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High-Speed Machinery

08/08/2017 10:28 PM

I wanted to build a hollow doughnut section centrifuge with an outside diameter of at least 1500mm, which is to be rotated at 10000 (Ten thousand) rpm. Is it possible and safe? Can I have 75mm diameter shaft to rotate it? If the doughnut cross section is say 250 mm, what will be the HP needed?

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#1

Re: High speed machinery

08/08/2017 11:13 PM

It's possible but it will likely need to machined from a solid billet of high strength steel alloy material to work with reasonable safety given the ~8400 G's it will produce.

Why do you think you need such a device to begin with?

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#3
In reply to #1

Re: High speed machinery

08/08/2017 11:54 PM
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#8
In reply to #3

Re: High speed machinery

08/09/2017 9:41 AM

maybe have to go carbon fiber..

10,000 RPM at 1500 mm diameter with laminated carbon fibers,... I don't know about that.

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#2

Re: High speed machinery

08/08/2017 11:16 PM

Well I've seem them that big,, and I've seen them that fast,,,but I don't think I've seen them that big that fast....So you would have to have them specially designed I think,,,,very pricey... What, if I may ask, would you have to submit to that kind of force?

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#4

Re: High speed machinery

08/09/2017 12:47 AM

The idea is quite simple. We use a centrifuge with tubes to separate a heavier solid from a liquid. these centrifuges are more for testing, rather than production. if the solid has rigid particles, a basket centrifuge could be used. But if the particles are plastic and small, they would clog the basket filter medium. But the separation is fine with a dead end one. I wanted to combine the effect, by making a continuous ring in the shape of a hollow doughnut with a conical bottom, so that the liquid, I get would collect in the cone and could be drained after stopping the Machine, and the process could be repeated till the solid is reasonably free of the liquid. OK. The machine could of say a metre in diameter, or even less. will it be possible at all, is my question.

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#5
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Re: High speed machinery

08/09/2017 1:19 AM

We cannot see your design. I am trying to visualize it from your text, but I cannot to get a coherent image.

Perhaps this idea of yours is good, but there is no way to tell <..from here...>.

It would be great if you could draw a sketch and post it (with more information) using the [Insert Image] icon in the editor toolbox.

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#6
In reply to #4

Re: High speed machinery

08/09/2017 1:25 AM

Well the densest material will migrate to the furthest point of the spinning container perpendicular to the axis....Sounds more like you need a separator....

Long version...

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#17
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Re: High speed machinery

08/09/2017 6:59 PM

You're not spinning UF6, are you?

https://en.wikipedia.org/wiki/Enriched_uranium

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#7

Re: High speed machinery

08/09/2017 2:56 AM

<...If the doughnut cross section is say 250 mm, what will be the HP needed?...>

If the thing is to be rotated on magnetic bearings and all the parts moved in a total vacuum, very little indeed. However, if it were to be rotated on a conventional bearing in a medium of Lyle's Golden Syrup (other spreadable sandwich confections are available), then a small power station would be needed.

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#9

Re: High Speed Machinery

08/09/2017 10:08 AM

10000 rpm =166.7 rev per second

circumference at .75 m = 1.5 x pi = 4.7 m

velocity at edge = 166.7 * 4.7 = 785 m/sec

acceleration at edge = v2/r = 822796 m/sec2 = 822796/9.8 = 84000 g

There are some serious forces here. I wouldn't want to be standing next to it if something comes unglued...

Here is some useful information.

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#10
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Re: High Speed Machinery

08/09/2017 10:12 AM

I agree, not something for composites

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#14
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Re: High Speed Machinery

08/09/2017 12:29 PM
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#15
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Re: High Speed Machinery

08/09/2017 12:49 PM

..." there are 500,000 composite centrifuge rotors (used for enriching uranium) that have been operating 24/7 for 20 years. "...

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#16
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Re: High Speed Machinery

08/09/2017 12:50 PM

I yield

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#31
In reply to #10

Re: High Speed Machinery

08/10/2017 11:23 PM

Where's that bowyer I am sure he'll have some laminated woods knocked up in the bothy that will take the strain!

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#11

Re: High Speed Machinery

08/09/2017 10:37 AM

Please explain why an intensity as high as 84000G is necessary?

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#12

Re: High Speed Machinery

08/09/2017 11:52 AM

Because at low 'g' the separation is not good enough and the bigger size is to make it economical since it has to be a batch centrifuge. If friends prefer a lower diameter, but with a height, like a tube, but with a high 'g', okay, no problem but the material needs high separation force. Presently high forces in expellers do the job, but frictional forces create high temperatures too, which is not desirable.

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#18
In reply to #12

Re: High Speed Machinery

08/09/2017 8:21 PM

So this is for extracting oil from seeds? Palm oil maybe? Copra? Soybean?

..."Some companies claim that they use a cooling apparatus to reduce this temperature to protect certain properties of the oils being extracted.[2]"...

https://www.google.com/patents/US20170107447

http://www.oilmakingequipment.com/cold-oil-press-with-water-cooling.html

http://cnguangxin.en.made-in-china.com/product/rvmxeGIUIXcJ/China-Guangxin-Yzyx120SL-6-5ton-a-Day-Soybean-Oil-Expeller-with-Cooling-System.html

So maybe you just need a cooling apparatus for your expeller press.....

https://en.wikipedia.org/wiki/Expeller_pressing

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#13

Re: High Speed Machinery

08/09/2017 12:08 PM

If you need to find the HP... you need to find the torque first.

T = Torque, N-m

  • T = I*a
  • I = Moment of Inertia
  • a = Angular Acceleration, rad/sec^2

Then you can find the HP

HP = n*T/5252

  • n = rotational speed, RPM
  • T = Torque, ft-lbs
  • Moment of Inertia (I) for Hollow cylinder = m*R^2

Moment of Inertia (I), for Hollow cylinder = m*R^2

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#19

Re: High Speed Machinery

08/09/2017 8:53 PM

Our members are very intelligent. Yes. This machinery is intended to be a viable alternative to the well known expeller. I don't need to elaborate on the advantages but I felt that subjecting a paste made from an oil seed to very high 'g ' force would make the products better in quality and also eliminate a step - filtration. While the dimensions I propounded could be utopian, if achieved could be very acceptable to industry. Before an electric grinder was available, everyone in any country was using attrition as the means for particle size reduction, with two stone surfaces. What I need is to come to an optimum size and speed. your comments have been very useful.

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#20
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Re: High Speed Machinery

08/09/2017 10:07 PM

I would certainly explore the possibility of using a separator or stacked dish centrifuge that I mentioned earlier....these work well with paste and a low amount of husk material....but I don't know the specifics involved in your step process...

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#25
In reply to #20

Re: High Speed Machinery

08/10/2017 7:48 AM

Exploring and discussing is a good idea.

A separator, imo, would not be a good idea, a separator that you had previously posted is basically. for milk.

My experience is these do not hold up to solids very well. The experience that I had, one dairy plant (as most do) try to standardize their milk by adding Calcium Phosphate to the raw milk. This is normally no an issue. But they used a powder. (Some type of suspended liquid form is best).

And were ever they added it, raise hell on the process equipment... so they kept going up stream towards the Milk Intake.

Well, they eventually got to a point where it was added prior to the separator... and since Calcium Phosphate was not in suspension, it 'clumped'. And with the separator that runs at about 15,000-25,000 RPM??, it throws it out of balance and were constantly replacing bearings. and some of the plates.

Here is a link on separators (Dairy Processing Handbook) it gives a brief on sedimentation and flotation velocities.

Now, a decanter would be a possibility. I'll have to look and see if I can find information about that. The Dairy Processing Handbook may have some information about Decanters.

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#21

Re: High Speed Machinery

08/09/2017 10:26 PM

Unfortunately, the stacked disc or for that matter any continuous output centrifuges in the market cannot handle more than 5 to 6 percent solids. A basket centrifuge can handle higher solids, but if the particles are soft and sticky, they choke the pores of the filter in next to no time. That is the reason why I am trying for the design. I hope our members are with me.

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#22
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Re: High Speed Machinery

08/10/2017 12:39 AM

Well they do make ultracentrifuges that can produce over 500,000g, but they are usually small for laboratory use.....I guess the question is what is the desired throughput? I think you would have to do a test to see what g force is required for satisfactory separation....once we know the g force required and the throughput desired, then the machine can be envisioned...The question isn't can it be done, it's how much it will cost, and is it practical....

https://www.slideshare.net/vraaz/ultracentrifugation

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#26
In reply to #21

Re: High Speed Machinery

08/10/2017 7:52 AM

Unfortunately, the stacked disc or for that matter any continuous output centrifuges in the market cannot handle more than 5 to 6 percent solids.

Just posted about that draw back about separators...

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#30
In reply to #21

Re: High Speed Machinery

08/10/2017 10:10 AM

Again, insufficient information about the process. If the solids are sticky, you might try a basket centrifuge then cut the solids and dry them.

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#23

Re: High Speed Machinery

08/10/2017 1:00 AM

These tall skinny centrifuges are used in nuclear fuel enrichment, they are operated in both series and banks of parallel in a continuous process...50k rpm

https://en.wikipedia.org/wiki/Gas_centrifuge

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#24
In reply to #23

Re: High Speed Machinery

08/10/2017 3:32 AM

Why are we doing this guy's home work research? My old milk separator worked just fine, no Hi-Tech just a hand crank. On a good morning I could get about 2,000 RPMs out of that puppy

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#27
In reply to #24

Re: High Speed Machinery

08/10/2017 7:55 AM

Why are we doing this guy's home work research?

Its interesting...

My old milk separator worked just fine, no Hi-Tech just a hand crank.

Yes works great for separating Cream, but not for splitting atoms.

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#33
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Re: High Speed Machinery

08/11/2017 2:48 AM
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#37
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Re: High Speed Machinery

08/11/2017 7:51 AM

interesting link... I learned something this morning... I wish I can go home now.

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#28

Re: High Speed Machinery

08/10/2017 8:03 AM

I may have missed the reasoning, but have you considered filter presses. Is the product pressure sensitive?

Belt Filter Press (continuous)

Membrane Filter Press (Batching)

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#29
In reply to #28

Re: High Speed Machinery

08/10/2017 8:05 AM

Continued Filter Press didn't show up after editing.... got it to work...

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#32
In reply to #28

Re: High Speed Machinery

08/11/2017 2:47 AM

Sounds like a possibility...and it's a continuous process...

http://www.oilmillmachinery.net/Oil-Milling-Plant/Oil-Filtering.html

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#34

Re: High Speed Machinery

08/11/2017 3:08 AM

This is a Chemical Engineering problem, and not a Mechanical one. Engage a consultant Chemical Engineer.

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#38
In reply to #34

Re: High Speed Machinery

08/11/2017 7:55 AM

when you talk about the 'Mechanics' of isotope exchanges,... yes consult a chemical engineer.

Otherwise, its not too uncommon for a ME to get involved with separation,... or even fracturization of liquids.

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#35

Re: High Speed Machinery

08/11/2017 3:10 AM

The Alexanderson Alternator (ca 1906):

The rotor is chrome-nickel steel, one ft in diameter, with 300 slots cut 1/8" apart near its edge, filled up smooth with phosphor-bronze wire securely anchored to withstand 80 lb force on each filler. The rotor speed is 20,000 rpm, peripheral speed 1047 fps (700 mph). Centrifugal force at periphery X 68,000 of static value. Safety factor 6 assured. Main bearings self-aligned, forced lube. Middle auxiliary bearings (1/64" clearance) take up excessive end thrust, and steady the flexible shaft thru critical speeds at 1700 and 9000 rpm.

Rotor driven by a 10 hp shunt-wound motor 1250 rpm, connected by chain drive to intermediate shaft 2000 rpm, in turn to De Laval 10:1 gearing to drive the flexible shaft.

Output 100,000 cps, 2 kW. Later machine 800 slots and 200,000 cps (Hz).

W.H. Eccles, Wireless Telegraphy and Telephony, Benn Bros Ltd London 2nd ed 1918

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#36

Re: High Speed Machinery

08/11/2017 3:11 AM

You know it seems to me you should be able to add some chemical to act as a thinner and perhaps even a vibrator or oscillator container that separates the oil via harmonic resonance....It just seems easier to add a treatment to the "paste" material you are trying to process to make it more suitable for the cheaper available methods at hand...

Advances in magnetic resonance

https://www.google.ch/patents/US20080035531

https://benthamopen.com/contents/pdf/TOACOJ/TOACOJ-1-66.pdf

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#39

Re: High Speed Machinery

08/11/2017 11:58 AM

Any possibility that supercritical fluid CO2 extraction might work? Hardware costs would likely be lower and continuous processing becomes a possibility.

For the speeds and forces you are talking about, the specific gravity of the solids vs the oils cannot be very far apart and it is likely that a lower specific gravity solid would float to the top of the oil. Sounds a bit like throwing things down a technological rat hole.

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#40

Re: High Speed Machinery

08/12/2017 12:19 AM

Dear Mr. Subrahmanyam,

You have mentioned 75 MM dia shaft. But you have not mentioned whether it is over - hang or supported on both ends, and whether it is horizontal or vertical mounted, and what is the material of the shaft.

To spin this shaft at, 10,000 RPM, the mounting with proper bearings will be a serious issue. Very very small unbalance weight will create severe unbalance since unbalanced force is governed by F = (W/g) x ((2 x (3.14) X ((10,000)/60)) ^2 x (0.750) which is tremendous force.

Asper the above equation, 0.1 MILLIGRAM of unbalance force will create a centrifugal force of ((0.1)/(1000) x (1000)) x (27,777.777) = 3600 Kgs. which is tremendous force and bearing supporting is a severe issue - as Mr.Rixter (Post No.9) have stated the "g" effect - is very intensive and not worth to take such high risk.

Next point to considered for the stability of your shaft size for this speed in terms of critical speed - how many times it has to cross before reaching 10,000 RPM.

DHAYANANDHAN.S

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