I want to get a high vacuum (0.01-0.001 mbar) by connecting two or more vacuum pumps. But I'm not sure about the know-how of this technology (parallel or serial concetion system? which of them is better?). Each individual vacuum pump that I have could provide a vacuum around 30-40 mbar! Is there any chance to achieve 0.01-0.001 mbar by combination of these pumps? I really need the answer to this question.
Farzad,
The best solution depends on several other matters:
a) Your budget
b) The cleanliness of the pumped system
If you don't need a particularly clean system, then a diffusion pump backed by a rotary pump will easily get to those pressures.
If you want a cleaner system, you could add a cryogenic baffle to the diffusion pump inlet, or instead use a turbo pump. You will still need a backing pump, and you might want to use a scroll pump if you don't want to be concerned at all about oil mist.
If you have two pumps in parallel you simply double the pumping rate. The final working pressure will be unchanged. Do not attempt to pump the 'outlet' of a rotary pump with another pump - they are designed to exhaust to ambient pressure.
I need to have a speed vacuum more than 1500 m3/h, so I think scroll pumps do not designed for these speeds. And the cleanliness is not vital for me. I can use the following vacuum pumps:
Roots Vacuum Pump; SIDE CHANNEL Vacuum Pumps; Liquid Ring Vacuum Pumps and Rotary vane Vacuum pump!
In fact, I want to use vacuum distillation for purification of a liquid with boiling point around 620 centigrade.
The overall size of chamber will be about 50000 Lit! And it is made of black iron sheets!
I can provide pumps with speeds about 1000-1500 m3/h. I have no idea about the flanges! is it important?
unfortunately, I have a little knowledge about vacuum technology! What should I do now?!
Farzad,
Crikey, 50,000 litres!
I'm imagining an array of diffusion pumps (cheap, no moving parts) backed by a cohort of big rotary vane pumps. The fact that this is a distillation rig means that the cleanliness is by-the-by - and I wonder if even a cryo baffle is necessary for the diff' pumps.
A final question - how often is this brought up to air, and what is the acceptable timescale to go from ambient pressure to the desired working pressure? That will fix the number and size of the rotary pumps.
50 cubic metres - that's getting on for 'full-scale-spacecraft-simulation-chamber' size.
I'm glad that Kevin put the link it to O'Hanlon's work - and may I also suggest Delchar's Vacuum Physics and Techniques - the first chapters anyway - as a good starting point.
we have a mixture of hydrocarbons with a wide range of boiling points (150-620 centigrade)! so we distill them step by step! First we start with a vacuum around 50 mbar! After distillation of light fractions we will go to higher vacuums:1 mbar, 0.1 mbar, and finally 0.01 mbar!
First to answer your question: NO. Second, what you are doing is exactly how a diffusion pump would work in the old days, 30-40 yrs ago. Their range would be 10 to -6 to 10 to -7 torr, so you are close ( 0.01 mbar is in the 10 to-5 torr, right ?)
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