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Vacuum Pump Woes

2/29/16       
Jay

Website: http://jayscustomcabinets.com

Aloha from Hawaii.....I purchased a used SCMI Record 125 about 6 months ago. I have been pleasantly surprised at how well the transition has gone, and am now pretty dependent on our CNC running to keep jobs moving in the shop. About a month ago one of our vacuum pumps, Ritschle VTB 250, started to make a horrific noise and stopped producing vacuum. I took it apart and saw that the vanes had broken apart and needed replacement. I knew this was inevitable, and is a fairly normal occurrence when the vanes get worn. I ordered new vanes, cleaned out the machine very well and reinstalled the new vanes, pretty simple process. I was very careful to get all the rubbish out of the machine, and also to put the bevel on the vanes, in the correct direction. When I started the pump up again, it sounded great and ran for about 30 minutes, then the horrific noise returned, and the pump stopped producing vacuum. Thinking I had screwed up the install, I called the reps, talked to them and they assured me I did everything correctly. I repeated the process again, taking extra extra extra care to make sure every spec of dust was out of the machine. I also inspected the outer rim of the cylinder for any burrs or grooves and it appears nice and clean. Long story short, I changed out the vanes again and the same thing happened. Well, that's $3000.00 down the tubes in a matter of minutes. Soooooo I bit the bullet and sent the pump back to the manufacture to have it inspected and new vanes put in. Being in Hawaii, that's a 5-6 week process, not to mention the huge shipping bill, oh well, cannot be helped right? So, for the last 3 weeks , we have been getting by with the second pump, same model, and everything was fine. Well, you guessed it, today it went kapooi too. My question is this, when the vanes in a pump finally are worn out, is it normal for them to break apart, chip etc. Or do they just slowly wear down to the point that there is nothing left. In this case, the vanes all were chipped and cracked, and pretty much broken apart. Now of course I am dead in the water and need to get up and running as soon as possible. The first pump probably wont be back for another 2-3 weeks at the earliest. I could order new vanes, over night them, and be back in business in a few days, but it is another $1500.00 experiment. My understanding is that replacing vanes is fairly simple, should be able to replace them on site. Is there any one out there who can give me some advice, or share your experience with me. Maybe there is some simple thing I am over looking that I could do differently that would result in a better outcome......Help!!

3/1/16       #2: Vacuum Pump Woes ...
Mike

Jay,
Wow, that story is horrible. My current machine does not have that type of pump, but I have changed vanes on 3 different types of rotary vane pumps in the past. The only thing that I can think of that you can do is to check the wear periodically and have guidelines on when to change them out. These are obviously wear items. They get smaller as they accumulate hours and if not changed, they break. Get feedback on how many hours you can expect and keep it in the routine maintenance schedule. If you notice wear in the future, you can order the vanes as a set and have them in plenty of time before things get critical. I would also recommend changing them on both pumps at the same time. Good luck. At least the weather is better there than in the Midwest.

3/1/16       #3: Vacuum Pump Woes ...
Dropout Member

Sounds like mechanical damage of some kind. Either it's ingesting solids or the pump rotation is backwards or something. Check the voltage. Maybe its spinning too fast.

The fact that the OE rebuild pump blew up indicates the problem is external to the pump.

3/2/16       #4: Vacuum Pump Woes ...
Maurice Phelps

Website: http://mcpservice

My question would be what did the rebuild of the pump include.

Did they remachine the bore (egg shaped) or did they do a basic rebuild of the pump.

3/2/16       #5: Vacuum Pump Woes ...
Jay

Website: http://jayscustomcabinets.com

I have not received the pump back yet from the manufacture. I sent the first pump out to be looked at 3 weeks ago after two failed attempts at changing the vanes. At this time I haven't heard what kind of work needed to be done. I should receive a new set of vanes today to attempt once again to repair the second pump. praying that they do the trick.

3/2/16       #6: Vacuum Pump Woes ...
B.H. Davis  Member

Website: http://www.curvedmouldings.com

This is a long shot but is there any chance you are reading the pump rotation in reverse? If so you could be chamfering the wrong edge of the vane.

Also are the vanes spring loaded to hold them against the outer housing surface? If so is the fit of the vane in it's slot a touch too tight? Perhaps heat expansion of the vanes is causing them to bind and subsequently shatter.

Wish I had better then just some wild guesses to help. I've only rebuilt one pump and it was about 15 years ago.

BH Davis

3/3/16       #7: Vacuum Pump Woes ...
Mike

Jay,
How did the vane install go? Since I, and most of us have been down the "repair with a prayer" road before, I'm kind of invested in your story. Hope it went well.

3/3/16       #8: Vacuum Pump Woes ...
Jay

Mike.....Well not too well actually. I put in the new vanes and the pump worked well for about 2 hours, then boom the vanes self destructed. I took the machine apart again and cleaned it all out. Thinking I must be missing something, I looked and looked. I think I may have found the problem. When blowing out the machine and trying to get all the debris and powder out, I have taken off both the intake and exhaust cover. I then removed the filters on the intake side and cleaned them real well. On the exhaust side, there is a set of valves, that let the exhaust escape, but not let air into the cylinder. I discovered on this attempt, that I can take those valves off, which I did. Low and behold, there was a lot of debris trapped between the valves and the cylinder. I was able to clean those out and now I am fairly confident that things will turn out better. I am pretty sure those pieces were being sucked back into the machine and causing the damage. I sure hope so. Now I just have to wait for the next set of vanes to arrive and I will try again. It's only money right, at least I am healthy......for now.....until I go crazy. LOL

3/4/16       #9: Vacuum Pump Woes ...
B.H. Davis  Member

Website: http://www.curvedmouldings.com

Jay,

I have an intake filter right at my CNC. Quite simple actually. I took a Cuno style single cartridge whole house water filter with a course filter installed and put it at a corner of the router. All sucked air goes through this filter before it heads down the lines to my Gast vacuum pump.

We check this filter on a regular basis and over 10 years have never had to replace the cartridge so we're not getting much dust being pulled by the pump.

This works on our system because we are using vac pods and the vacuum is plumbed with 1" pipe. Probably wouldn't work on a system using 2" or larger piping though.....at least not with a water filter cartridge system.

BH Davis

3/4/16       #10: Vacuum Pump Woes ...
Brian

I have seen this happen on both a vane style vacuum pump and the old vane style compressors. What happens with the compressors at least is that over time the elliptical bore wears and the new vanes which fit closer in the slots cannot follow the changes in the bore fast enough and get impacted. Hard to describe. Don't know the cure on a vacuum pump but on a compressor it was a new housing which if you have been around those units you know it's not worth it.
Darn tough luck, try to get a rotary screw (roots style) as soon as you can they run many 10's of thousands of hours with just the yearly oil filter change. We have one that has run for 14 years 16 hours a day.

3/6/16       #11: Vacuum Pump Woes ...
Zach

Website: http://deasmillwork.com

I have two of these pumps as well as a few beckers. I have replaced the vanes a few times and rebuilt the VTB 250s once. I assume that you did not totally disassemble the pump intake and exhaust. On the exhaust side of the pump there is a ported block that assist in removing some heat prior to exhaust. When the vanes explode this fills with carbon. You cannot completely remove all the debris without removing. If it is not clean when you turn the pump on you suck this trash into the pump and distroy the vanes again. You also have to completely clean the grooves in the rotating shaft that the vanes ride in. If anything prohibits a vane from moving up and down the vane will break and this will distroy all five. You should not have any trouble once you get the pumps back. The pumps you have work very well. They require a little more maintainence than a Becker but they are still good pumps.


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