OT vacuum pump.

I usually used Alcatel ones at IBM, but there were half a warehouse full of them available.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

the best forum, and if some of you know a vacuum related forum then please do share.

a turbo molecular or diffusion pump. (and not for HVAC work). I found a recommendation on "The bell Jar"

uctDetails

0

ld, Alcatel etc. as these all go for more than a kilo buck.

When you look for "lab" or research vacuum pumps they all sell big bucks. (I couldn't find one in Kurt J Lesker for less than $2k, but I didn't look too hard.) And then there are all these "commercial" pumps for the HVAC industry. The two I listed are made in USA and thus a bit more expensive.. There are Chinese ones for less than $200. The ultimate pressure is not quite as goo d..maybe 10-20 milli torr. But I've also heard you can put in better pump oil and reduce that.. But heck lots of times 20 mTorr is plenty... (well fo r vacuum the opposite of plenty :^)

George H.

If it gets much worse than that, you'll stall your turbo, and you know what happens then. :(

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

The cheapest cheap two stage pump I've noticed is the Harbor Freight for about $160, and they have 25% off coupons in almost every flyer. If you want a pump you can run for an hour here and overnight there, but mostly live on the shelf waiting to be used, and have it last several years, go to the hvac world. If you want a pump you can run 24/7 for a decade backing a diffusion or turbo pump, only shutting down for regular oil changes, pony up the $2500 for an Alcatel, Edwards, or Leybold. You really do get what you pay for here.

----- Regards, Carl Ijames

If it gets much worse than that, you'll stall your turbo, and you know what happens then. :(

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Thanks Carl, This is a bit of a rogue project*. But I make things for physics advanced labs, so the use could be from almost nothing, to a maximum of maybe ~30 hours/week for ~30 weeks/ year. But I'm thinking of a middle type user. (If they want more they can buy the $2k pump.) $250-$350 is a nice number that doesn't blow the budget*

George H.

*So I was bitching to my wife the other night about the latest project. Saying that I should just build my own LN2 flow cryostat... (Designs have been floating around in my head.) "How much would it cost?" she asked. "I think I can do it for $1k or so" , I said. (this doesn't include the LN2 dewar.) "Well do it then." she said, "if that's what you need to do." (My wife is OK!) After I get the pieces I hoping for ~2 solid weekends of work... maybe it 4-5 1/2 weekends, 'cause there's always other stuff to do.

Yes, I second Carl's idea about the 2 stage. The spec on that one says it goes down to 10 microns as I recall. It is for sale for 150, and I *think* you can put a coupon on it for a 120 price. Plus - you can buy a 2 year warranty for $20-30 and get a return if you want. These have good reviews, and I sometimes ask the store manager whether he gets any returns. At any time, I see diffusion pumps on ebay for 100-200. I'm not sure what you are doing, though. I have the impression some hobbyists have sputtered without the DP. jb

I think we use these guys...

Call he might have something. If I remember right your upstate, so its relatively close.

Cheers

Thanks Martin, I think a good rebuilt pump is still going to blow my budget. They've got some big pumps... We had this big Kenny in grad school.. KT150 maybe.

Well sorta close. (Buf, NY.)

George H.

George Herold scribbled thus:

An old fridge compressor makes a reasonable vacuum pump !

--
Best Regards: 
                     Baron.

Thanks Baron, Someone mentioned that on RCM too. Any idea of the ultimate pressure? Do they make two stage compressors? They are certainly quieter than the direct drive vacuum pumps. (Not to worry I'll look on the web.) George H.

George Herold scribbled thus:

If its any help, mine will easily produce 250psi. I use it to inflate my vehicle tyres. Vacuum wise I don't have anything to measure it with, and my pressure gauge only does 250psi (18bar).

I have only ever taken one apart and it contained what could be a three stage pump. Three cyinders, three pistons and some pipes and a lot of oil. Nasty smelling stuff a weird greenish colour.

HTH.

--
Best Regards: 
                     Baron.

Den torsdag den 1. maj 2014 22.30.00 UTC+2 skrev Baron:

250psi is about right for r134a at ~65'C which is about what a high temperature compressor will be rated for short term. r404a is close to 450psi

a normal refrigerant compressor isn't really meant to do vacuum, much of the cooling comes from the return gas when run in a refrigerator

The oil is supposed to circulate with the refrigerant, so if you use it for anything else you need to make something to catch the oil and return it to the compressor

-Lasse

I like the Alcatel pumps like 2010 etc. (now renamed Adixen or something).

If you keep looking you will perhaps find a used one for a couple of hundred dollars. I bought one in the UK for 220 GBP from a dealer I found via ebay. He used to put new pumps on electron microscopes when upgrading them, and refurbish the old pumps and sell them.

I have also retrieved two similar pumps from dumpsters around a university, and both were in good working order. Maybe get to know some maintenance staff in the labs at a local university and ask them to keep an eye on the dumpsters.

Chris

Re: refrigeration compressors as vac. pumps.

OK scratch frig pumps. I'd really like something quite. There is a certain charm to the old belt driven vac pump. (as long as you don't mind oil spraying off the belt as the oil seal fails.) George H.

I have a Robinair 15500 that works very well.

The difference between these and a lab pump is how quickly you'll reach a high vacuum. These inexpensive pumps pull a somewhat constant intake volume, and that volume contains less and less mass as the vacuum increases. A lab pump has an ultra high speed turbine that can grab low pressure air in high volume. The inexpensive pumps also foul their oil quickly so buy extra bottles.

From what I've read, the second stage is NOT for faster pumping. Air is injected between the two stages to reduce the condensation of water and solvents into the oil. Impure oil boils on the low pressure side of the pump and ruins the vacuum, so the longer it lasts the better.

The pump works well for what I bought it for:

- Evaporate water and solvents from circuit boards before soldering or coating them.

- Degassing 2-part adhesives.

Other uses that I've found:

- Degassing water for cut flowers.

- Drying out small kitchen appliances after washing them.

- Rescuing chocolate milk that won't mix because too much milk was added to the cocoa powder before stirring.

- An electrified vacuum chamber is really pretty.

- Drying out camera parts after a 3L water bottle shattered.

It does not:

- Dry shoes

- Pop a lemon

- Evaporate water quickly enough to make ice

Lasse Langwadt Christensen scribbled thus:

Ups ! I didn't know about the oil. I just push the output into the pressure gauge and air line straight into the tyres...

--
Best Regards: 
                     Baron.

Hi Kevin, Thanks for take. So lab mechanical pumps and these HVAC pumps wo rk basically the same way. As you say they displace (move) a volume from t he low pressure side to the atmosphere. The main difference (besides cost) that I can see is that the lab pumps are made to run 24/7 and they typical ly have a lower ultimate pressure.

Well I'm guessing, the "fouling" rate depends mostly on the foul stuff you pump through it. :^)

The second stage is for a lower ultimate pressure.

Say how noisy is it? I realized last night that what I care about most rig ht now is having a noisy pump.. and all the direct drive pumps (lab and I a ssume HVAC) tend to be noisy.

This question is a bit moot. I went on ebay last night and found what look ed to be a nice old Sargent Welch Duo seal 1400. (~$100 + $85 shipping) like one of these,

Just looking at it made me nostalgic, it's just like the one I rescued from the loading dock at UB years ago. I hoping someone still makes parts if I need to repair it.

And look at the pumping curve!

(page 15)

For a small enough volume (and a good pump) I'll be able to get below 1 mTo rr! That and a little cryo-pumping and I'll be good to go!

Sorry, just getting all excited.

Hey I saw this circuit that used a thermistor as a pressure sensor. You ru n a constant stimulus through it. (I need to think about constant current or voltage?) Such that it self heats in the "air". The resistance then tel ls you the temperature which depends on the pressure. Similar to a thermo- couple gauge But w/o the very low impedance of the TC. (I find cheap TC gauges can be a bit flaky at the low end.. the signal bounces around as you wiggle the con nection.)

Anyone ever done this?

George h.

You just described the standard vacuum sensor ;) They use a fine wire, not sure what it is, and then it drives a bridge circuit. The heat removed during vacuum is proportional to vacuum.

Another source of Vac pumps are the old dental vacuums, Airtechniques. They are 2 stage pumps, lots on ebay.

Cheers

run a constant stimulus through it. (I need to think about constant curre nt or voltage?) Such that it self heats in the "air". The resistance then tells you the temperature which depends on the pressure. Similar to a ther mo-couple gauge

e a bit flaky at the low end.. the signal bounces around as you wiggle the connection.)

This is "a" standard vacuum gauge, not "the" standard vacuum gauge (which d oesn't exist, unless you refer to the "standard vacuum gauge" used in Natio nal Standards Labs which aren't all that practical in vacuum systems.

The capacitatively sensed stretched membrane vacuum gauge - aka Baratron

comes closer, but it costs a lot more.

--
Bill Sloman, Sydney