Fixing a leak in UHV chamber
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- Опубликовано: 24 апр 2021
- The first part of the gas analysis system I am building is an ultra high vacuum chamber, it is almost ready - the only problem is that it is not vacuum tight. In this video, I am fixing the leak.
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It is nice to have you back
Love those white bright work rooms
Your laboratory is very clean and beautiful with some very awesome equipment. I cant wait to see how the nixie tube will be connected and sealed to the chamber.
You need a torque wrench.
UHV is voodoo magic, fake leaks, vented screws, torque wrenches, conflat fittings, so much to learn.
Dalibor, I work at a national lab as a mechanical technician, if you have any questions I could ask my knowledgeable coworkers about ultra high vacuum systems for you, they love to share. Don't hesitate to reach out!
Upvoting + Commenting on this to help the algorithm !
You should tighten the bolts diagonally to prevent skewed tightening of the seal.
As a HVAC tech I feel your pain. I've delt with plenty of frustrating leaks. Make sure to use a soft metal or plastic tool when taking off orings, it helps avoid accidental scratches on the sealing surface. Excellent work 👍
Remember, High Vacuum systems are sensitive to any contamination in the chamber like finger prints. They'll off gas for days and prevent a good vacuum. Even the wrong kind of oil and gaskets will look like a leak. I'd expect 10-4 torr starting off, keep it running for 24 hours to allow things to offgas. Getting heating tape made for baking vacuum chambers helps a lot. I used to build these if you like any help.
when it reacts to helium being applied to the outside its pretty clear that there is a leak,no?
Commenting below this to help with the algorhythm!
This is amazing!!! I would have thought that carefully controlled torque on the head bolts, evenly applied, is critical though.
This was a really good example of helium leak detecting, I'd love to see more videos on your vacuum system
Looking forward to seeing what you find out with this new UHV rig.
Just something you may find useful, is heating the the vacuum system up to help remove other chemicals that could give you a false reading on the detector.
As everything out gasses can impact your reading.
Most of all take great care with the turbo pump, as the system needs to be down below it’s working pressure before you turn it on.
I thought the same: do not run turbo pump at atmospheric pressure! You can do it after the initial vacuum is reached. However I do not know Adixen equipment in details, but I think these rules are valid for all turbo pumps.
Glad you are back!! Just two days ago I went to your channel page just to make sure I didn't miss any videos..
I know how frustrating this can be, ha ha Great information about the process and quick owerwiew of how this type of Helium sensor systems works!
Having a leak detector is sooo cool! I haven't managed to come even close to UHV just using a turbopump. I could approach UHV range (10^-9 Torr and below) only with help of magnetic ion pumps.
Always a pleasure to see you and your work.
Hi Dalibor, nice to hear from you again!
Great to see a new update!
Nice to see you back
That pump sounds exactly like a Wookie when it starts up! I am so interested in everything you're doing, so these videos are like crack to me...let me know when you want to introduce a Robot into the mix!
The lab looks great!! :D Love it!
Fascinating Video. Looking Forward to more
Beautiful machines, great video, hoping to see more :)
I liked the way you attacked the leak problem. Glad you're back up and doing things as we slowly beat back the pandemic.
I love your work...
Hey! Great to see a new video. With COVID and everything, I was getting worried you'd gotten sick. I'm glad to see you back on RUclips!
Good to see you back, always interesting to watch. Looking forward to seeing more in the future. By the way the lab looks fantastic in all white. 👍
Perfectly understood!
The XDS is a great pump.
That’s one clean room😊
You must have some really interesting surplus and manufacturing connections. To turn around a pull such interesting parts out container like that to fix your problem. Always neat seeing the different problems and solutions you come up with.
11:01 Ah, Chewbacca!
The machine sounds so cool. reminds me of some SF movies in the 70s!
He's alive!
These small turbopumps from Leybold/Oerlikon are really nice and easy to disassemble.
What I noticed was that you did not use any vaccum grease or oil to help the o ring to seal?
This makes a huge difference try Dow Corning vacuum grease or oil for diffusion pumps, dry o rings do not seal very well!
apiezon m grease is a easier to clean grease then dow i recommend it highly. All you need is 99% iso alcohol for cleaning
Please, no grease! No No No. Use proper O-rings and tighten them. Good enough for 5e-8 mbar. No need for grease
@@demolitionb i would only use this grease for stopcocks and for compression fittings.
Wow. So fascinating how much a small leak is giving problems.
Love a good vacuum pump!
What a nice place you have made for tests. I will come as a tourist to help you :D
Wonderful :-) I am thinking about making some volunteer gathering and working together on some project..
You need a torque screw driver if you play with that level of detection. Gaskets are specced to work at an exact amount of pressure determined by the torque applied on the bolts. Exceed it or install the gasket incorrectly, and you'll have issues. In the moment, or later.
Dalibor! Long time no see!
Usually the KF flange on the turbo should be welded, not attached with epoxy. Edwards nxds 6i ... good choice! However, please read the manuals when using vacuum components... not every button on the scroll pump is self explaining (for example long press on-button for auto restart after powre loss). The itr90 might be overkill, you don't need a Bayard-Alpert I guess... I can recommend pfeiffers PKR251 (pirani + cold cathode). do you have a leak valve between nixie tube and your test chamber? Even this mini turbo will pump ~60 liter/s. Your residual gas might be gone before you could analyze it. You maybe need a CF-valve (expensive) between turbo and test chamber to store the gas inside your test chamber for testing. However, you will need to make your test chamber REALLY tight, otherwise pressure will increase fast! you should also add a vent valve on the turbo. venting from the back will reduce it's live time and you will push the bearings-oil from your turbo into your test chamber (way not that much compared to a rotary vane pump) and in the pressure range you will achieve with the small turbo this will not be important I guess. What's your personal goal for this chamber? 1e-7mbar?
We always apply a small amount of Vacuum Grease to all the seals in our vacuum system
in our lab, a very thin layer.
Glad to see your back and i have no idea for sure but i would think that every screw and nut and bolt would have a torque spec so you don't run into problems like that in the future ...... just a thought and maybe something to look into
That tone sweep from the helium detector sounded like Voodoo People by Prodigy.
The Oring should be vacuum baked prior to install.
just thought of you yesterday ☺️
I hope you are using clean vented screws!
That is the sexiest vacuum pump.
Lmao that heavy breathing when you couldn’t figure out where the leak was is very relatable ! Haha vacuum is probly one of the most frustrating things lol
When I have several flanges close by where one might be leaking I use electrical tape around the ones I'm not testing to help isolate them from the helium. It really helps with narrowing down exactly which one is the culprit. Obviously this doesn't help if your mass spec or the room is flooded with helium though. If it's a large leak (perhaps anything larger than 10E-7) diluting your helium concentration with nitrogen or argon gas to something like a 25% or 50% mixture can also help.
Two genius ideas, thank you! I will try them both. Cheers
Отличный детектор вакуумных утечек кстати.
I was wondering if you could find the leak by pressurizing the chamber and applying water or alcohol to the various joints and look for bubbles? Regardless, glad you found it.
How is that floor given that smooth surface? [ oh, and welcome back. :-) ]
Thx :-) epoxy - easy to maintain (Roomba robot), plenty of light, it might be a bit more resistant to scratches, but other than that is very good!
It’s been a while
Quick tip, always start leak checking from the top as the helium is gonna pass everything above you, RGA was very useful to me at work, any part of this bakeable ? I see copper and rubber (Viton?) gaskets....cheers.
Yes - I work top to bottom as well, I knew location of the leak from previous testing, so I went straight to the point :-) the chamber should be fully bakeable (copper gaskets) with just the turbo on rubber orings in low vacuum section. In the next video :-)
Zdravím Dalibore, už jsem měl strach že jsou v té dlouhé odmlce nějaké ty problémy které trápí nás všechny, uf to byly nekonečné čtyři měsíce.
Už nám to nedělejte, příště až Vám dám volno tak max na 2-3 týdny :-D . Přeji hlavně zdraví a těším se na další video.
Děkuji, covid na tom má podíl jen 3 týdny, ten zbytek je zahlcenost rekonstrukcí :-) budu se snažit se zase nezahltit..
...and to think i though Gas Bottle Fitting/Hose leaks were annoying !
What happens if you look at the light that comes off a nixie - what does that spectrogram show compared to the complicated machine?
We tried, spectrometer gives too low resolution - we will be looking for contaminations with partial pressures probably in 10E-5 mBar region, which is ration around 1:10000000 contaminant:gas filling. Impossible to identify the contaminant between spectral lines of neon/argon. But we went this way first as well :-)
Why are most high vacuum setups look like they could resist an earthquake? They only need to hold 1 atm from outside, yet the pipes and flanges are massive.
As with many things mechanical, rigidity is more important than things purely not collapsing. for example if the pipes were flexing, that means the seals would move as well, which leads to problems.
And of course there are always big safety margins to tolerate shocks (sudden air inrush, hitting it from the outside etc). Especially Turbomolecular pumps could literally explode purely due to how fast they spin if they were built less solidly. Apparently this used to be a common problem with them when they were actually built with thinner walls.
Furthermore, parts like this are produced in low volume and the material cost is insignificant compared to asking prices.
you need to pump it down before turning on the turbo pump. You are destroying your pump. It needs to be BELOW 1x10-2 BEFORE turning on the turbo pump. That is the safety shutoff turning off the turbo.
nXDS pumps are even more silent (especially in the beginning) if you mount silencer on the exhaust.
But why epoxy seals on the pumps?
Thanks for the tip, I will look for the silencer. The epoxy joint is made in factory to connect roughing port to the body of the turbo.
Because it does not matter on intermediate pressure level - possible leak rate or outgassing is quite irrelevant from perspective of the roughing pump. The whole turbo pump assembly is not meant to be UHV-tight when not in use with isolation valve on the turbo pump outlet port. And as it is the cheapest way from perspective of manufacturing and assembly - why not, it does the job.
use a silicone lubricant on the o-rings, makes a better seal and keeps them from pinching or tearing
this can easily ruin your vacuum from outgassing. I think in this application it might not be as bad as these seals seem to be on the output side of the turbopump, but still not great
@@Basement-Science orings need to be lubricated, you will get more out gassing if they tear . lubricants help seal the oil in a motor actually seals the piston rings .
@@Basement-Science thats why you vaccume the silicon sealant in another vacume tank prior to using it for this application.
@@rafaeldiegonavarro This is not about dissolved gases. The lubricant itself will slowly evaporate and contaminate the vacuum. That's why if anything, you need to use a lubricant specifically designed for vacuum applications, such as vacuum pump oil, which has a very low rate of evaporation.
@@Basement-Science teflon coated orings !!! teflon does not out gas hence used in cooking pans!
So, did you have any better luck with your giant display nixie tubes, yet?
o rings instead of crush ring...for a vac chamber...but why
What analyzer are you going to use, MKS?
Yes, MKS HPQ2S high pressure sensor.
@@daliborfarny cool if you need anything let me know
How much did the roughing pump cost?
It was 1850 EUR refurbished from Edwards.
@@daliborfarny good price!
Trying to fix a leak in our pressure chamber, it's been two days🤦🏾♀️
Everything in this video looks really expensive. 😬
I think the most annoying part is the noise that the testing machine makes
I'm concerned about the level of expertise demonstrated in handling seals and gaskets aspecially considering the equipment avaiable. It's crucial to understand that copper gaskets, once used, cannot be effectively reused. They deform during the initial installation to create a proper seal, and reusing them compromises this seal. While it's true that some installations may leave gaskets slightly uncompressed for potential retightening, this doesn't imply that they should be reused.
Moreover, the complexity of O-rings is often underestimated. They are not just simple components; their effectiveness depends on applying the correct force, which is usually achieved through specified torque settings for the bolts. The design of the sealing surfaces and the arrangement of bolts are meticulously calculated to ensure an even distribution of pressure, ensuring a proper seal. Incorrect torque application can lead to uneven pressure distribution and compromise the seal's integrity, as evidenced by the need to replace the seal multiple times.
Additionally, the material and hardness of O-rings vary significantly, making the choice of a specific type crucial for each application. Generic O-rings are not always suitable. Their dimensions, including cross-sectional area and diameter, are critical. For instance, a 50mm diameter application might require slightly smaller O-rings to introduce the necessary stretch, depending on the specific requirements of the system.
I am not suprised you haven't reached UHV.. I don't think you realize the process difference between UHV and HV
This was not a final assembly, so I am reusing the copper gaskets here - followed by He test. Once the design is confirmed, the chamber will be disassembled, cleaned and new gaskets used in CF connections. The standard KF connections with o-rings cannot be overtightened - there is a metal centering ring inside the oring that serves also as a limit of compression.
I was like WOW when i saw that the pump had USB interface :D
Now you know the true hell of high vacuum leak detection. 🤣🤣 Imagine trying to find a leak on a 3 meter diameter chamber with over 100 ports and over 120 large sealing surfaces 300mm in diameter each that all have to be changed at once....every month.
Sounds like a lot of (full-time) fun 😀
@@daliborfarny Nuclear fusion target chamber....
Incidentally, you have the same scroll pump we use throughout our labs and we just had a safety memo go out to everyone about them. Apparently there is an internal wearing part inside the pump that is made from a complex variety of compounds including teflon, a trichlorobenzene polymer, iron and aluminum oxide dusts, zinc chromium compounds, and some other strange things that get turned into a brown dust which is regularly emitted from the outlet port of the pump. Our health and safety group considered it enough of a hazard to require we all now attach the BOC exhaust filter / silencer for these pumps to prevent the dust from getting out. If nothing else, it will make the pump even quieter and prevent any nuisance dust in your sparkling clean white lab!
This is a very good point, I wasnt aware of it - I will definitely get that outlet filter too! And will read manual as well :-)
Please never stick your hand near any pump holes. Ever. Even if you are sure it's not an intake. A friend lost a chunk of their hand very painfully that way...
This hugely depends on the size (cross section area) of the hole.
from 1 bar? what happend? I always put my fingers to test if there is still air flow....
@@demolitionb The pressure itself is not the problem. Pressure is Force per Area.
If you were to get your hand over a large opening and a sufficient vacuum builds on the other side, the Force could get so big that you are unable to pull your hand away. At the same time your skin gets pulled away from your bones, although it shouldnt do permanent damage in most cases if you manage to get away in time.
With a much bigger vacuum pump this might actually be a significant danger. But with this, you would really have to try hard to get hurt.
@@Basement-Science your right, but than we talk about more than the area of a cent / 1 cm2
@@demolitionb Yes. Only dangerous in extreme/special cases.
What a pain in the arse.
Leak on vacuum equipment is a disgrace. ps: You need to put a little of silicon grease on the o-ring
I am trying without greases/oils first - they might become potential contaminants (bakeout process might evaporate the greases..)
@@daliborfarny I would highly recommend Apiezon L grease as a suitable ultra high vacuum and high temperature vacuum grease. We regularly use them in chambers that are in the ~5E-9 Torr range at high temperatures (300-800C).
@@willman1011 That sounds good, I will look at it. I want avoid greases as long as possible :-) it will be all based on CF flanges, metal to metal.. should work without grease
I'm first... 😌
Dang it I was almost first haha
Would'nt it be more simple to just put a little bit of pressure and diagnose leaks with a little soapy water ??
No. The amount of leakage that is too much here is so small you will have no chance of detection whatsoever with those methods.
@@Basement-Science Ok thank you for answering !
That's a lot of money.
What's the purpose?
finally remembered your password huh? 😁