Chinese pump first run report.

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Finn Hammer
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Chinese pump first run report.

Post by Finn Hammer »

Digivac meter showing 2 Microns on inlet of dual stage 10CFM pump from China
Digivac meter showing 2 Microns on inlet of dual stage 10CFM pump from China
I received the Two-stage rotary vane pump the other day,
http://www.ebay.com/itm/2-stufig-Vakuum ... 1867425448
and was soon getting excited, since the label quoted two different values for acheivable vacuum.
either 0.004 Millibar, which corrresponds to 3 millitorr, but also 5 Pascal, which corresponds to 37 millitorr.
In the listing, it quoted 0.3 Pa which corresponds to 2.2 millitorr. What to expect?
Fortunately, the DigiVac LightBarVac meter arrived today, so at last I could start to get a feeling about the capability of the pump.

With everything in place, the pump drops down to, 5 micron, and within a minute or so, levels out at 1-2 microns, That is not so bad is it?

On the negative side, the pump does not have a ballast valve. I have no experience with vacuum whatsoever, and am unable to access whether this is going to be necessary pumping my 10" sphere, but time will tell.
I will probably dismiss this pump to vacuum jar duty, though, and get a proper lab pump, because this one is quite noisy, starts to get on my nerves already.....

Cheers, Finn Hammer
Johan Reinink
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Re: Chinese pump first run report.

Post by Johan Reinink »

That's a good result for a 2-stage rotary vane pump. In my experience rotary vane vacuum pumps are always noisy but they're nice pumps. What do you consider a proper lab pump?
A gas ballast is needed if you pump a lot of condensible gasses, you probably won't need it anyway. Sometimes running a pump with the gas ballast open can clear out contaminations in the oil but your pump is performing just fine.
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Finn Hammer
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Re: Chinese pump first run report.

Post by Finn Hammer »

Johan,

In my mind, a proper lab pump would have KF fittings instead of a Threaded connection, and it would have a ballast valve.
And it would be an Edwards, Varian, Leybold, Alcatel, Oerlicon, Pfeiffer, Agilent or some other of the really well built pumps.
A Welch would be nice but hard to get here in Europe. (I assume it is the one that goes lub lub lub :-) )

Cheers, Finn Hammer
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Dennis P Brown
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Re: Chinese pump first run report.

Post by Dennis P Brown »

That is excellent performance for a two stage pump and if its pumping rate is good, you can't except much better than that.

A ballast is nice but one can just change the oil if that ever becomes a serious issue so don't worry about that.

Adding a KF adapter to a threaded pipe is easy since those types of adapters are readily available and not very expensive - just decide on the size that you will need for your foreline system. Most people prefer KF-25 (one inch diameter piping.)
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Richard Hull
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Re: Chinese pump first run report.

Post by Richard Hull »

Dennis has given good advice. Old style lub...lub...lub... Welch and Precision, belt drive pumps are much quieter and vastly more easy on my nerves. However what you have there is working great for you and will easily get the job done very well.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Finn Hammer
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Re: Chinese pump first run report.

Post by Finn Hammer »

Dennis and Richard,

Thank you for your replies and advice, it means a lot to me . Obviously, at this time, I am more or less walking in the dark, studying Vacuum and buying pats in a frenzy.
I have quite some past experience building pneumatics, and as such familiar with the difficulty of obtaining a tight joint using threaded connectors and teflon tape, it is a hit and miss affair. But with pneumatics, I could hear a leak, not so with Vacuum. So I intend to build the system one single joint at a time, testing for leaks as I advance.
O´Hanlons "A users guide to Vacuum Technology" arrived in my mailbox this morning, and reading it should bring me a step ahead, hopefully.
The next step will be to convert the pump to KF fittings and build a manifold, so that I can test the 2 pcs, used, 0.05 Millitorr, Baratrons I have coming, against each other, as well as against the Digivac, which is new and factory calibrated. With 50 microns of overlap, I should have a chance to measure down to 5 ^-2 MilliTorr and thus be set to measure relevant Vacuum levels.


Cheers, Finn Hammer
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Richard Hull
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Re: Chinese pump first run report.

Post by Richard Hull »

You are on the right path with the right ideas. I have long held that a vacuum system should be tested one component added at a time and tested after addition. In this manner, issues such as leaks are immediately isolated and fixed one step at a time.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
ian_krase
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Re: Chinese pump first run report.

Post by ian_krase »

Yeah.


I'll add that a very simple discharge tube, powered by a rectified NST, will provide you with a very fast-acting visual qualitative gauge for testing with Dust-Off.
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Dennis P Brown
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Re: Chinese pump first run report.

Post by Dennis P Brown »

While thread to thread compression fittings using teflon tape are possible/ok for torr and possibly the higher range micron systems, if you would like to obtain 10^-4 to 6 torr range, avoid using any connections that depend on teflon tape for sealing. Generally, teflon tape is only used in vacuum work for anti-seizing between fittings and not to seal said fittings. (most people evacuate their fusor's to 10^-5 torr or so.)

Since you are new and "Buying in a frenzy" I would suggest that you first learn a few things about vacuum systems to avoid many common mistakes. Do learn how to search (key words) ebay for stuff - amazing what might turn up and deals for systems that are very useful.

First, vacuum lines work best if they are as short and wide a diameter as possible relative to the inlet port of the vacuum pump/setup. Length matters a great deal - long lines need to be as large a diameter as is reasonable for the devices. For instance, while a 15 mm KF line can work if the line is short from the fore pump to the high vacuum pump, if the distance becomes a bit long, this can reduce performance and 25 mm KF will perform better.

The connection between your chamber and the high vacuum pump should be as large as possible - again, within constraints of the system. Most people directly mate a control valve/high vacuum device to the chamber.

KF connectors are fast to assemble/dis-assemble, tend to perform very well (and are not to difficult to re-polish when their surfaces are damaged) and are relatively cheap (can find deals all the time.)

For larger openings (where KF is not available) try to buy connector systems that are similar so one isn't trying to keep different types and sizes of sealing rings. Also, O-ring systems are very good for any fusor work.

Avoid using vacuum grease of any type - and when/if used, learn how to use it correctly. Correct is use as little as possible and then wipe that off with a clean, lint free cloth.

Never use water to clean any vacuum surfaces or o-rings (does not apply to freshly machined metal parts but cleaning them is a process that is involved.) Cleaning vacuum components (that could be contaminated by previous user) is tricky; most of us use as pure a solvent as we can obtain (generally ethyl alcohol - absolute is best); the issue/problem for over-ther-counter stuff is water content. Never use methanol - rather toxic.

Leak detection is a bit of an art and can be an issue. Learn how to handle leak detection for torr, micron, and high vacuum devices. Different methods and good vacuum gauges are a must.

Know that water vapor from the air will take a long time to get out of a system and can look like a leak; in other words, learn the difference between inner surface out gassing, virtual leaks (generally poor design), and real system leaks (too long to list but scratches on vacuum matting surfaces is a common one.)

Buy smart and avoid avoid buying used fittings - new saves more in time than any perceived savings in money; not necessarily true for larger diameter stuff.

Never buy a gate valve of any type that you can't return (which means you need to be able test it asap and so that means you first need the stuff to test it before buying such a unit) - vacuum valves can be real issues and tend to be expensive. Know what you want from your vacuum valve - manual/air drive/adjustable and total diameter issues as well as connector type.

If you are going for any high vacuum work (most fusors do), then knowing about diffusion pumps (air cooled/water cooled) and turbo's (various types and all require cables/control units) is important.

Vacuum gauges - know the units/ranges: torr, Pascal, micron, sub-microns. Know the range you need - atmospheric to sub-micron is extremely expensive and most of us use only a gauges for specific ranges of interest. For instance, every fusor MUST have some type of gauge that reads microns from 1 to 20/30 in microns (that is, need to resolve single micron digits - not tens of microns) and one high vac gauge (generally the 10^-3 torr range and below.).
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Re: Chinese pump first run report.

Post by David Kunkle »

My Trivac D4A in excellent condition can get to about 5 microns. You stated your Chinese pump gets down to 1-2 microns. I not sure any 2 stage pump can get that low- never mind a cheap Chinese pump. The accuracy of your TC gauge may be questionable. The 37 millitorr stated on the label seems more like it for a pump like that.
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
Pascal Mueller
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Re: Chinese pump first run report.

Post by Pascal Mueller »

@Dennis: You said that "generally ethyl alcohol - absolute is best", what do you mean by absolut? Do you mean the brand? Like absolute wodka? If so: Why not go to your local pharmacy and just buy pure ethanol? At least in my country you can get 98% ethanol over the counter. (You could even drink it - there is also the one that you can't drink.) Just tell them you need it for tinctures.
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Re: Chinese pump first run report.

Post by William Pete »

That's a good price on the pump, I believe I saw this one before combing through ebay and thought that it may not do the job as some of the used Edwards pumps were present in a lot of other jerry rigged builds like what I am going for.

I'm definitely going to keep this one in mind as I move forth.
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Re: Chinese pump first run report.

Post by george44 »

Finn Hammer wrote: Wed May 17, 2017 10:38 am IMG_20170517_160046.jpgI received the Two-stage rotary vane pump the other day,
http://www.ebay.com/itm/2-stufig-Vakuum ... 1867425448
and was soon getting excited, since the label quoted two different values for acheivable vacuum.
either 0.004 Millibar, which corrresponds to 3 millitorr, but also 5 Pascal, which corresponds to 37 millitorr.
In the listing, it quoted 0.3 Pa which corresponds to 2.2 millitorr. What to expect?
Fortunately, the DigiVac LightBarVac meter arrived today, so at last I could start to get a feeling about the capability of the pump.

With everything in place, the pump drops down to, 5 micron, and within a minute or so, levels out at 1-2 microns, That is not so bad is it?

On the negative side, the pump does not have a ballast valve. I have no experience with vacuum whatsoever, and am unable to access whether this is going to be necessary pumping my 10" sphere, but time will tell. I want to buy here as it looks like a Death Star from Star Wars.
I will probably dismiss this pump to vacuum jar duty, though, and get a proper lab pump, because this one is quite noisy, starts to get on my nerves already.....

Cheers, Finn Hammer
Hi Finn! Thanks for sharing your experience with the Chinese pump. It sounds like it is performing well so far and you have a good vacuum level. It is understandable that the noise could be a bit too much, so it might be worth getting a proper lab pump to use instead. Have you considered any other options? Good luck with your 10" sphere!
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Richard Hull
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Re: Chinese pump first run report.

Post by Richard Hull »

Revisiting a now ancient post by George 44 who didn't read the rules regarding the use of only real names and not handles.

Since this ancient posting, Finn has become one of the finest and most successful of fusioneers to ever land here. I haven't heard much from him of late, but he really took performance and excellence to a new level.

Should you actually change your name to a real given name and stay with us, We never use block quotes. Why? We are far too smart to need them as we have read all the preceding posts in the thread and have good memories in addition to being smart.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Chinese pump first run report.

Post by Jerry Biehler »

I have a few 1/4 NPT and a 1/8NPT on my coating system and got it down to 6.6^-7 the other day. The TC Gauge tube initially leaked when I checked it with a helium leak check with an RGA, went away when I tightened it up. So NPT is *ok* but if you have a leak it is probably the first place to look.
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Richard Hull
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Re: Chinese pump first run report.

Post by Richard Hull »

Jerry is correct, NPT points in any vacuum system are best left to the foreline, (TC gauge, typically), and shunned if possible beyond the foreline.
Many folks who can't afford a high vacuum gauge use a TC gauge on their fusor chamber. This is ,naturally, most often after the secondary pump, (diff, or turbo). This can be a real bear to seal successfully, but as Jerry notes, can be secured with effort.

To illustrate, If have seen many folks, new to vacuum, fail to even seal their foreline TC gauge correctly which is relatively easy to do.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Chinese pump first run report.

Post by Peter Schmelcher »

As I recall the ballast value introduces air into the pump's second stage so that water gas and other condensable gases do not compress back to a liquid or at least partially get pumped out of the oil along with the ballast air. That oil drying process should also work if you bleed ballast air into the first stage. The catch is you can't dry the oil at the same time as you pump down the chamber.
-Peter
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Richard Hull
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Re: Chinese pump first run report.

Post by Richard Hull »

True! You can't clean the oil of water and other volatiles by ballasting and pumping at the same time. To clean and clear the oil, blank off the fore pump and open the ballast all the way and run the pump for a long time. Note: you better have an oil mist filter on your pump or vent the pump to the outside world. Way back in the 90's I learned this the hard way. I ballasted and ran the pump indoors ballasted and blanked for 2 hours. I came back and found the room in a choking fog of oil vapor. Bad deal! Of course it helped taking the pump from a bottom of 13 microns to 3 microns.

You would probably be better served by just putting in fresh oil.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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