Vacuum Pumps for Veneering/Laminating

[David Pascoe]

For those of you who may be looking for a good quality vacuum pump, at a reasonable price, that won't burn up in a couple months, here is something to consider.

I've done almost daily vacuum laminating of shop-sawn veneers for about three years now. In that time I've gone thru three Robinair and one other Hvac pumps that lost vacuum power and started spewing smokey vapors. Two were replaced on warranty and crapped out within months. Finally exasperated, I did some research and discovered that these HVAC pumps (so called because they were designed for use with evacuating refrigerant from refrigeration and air conditioning systems. They are not intended for continuous duty operation that a vacuum press may require.

Armed with this info I gallantly went forward looking for a continuous duty pump, of which there is no shortage available. But I got a real slap in the face at the prices of these commercial grade machines is . . . . $1200 to over $2,000 for a small, portable pump pulling at least one atmosphere (29" Hg). I next went to Ebay looking for used machines where I was surprised to find a plethora suitable candidates, priced at almost ridiculously low prices. There were at least 8 used Leybold model D2.5E pumps priced at $300 or less. I picked up one for $108.00 INCLUDING shipping. Folks, this pump retails for $1826.00 new. Its 220V, 60 Hz with a rather slow but very powerful draw of 1.5 cu.ft./min. Note: large CFM's are not needed for small bags of 16'sq. or less. These prices were so low that it made me suspicious: what's wrong with them, worn out, inoperative, What?

Why so cheap? These pumps are used by the thousands in research, pharmaceutical and bio med industries and they apparently change them out like changing underwear, and dump them off to salvagers, so that's why there are so many of this and other big name brands. The market is pretty much flooded with them. Mine was in excellent condition and worked perfectly. It was a risk, for sure, but at that price well worth risking a hundred bucks to find out.

This pump runs for hours on end without overheating or excessive smoking. But like all rotary pumps, it will leak back thru the pump, so a check valve is needed (costs more than the pump) in the suction line.s-l500.jpgLeybold Trivac D2.5E;Weight, 33 lbs.; Single phase 220V., 1/4 hp; Dual stage, rotary vane; speed, 1.9 cfm; ultimate pressure: 29" Hg.; noise: 46 dbl.

[Art Mann]

The Joe Woodworker website describes a vacuum system that includes a reservoir to maintain adequate vacuum for a long period of time, which allows the pump to cool. Is this not a satisfactory solution instead of running a vacuum pump continuously? It certainly works in the other direction - air compressors.

[David Pascoe]

Depends on how fast your bleed-down is (leakage) and how big of a tank you want to deal with. I don't have the space for a tank at my small laminating table. And there is also the issue of cycling the pump, turning it on/off manually, or buying an expensive timer control switch. You are very unlikely to get by with running the pump w/tank just once as leakage rates can be pretty high. My bag time is usually two hours or less and bleed-down is about 45 minutes, so I opt to control it manually, which means I have to restart the pump at least twice. And yes, sometimes I forget and have to start over. But you can also forget to turn the pump off no matter what system you use unless you have a programmable timer switch. (Note: Ebay lists numerous timer switches at extremely low prices ($8) but BEWARE that these are Chinese and are shipped from China, involve buyer arranging for payment of customs duties and can take months to receive. The customer satisfaction ratings are obviously rigged - seller even admits this.)

[roger wiegand]

Pumps used in labs run continuously for years. There's a device that will even allow you to change the oil without turning the pump off. After several years of use they won't maintain high enough vacuum any more and need to be rebuilt or replaced, most labs opt for a new pump at that point, hence the ready availability of used pumps. They ought to be fine for vacuum bagging, you don't need or want a pump that can pull 0.001 mBar for that.

[Robert Engel]

Have you looked into the compressor/venturi route? Looks fairly easy to build and from what I've seen it works quite well.

I think there is info on that website.

[Art Mann]

The machine to which I referred has a regulator that turns the pump on and off automatically as the vacuum drops. I know some (maybe most) people use the type of system to which I have already referred. Perhaps the real problem is leakage.

[Bruce Wrenn]

HVAC vacuum pumps are just that, not air pumps. Sometimes it takes days to pump down a large system, with pumps running for periods in excess of 24 hrs. Sometimes two or more pumps are used to allow for oil changes. Do you use an inlet filter between bag and pump? If not, glue vapors are being sucked into pump. I use a METAL fuel filter on my pumps. The plastic ones can fail. A vacuum resevoir and a pressure switch will save a lot of wear on your pump.

[Bruce Wrenn]

This pump runs for hours on end without overheating or excessive smoking. But like all rotary pumps, it will leak back thru the pump, so a check valve is needed (costs more than the pump) in the suction line.s-l500.jpgLeybold Trivac D2.5E;Weight, 33 lbs.; Single phase 220V., 1/4 hp; Dual stage, rotary vane; speed, 1.9 cfm; ultimate pressure: 29" Hg.; noise: 46 dbl.

Check valves are "a dime a dozen." Use both resevoir and pressure switch. Rebuild packs for HVAC pumps are a drop in item.