Sciencemadness Discussion Board

New pump

User - 9-10-2009 at 04:46

Hi,

I recently obtained a new vacuumpump for next to nothing.
Its a speedivac 2 single stage pump.
Model: A210-04-003 from boc edwards.
I cant find the sheet resembling the pump only similar types.
It very much looks like this one:
http://www.nelabgear.co.uk/window.asp?id=151391930

Anyway ive send them an e-mail and hope to get an answer
soon.


Well the point is ive never operated a vacuum pump.
Only been in the luxurious position of turning a valve , where i was educated.

At first it does run and pull vacuum, thats a relief.
The oil level is very low, still within acceptable levels, but still i will buy new oil first.
I will then let it run for a couple of hours and make sure the oil level is still oke.
And let it clean itself by turning the gas ballast fully open.
(is this right?)

Then comes the part where I am fully uncertain.
I guess i do need a valve for checking vacuum strength.
I guess i do need a kickback flask to prevent water from bumping into the pump...
I guess i need a washing bottle to neutralize corrosive/acidic gases.

Can anyone explain a couple of things to me.
Do's and donts etc?
Also has anyone experience with this type of pump or similar?
Maybe other tips and tricks?



Thanks for the help.

[Edited on 9-10-2009 by User]

entropy51 - 9-10-2009 at 05:42

Congratulations to the proud father of a pre-owned pump!

I would recommend draining the old oil and refilling. Then run it for a few hours and drain and refill again. This helps to flush anything left by the previous owner out.

You would need a trap with soda lime or similar if you're going to let acidic gases into the pump, but better not to let them have a chance. Alkali traps are no match for a huge burst of HCl. There is nothing less fun than re-building a seized pump. I know of people who clean them with dichloromethane if they get contaminated, but I don't recommend it.

I use an aspirator whenever that gives sufficient vacuum, thus saving the pump for only those jobs that require it and reducing contamination of the pump.

I prefer a dry ice cooled cold trap to keep out condensible vapors.

If I expect corrosive gases during a distillation, I degas the distillation with a water aspirator first, then cool it down and switch to the pump. But this doesn't help if the material decomposes later in the distillation.

I'm not a big fan of the gas ballast. Some people use them religiously after using the pump, but I just try to keep the nasties out of the pump to begin with. I bought my pump in 1970 and it still works like a charm, so it's worth the effort to take care of your pump as best you can.

There are a lot of references to vacuum methods, but many tend toward the physicist rather than the chemist. The book "Laboratory Companion" by Gary Coyne is pretty good and you can find it if you search around. There are a lot of web references as well. One of them is Sam's FAQ

[Edited on 9-10-2009 by entropy51]

watson.fawkes - 9-10-2009 at 05:43

Quote: Originally posted by User  
Then comes the part where I am fully uncertain.
I guess i do need a valve for checking vacuum strength.
I guess i do need a kickback flask to prevent water from bumping into the pump...
I guess i need a washing bottle to neutralize corrosive/acidic gases.
Everyone else is uncertain too, because there are many things to do with a vacuum pump, and you haven't said what it is you're doing. I'm inferring it's some kind of distillation, but I don't know. For all I know, you're evacuating a vacuum manifold.

User - 9-10-2009 at 06:10

Sorry for not being clear on that part.

Iam planning to use the pump for destillations under reduced pressure.
I have no specific plans on what exactly those will be now and in the future.
They might include corrosive gasses/volatile solvents etc.
Keeping these vapors out of the pump would be a must.

Further just filtrations, desiccation etc.

I can imagine knowing the pressure and thus the boilingpoint(s) would be very pleasant.

*edit*
Ive read somewhere that letting the pump warm up helps protect it, as in letting it run for half an hour before using it.
I think the idea would be that the oil is warm and thus vapors tend to escape instead of mixing with the oil.




[Edited on 9-10-2009 by User]

vulture - 9-10-2009 at 13:44

When shutting the pump down, be sure to vent your setup first, then shutting down the pump. This will prevent suck back of oil, which can be rather nasty.

There are some fluorinated oils available, that won't mix with anything. That means contaminants float on top of the oil, can't attack the pump and can be simply decanted off. The problem is that it's rather expensive and I don't know if you can interchange oils. One would expect problems when they have different density and/or viscosity.

http://www.vacuumoil.com/fomblin.htm

You also have to check whether your pump is made for high vacuum or high flow applications. High vacuum pumps usually pull very good vacuums but are not suited for pumping large amounts of gas continously, eg they are designed to evacuate an apparatus and hold it at that pressure.

watson.fawkes - 9-10-2009 at 16:30

Quote: Originally posted by User  
Iam planning to use the pump for destillations under reduced pressure. I have no specific plans on what exactly those will be now and in the future. They might include corrosive gasses/volatile solvents etc. Keeping these vapors out of the pump would be a must.
If you are interested in building a piece of lab infrastructure (which seems to be the import of your question), I can suggest a number of specific things to include in it.

User - 9-10-2009 at 17:41

Thank you all very much, I will have to reread the stuff to-morrow because I am rather wasted in this long lasting night, and i will :) .

Infrastructure in the lab is very nice, it somehow feels more and more like a real lab.
I installed some industrial grade switches for my circulator pump and other devices.
The same goes for water circulating unit which has a lead to 2 taps on the working bench.
I personally like to fix those things properly so no bullshit occurs and I can just get started without fixing stuff first.

Before I drift off to far just dreaming.
Indeed building a vacuum system with valves etc would seem a good idea.
It now popped to mind that a kickback system could also be made out of copper or other than buying more glas, downside would be that for e.g. copper isnt that resistance and I dont know if it is an acceptable medium for vacuum operations, i guess it is.
Even internally coating comes to mind here.
Somehow I always feel a lot better to actually see what's happening, for that matter glass would be a better option.

Also last couple a days i found out that manometer especially digital and other vacuum stuff costs a dirty lot of money. So building most of the this myself would mean less spending money.

Another question, would it be best to solder (in case of copper) or to screw(with use of the typical white tape used in gas piping) the pieces together.


Really time to go to bed.
Alcohol always seems more of a problem tomorrow :)
Greetings.

entropy51 - 9-10-2009 at 18:25

Quote:
Alcohol always seems more of a problem tomorrow

So you're making acetaldehyde even before your lab is finished!

Trifluoroacetic - 9-10-2009 at 19:20

I believe those fluorinated oils are sold as fromblin ( used in oxygen service) they will sieze up pumps that have other oil residues in them.
Quote: Originally posted by vulture  
When shutting the pump down, be sure to vent your setup first, then shutting down the pump. This will prevent suck back of oil, which can be rather nasty.

There are some fluorinated oils available, that won't mix with anything. That means contaminants float on top of the oil, can't attack the pump and can be simply decanted off. The problem is that it's rather expensive and I don't know if you can interchange oils. One would expect problems when they have different density and/or viscosity.

http://www.vacuumoil.com/fomblin.htm

You also have to check whether your pump is made for high vacuum or high flow applications. High vacuum pumps usually pull very good vacuums but are not suited for pumping large amounts of gas continously, eg they are designed to evacuate an apparatus and hold it at that pressure.

merrlin - 9-10-2009 at 23:15

Quote: Originally posted by vulture  


There are some fluorinated oils available, that won't mix with anything. That means contaminants float on top of the oil, can't attack the pump and can be simply decanted off.
http://www.vacuumoil.com/fomblin.htm



Fomblin can be cleaned with isopropanol and is miscible with other compounds. What fluorinated oils are you referring to?

vulture - 10-10-2009 at 01:59

Quote:

Fomblin can be cleaned with isopropanol and is miscible with other compounds. What fluorinated oils are you referring to?


There are different types, as you can see on the data sheet on that site. In the lab we have an alcatel pump that uses one of those oils, don't know exactly which one, but it has seen some pretty nasty stuff, organic and inorganic, over the years, without the oil becoming tarnished. In fact I can't remember it needing exchange in over three years.

merrlin - 10-10-2009 at 13:39

Quote: Originally posted by vulture  
Quote:

Fomblin can be cleaned with isopropanol and is miscible with other compounds. What fluorinated oils are you referring to?


There are different types, as you can see on the data sheet on that site.


I also see from the datasheet that the fomblin oils as a group are "resistant to most reactive chemicals" and have "good aqueous and nonaqueous solvent resistance." I don't interpret this as "won't mix with anything." I have read that a volume of Fomblin dissolves approximately 20 times more O2 than an equal volume of water. And, of course, there is Perfluorosolv PFS-1, formulated to be fully miscible with perfluoropolyether (PFPE) oils. Lastly, the fomblin oils are characterized by an average molecular weight, and are inherently a mixture of various molecular species.

Attachment: fom_vac.pdf (111kB)
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vulture - 11-10-2009 at 02:23

Quote:

I also see from the datasheet that the fomblin oils as a group are "resistant to most reactive chemicals" and have "good aqueous and nonaqueous solvent resistance." I don't interpret this as "won't mix with anything."


I see you are intent on turning this into a nitpicking contest. Very well. I should have said won't mix with or dissolve most compounds typically encountered in chemical lab procedures which are in the gas phase at such vacuum levels.

The point is that the fomblin oil can be exposed to solvent vapour without going fubar.

Quote:

I have read that a volume of Fomblin dissolves approximately 20 times more O2 than an equal volume of water.


Yes. Typical for highly fluorinated compounds. My turn for nitpicking: at which pressure? Water dissolves 0,023L O2 per liter at partial O2 pressure of 1 atm. In the same conditions that would mean 0,230L for fomblin. In comparison, petroleum ether then dissolves 0,409L of O2. Your point being?
Quote:

And, of course, there is Perfluorosolv PFS-1, formulated to be fully miscible with perfluoropolyether (PFPE) oils. Lastly, the fomblin oils are characterized by an average molecular weight, and are inherently a mixture of various molecular species.


I really don't see the relevance of this comment. Unless of course you interpret this as different compounds mixing with the fomblin oil? Sheesh. Show some fucking practicality.


[Edited on 11-10-2009 by vulture]

indigofuzzy - 11-10-2009 at 07:45

If nitpicking is the game, then one could comment that when speaking english, the correct symbol for a radix point is a period, not a comma. A comma in English is used as a thousands separator.

Not to be mean spirited or anything :P

[Edited on 10.11.2009 by indigofuzzy]

vulture - 11-10-2009 at 11:00

I thought this was a chemistry community, not just an english speaking community. Hence, one should abide to SI units. Furthermore:
Quote:

For example, the International Union of Pure and Applied Chemistry (IUPAC) suggests to never use a comma or a point as thousands separator: "For numbers with many digits, the digits may be separated in groups of three, counting from the decimal sign toward the left and the right. The groups should be separated by a thin space (half space), and never by a comma or a point, or by any other means."


That being said, let's get back to the topic. I'm merely suggesting fomblin oil will increase resistance to chemical attack. Number crunching isn't going to change anything about that. You are welcome to suggest another alternative.


[Edited on 11-10-2009 by vulture]

User - 11-10-2009 at 11:36

Ive often seen filters for the exhaust vent.
How necessary is this?
I can imagine breathing the vapours coming off could be bad.
Would it otherwise be smart to put a tube on and put the other end into the cold night air?

entropy51 - 11-10-2009 at 12:28

Quote: Originally posted by User  
Ive often seen filters for the exhaust vent.


The only filters I've seen for pump exhaust are to trap the oil mist that boils out when pumping down the system or gas ballasting.

The accepted practice nowadays is to to vent the exhaust to the outside.

vulture - 11-10-2009 at 12:31

Filters on the exhaust vent usually have the purpose of preventing oil mist from escaping. This usually happens when atmospheric pressure is resumed and the pump is pumping air. The filter catches the oil mist and allows it to drip back into the pump, hence this reduces oil loss and contamination of the surroundings.

I've seen "filters" that were just conical gratings of metallic wire mesh. Apparently this is effective.

[Edited on 11-10-2009 by vulture]

merrlin - 11-10-2009 at 13:22

@vulture:

The point is that there are probably a lot of materials that will be miscible in fomblin. Although it is unlikely that these materials will react with the fomblin, they may react with each other or with oxygen. They may also react with the materials of which the pump is constructed. Most of the pump oil is not at "vacuum level", but at the exhaust pressure, and vapor condensation can occur during compression before exhaust. That is why pumps have ballast valves. You've made a sweeping generalization and I have made a rebuttal. The practical matter is equipment reliability (and possibly safety) due to unforeseen reaction products. An inexperienced person is seeking information on the use of a single stage rotary vane pump. Your post was dismissive of potential problems. I tried to point out that a lot of things can happen in a pump with fomblin oil, and you responded with profanity.

If I had wanted to nitpick, I would have pointed out that the the decomposition products of vacuum pump oil are usually referred to as "varnish," and that I have never heard of pump oil becoming "tarnished." I would have also directed you to O'Hanlon and his discussion of potential reactions between perfluoropolyether and Lewis acids or aluminum and magnesium.




merrlin - 11-10-2009 at 13:58

Quote: Originally posted by User  
Ive often seen filters for the exhaust vent.
How necessary is this?
I can imagine breathing the vapours coming off could be bad.
Would it otherwise be smart to put a tube on and put the other end into the cold night air?


While at university, I worked in a vacuum deposition lab and we had several deposition systems (diffusion pumps backed by roughing pumps). The exhaust lines were loosely inserted into risers that were connected to a blower on the roof of the building. One system was being used to deposit cadmium sulfide and copper sulfide for a heterojunction solar cell project. Hydrogen sulfide was being fed into the chamber as a reactant. During the night, the blower on the roof failed. A significant amount of hydrogen sulfide greeted us in the lab the next morning. After airing out the lab--and experiencing olfactory deadening--we went about our business. For the rest of the day, any visitor would recoil upon entering the lab, while we could no longer smell the hydrogen sulfide.

I recommend that you exhaust your pump to the outdoors using as short an exhaust line as possible, but the most important thing is to be aware of the chemical species in the exhaust flow. Are they heavier or lighter than air? At what partial pressure/temperature will they condense? Are they flammable? Forced exhaust systems can fail, and sealed passive exhaust lines can collect exhaust species. I have a small two-stage rotary vane pump that I use for air evacuation. When pumping only air without a mist filter, I have noticed some irritation.

merrlin - 12-10-2009 at 09:56

If you are going to use fomblin with corrosives, you might consider Drynert. I'm not sure if it used in rotary vane pumps or just booster pumps. From the Edwards website:

"Edwards, in conjunction with Ausimont UK, has developed Drynert fluid which contains anti-rust and anti-wear additives soluble in Fomblin®. These additives cover metallic surfaces with a protective, corrosion resistant film"


http://www.edwardsvacuum.com