Venturi Vacuum

[richards]

This is a photo of a venturi vacuum that I built, based on the GAST vacuum that Bill Palumbo posted on his web site. With the addition of the tank, check valve, MAC valve, and vacuum switch, the venturi system uses the compressor only a small fraction as much as it did before I added the additional parts. The actual air consumption depends on the porosity of the material being held by the vacuum pucks.

This particular venturi vacuum pump pulls 20-inches of mercury. (Remember, I live in Utah's Salt Lake valley, with its 4,500 altitude.) The vacuum switch is set to turn off the MAC air valve at 19-inches and turn the MAC air valve back on at about 16-inches. The pods that I use work well at 14-inches of mercury. Another venturi pump that I have pulls 25-inches of mercury.

Total cost for the entire unit is in the $200-$300 range depending on specific parts and the vendor selected.


5333

[stickman]

Mike,

Can you give us a parts list of the things that you used to create this pump? And your preferred vendors?

Jay

[richards]

Jay,
The tank (part number 41712) was purchased from Harbor Freight. All other parts were purchased from either the Utah branch of Fiero Fluid Power, Inc. (801) 567-1188, or from the local Home Depot store.

The non-connector parts purchased from Fiero are:
(The parts are listed basically as seen in the photo, from the inlet end (compressor) to the outlet end (puck).)

Quick release connector, 12-3
Ball Valve (small), S34AM1
Regulator, R384-01C
Pressure Gauge, 9690242
Mac Valve, 113B-11BA
Muffler (small metal), P28
Verturi vacuum generator, VG-015-00-00
Muffler (large plastic), F1-2
Check valve, ICV-FF-250B-V-1
Vacuum gauge, 4231279
Vacuum switch, VDMA-2-2M-C-FL
Ball Valve - Large, S34BM0
Filter, FLTP1/4F
Air hose connector, PC1/4-N24

Brass nipples, Tees, Elbows, etc. were mostly purchased from Home Depot.

NOTES:

1. The vacuum switch has an allen lock screw sitting on top of the allen adjusting screw. Remove the lock screw to get to the adjusting screw.

2. The vacuum switch can be configured either as Normally Open or Normally Closed. I wired the 120AC HOT/LINE lead to the Normally Open connector (green), the switch's ground/neutral (black) to one of the Mac valve's leads (black), and the other Mac lead (black) to the 120AC NEUTRAL line.

3. Fiero is licensed by some of it's suppliers to only sell within a specific geographical area. You may not be able to buy all items directly from them.

Ball-park-price is around $200-$250 before shipping/handling fees are added.

-Mike

[phil_o]

This website has complete instructions on building a vacuum for a veneer press. It looks like it would do well for a vacuum table as well.

http://www.joewoodworker.com/veneering/welcome.htm

[billp]

Phil,
"Joe Woodworker" is also the same company as Veneer Supplies. That's where I got a bunch of the parts to make the vaccum rig which I showed at my Camp. They have everything from the tubing, vacuum bags, check valves, fittings, etc.

[richards]

I just looked at www.joewoodworker.com (http://www.joewoodworker.com). It looks like a great site with clear instructions on building a vacuum system.

Until now, I've mainly used a Fein vacuum for most of my holddown requirements. For smaller parts, I've used both a venturi system as well as a GAST 3/4 hp vacuum pump. All three work very well. With the addition of an air tank, check valve, MAC air valve, and vacuum switch, the venturi system seems to be a winner for holding small parts (assuming that you have a suitable compressor). Without those parts, the venturi systems still works, but it's awfully hard on the compressor. The GAST vacuum pump pulls a few more inches of mercury, but the people at Fiero cautioned me against constantly starting/stopping the GAST. In their opinion, the GAST was not made for that particular use. Since I have a choice, I've decided to use the Fein and the venturi system for awhile with the GAST as a primary backup if either of the others give me problems.

[3imoh]

Howdy All-

Here is a pic of a similar venturi setup I built using parts from joe woodworker...he is really helpful. I ended up using one of those portable air tanks you can find at an auto parts store. I added the latching foot switch with another solenoid, which is nice for controling the vac.

Here is a link to the photo, as I am getting an error trying to post an image here:
vac photo (http://crazycat.org/temp/vacuum/123_2349_1.JPG)

[beacon14]

I use a gast pump for holddown as well as for veneer pressing, and instead of turning it on and off I leave it running and use a shut-off valve in the line to isolate the vacuum from the fixture. If your setup is sealed real snug you may need a release valve as well or else you have to wait a while before you can get the part loose. This method also provides faster response time and the built-up vacuum in the line can give you an initial "suck" that can help grab warped parts. Plus, I'd much rather run the pump full time than my compressor.

[richards]

David,
I'm modifying the plumbing on my Gast pump to be similar to the venturi. My conumdrum right now is deciding whether to turn the Gast on/off as pressure is needed or whether to use an air valve and just bypass the pump when vacuum is high enough - which would let the pump essentially free-wheel. Letting the Gast run all the time is probably the way that I'll go, but that little 3/4-hp motor really generates some heat.

On the other hand, the venturi system, with the 5-gallon resevoir, only cycles the 5-hp compressor once every five minutes - depending on the porosity of the material.

The resevoir would give either system 'instant' suck-down. The ball-valve on the outlet side (which you can barely see in the photo) shuts off the vacuum so that the part can be released. If too much vacuum force is still holding the part, even after the ball-valve is closed, an additional ball-valve can be used to vent the vacuum on the part-side of the shutoff ball-valve.

[rjguinn@optonline.net]

Mike,
I've been running tandem Gast rotary vane pumps for several years with excellent results. The secondary pump is controlled with a vacuum switch & used primarily to quickly evacuate the tank at start-up & to make up any loses. I think I'll add another vacuum switch to the primary, set higher than the secondary, to preserve pump life. I wired a 3-way solenoid valve between the switch & pump. The valve is physically located between the part & the tank. Turning off switch vents line,instantly releases part & seals vacuum in tank.
Call Gast technical support for best info on cycle times for your specific pump. My pumps are made to run 24/7 at approximately 203 F. I've never had a problem cycling them every 10-15 minutes.

[richards]

Jeffrey,
Thanks for the advice. Maybe I'm a little too tentative on my expectations for the Gast. If I install a 5-gallon resevoir tank on it and if it cycles like the venturi system, it might turn on for about 5 seconds every minute or so.

The venturi system draws against the compressor's air resevoir, so the air compressor only cycles about every five minutes or so. That's when I'm cutting plaques from MDF - which take just over one minute each. When I cut plastic or other material that doesn't leak vacuum like MDF, the compressor almost never cycles.