Vaccum Pumps

Radar67 · May 20, 2006, 12:22:33 PM

Anyone know of a source for a vaccum pump that will pull 20 - 25 inches of mercury? This is for small scale on a 1 to 5 gallon tank. I'll be using it to stabilize small blocks of figured wood.

Stew

Larry · May 20, 2006, 01:04:45 PM

This one.

Surplus Center vacuum pump

I've used my pump hard for several vacuum experiments. One was stabilizing wood with a pentacryl/home brew mix.

It's a commercial duty pump...only draw back it's 220V. Couple more inches vacuum would reduce the heat requirement for bag drying. Guess ya can't have everything for this price though. ;D

Radar67 · May 20, 2006, 02:25:28 PM

Larry, thanks for the link.

I can run the 220 off my generator with no problem. I read that this is a continuious duty pump, can it be used to pull the vaccum to 20 inches then close a valve and shut the pump down?

I'm new at this so please bear with me, I'm learning as I go.

Stew

Larry · May 20, 2006, 04:41:53 PM

I think the pump would work fine in that application Stew.

A venturi pump or even an old fridge compressor might also work for you. You need an air compressor to run a venturi pump...but the pump is cheap.

Another link with all kinds of gadgets and ideas.

http://www.joewoodworker.com/

The stuff is mainly for making veneer presses.

thurlow · May 20, 2006, 05:48:50 PM

I've used a compressor from an old air conditioner (220 A.C.) to pull the vacuum on my farm equipment air conditioners for about 20 yrs. It only laks this much () 8) pulling 30 inches of mercury.

Radar67 · May 21, 2006, 01:29:55 AM

Larry, that venturi pump my be the ticket for what I'm working on.

Thurlow, you got any info, diagrams or anything about how to set up an AC compressor?

Somebody correct me here if this is wrong. From reading some of the other posts, I gather that 50 torr is roughly equal to 28 inches of mercury (Hg) and at that level, water will boil at 84 degrees. At these levels, without a heat source, the chamber will cool down because of the vapor leaving the wood. Is my understanding of this correct?

Stew

iain · May 21, 2006, 04:52:15 AM

Here's a couple of links for you to be going on with

the second one will answer you question about 50 Torr

the first one is more info than you can shake a stick at

I've got both air and water venturi valves
one works of my compressor the other of a running tap both pull around 95%

i use a vacuum cleaner to get most of the air out, then hook up the venturi at 150psi a 150 litre tank lasts about an hour if i leave it hissing

if you got a good air tight seal with no leaks you can shut to valve and leave it sucked BUT IF YOU ARE EVER VENEERING KEEP AN EYE ON IT

iain

Den Socling · May 21, 2006, 08:57:39 AM

Yep. '28 inches' refers to the removal of 28 of the 30 inches in one atmosphere. That leaves 2 inches. 2 x 25.4 = 50.8 mmHg (or 50.8 torr).

At 50 torr, the boiling point is closer to 100'F. You have to get down to 30 torr to achieve 84'F.

When water changes from liquid to vapor, the vaporized molecule carries heat with it and the water left behind is cooler. Cooler water has lower vapor pressure so less will vaporize.