How do you run vacuum pumps in series?

[industria77]

can anyone refer me to a graphical representation of how this works so i can build one?

 

[Nidum]

We'll need a bit more information than that before anyone can give a sensible answer .

 

[industria77]

We'll need a bit more information than that before anyone can give a sensible answer .

i was watching a video on vacuum forming, the author had built a home made vacuum former with two shop vacs to increase the vacuum pressure. in the comments someone suggested to run the vacuums in series to further increase vacuum. i have a need for stronger vacuum and have several pumps, i need to build a framework to run them in series, i looked into this and can find no illustration of the positioning of the pumps or the airflow, i need to see how it works so i can build the cabinetry to make it work myself.

 

[industria77]

i was watching a video on vacuum forming, the author had built a home made vacuum former with two shop vacs to increase the vacuum pressure. in the comments someone suggested to run the vacuums in series to further increase vacuum. i have a need for stronger vacuum and have several pumps, i need to build a framework to run them in series, i looked into this and can find no illustration of the positioning of the pumps or the airflow, i need to see how it works so i can build the cabinetry to make it work myself.

basically i need to see the route the air flows through the pumps

 

[industria77]

to be clear, I am not using this to vacuum form, i need the pump for general service

 

[Vanadium 50]

Vacuum pumps don't work this way. There's only so much air that can be taken out, and when it's out, it's out. If you have a pump that will let you get down to a certain pressure, adding a second pump that can also get down to the same pressure will not substantially improve the vacuum.

 

[Bystander]

Running "vacuum cleaners" as opposed to vacuum pumps is an invitation to burn wards; block an air cooled electric motor's source of cooling air and temperatures will rise.

 

[JBA]

You say you have several "pumps" what type do you actually have?

 

[industria77]

You say you have several "pumps" what type do you actually have?

compressors and fans, i was thinking of with the fans, mostly various vacuume cleaner motors

 

[industria77]

Vacuum pumps don't work this way. There's only so much air that can be taken out, and when it's out, it's out. If you have a pump that will let you get down to a certain pressure, adding a second pump that can also get down to the same pressure will not substantially improve the vacuum.

thats what i had always thought. but the guy needed more vacuume and he ran two vacs to get it ans some guy claiming to be an engineer suggested to run them in series, i looked into it and got intrigued because i need a better vacuume cleaner to clean up my floors. there seems to be a lot on the subject as if it is commonly in practice but i can't find any depictions of it in pictures so i can't understand how theyre saying this works, but they claim there is a substantial increase

 

[industria77]

Running "vacuum cleaners" as opposed to vacuum pumps is an invitation to burn wards; block an air cooled electric motor's source of cooling air and temperatures will rise.

not the way i invisioned it the second pump would be in the airflow of the first and so it would actually be supercooled but i think the second motor might overheat, i don't know the idea just intrigued me i haven't built anything, but i could.

 

[industria77]

i was curious as to the positioning of the fans and i guess now, how they keep it cooled, https://www.google.com/search?q=vacuume+in+series&ie=utf-8&oe=utf-8#q=vacuum+pumps+in+series , lol, I am an idiot, https://www.physicsforums.com/threads/vacuum-pumps-in-series.448085/ , i didnt realize this is where id got caught up in the idea in the first place.

but i still don't understand how the machinery here works in a series pump is there a picture of this?

 

[industria77]

Vacuum pumps don't work this way. There's only so much air that can be taken out, and when it's out, it's out. If you have a pump that will let you get down to a certain pressure, adding a second pump that can also get down to the same pressure will not substantially improve the vacuum.

isnt what your referring to as running them in parrelell?

 

[industria77]

Running "vacuum cleaners" as opposed to vacuum pumps is an invitation to burn wards; block an air cooled electric motor's source of cooling air and temperatures will rise.

Running "vacuum cleaners" as opposed to vacuum pumps is an invitation to burn wards; block an air cooled electric motor's source of cooling air and temperatures will rise.

thanks for the tip,i didnt realize there was a difference, at any rate, i still am curious as to how it works it seems even more difficult to understand the housing now if it is two compressors

 

[russ_watters]

not the way i invisioned it the second pump would be in the airflow of the first and so it would actually be supercooled but i think the second motor might overheat, i don't know the idea just intrigued me i haven't built anything, but i could.

You're misunderstanding the objection. When you run a vacuum cleaner as a vacuum pump, you are cutting off almost all of the airflow. So you have one fan that heats up its tiny airflow a lot, then passes that really hot air to another fan that heats it up even more.

 

[Vanadium 50]

isnt what your referring to as running them in parrelell?

Did I use the word parallel?

 

[industria77]

You're misunderstanding the objection. When you run a vacuum cleaner as a vacuum pump, you are cutting off almost all of the airflow. So you have one fan that heats up its tiny airflow a lot, then passes that really hot air to another fan that heats it up even more.

yes i understand that, i don't think ill make anything like this but i was curious about the design, apparently someones manufactured a machine like this though according to http://www.cleansmartsupplies.co.uk/in-series-versus-airflow-vacuum/ , and id seen a little more on it in other places.

 

[industria77]

Did I use the word parallel?

no, you described it and used the phrase in series

 

[industria77]

i was just thinking it would be nice to have a better vacuume cleaner, ever try to vacuume sawdust off of carpet? lol, well you all have helped me to better underwstand some principles on the subject, it has been very informative, thanks.

 

[Plat]

The first thing that comes to mind is running one pump in a vacuum chamber that was evacuated by another pump. But then you have no cooling airflow so it wouldn't run long.Also this probably wouldn't reduce your ultimate pressure because those pumps already operate at the lower limit of what a rotary-vane pump is physically capable of, assuming you are using that type.For mechanical pumps, a lower pressure limit exists because when the pressure is low enough, the mean free path of the gas molecules grows larger than the internal clearances between parts in the pump, and it stops flowing as a gas.

 

[mfb]

For mechanical pumps, a lower pressure limit exists because when the pressure is low enough, the mean free path of the gas molecules grows larger than the internal clearances between parts in the pump, and it stops flowing as a gas.

Mechanical turbomolecular pumps need the large mean free path to work.

 

[Plat]

True but I figured for his application, turbomolecular pumps were not on the table.

 

[Lorcan]

For a souped up vacuum cleaner, wouldn't you want increased air flow rather than lower vacuum pressure? Running them in parallel would make more sense to me, unless I'm missing something.

 

[JBA]

Apparently the vacuum you are using doesn't have a rotating brush; if so, more vacuum would not to solve your problem. You need a vacuum cleaner with a rotating brush to free the sawdust trapped around the fibers of the carpet.

 

[johnbbahm]

For high vacuum systems you use two pumps effectively in series.
The roughing pump is attached at the bottom of the diffusion pump,
and lowers the pressure to between viscous flow and molecular flow.
The diffusion pump takes over, and collects molecules at the bottom for the
roughing pump to evacuate.
Here is a page with a good description.
http://galileo.phys.virginia.edu/classes/317.gbh.fall04/vacuum/vacuum-Updated.html
I think most roughing pumps can get down to at least 1x10−3 torr.