Introduction: Repairing/Cleaning/Unsiezing Edwards RV8 Vacuum Pump
The Edwards RV8 Vacuum Pump is a very common rotary vane vacuum pump used in the scientific community. It is sold under a variety of names such as the Labconco 195, Cole Parmer R140/EW-79303-00 and likely several others. These instructions should also apply for the RV12 (and the RV3/RV5 should be similar but not identical). The one I am working on is a dual mode pump, meaning it can be run as a single stage (for high volume) or dual-stage (for high vacuum).
Why am I doing this? I was pulling trace solvent out of a powder and at some point over night it decided to travel up the hose, through my Schlenk line, through the solvent trap and into the pump. Gunking up EVERYTHING. It had begun making a loud chuffing and stuttering, which had me worried it had seized or was going to seize at any point.
-You are at your own risk doing this. I am in no way responsible for any damage that may occur from your following my instructions. I am just posting this up for people who want to see how it is done. I am in no way AT ALL an expert at this. Just someone who is a bit handy.
-Remember, the oil in this pump will contain traces of whatever was being vacuumed down. This means it may contain solvents, toxic metals, acids, fluorinated compounds (which can break down into HF), etc. Be careful and follow appropriate precautions.
-Some of these parts can be heavy and/or are slippery. They could break your toes, hand, fingers etc. if they were to slip and fall on those. Remember most of the stuff you will be touching will be covered in pump oil.
-Please dispose of pump oil properly. Mine goes with other organic wastes. If you don't have access to this contact your local authorities on how to properly dispose of the waste. Don't put it down the drain or just in the trash.
Lastly, I will be the first to admit I am not the greatest author in the world. If anything in this 'able needs clarification or you have suggestions for improvement feel free to mention it. I will try to explain things better and/or make changes.
Step 1: Why Do Pumps Seize?
As you can see, the vanes rotate around the device "pushing" the air out. You can see they move in two directions, first they move around the rotary chamber and second they move in and out of the rotating spindle. In the RV8 there is no spring in the middle, they are solid against each other, which means they have no play in their travel. As they rotate, the pressure of the walls against the vane pushes the vane into the spindle, which then pushes the other one out. Also, note on top there is a backflow preventing valve. If your pump is rotating just fine but for one reason or another isn't getting a vacuum it could be either the vanes have failed and aren't holding a pressure or this back flow valve is stuck open allowing oil to enter the chamber.
Knowing this the pump can seize in three ways:
1) The walls of the chamber can be coated in junk which cause the vanes to stick in place, not allowing them to move forward.
2) The vanes can become "glued" into place in the spindle, so that they can not move in and out of the spindle as necessary. When the vane hits the wall it can't move into the spindle, essentially freezing the spindle in place.
3) The vanes can catastrophically fail and jam themselves up with their own pieces.
Step 2: Required Equipment
The tools needed for this task are not overly complex or hard to fine. Many are improvised at will with what you have around.
1) Something to drain the oil into. I used a beaker but anything should work. Just remember to dispose of it properly
2) A 3/16" allen wrench (aka a hex key). Every bolt/screw in this pump uses this. It is a very simple aspect that makes disassembly a breeze.
3) Needle nose pliers - for helping remove bolts which have been unscrewed but need a bit of help being pulled out of their hole.
4) A flat head screw driver. This is mainly for gently prying joints apart. So plastic will actually work better but I didn't have one so I was just careful.
5) Forceps - For scraping away debris and getting paper towels into tight places.
6) Needles or picks or something to scrape out tight places. I had a variety of metal needles on hand (sharp ones) so I used those.
7) Some sort of flat device for scraping. Being a chemist I used a chemist spatula, which worked perfectly for scraping.
8) Edwards Grade 19 Pump Oil (enough to drain and fill ATLEAST once to get rid of free debris. Each fill takes ~0.75L).
9) Paper Towels - LOTS AND LOTS of paper towels.
10) Rubber Gloves - I used my standard nitrile gloves to protect myself from the nasty stuff in the oil.
11) Some sort of solvent for cleaning off the oil. I used chloroform because I have large amounts of it at my disposal, it dissolves the oil well enough and dries rapidly (you don't want any solvent in your oil). A more commonly used solvent is hexanes, it dries just as rapidly and is more non-polar so it dissolves the oil better. A person without access to solvents could likely get by with mineral spirits/kerosene/toluene/some paint thinners. Just make sure all of the parts are well dried before putting everything back together.
12) A place that you can get really oily and messy and then clean up. There is no way around it with this process. Oil is going to get EVERYWHERE! I can't emphasize that enough. I did this in my fume hood and on my chemistry lab bench (the one exposed to chemicals).
A rebuild kit. If you need to replace the vanes or seals a rebuild kit is your best option. These will run you around $100-300 depending on where you source it from and what parts you need rebuilt.
Step 3: Dissassembly (part 1)
First, before doing anything else. UNPLUG THE PUMP! You do not want it turning on at ANY point during this procedure. PERIOD! Just unplug it and set the cable to the side.
Now, drain the oil by opening the oil refill holes and the oil drain plug. Make sure you have your collection container underneath the plug before opening it; the oil will shoot out of there. If you don't know where the parts I am talking about are located, mouse over the squares on the first image to find these parts. Drain the oil completely (you will likely need to prop the pump up at an angle for a bit to let it fully drain).
Now to remove the front cover, it is quite easy. See those four bolts on the sides (two per side). Their location is highlighted in the first image, while the second image shows a close up of these two bolts. Remove these four bolts and the cover will just come off. Depending on the condition of the insides, the cover may just come off or you may have to wiggle it to get it off. While doing this you can also remove the front level window for cleaning. Set it to the side in a safe place (it is glass).
You will also see a gasket between the two metal parts, note its orientation for replacing it later. If the gasket it is in bad shape it may require a replacement.
Step 4: Dissassembly (part 2)
Alright, now that we have the cover off you will see a long round cylinder (the pump body) with two bolts in it and a large cap on top with one bolt in it, shown in the first image.
This cap covers covers the back flow prevention valve. The air exits here so this will likely be dirty and need cleaning.Remove the bolt in this large cap and set the cap to the side.
With the cap removed, you will see the back flow prevention valve (see Image 2). It consists of a footplate with some reed valves underneath. The footplate is held down by one bolt. Remove this bolt as well. Set all of this to the side for cleaning as well.
Now returning to the cylindrical pump body. Remove the 2 bolts indicated in picture 3. Now depending on how dirty or what not your oil pump is, the 2nd stage may just fall off, or it may take some work. In my case even though it was dirty as heck it just came off. If it requires some work, looking at the cylinder you will see three seams in the cylinder. These are actually the separate sections. The first appears and closest to the bolts appears to be the oil pump. The second, getting farther away is the 2nd stage of the pump, and the third is the first stage of the pump.
Now pry off the cover over the oil pump by inserting a flat head screwdriver in the first seam (the one closest to the bolts you just removed) and carefully working it open by gently forcing it at different points around the circumference.
The cover should come off and you will be faced with the oil pump as shown in picture 4. Picture 5 shows a closeup of this. You can see it is a tiny rotary vane pump, with a solid single vane in the center.
Carefully, remove the oil pump rotary spindle and then putting your screw driver in the next seam, pry the oil pump body off. As shown in picture 6. You will then have exposed the SECOND stage of the vacuum pump (it goes backwards here).
Step 5: Dissassembly (Part 2)
Now you have the second stage of the oil pump exposed.
You will notice that this section consists of a cavity with a circular metal piece in the middle with two gray plastic pieces, I call this the rotary vane assembly. Those plastic pieces are the vanes. They are VERY soft plastic, be VERY careful with them. They also are often what sticks when the pump gets seized up (either these or the ones in the first stage which we will see later). As I stated before, seizing can be caused by two different modes. The first is that the surface around the outside develops a layer of gunk which prevents these vanes from sliding along the edge and they get stuck in place. The second is that a layer of gunk develops between these vanes and the channel in the center circular piece. These parts have VERY tight tolerances and a gunk build up in there prevents the vanes from moving, sticking them in place, so that when they hit the wall and are supposed to contract in they don't. This can actually cause vanes to shatter, which will require a rebuild kit.
You will notice there are two bolts in the wall, these hold the second stage onto the first stage. Remove these and pry off the second stage, just as you did the other two seams. Note, that there is a little cylindrical adapter with groves in it which transfers motion from the rotary vanes in stage 1 to those in stage 2. Depending on where it wants to stick, it can either stick to the rotary vane in stage 1 or to the back of the rotary vane in stage 2. Don't loose this piece, so make sure you locate it before preceding. We now have exposed everything we needed to for cleaning out the pump.
Step 6: Cleaning the Pump (First Stage)
The easiest way to clean this is with some sort of fast drying non-polar/low-polarity solvent such as chloroform, toluene, hexanes, mineral spirts, etc.
Now lets test the first stage, with a pair of pliers, rotate the first stage, it should rotate relatively easily. If it seems to stick anywhere, note it for cleaning and testing.
Also, check the vanes, make sure they are coming in and out as they should. If the rotor sticks at a place, it could be because the vane won't move in any more. This would require removing this stage (which I don't discuss).
Once you know that it rotates just fine, time to clean. I just used a paper towel and solvent to fully clean the insides of this stage. It cleaned quite easily (albeit was a bit difficult for my large fingers). Scrape off any major stuck on gunk and in general make sure that it is perfectly clean paying attention to holes, flanges, the sectiongs that join to stage 2, etc.
Make sure to clean this little dark metal thing up here. It is related to the gas ballast area (which helps get rid of water). This was quite clogged on mine. It took a needle and a lot of work to get it clean.
Scrape the whole pump resevoir area around the first stage. Make sure it is nice and clean with as little dirt or dust leftover as possible. It takes a bit of work and a lot of scraping but remember the area around this is part of the oil reservoir and as such your oil is basically going to be sitting in contact with this almost constantly. So the cleaner the better.
Once this stage is clean, time to move on to the second stage, which in my case was the problematic one.
Step 7: Cleaning the Pump (Second Stage)
First thing is lets get the rotary vane assembly out of the second stage (if it hasn't come out on its own). Turn the first stage over in your hand, with your fingers supporting the rotary vane assembly.
Push your thumb through the hole on the backside, forcing the rotary vane assembly out.
Remove the rotary vane assembly. Be careful, remember everything is oily. You don't want to drop this.
Now it is time to focus on the rotary assembly.
Remove the vanes from the rotor VERY VERY carefully. If you damage them, you need to buy new ones. They have very tight tolerances. It took me a LOT of work to get these out without damaging them. A lot of careful prying with small allen wrenches, some 8G needles, etc. Good luck.
Now that we have these parts free, we can clean them.
Clean the central rotor thoroughly including all holes and groves, use a piece of wire (I used a 12" long 18 G needle that I have for pulling aliquots from reactions) to get inside the small holes and remove any solids.
Use a nail, needle, etc. to scrape out any and all solids anywhere else.
When finished the rotor should be perfectly clean.
Now to clean the vanes. Scrape them clean with a flat object (like a small screw driver), using a small needle to get in the fine places. You want these things PERFECTLY clean if you can. Remember any gunk could make them stick and seize up. There will likely be on the wide sides as well as the small sides so don't skip any area.
Now clean the body of the second stage just like you did with the rotor. This part took me 30-45 minutes to clean right. There was stuck on gunk EVERYWHERE. Make sure you get all of the ridges and places where the various sections join with each other.
Don't forget to clean your bolts and the piece that goes between stage 1 and 2 and connects the rotors.
Step 8: Cleaning the Pump (Oil Pump and the Rest)
Now lets move on to the oil pump.
Just like stage 2, it has a small rotary vane assembly in the center (though in this one the vanes are all one piece) with a piece that links this rotary assembly to the previous stage.
Press it out just like before and begin cleaning.
Once again scraping and making sure you have cleaned everything all of the holes, grooves etc.
This was pretty easy for me, much more easy than stage 2.
Clean and scrape out the cap and back-flow preventer parts.
Clean and scrape out the outside body of the pump basically the oil reservoir, including the oil level window. This took about 1hr for me. It was honestly, quite disgusting.
Step 9: Reassembly
Now that we have cleaned everything to our standards. Time to reassemble the pump.
To reassemble first put that metal piece that connects the stage 1 rotor to stage 2.
Put the Stage 2 pump body, making sure to align the screw holes.
Screw stage 2 into place.
Insert the stage 2 rotor.
Insert the vanes (the angled corner goes inside and towards the middle).
Now this next part gets tricky
You need to put the oil pump on but it doesn't have screw to hold it in place.
So you have to line up the notches on the oil pump rotor assembly with those on the stage 2 rotor.
Attach the oil pump lining up the screw holes and while holding the oil pump in one hand attach the oil pump cover, lining up the screw holes.
Then while still holding all of this with one hand, screw in one of the screws to hold it in place.
Screw in the other screw, the pump body is back together.
Now reattach the backflow preventer valve. It goes on like shown.
Now reattach the housing that goes on top of the backflow preventer valve.
Lastly, reattach the pump body. Don't forget the gasket that goes in between the two parts.
Step 10: Finished!
Now we are done. It is time to flush the pump with some oil.
Fill the pump with 0.75L of pump oil
Run it for aroudn 30sec-1min. This should sweep up any free debris.
Drain the pump oil and refill again.
Run the pump again this time listening for any weird sounds.
Check and make sure the pump is pulling a good vacuum and you are finished.
All that is left is to clean up your area. Good luck with things and if you have any questions feel free to ask them here.
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Please be positive and constructive.