Difference between Vacuum pumps

General Composites Discussions Equipment Talk
#1

I’ve started looking around for a new vacuum pump and I’ve noticed a huge disparity between prices. On the low end there the Harbor Freight pump and on the more expensive end there’s brands like Varian and Welch.

For example why is there such a big price difference between this Harbor Freight pump and this Welch Pump ($150 vs 2130). Both have the same horsepower (1/3hp), about the same vacuum level (25 microns vs 15 microns) but the HF pulls more air (3 cfm vs 1.2 cfm) yet costs about 14 times less. I feel like I’m missing something.

http://www.harborfreight.com/two-stage-3-cfm-air-vacuum-pump-66466.html

http://sargentwelch.com/vacuum-pressure-pump-with-plate-and-belt-guard/p/IG0037665/

#2

1: quality
2: the HF one is for HVAC, The Welsh is for long lasting vacuum
3: meaning the HF might not run for 3 days straight under vacuum, the Welsh will.
4: quality

3 vs 1.2cfm isn’t much unless you are doing lots of parts often, or at once. Also depends on how long it takes to GET to the absolute rating.

#3

ps: look for a Gast rocking piston. I have 2 and love them. Sometimes they draw lower than our house vac, which is a very large system (order of 50k$)
530$, and they run all the time. Oil free, albeit a little noisy. Easily taken apart to clean if needed.
I got mine from Kine Equipment

#4

Don’t be tempted to buy the harbour freight one. It is for vacuuming aircos. Unless you reach an (almost) full vacuum, it will start throwing oil at you. Within 30 minutes the room where the pump is running will be completely cloudy.

The vanes are epoxy-glass, and are not that durable. The vanes of a higher quality pump are cast iron.

I have had a Welch. A sign on the motor said: “kindly oil every 10 years”. That says something…

Welchs and most other industrial pumps have air filters which filter the exhaust air. They can manage running some 10 minutes out of spec. Mostly the allowable vacuum level is much wider, such as 0,5-0,95 bar. This gives much more usuability.

So either choose a dry pump, or a rotary vane pump of better quality.

#5

Makes more sense now. Thanks for the information. I have to pinch pennies now or hope someone goes out of business to pick up a cheaper pump.

Thanks!

#6

What about ac compressers? Im using a 1hp unit from a window ac unit. New the unit is 95$ at walmart. It pulls about 27" at 5000ft and I have left it going all weekend with a pressure switch to turn it on and off when needed. Doesn’t blow oil everywere either… once some vacuum is being built anyway. I just plumed a small bowl on the outlet and it allows the oil to drainback into the pump when it shuts off.

#7

People have used AC compressors for ages. I think they are good systems as long as you have good lubrication, and oil mist filters. Don’t know how good they are in CFM, or ultimate vacuum, but always a good source from old fridge units. I had one for a few years working on a nitrogen laser, but it started seizing. But, it was free!

#8

They work great! here’s mine:

http://www.flickr.com/photos/polytube-cycles/5692989896/

Cheers

#9

If I were to recommend a pump definately get a rocker type pump. I use a mini two rocker setup and have left it running with no problems what so ever. The second recommendation is the air-vac Venturi setup. I sometimes use them for infusions and have a resin catch that has an air vac mounted on top. I can pull quite a bit of vacuum with it and with the quick connect, I use them to quickly evacuate a large bag and let my pump take over if need be. Most of the time I never have to use my pump so long as I have shop air. Look into www.air-vac-eng.com. Very simple vacuum generator.

#10

This venturi is amazing! http://www.airvacpumps.com/UVpump.htm

#11

Can you explain the two stage and what benefit there is? Also what’s the control board/box on top? Do the pumps cycle on and off with vacuum?
Im assuming its one pump"slave" pulling on the exit of the “master” pump currect? Or is it both pumps pulling on one vacuum source basicly doubling the cfm?

#12

i am interested in more info also. home made tools rock.