Vacuum Diffusion Pump Cleaning?

[dexters_lab]

i am about to start cleaning up a diffusion pump ready for resale, it's very very black with carbonised deposits and oil, the oil came out like black treacle with chunky bits in it!

From what i can see acetone and steel wool to clean all the parts seems to be an accepted method but i was wondering if other things like Brillo / SOS type of soap filled steel wool pads might also work and not involve me buying in and using liters of solvent?

all the parts seem to be either steel or stainless steel so i can't think why i couldn't use them but thought i'd see what the collective opinion is before i start.

[CM800]

As long as it's only stainless steel (no plastic or standard steel, bronze etc)

Piranha solution might be a good option (if you feel you can handle the responsibility)

Oxalic acid maybe? I don't know, i googled 'Cleaning organics off metal) and that's what came up.

[mikeselectricstuff]

Don't take anything vaguely abrasive anywhere near any vacuum flanges - any marks can impair the vacuum performance

[dexters_lab]

As long as it's only stainless steel (no plastic or standard steel, bronze etc)

Piranha solution might be a good option (if you feel you can handle the responsibility)

Oxalic acid maybe? I don't know, i googled 'Cleaning organics off metal) and that's what came up.

from the searching i have done they do appear to be pretty easy to clean up so i would rather not deal with exotic cleaning methods and i'd prefer acetone over piranha!

Don't take anything vaguely abrasive anywhere near any vacuum flanges - any marks can impair the vacuum performance

i wasn't intending to touch them, it's really the inner body and the jet assembly that needs proper cleaning.

Talking of the flanges etc, all the flanges from the SEM sample chamber downward towards the oil baffles and pump use rubber O ring gaskets, the flanges are not as highly finished as the ones in the upper beam column which use crushable copper gaskets. Maybe they need more compliance from thermal expansion/contraction from the heat of the diffusion pump?

[Kleinstein]

For the bottom part it can help to just boil some water inside.

For the black residue, it will be mainly mechanical abrasion. So acetone helps most in the beginning and for the last finish.

[jpanhalt]

There are a variety of water-based engine cleaners available.   Not talking about the home stuff for getting just outside crude.   These are cleaners for the rebuilder.  Piston Clean is one version.   They are usually used hot as in boiling and are designed to remove carbon deposits.   

You might also consider one of the older carburetor cleaners that had phenol and other organic solvents under a water layer.  Gunk was one such cleaner, but they have mostly disappeared from the market due to environmental concerns.   I can still get it in Ohio.

Finally, engine rebuilders have washers (like industrial dishwashers) that remove everything.   I had some really dirty parts and a local rebuilder cleaned them for a nominal charge. 

John

[dexters_lab]

thanks for the other suggestions... i tried cleaning up the top cap with a brillo and it has come up pretty clean but did take some effort to get it all off!

good call about Gunk, we still have it here in the uk so i'll give it a try, thinking about it oven cleaner might also be a good option?

i will try it next week when i have more time, this weekend is all about the Le Mans 24 

[jpanhalt]

Be sure you get the Gunk with the water layer, phenol, and chlorinated hydrocarbons.  Gunk reformulated to a "green" version several years ago.   I was very disappointed with that version -- it barely dissolved fresh grease.

Phenol has a very characteristic odor.   Also known as carbolic acid.

John

[edpalmer42]

I've been impressed by the ability of the various Oxygen-based laundry cleaners to deal with organic stains.  I don't know if it would touch these deposits, but it's cheap and benign to the metal and the environment.  Just use hot water and let it soak.

Ed

[dexters_lab]

I've been impressed by the ability of the various Oxygen-based laundry cleaners to deal with organic stains.  I don't know if it would touch these deposits, but it's cheap and benign to the metal and the environment.  Just use hot water and let it soak.

Ed

i've not had good experiences using the oxygen stuff on aluminium, probably fine on a raw casting but anything with a machined surface just gets pitted

[MadTux]

I often use round steel wire brushes mounted into an air die grinder for cleaning machines from old, dried oil residue.
Perhaps a softer brass brush might work here, maybe use a bigger version:
http://www.orecozone.net/images/parts/brass-power-wire-brushes-composite-sized-lettered-drop.jpg
Die grinder, only if you have a good compressor:
https://sc01.alicdn.com/kf/HTB1Rh88JVXXXXXJXVXXq6xXFXXXT/pneumatic-tool-air-drill-china-supplier.jpg

Other ideas: high pressure water cleaner or air blasting it with ground  nutshell media

[edpalmer42]

I've been impressed by the ability of the various Oxygen-based laundry cleaners to deal with organic stains.  I don't know if it would touch these deposits, but it's cheap and benign to the metal and the environment.  Just use hot water and let it soak.

Ed

i've not had good experiences using the oxygen stuff on aluminium, probably fine on a raw casting but anything with a machined surface just gets pitted

Okay, but if it's aluminum, wouldn't steel wool destroy the finish?  Maybe use nylon scrubbers instead.

Ed

[Conrad Hoffman]

One you get the bulk of it off, Bar Keeper's Friend works great on stainless steel.
https://www.barkeepersfriend.com/

[JohnG]

In my beer-brewing days, I learned that you should not use regular steel wool on stainless steel. The reason was that you could embed small bits of the steel wool fibers into the stainless steel, and corrosion would occur at these sites.

I never verified this, but just avoided steel wool when cleaning stainless and used a non-metallic scrubber or stainless wool scrubbing pads. The latter are made out of stainless steel fine ribbon rather than fibers. They were also excellent for scrubbing labels off of bottles.

John

[Conrad Hoffman]

Yes, standard procedure for machinists too. You never use tooling that was used for steel, on stainless. Customers get annoyed if their stainless parts start developing rust!

[Teledog]

Arrgh! The drawback of hydrocarbon vacuum oil!
Not sure about that gunk, but for aluminum model airplane engines, I used to toss the entire blackened unit in a coffee can filled with that (lower-buck) green automotive antifreeze.
Plop a loose fitting lid on it, put it on a hot plate and let it cook ~80C for 2-3 days.
Always came out looking brand new!
Perhaps fill the unit with the same & regulate the pump heat with a lamp dimmer?
Just a thought anyway.

[CJay]

Dishwasher

Just make sure you don't get caught.

(mostly joking, I have no idea if the detergents will affect the surface or not )

[macona]

The black stuff is just burned diff pump oil, someone let some air into the pump while it was still hot. Just going to take some elbow grease and some scotchbrite pads or some other mild abrasive.

The christmas tree (center part) is made from aluminum so no ammonium hydroxide based cleaners. The housing of the pump is either nickel plate steel or plated brass. I have never seen one made from stainless.

You really dont need to worry too much about the flange on this one, it is an o-ring seal which is very tolerant. And you would have to get down inside the groove to do anything.

[dexters_lab]

thanks for all the replies

nice idea filling the whole pump up with cleaner and using the heater to help it, i could use my variac to control it.

The christmas tree/ nozzle/ jet thing is steel on mine, i cleaned the small top cap which unscrews to dismantle it, i used brillo and it did come up pretty good but took a lot of effort to get the burned oil off. The steel wool has made no visible surface scratches on the surface of it so the jet assembly could be made from stainless. The main body of the pump does look to be nickel plated steel though at least on the inside, the outside just looks to be a silver high temp paint

[Teledog]

I wouldn't use "any" cleaner, the green antifreeze is definitely not harmful to 99.9% of metals.
Read about that method & thought it was BS, ..until I tried it..utterly amazed!
Might want to rinse it with lots of soapy water then dry & wipe with acetone after.
BTW, I DO believe the main unit is a very high quality stainless (not plated), as other metals tend to gas out @ 10-7 torr.
Also, Santovac (x) or other synthetic oils don't blacken the unit if you blow the vacuum while it's hot.
Synthetics are horrendously expensive, but..good deals on eBay once in a while.
Keep it!
I'm a hoarder- have an old monster Varian. ;-P
Read up on vacuum vapor deposition..groovy stuff ..tungsten crucibles are sometimes dirt cheap on eBay also.

[T3sl4co1l]

Definitely don't use anything acid.

Organic solvents are fine, as long as they're baked away later.

Bases are okay, if there is no aluminum around.

If you want to passivate the stainless -- especially if you've done kind of a lot of wear on it, or stuck some steel into its surface (as mentioned above) -- you can do that with a soak in citric acid, supposedly.

Tim

[jpanhalt]

Since it is stainless, why not use an acid like sulfuric or oxalic?  Just don't use an acid in the presence of a halide (e.g, chloride).   

By the way, citric acid is a relatively strong acid (pKa 3.13) and is stronger than acetic acid.  For passivation of glass, we used a solution sodium acetate.   No experience with passivating stainless. 

John

[macona]

Pretty certain it is not stainless. Steel can have some outgassing but nickel plating stops that.

I have two large vacuum systems, one with a 24x30 chamber and a 2000l/s turbo pump and a smaller system with a 18x30 bell jar with planetaries and a veeco 6" diff pump. The big system I am setting up for ion beam assisted electron beam deposition and sputtering and the smaller ones currently set up with 3 source thermal evap, I am adding ion beam assist to it soon. I also have a little desktop system I made for carbon coating for my SEM and another turbo pumped RGA setup.

The e-beam power supply is a beast, 0-10kv at up to 1.5A, I have an old military generator just to run it.

[richnormand]

You might find this link useful:

http://www.fusor.net/board/viewtopic.php?f=46&t=10995&p=72771&hilit=+cleaning+diff+pump#p72771

I am not familiar with the proper use of the MEK cleaner mentioned however.

[dexters_lab]

thanks for all the replies everyone

i started the cleaning the other day, i opted to try oven cleaner and stainless steel wool for cleaning, it has worked ok but the oven cleaner i have isn't really strong enough, it's probably too weak concentration. So i'll probably use it to just get the the bulk of the burned oil off and then switch to something a bit stronger to just finish it off... the small black specs on the cleaned bit are extremely hard and glassy. I might order some of the MEK  and see how good it is. Now i know i only need to finish off the nozzle i can order a smaller quantity. As you can see from the pic of the other parts there is still lots of hard work to come!

The main body was stripped down and flushed with solvent to get the bulk of the crap out, the walls of the pump are actually clean, it seems all the burned on oil is only on the nozzle thankfully