# Tubular length to circular diameter?

Discussion in 'Math' started by GRNDPNDR, Jul 7, 2014.

1. ### GRNDPNDR Thread Starter Member

Mar 1, 2012
449
7
Title might sound confusing but what I want to do is figure out the size of a filter I need.

I have a tube that's 3" dia x 12" long. I want to shove a circular filter into this tube so it reaches the bottom, and has plenty left over at the top to fold over the edge and clamp down.

Does anybody know what kind of formula I'd need to figure this out?

2. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,699
909
Ah, nothing like a good old chemistry question...

What is the filter made of? Is it flexible? Will it be fluted to prevent adhering to the walls? Are you aware that if the filter "sticks" to the walls of the tube, filtration flow through those areas will be nil?

I suspect you need a rigid cone (look up the equation for a cone) or just a simple filter the diameter of the tube plus a little for overhang.

John

3. ### GRNDPNDR Thread Starter Member

Mar 1, 2012
449
7
You know what? I just realized this is basically a moot point since I don't need to filter through the sides, and I could just get a 5" round filter to clamp to the bottom.

It's basically two pieces of tube with flanges that clamp together. The filter will be between the flanges.

so I really don't need a filter to run the length of the tube.

What I would like to find is some kind of resuable filter or a filter with a rubber seal around the outside so it would fit between two of these when they are clamped together, and still be able to make an air tight seal.

4. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,699
909
What size particles are you trying to remove? What is the fluid?

John

5. ### GRNDPNDR Thread Starter Member

Mar 1, 2012
449
7
Well I'm not entirely sure what particle size at the moment. But the fluid will be either ethanol or N-Butane.

My buddy and I are looking into starting a small essential oils company to make some fragrant oils and tinctures and what not.

He's handling the business side of things, I'm researching/assembling equipment.

The filter unit will be to remove plant waxes and lipids. I haven't yet determined what particle size those would be just yet, but a coffee filter works fine so something about that micron size. (Can't find that info out either.)

EDIT.

Looks like 15 micron would do the job.

Last edited: Jul 7, 2014
6. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,699
909
I am not sure how practical it is to remove waxes and lipids from essential oils by filtration. Some other preparative techniques to consider are steam or vacuum distillation and (ultra)centrifugation. Chromatography can also be used. Large-scale chromatography is possible, but can be complex. If the lipids are phospholipids, you may be able to extract them quite simply with alumina powder and similar materials. If you can get the waxes and lipids to solidify, then centrifugation may be a good bet.

Teflon and other chemically resistant membranes are made with closely controlled pore diameters. Millipore (now EMD Millipore -- check for current names at Wikipedia) and Nuclepore which is now apparently Whatman Nuclepore were two manufacturers. There are probably more now. One problem you can anticipate is clogging of the filter. Pre-filters help. Also, depending on what you are filtering, it is not necessary to have pore diameters smaller than the particle being filtered. Using the largest pore diameter possible to get what you need will also help.

Good luck.

John

Last edited: Jul 7, 2014
7. ### GRNDPNDR Thread Starter Member

Mar 1, 2012
449
7
You'll have to take my word here, but for what we'd be doing in the beginning filtration is fine. We've already been doing it with some of the equipment we have it's just up to my parter to handle the business end of things.

I know the filter will will get clogged but for our purposes it isn't a huge issue as we aren't continuously pushing fluid through it, only small batches right now so it would basically just be a single run and then cleaning of the filter if it's re-usable.

It's kind of difficult to locate a 15 micron filter that's 5" diameter.... or I havent been able to yet.

8. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,699
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Just a very quick search found that Whatman has paper filters of 20-micron and 11-micron pore size from which your 5"-diameter could be cut.

John

Edit: Have you considered that the "filtration" you are observing may really be an adsorption phenomenon dependent on the paper being used? In that case, pore size may be unimportant and ordinary Whatman #1 may suffice. There are many tricks one can do with filter paper, including phase separation.

Edit#2: If Whatman#1 works, then consider a filter bed made of cotton or other adsorbent for preparative work.

Last edited: Jul 8, 2014
9. ### GRNDPNDR Thread Starter Member

Mar 1, 2012
449
7
I could probably use a #1 whatman.

My concern was that because the tubes are clamp together the filter would prevent it from sealing air tight.

This is to be a pressurized filter. The filter gets clamp between two pipes at the bottom, and the top has a cap to which compressed air connects. the liquid to be filtered is pumped in then the vessel is pressurized.

I don't want to see solvents seeping out the bottom where the two pipe halves clamp together because the filter paper is preventing a seal. It isn't high pressure but I'd still like it to have a good seal.

What I wanted to find was something like this but with a 15-20 micron mesh. although I hadn't considered the absorption phenomena.
http://www.glaciertanks.com/TriClam...amp_BUNA-N_Screen_Gasket_20_mesh_3_Black.html

I'll actually be using one of those to support the filter paper

10. ### BR-549 Well-Known Member

Sep 22, 2013
2,185
421
Go to youtube. Search for BHO. Use 60 micron. Be careful.

11. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,699
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So, you believe the OP is preparing a THC extract from marijuana? While that is consistent with what little information we have, I hope not. I was hoping the OP's description,
referred to more typical terpene extracts and such.

John

12. ### GRNDPNDR Thread Starter Member

Mar 1, 2012
449
7
Not THC extracts, legitimate essential oils extraction.

Besides if you look at what I'm doing, this thread was specifically about building a pressurized filter and that simply is all I was asking about.

We got it sorted anyway so the original topic is kind of a moot point now. But I do appreciate the input even though this got really off topic for the "math forum" lol.

13. ### wayneh Expert

Sep 9, 2010
12,406
3,256
Your filtration would likely be far more efficient if you abandoned the deep bed filter and went for more of a cartridge approach, like a whole-house filter you can get at a big-box store. Deep beds foul quickly at the surface, which is quite small with the arrangement you pictured. In industry where bed filters are used, they generally advance a knife to scrape of the fouled material and expose fresh bed. This is called rotary pre coat filtration and employs diatomaceous earth as the filter medium. For lighter duty, string wound cartridges are widely used. Spiral wound membrane filters are also common but tend to be used more with clean streams.

The big winner in small lab use is the vacuum filter, but it's limited by the ~14psi ∆P.