vacuum pump air line hookup

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tool-man

tool-man

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I have a used diaphram vacuum pump more or less like the one pictured. As you can see this type of pump has two pumping sections. Each has an air input and output port. In order to hook them together I am thinking I should hook the output air of the first pump to the input air of the second. Sort of running them in series. My vacuum line would go to the input (vacuum) port of the first pump. Is this the correct way to hook them up if I want maximum vacuum capability?
 

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tool-man said:
I have a used diaphram vacuum pump more or less like the one pictured. As you can see this type of pump has two pumping sections. Each has an air input and output port. In order to hook them together I am thinking I should hook the output air of the first pump to the input air of the second. Sort of running them in series. My vacuum line would go to the input (vacuum) port of the first pump. Is this the correct way to hook them up if I want maximum vacuum capability?
Click to expand...

I don't know if that unit would work as a two-stage pump.....if it's not made to be hooked up that way.....could mess it up!


Barney
 
" I want maximum vacuum capability".

The point for most vacuum uses with lathe work is that you do not want maximum vacuum capability --- That term ususally means the amount of vacuum as measured by inches mercury or by air pressure difference between inside and outside.

What you want is enough vacuum to to cause boiling at lower pressure (as in putting wood into a vacuum) or enough vacuum to hold am item on a chuck (vacuum clamping).

Diaphram pumps are not super high on the perfect vacuum scale, but are reliable and will get more than enough to fulfill either function.

Double stage, probably will increase the load (power consumption) but the diaphram pumps will not add more than a fractional of an inch vacuum.

If you are using a solvent in vacuum -- keep the second one in reserve for when the solvent chew up the diaphram or seals on the first one.
 
I just want to use this (cheap) pump to do some blank stabilizing using Cactus Juice (I think that's the name) sold over in the classified forum. Maybe 2 to 4 blanks at a time. Speed is not an issue. I guess I will try one side of the pump and see how it goes.
KenV said:
What you want is enough vacuum to to cause boiling at lower pressure (as in putting wood into a vacuum) or enough vacuum to hold am item on a chuck (vacuum clamping).

Diaphram pumps are not super high on the perfect vacuum scale, but are reliable and will get more than enough to fulfill either function.
Click to expand...
 
FYI --- Here is how someone had a pump like this hooked up. Both intake/inputs connected together, both outputs connected together. Pic was taken from a sale ad on eBay. How well that configuration worked and for what application is unknown.
 

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Diaphragm pumps by nature usually do not produce deep vacuum. Most of the ones I see only produce 25" Hg at sea level. Many rotary vane vacuum pumps will produce significantly higher vacuums, usually in the 29" Hg range. The difference, from direct personal experience, in stabilizing with 25" Hg vs. 28+" Hg is quite significant. If I run my pump and control the vacuum to only reach 25" Hg, the bubbles quickly stop coming out of the wood. If I then go on up to 28" Hg, it seriously starts pulling air out of the blanks to the point it will foam over if not gradually increased.

Rotary vane pumps are frequently rated in microns and the lower the better. For example, 25.98" Hg is equal to 100,000 microns and represents an 87% vacuum. My rotary vane pump is rated at 25 microns which equates to approximately 29.9165" Hg or 99.995% vacuum. ( A perfect vacuum or absolute vacuum is 29.92" Hg and can not physically be exceeded, contrary to what you see occasionally where folks claim to be getting 31" Hg!) Of course this rating is assuming sea level and is in a perfect world with no leaks, etc. For every 1,000' above sea level, you loose 1" Hg of vacuum due to less atmospheric pressure.

The pump you have will not gain any more vacuum by hooking the 2 sections together, it will just do it faster and that is if you do as the picture above shows. If you just hook one to the other in series, it will not even do it faster since one pump will just be pumping the exhaust from the other side.

Hope that helps some and does not confuse things too much!
 
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