Oil Free Roughing Pumps

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

11 posts Page 1 of 1
Has anyone used the oil free roughing pumps from Agilent?

I have an Edwards RV5 on my 7000C that has begun to leak oil and is only 4 years old, and I get emails from Agilent for the IDP series of pumps, just wondering how they compare to the RV5. Are they about the same noise level, and how often is maintenance required?
The past is there to guide us into the future, not to dwell in.
The Agilent one is a scroll pump; I don't know how it compares to other scroll pumps, but scroll pumps in general seem to work fine. Recently, someone tried to convert me to Leybold's Ecodry range. I hadn't got any immediate financial incentive but I'm intrigued by these as they are oil-free but also not a scroll pump (so they don't have the rotor thingy that scroll-pumps have that wears out and makes loads of black dust).
The person selling Ecodry pumps said that they only need servicing once every 4 years because there are no rubbing parts whatsoever in the design. I can't see how they work. The official explanation is that they're absolutely superb because they're German engineering, an explanation I'll accept at face-value, but which doesn't tell me much about the theory behind them!
At risk of hijacking this thread, how do third-party pumps like this stack up against Agilent's scroll-pumps or the traditional oil alternative?
My understanding is the Ecodry pumps are multi-stage Roots-type pumps. Here's a video of how they work:


I have no experience with oil-free pumps, although the next roughing pump will be oil free.
When I called Agilent after the Edwards pump on my 5975 started leaking probably a year and a half ago, they pretty much presented it to me as the only option.

Unfortunately, I couldn't scrounge up the ~$3K to get one-the department chair looked a lot more favorably on ~$250 rebuild kit and in-house labor(I'm still waiting on the latter-the Varian pump that was on my Saturn 2100 is doing its job in the mean time).

I'm certainly tempted, though, and will buy one if I ever have the money to do so. The instrument has never INGESTED oil during a power failure, but I've had oil in the foreline enough that I'd be happy to never have to deal with it again.

Of course, from what I've seen the Edwards pumps can manage 10+ years of continuous operation with an occasional oil change when backing a clean GC-MS. Even then, the usual first problem is that they leak oil and will still continue to pump decently even after they do that(they just make a mess). They're also cheap and simple to rebuild.
Our experience too, Ben: Just had the Edwards on our Thermo DSQ rebuilt after a complete failure after exactly 10 years.
Seems not many have used the Agilent pumps yet.

I have a building full of Edwards E2M2s that have been running non-stop(except to change oil once a year) for 20-30 years and never been rebuilt and not leaking oil. This new RV5 though is already leaking after 4 years :(

I have the Agilent service engineer coming in next week to work on a 5975 that I just don't have time to replace an HED power supply myself, I will ask her what the service record is on any she has in her area and report back what she says.
The past is there to guide us into the future, not to dwell in.
Thanks James - keep us posted.

I'm interested to know too what Brenda says-or at least that's who I'm guessing it is since she's our regional engineer and you're not too far away from me.

In any case, I've had a couple of E2M2s that have sprung oil leaks after almost exactly 10 years of service backing a 597x MS. Usually they will still maintain ~40 millitorr(at moderate flow rates) for a few years after they start leaking, but do manage to make a mess.

I've seen larger Edwards pumps run a lot longer.

Of course, as dated as they may be, I still am rather fond of my old Welch/Sargent Welch roughing pumps. Of course, I don't have ANY now that are backing instruments, but there are a whole lot around on Schlenk lines, rotovaps, and doing other "dirty" work. They just seem to keep trucking along with an occasional oil change. I did an internship in a lab as an undergrad where were pumping down a few dozen samples a day that had been dissolved in CS2, and I don't know when anyone had last bothered to change the oil on the pump. I took the initiative of changing the oil. Initially, we were getting 30+ torr from a vacuum gauge directly on the pump inlet, and more like 100 torr by the time it made it through the(bad) plumbing to the rotovap. The initial drain that came out was a biphasic mixture of sludge and something that looked(and smelled) like a nice solution of the lighter fractions of the pump oil and CS2. I did three oil changes that day, with about 20 minutes of run time on the intermediate ones, and watched the vacuum drop through the day. When I wrapped things up, the pump was not only a lot quieter but would manage 10^-2 torr at the outlet(I redid all the plumbing and was able to get 1 torr or a little less at the rotovap). I did change the oil again on my second to last day at that job, as the vacuum had started to deteriorate a bit. It wouldn't surprise me if it hasn't been changed in the 12 years or so since I last did it... Of course, that pump lived a MUCH harder life than anything on a mass spec sees-it just amazes me that it came back to life so well after so much neglect.
Normally it would be Brenda, but I think someone else is coming today.

I was using pumps like that in my school research and we always used a dry ice isopropanol chilled cold trap before the vacuum pump on the rotovaps, but we were using either Benzene or THF as the solvents. Those really work wonders keeping the pumps clean and are so simple to use and maintain it is a wonder how many setups don't have them.
The past is there to guide us into the future, not to dwell in.
Unfortunately, no one here regularly keeps dry ice on hand. I've worked with a lot of set-ups that made do with ice/saltwater. A lot of Schlenk lines run a coldfinger in liquid nitrogen, but most rotovaps are "sloppy" enough that I'd consider that set-up dangerous(too much air being ingested, and consequently too high of a risk of oxygen condensation).

The lab I mentioned above DID have dual cold finger type trap. When I started working there, they would just toss dry ice chunks in it. I put acetone in it and started putting as much "snow" as I could. Even with that, though, it's hard to keep CS2 out of a pump. The boiling point is 46ºC at atmospheric pressure. Also, the trap had a drain cock at the bottom, but it seemed like I was the only one who ever bothered to drain it(and I'd drain it a few times a day when I was using it). You'd see the condensed CS2 go crazy in the bottom of the trap when you started pulling a vacuum. There again, liquid nitrogen would have been nice, but way too dangerous.

Most of the rotovaps around our department now have Buchi(or other brand) diaphragm pumps on them. They pull enough of a vacuum to get solvents off quickly, but don't have oil and are pretty tolerant of ingesting solvent at least up to a point.
We had a dry ice maker where I could make about hockey puck sized pieces, then I would crush those and mix with isopropanol for the trap and make sure I changed it after every run. Does no good to trap it then let it set there until the next day and just evaporate into the pump, as many did.

Well I didn't get to talk to the tech, it wasn't Brenda and he was here and gone before I even heard he was here.
The past is there to guide us into the future, not to dwell in.
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