Discussion Category:  Centrifuge

Routine Maintenance

Besides changing diffusion pump oil and roughing pump oil, what other regular maintenance should be performed?  This is for a model LE-80K.

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Asked by

CTL
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avatar placemarkReply by
dpkleessr

Typically you would be checking the condition of the vacuum hose between the fore and diffusion pumps for cracking which is not at all uncommon because of the tightness of the bend in the hose and the high temperature generated by the diffusion pump. Also check out the condition of the filter on the vacuum pump. If there are any signs of oil inside of the filter assembly or if it has a very strong smell of oil then it should probably be replaced. You want to clean under the chamber door and if it is heavily caked with old vacuum grease then it should be removed from the centrifuge for proper cleaning or if you are careful you may be able to get to the right hand underside of the door by sliding it part of the way over and wiping underneath. Also clean the o'ring at the top of the centrifuge. If you remove the door then also remove the o'ring to thoroughly clean it before regreasing with high vacuum grease. This is probably the biggest pain in the butt about the whole process but if you get an accumulation of debris around the top plate and the o'ring it can cause vacuum issues. Check for smooth operation of the door latch assembly because over time, vacuum grease can work its way down into the hole where the latch plunger goes up and down causing door latch errors. Carefully remove the safety plate around the drive spindle and check for any accumulation of oil underneath it. If so, then mop it up with paper towels. Also check for any oil accumulation within the radiometer assembly. If there is ANY oil in it then it must be cleaned out. being very careful to not bump the tach and ID rotor sensors, remove the radiometer and carefully use a kimwipe to try to absorb the oil but you need to be VERY careful around the flake inside of the housing. You can use 95% ethanol to flush out any oil residue. Afterwards, after cleaning off the mounting plate of the radiometer of any old thermal paste, reapply a THIN layer of thermal paste before reinstalling the radiometer. If the old radiometer cover is really messed up then you should replace it or at the very least carefully remove any excess oil from it but do NOT use anything to cover the radiometer other than the original film or get a replacement one. Saran wrap or any other plastic wrap will NOT work properly on the radiometer.

If I think of anything else other than just cleaning up the panels, I will let you know but this should keep you busy for awhile. A typical pm call should take around 2 to 3 hours but that depends on the condition of the centrifuge and your own abilities.

Don

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avatar placemarkReply by
CTL
Wow! Thank you for this detailed post. Much appreciated! Can you please verify the amount of oil I'll use with the diffusion pump? Is it 90mL? I saw this volume on another post, but just want to be sure.
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Pohli, Inc.Reply by
Pohli, Inc.

Don,

Thank you for your detailed post. Much appreciated!

Peter

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avatar placemarkReply by
mahshad.maghoumi4767
Is there a manual that specifies how to replenish or replace the diffusion oil pump in the ultracentrifuge? Is it feasible to accomplish this using the plastic hose? please I really need this information
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avatar placemarkReply by
dpkleessr
Well, apparently my reply did not go thru so I'll try again. Before replacing the diffusion pump oil you need to drain the old oil first. Remove the drain plug from underneath the diffusion pump and catch any oil in a beaker or other container. If nothing comes out of the drain plug then use a small bladed screwdriver and insert it into the opening to make sure that there is no debris blocking the drain opening. If there is then you most definitely need to remove the entire assembly and clean it out. If this is required then also remove the rubber o'ring from the top of the diffusion pump, clean the o'ring and the groove that it came out of of the old high vacuum grease. Apply fresh vacuum grease to the o'ring, reinsert it into the groove, add the fresh diffusion pump oil AFTER replacing the drain cap, and then reinstall the diffusion pump. While you are at it, check the large vacuum hose for any cracking and if there are any present, especially at the ends, then replace it too. changing the vacuum pump oil too should be done at this time so you are starting with a fresh vacuum system too. The other possibility is that the diffusion pump heater or the relay that controls it may have failed. If the diffusion pump does not get HOT then that is what you are looking at. Hope that helps. Don
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avatar placemarkReply by
mahshad.maghoumi4767
Thank you so much, Don, for your accurate, illuminating, and quick response. I have a brief question: can I just add more diffusion oil from Robber or a hose linked to the diffusion pump if I don't want to unscrew the diffusion pump?
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avatar placemarkReply by
dpkleessr
Can you just add oil thru the hose? Yes, you can do that but pouring the oil directly down thru the hose is going to negatively impact the rubber of the hose. The heat of the diffusion pump itself combined with the hot oil vapors cause the rubber hose to frequently swell up , crack, and swell up. The last thing that you want is to have a sudden loss of vacuum because the hose failed which would result in an inrush of air into the chamber and depending on the rotor that you are using could cause a catastrophic rotor mishap. And yes, I have seen the aftermath of such a thing happening with the cost or repairs being something that the customer really had no means of paying for. Don
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