Hi guys, i’m trying to buy a new vaccum pump but i’m a bit confused with the specs (i will mostly be doing infusions on a small scale). the types of pumps they have are as follows:
single stage 8 CMF’s
two stage 2 CMF’s
the 2 stage one fits my budget but i’m not sure if it’s good for infusions. any suggestions will be greatly appreciated and lastly what’s the difference between a single stage and a 2 stage pump and which one is great for infusions.
2 stage are basicly 2 pumps behind each other. They draw a deeper vacuum.
If the pumps are dry running ones, 2 stage can be a benefit, as 1 pump draws just a tad too little.
IF the pumps are oil lubricated, 2 stage is not needed.
More important is the ability to run “out of spec” without spitting oil. The cheap oil lubricated ones have no filter or oil recapture means, so basicly an oil-loss system, which smokes like hell at times.
I saw some on eBay recently, I run a Busch RC21 vac which cost over 3K new with the timer and manifold etc…etc…
I just received last week a rebuilt unit the exact same, under auction for $200 bucks plus shipping off EBay. Good deals can be had on a higher end used pump versus lower end new pump. Just a thought.
hi, thanks for the update, i think the 2 stage pump is oil based, so are you saying i should stay away from oil based pumps? lastly does a higher CFM value mean the pump is better?
CFM and quality are loosely connected. Or lets put it this way:
The cheap airco vac units are not suitable for composites. These all come in small CFMs. These usually are oil based double stage pumps.
They usually look like this: (all these similar looking pumps are made in one small area in China)
These are very cheap, but you get what you pay for. Vanes for instance are epoxy laminate, and prone to wear. I once made the mistake of reselling them to the composite industry, and now a year or so later I am not aware of a single pump that still runs OK. They ARE great for degassing though. In airco vacuuming they reach their end vacuum quicker, and stop spitting oil and smoking.
Industrial stuff usually comes larger. They can be bought in single stage or multiple stage, but single stage should do the job already. They have an exhaust filter which captures the oil, which is brought back into the pump. The working pressure is much broader.
An example might look like this:
Hi Herman, thanks for the quick update, this is getting complicated by the hr 
as i’m getting confused :(, i thought it will be easy to choose a vaccum pump. but its seems a lot of people are aircon vaccum units for composite works, are they not aware of the issues u’ve stated or they have a way of getting them to work/maintain them?
thanks
They probably do not mind the smoke.
I would opt for a double stage dry pump.
They look somewhat like this:
I have several of these cheap 1stage pumps and they all work perfect since several years. The problem is that they all produce oil smoke when the mould is not tight.
If they run out of oil they will be damaged immediately. I haved yoused all kinds of oil (no olive oil:D) and had no problems.
But for business use I would prefer a good oil pump like a Busch pump, they work perfect 24h and never produce oil smoke.
The membrane pumps I had never worked long til the membrane died.
I agree. The best pumps are industrial oil lubricated vane pumps, these are very hard to kill.
2nd best are the membrane pumps. These are cheaper than industrial pumps.
3rd are the airco pumps. Cheap, but cheesy.
Hi Herman, i ended up buying a 2 stage 2 CFM airco pump but i need to know how long i can have it running in order to achieved good suction
Do you mean how long you need to keep it running to get a good vacuum?
If so it depends on the bag size and if you have any leaks. You definitely need to get a vacuum gauge though so you can see if you have a good vacuum or not, this way you don’t have to guess using time to estimate.
Usually the Airco units come with a gauge, so that is good. Try not to run it without actually creating a vacuum, or it will spit on you. On large items use a vacuum cleaner (stuck through the last bit of bag to close) to get rid of most of the air.
After that it is a matter of size and amount of leaks.
ah the pump came with a gauge, but what i needed to know is that after pulling enough vaccum and provided there are no leaks can i turn off the pump? attached are pictures of the pump[ATTACH]
In theory, yes. In practice I do not recommend turning it off.
Try to source a pressure vessel, such as an old (defunct) compressor, or an LPG/GPL tank for cars. these make excellent “vacuum reservoirs”. Then at least it takes longer for the pressure to rise above a critical level, in case of a tiny leak, or some porosity.
hi Herman, can you send me pics of how the reservoir setup looks like.
thanks
I can send you a picture of mine. http://www.harborfreight.com/2-1-2-half-gallon-pressure-paint-tank-66839.html
As Herman said all it is, is large volumes of space that you’re drawing a vacuum on, anything airtight and sufficiently strong, to hold a vacuum will work
Hi Canyon, thanks for the picture, but i’m still confused as to how i will connect this to the pump
does this mean i build up the required pressue on this tank then switch off the pump and let the pressure tank take over?
Basicly, yes. The tank can be connected on any way. You can use a T-connector, or connect the pump to the tank, and the part to the tank as well. It really does not matter. (at least not with these small pumps, as airflow is very limited).
And yes, the tank takes over.
For instance if you have no resevoir, and turn the pump off: The volume of the piping is 1 liter (assumption, and on the large site). If you have a leak which leaks 1 liter per hour, pressure is gone in 1 hour.
If you have a 100 liter tank, you are good for at least 100 hours. (I know technically I am way off, as I skipped all kind of other factors, but you get the idea)
Oh, 1 liter = 1 quart (about).
And we pay some 2 dollar for 1 quart of gasoline…
wow thanks for the explanation, now it kinda makes sense
