home made thick silicone rubber gasket was added to take up the imperfection the surface and spread the load more evenly. It successfully held a vacuum without imploding.

I suspect your flange has a smaller diameter but much larger width than my demijohn but you apparently need to grind off about a mm. With the right sized grind medium by hand that will be a day or two of hand grinding.

If your not going to use a thick silicone rubber gasket you will need a perfectly flat surface ground finely.

If i had to do it again I would use a brushed washing machine motor (easily controlled speed and torque) to rotate the demijohn and cheap diamond cutoff discs glued to a car break disk. Using a silicone gasket for final sealing.

When I get round to it, I have a couple of large pyrex mixing bowls that I need to grind flanges on so they will mate with a car break disc with a gasket to make a cheap vacuum chamber.

Diamond coated cutoff discs for glass, stone and tungsten carbide tool sharpening are available on ebay from China for about £3 a disc:
di-disc-s-l500.jpg - 11kB

[Edited on 10/1/2020 by wg48temp9]

Chemetix - 1-10-2020 at 04:04

Find some carborundum grit ( fine but not too fine) and just add some with water to make a paste, to the flask and the unground lid. If the flask is well supported the lid can be moved in small circles by hand and occasionally rotating the lid a little bit at a time until the surfaces are ground flat against each other. You can do this with the lid on a piece of window glass or a flat steel surface as well. Wash the surfaces from time to time and keep reapplying the abrasive. It wont take too long until the lid is ground flat.

pneumatician - 1-10-2020 at 07:09

No guys!! I apreciate your help but I can return the item, but I want to understand what is going on here... Sell this expecting you or the wholeseller grind it with "redneck" tech is ridicuolos in a "high tech" expensive glass piece, no? :-D

Sorry but I never stop, no matter if all the universe say: "uh?", "I don't understand", "what the Hell is this" etc :-D

In reality this work better not grounded IF THE silicone or the other seal is put between the 2 glass pieces but nobody can tell me if this is ok or if is a very bad commercial procedure...

Well tightened with the plastic or silicone ring when I drop the cap it bounces, sign that it is well sealed, and really if not grounded the contact between the rubber and the glass is better.

Well, now I are making others works, in some days I try it distilling HCL to see if I need to run away fast! :-D

Chemetix - 1-10-2020 at 13:48

Ok I'm getting my head around your problem, your phrasing is a little awkward, English is not your natural language so I understand that and can appreciate the difficulty explaining technical concepts.

Having an unground lid is not uncommon, it's expected that both faces are the same for whatever reason you decide to not use a ground surface and use a gasket material in between the faces. It's not common practice because choosing a gasket material is completely dependent on your application such as the chemistry, temperature, solvents, pressure/vacuum.
If you are using a gasket material or o-ring this means the clamp must be designed to hold the glass and the gasket, and because the great variability in the thicknesses of the chosen gasket material it means the clamp has to be chosen for the application. You can find a clamp here:
Getting all the components to match is more complicated than using a ground surface and some grease.

So to answer your question: Yes a gasket and unground faces work, but it's more complicated to do and so isn't done very often.

And I grind surfaces like I advised after repairing a chip or sealing a crack on a flange. It's not some unprofessional farmhouse technique.

OldNubbins - 1-10-2020 at 19:44

Most industrial manufacturing processes are just "unprofessional farmhouse techniques" with some lipstick and jet fuel applied to justify the capital expense.

BromicAcid - 2-10-2020 at 03:59

I used to regularly use the type of clamp and gasket that you show in your second photo. No, both surfaces do not have to be ground for that style to work, however there has to be a groove for the gasket to rest in. I cannot tell from your photos if you have such a groove in the glassware. The groove would be on the bottom face and the top face would be smooth, the seal being formed between the two with the gasket. If there is no groove then these pieces are not destined for oneanother with this setup.

pneumatician - 5-10-2020 at 17:48

yes the groove is on the bottom face of all my vessels. So basically all reactors brands are compatible if the "DN" or diameter is the same? using or not the seal of course...??? and if enter in the clamp :)

well, quickfit use a flat surface in both sides all grounded, so here you are forced to use grease or not, is your choice, umm