05-13-04 09:46
No 506808
Hey all,
Giving up on the aspirator, i like it and all, but the pump seal blew the other day and water went everywhere
NOT IMPRESSED!Looking at a vac pump (so many to choose from) found this one which is not to bad price...
Robinar - 6cfm, 20micron (0.02torr???), 1/2HP motor, 2 stage vacuum pump for automotive a/c uses.
0.02torr? thats REALLY LOW, thinking it might be tooo low...
1) implosion risk
2) safrole (from nomograph) bp comes to ~30oC
3) problems seperating boiling fractions
well? problems or not?
If not this means safrole could be distilled in a warm water bath..... hmmm....
aspirator got to 12mmHg with the pump i had....
suggestions?
Its just my opinion, but no-one listens to me anyway, and rightly so...
(Hive Adickt)
05-13-04 10:54
No 506815
with an two stage you will need coolingtraps, with dryice or liquid nitrogene. Iff you don't have acces to that by an diaphragm pump.
(Hive Addict)
05-13-04 10:58
No 506816
just suck some solvents in there and the vacuum won't be that
good anymore
.honestly, if necessary, you can introduce controlled leaks in your
setup to control vacuum.
> 1) implosion risk
bullshit. think about why implosion occurs and realise that it doesn't
really matter whether your pump has 1 torr, 0.1 torr or 10^-12 torr.
(hint: outside pressure varies by more than 1 torr)
http://www.animalyawns.com
(Hive Bee)
05-13-04 14:29
No 506846
Just leave the vacuum grease for the NS connections.
You will see some small leaks in there bubbling from time to time.
(Hive Bee)
05-13-04 16:39
No 506868
hest: Cooling traps? this pump is made for automotive air con purpose.... what is a cooling trap and why would i need it? the pump is rotary vane type.
hypo: Haha, thats always a solution, yeh got told that small pinholes in the vac line (cover and uncover with band-aids as required) would fix it.... as for implosion, thats caused by the external pressure crushing not internal pressure pulling it in.... so yeah makes sense now, had to think about that for a sec, but ill put a screwgate on the line to slowly introduce vacuum, good idea? i doubt the pump has any mode apart from on and off, ie no variation valve.
BieneMaya: grease joints with just something to stop it sticking but no vacuum seal? so that would be my leak source... not a bad idea.
Thanks all.
Its just my opinion, but no-one listens to me anyway, and rightly so...
(acetaminophanatic)
05-13-04 16:54
No 506875
A cooling trap freezes any vapors that get past your condensor, before they reach the vacuum pump. A diaphram pump doesn't have piston seals, so those vapors won't contaminate its pump oil and ruin the vacuum.
...it's an AOL chatroom for dyslexic spider monkies...
(Hive Bee)
05-14-04 04:07
No 507031
About oil pumps and cold traps.
Bought an oil pump on an auction site for 5o bucks 2 years ago, pulls amazing. In between my system is connected in series 2 filter flasks left empty since I dont have easy access to nitrogen or dry ice. I put them there cause I convinced myself that it would catch anything that did fall in my recovery flask.
Anyway, its been 2 years and it still pulls the same. Now I dont use it so often so maybe thats why. But safrole still comes over at 60-62 and I havent had any problems with it yet.
(Hive Bee)
05-14-04 07:56
No 507070
okay i get you now....
dry ice is easy to get... liq N2 would be a prob tho... hahah
Thanks.
OcoteaCymbarum - what is the strength of your vac?
Its just my opinion, but no-one listens to me anyway, and rightly so...
(Hive Bee)
05-14-04 16:29
No 507131
Since my vacuum guages states about 27.5 inches.
It has to be wrong because I pull safrole at 60-62.I could print out a nomograph and figure it out but I got no ink in my printer and since I hardly print anything here...
(Hive Bee)
05-15-04 00:50
No 507207
OC, do you us the gas ballast on your pump (if it has one)? These are generally good at purging crap while you are pumping down a vacuum system. I've never bothered with a cold trap. I open the ballast a bit when pumping down and then turn it off. If things get bad, I'll just change the oil.
The Gas Ballast
http://www.hyvac.com/tech_support/Gas%20
Gas Ballast Valve, What it do?
Most HyVac Products, Inc. vacuum pumps are shipped and contain a feature known as the gas ballast valve. This is viewed as a black adjustable knob on top of the pump.
Often in vacuum work, the user will get water vapor, solvent vapor or other bad contaminants as part of the gas stream being evacuated from the vacuum chamber. These contaminants come over because they have turned into a gas molecule from a liquid molecule under "X" vacuum pressure and the pump pumped them out of the system. They then travel to the pump and turn back from a gas to a liquid in the pump oil.
All liquid chemicals have a value known as vapor pressure. This vapor pressure is a function of physical chemistry law. The basic formulae is PV=nRT. I could get into an explanation more detailed here, but suffice to say that as a result of this formula, water will boil at room temperature when a vacuum pressure of roughly 29.5" mercury vacuum is achieved. When water boils it is turning from a liquid into a gas. All chemicals have this feature, just at varying temperatures and pressures based on their molecular construction.
It is possible to throughput some of these contaminants from your system and through the pump and that are where the gas ballast valve comes into play. If you do not require high vacuum less than say 300 micron for instance, then you can open up the gas ballast valve during the evacuation procedure and get some of these bad molecules out of the pump through the exhaust port of the pump. Remember also if they are coming out the exhaust they potentially are entering your workplace. This may pose a hazard either health based or fire based. If you are looking for better vacuum pressures, the valve is adjustable. This feature is not the total answer; it helps, but should not be considered the solution in problem applications with lots of contaminates.
If and once the pump is contaminated you can again use the gas ballast valve to assist in purging some of these contaminants from the vacuum pump oil in which it now resides. Close the pump inlet port off to full vacuum and allow pump to run/actuate with gas ballast valve in open position. This again will help purge the pump. Take a long lunch or let the pump actuate overnight with the valve open. Care again should be considered to the exhaust stream. If the pump is "smoking" or exiting oil mist in good quantity, you may come in the next morning to a room full of oil mist. Piping to a hood or using a coalescing filter like the HyVac Capture filters can help eliminate this problem area.
If you have big problems in this area, or if you are always finding contaminants in your oil, you probably need a different solution and should call us.
It is common during operation of the pump with the gas ballast open for there to be seen oil mist or "smoke" coming from the exhaust of the pump. Continuous duty at these pressures generally causes the user to desire a HyVac Oil Mist Eliminator or HyVac Capture filter available from us for most vacuum pumps.
If you have no problem with contaminants you should use pump with the gas ballast valve closed. We consider this normal operation.
Sredni Vashtar went forth,
His thoughts were red thoughts and his teeth were white.
(Hive Bee)
05-15-04 23:30
No 507365
And I leave it open exactly for that reason. And as a matter of fact, it does produce a little smoke so the outlet has to be plugged to the outside, otherwise there would be tons of smoke in the room.
I cant remember the CFM of my pump but its alot so the vacuum is just amazing even with the gas ballast open.
The oil seems to last forever. OF course every once in a while, I change it, but the vacuum hardly even changes
OC