vacuum pumps

Where can I locate information regarding vacuum pumps and how you select an appropriate one regarding size and type for vacuum-bagging? Are there formulae to use or simple rules of thumb?
Thank-you for any help you can supply

 

The June/July issue, #83, of Professional Boatbuilder has a great article on setting up a vacuum system and what to look for in pumps.

Gary

 

thanks very much for your help Gary.
roger

 

Hi,

use a simple vacuum cleaner like suggested by Derek Kelsall. Its use is documented here:

http://www.mycv.asn.au/gallery/Kelsall/pic_1/photo20.jpg

just step back in the path to see the whole story - interesting stuff.

Cheers
Mike

http://www.messwerk.at/flame-sailing

 

Thanks Mike for the link to the great pic! I realize that any vacuum source can be used but I'm thinking there must be a way to quantify the whole process-match the pump to the job in terms of square meters of area or whatever. I'll follow up on that Pro. Boatbuilder article mentioned earlier by Gary

 

Hi Roger,

I wanted to do some more speculation about the subject, but then I checked my link collection again and found this

http://www.quigs.org/Farrier/bagging.html

I think it should answer many questions

Good luck
Mike

http://www.messwerk.at/flame-sailing

 

Mike, thanks again for your efforts! I had a look at the link you gave me and it is excellent - gave me lots of ideas for how to go about this whole process.
roger

 

Vacuum cleaners can be very dangerous as a pump. The fumes of the resin and solvents are very volatile and explosive. Any electrical motor in an explosive atmosphere must be sealed!

 

Point taken Gonzo! Thanks for your advice

 

Hello gonzo,

fully agree with you - non ex-proof pumps used with polyester or sim. could turn to road to heaven ...

solvent = 30% at 500g polyester rolled over glass fibers would give quite a bong

epoxid resin systems like WEST SYSTEMS contain no solvents, i.e. resin & hardener react in stoechometric quantities (therefore they put so much emphasis in correct mixing proportions), plus they evaporate much slower than conventional solvents and won't accumulate to an explosive mixture at all

in any case it is advisable to consult the data sheets of the substances in use.

Cheers
Mike

 

The General rule would be …the bigger the better ….remembering most of the leakage loss occurs around the perimeter of the Bag thru failures in the taping or sealant system Tacky tape or whatever so the length of this is more critical than say area in any calculations..

The second thing is do not be “over sold” on any system if all your work is in say the 18 Hg range and down then there are a number of Cheaper High Air Volume systems around.

Example when I was in the Middle East after the first gulf war there was not much equipment to work with Scavenging around I found at a Arab junk shop…. an old air raid siren (roots Blower powered) which was in pieces Also Lucky Finding a 10 horse power motor we got it working.

It would pull 26 Hg but got very hot…. while at 18 Hg it would run cool all day this thing had 3” inlet and exhaust (I put a truck muffler on it) and this was around 800+ CFM I have also seen these Roots systems at 3000 and up CFM so do not turn up your nose at an opportunity to buy one...

Now Infusion that’s a totally different animal very high sustained levels DO NOT BE UNDERSOLD HERE.

Positive displacement style with big motors and liquid cooling is a good rule, my system is…. Two…. One backup... 7.5 hp double head (4 cylinders each pump system) water cooled!!

By the same token I also have a friend coring the deck and hull on a 38 foot powerboat using only (he does a good Bag job with good material) an PIAB air powered vacuum pump (need a very good compressor) these sell on E-Bay for between 15 and 40 Dollars.

If you need to use a vacuum cleaner (I do not advise it but there are many doing it) fill it with water.

 

how about one or a few of these?

Vacuum level: 28.3" of mercury at sea level
Air consumption: 4.2 CFM
Air inlet: 1/4'' NPT

hard to beat for $9.99

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=3952

 

You are kidding right ??

 

I can’t tell but the box is likely hiding a small air driven venturi type vacuum generator. If it works, that is very cheap, even for them. The big disadvantage is you need a large supply of high pressure air, and they are noisy.

Gary

 

They work well, but have very little volume.