Problems with the MVP

Hey guys hoping someone can help figure out what’s going on with my master vapor pump. I just purchased the mvp a few weeks ago. Got the three phase model and having serious issues trying to pull a negative pressure with it. First a little bit about my setup I run crude on a 8 tube non jacketed 6x48 racked system with two “collection” pots. One I call a transfer vessel the other the evaporation vessel, similar to how a bfe from bhogart would run so I can continually run. Rn I have a smaller 4x24 tube and shell heat exchanger from hfs cooled with ice water(just bought a polyscience durachill and a 6x24 heat exchanger) I have three recovery tanks that hold appx 110lbs of solvent each and I exclusively run isobutane. From what I’ve read around the forum you need to keep a lower back pressure in order to pull a negative pressure with the mvp. After being on the phone for hours with bhogart who I bought it from we came to a similar conclusion, we also discussed the wiring but they were very rude about info and advise even though their was two extra wires “p1 and p2” that weren’t in the diagram in the manual (had a professional wire it) . I normally see a back pressure around 45-60psi. And my inlet pressure from 30-60 psi. My evaporation vessel is jacketed and hot around 55c-65c so that is not an issue. The problem is I bought the pump specifically to recover more vapor from the tubes before I take them off. I even switched to nbutane and saw my inlet pressure at 5-35psi and my back pressure at 25-35 psi and the pump still won’t pull a vacuum as it’s advertised. On top of that I even kept one of my recovery tanks completely empty at 10psi and once I got the tubes to 5psi I changed the recovery to that tank and it still didn’t pull a vacuum. Even when I isolated the desiccant tube it stayed at 1-0psi…It was so frustrating that I decided to put two of my four cmeps recovering while the mvp is also on and I noticed that they were recovering at a faster rate even with one or the other off to test and see. When I turned off the cmeps the pressure on my desiccant tube went up and when I turned off the mvp it went lower… 2.5 cfm of pumping better than 6cfm?? is their something I’m missing ? I’ve tried everything I could think of to get this thing to work how I need it too. I even brought it back to bhogart to get serviced and they said nothing was wrong. I talked to a friend who has a purge labs mag who also runs isobutane and mvps with similar back pressure and there’s are pulling vacuum… some buddy’s said I should run with jacketed tubes and that might be true to recover more gas but the problem is still the same it’s not pulling negative pressure. at this point I can’t afford to have any more days off or running at lower capacity as I had to get the three phase wired. Dewired and now wired again tom or the next day. I’ve been running cls for 5 years and large rack systems for over two years and haven’t had an issue like this that has significantly impacted the op. Ive even ran a knf too so I understand that diaphragm pumps are different than cmeps. I think I should have just saved and bought a corken instead… maybe I got sold a bunk mvp… Any help is greatly appreciated! Also my co2 inlet is at 70psi aswell
Thank you
Enigma

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High pressure on outlet-end of pumps is a common problem I hear about through the grapevine which causes MVPs to have trouble recovering below zero.

Master Vapor Pumps are a positive-displacement diaphragm pump. They are great for moving a lot of solvent very quickly but they don’t actually create anywhere near the differential pressure of some of the piston compression pumps. This effect is particularly pronounced when exacerbated by the diminishing returns seen at increased vacuum depth.

I find that even getting above 15 PSI or so will noticeably diminish my ability to pull vacuum.

The only other thing I can think of is maybe there’s an issue with your diaphragms. We have always been able to recover down to deep vacuum just fine, but if I try that pushing against 40PSI it is a really painful process.

Thank you for the reply makes a lot of sense now why but how do you keep your back pressure that low? Are u using straight nbutane? I got a 1.5 hp durachill polyscience chiller I’m hooking up to replace ice water on the heat exchanger I know that will def help but I feel not being told this crucial piece of info on this pump when I bought it is messed up. I replaced the diaphragms they were slightly worn. I have vapor release valve on one of my tanks so I can relive back pressure into my first pot. I just feel it takes too long that to get it that low to make it worth it. Trying again right now to see what’s up

We have the 2.5HP Iced Tech chiller. It’s been satisfactorily keeping our pressures low for solvent recovery even using two master vapor pumps.

If our pressure is two high, I have our manifold system set up so that I can isolate one master vapor pump and recycle vapor with one pump, and still be able to recover solvent with the other. It’s a handy little trick that drops pressure lower faster than releasing the vapor all the way back into your evaporator.

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I just got the 2.5. I’m interested in this setup @GandalfTheGreen. Could you help drop some knowledge on a noob?

Well, to start obviously you’d need two pumps. One pump recycles vapor from the solvent/recovery tank, while one recovers just like normal. Not sure if I can explain that any easier… if you have a specific question lmk

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Will 2 mvp 60s work? Or is that overkill? I have a cmep also

Yes. Using one of those pumps simply to recycle vapor from your tank will drastically reduce the pressure inside that tank, allowing the second pump to recover into it much more efficiently. With your CMEP, I’d dedicate that to recover from your material columns.

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Thanks brother. I’m new to the Iced Tech. Bought it to do a cold vapor loop. I figured your head pressure loop would be similar.