alking - 30-4-2016 at 12:17
As I expected to happen sooner or later I have killed my rotary vane vacuum pump so I need a replacement. Looking on ebay at diaphram pumps this seems
to be a fairly inexpensive listing.
http://www.ebay.com.au/itm/Jelenko-JelCraft-model-DAA-V132-E...
Assuming this works properly (description says it powers on and pulls a vacuum) would this be a good unit? Also I cannot tell from the pictures, but
where exactly does the vacuum get pulled from? I am assuming I will need some kind of adaptors or something to hook up a hose to it, would anyone
happen to know what exactly I would need or where I could find that out? I've googled the model number and all that comes up are people selling used
ones, I can't find any decent description of the model or anything of use. If this is no good, or questionable, would anyone have any other
recommendations? I'd like to spend no more than 200$ max, if I have to go over that for a decent pump I'd rather spend ~50-75$ on another disposable
rotary pump.
XeonTheMGPony - 30-4-2016 at 12:39
You'll need a well built scrubber when doing acids.
Rosco Bodine - 30-4-2016 at 13:11
Savant gel pumps have replaceable PTFE diaphragms, valves, and piping and fittings
for example
http://www.ebay.com.au/itm/Savant-Gel-Pump-GP110-Gel-Vacuum-...
XeonTheMGPony - 30-4-2016 at 13:24
there's the price scam so popular on ebay! (Look at the shipping price!)
Look at the chemglass pumps, pricey but apparently well worth it.
alking - 30-4-2016 at 16:46
After doing more research it seems that I'll need a decent diaphragm pump to pull much under -25in/mg so I bought another rotary pump to tide me over
for the time being. I'm still in the market, but diaphragms being so much more expensive I want to make sure I get one that will be capable of
everything I need which I may or may not have to save up for.
That Savant has a nice price tag and seems to be of decent quality though (and shipping is < 50$ for me). Looking up the specs it says it pulls a
max vacuum of 10 torr, but I don't understand how that translates to in/hg, could someone help explain this to me? Converting it directly google tells
me is 0.393701 in/hg, but I'm used to measuring a vacuum in negative numbers for one and I doubt this only pulls -0.39in/hg. Is this a different kind
of vacuum measurement or am I (google) doing the conversion wrong, what am I missing?
XeonTheMGPony - 30-4-2016 at 17:09
same as inches of mercury
So 10 Torr = 10 mmHg or ruffly .39inches
Torr is a much higher resolution scale for vacuum
yobbo II - 30-4-2016 at 17:47
Check this for getto
http://laserkids.sourceforge.net/eng_vpump.html
Rosco Bodine - 30-4-2016 at 19:33
10 Torr is a pull down to a 1.3% atmosphere or .013 atm or about 0.2 psi or 29.5 inches mercury but that would be for a new unit and a used unit would
probably do about half that, meaning 20 Torr which is still good for a chemical resistant pump.
If you need chemical resistance this would be good.
As for the shipping, it is a heavy cast aluminum, heavy duty item.
Savant gel pumps are high end, high priced stuff. I have two of them, one used and the other brand new.
http://www.engineeringtoolbox.com/vacuum-converter-d_460.htm...
https://www.youtube.com/watch?v=9_JKd1gUNHw
https://www.labequipmentparts.com/labware/product.aspx?b=225...
this has come up before
http://www.sciencemadness.org/talk/viewthread.php?tid=23287&...
[Edited on 5/1/2016 by Rosco Bodine]
alking - 30-4-2016 at 19:39
What exactly wears down over time that causes the vacuum to decrease? Is it anything serviceable that could be repaired, or worth repairing if so?
Rosco Bodine - 30-4-2016 at 19:54
valve poppet seats but a valve and diaphragm kit is hugely expensive.
Some of the cheaper units may have polypropylene fittings and plumbing but mine are solid teflon and other fluoropolymer stuff all surfaces and the
motors are German made, probably the whole pump or maybe Swiss made on the pump itself maybe I can't remember, but they are top shelf and you don't
want to buy one new, grab your wallet.
They are fully rebuildable and you could cannibalize parts from several less than perfect working units to build one good one cheap.
They come with a free radio 
https://www.youtube.com/watch?v=MUV8BR3qf6s
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[Edited on 5/1/2016 by Rosco Bodine]
prettypolymer - 1-5-2016 at 12:02
If any of you would need a sturdy dual head diaphragm pump, drop me a line, i have plenty. They're all from KNF, so heavy duty german quality, easily
servicable with very affordable spare parts.