Vaccuum issues

Hello everyone ! I’m a new comer to this forum and have come here because I need some help. I’ve been running a 12l lab society short path with a t 40 cold trap and Edward’s 28 pump. Things were going well progressing better and better till recently. I Have recently run into vaccuum issues. When the system is fully set up with nothing in the pot I can only pull down to 2400 and if I remove the cold trap I can get to 1900. The last 2 distilations I did I really had to fight as the vaccuum was too high for proper distilation. Any and all help would be immensely appreciated as i have come to the end of my checklist and cant find anything obvious as to the vaccuum issue. I know the pump has the potential to pull down to 480 microns as I have had it there for a few 2nd passes but the average is usually 1000 and 1800 for 1st pass both numbers seem high to me and I was under the impression the ed28 could easily handle my set up.

The t40 trap won’t work on a system like that.

A single 12 liter system with one head requires at least -50c or less temps on two cold traps.

A t40 will barely suffice for a spd1 2l setup. You are most likely logging your pump with contamination if the performance is degrading as the days go along.


What does your pump run at not attached to the SPD ?

Like the above poster said it seems like you didn’t use appropriate cold traps and you have damaged your pump. You might have to send it off for a rebuild if you are only achieving 2000 microns , that’s really bad …

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how often were you changing the oil?

also do you have a secondary meter to validate (or invalidate) your meter?

your problem is obvious. you didnt go with a summit system! shame on your family


Sorry meant to say a t80 cold trap and my 12l is a dual head system. With guage hooked up to pump right at inlet I get 200 micron . By the end of the day we had sussed a few leaks in the heads where thermo probes go in. With cold trap on now was getting 1200 and with coldtrap removed 480 . So I think my issues mainly may have been leak oriented . The pump oil is changed every 4 distilations but might take that to every 2nd distilation down the road . I dont have a secondary meter to test accuracy of the one on the system now but maybe in future will obtain 1 to have as a backup or to calibrate.

I’m not a pro, but everything I’ve heard and instructed has been to change the pump oil after each run. And if you break vac to change flasks at main body then if you can. At least every run from what I’ve been told. I could be wrong though.


Your trap isn’t doing what it’s supposed to. You should try it with one head. Any 12 l system needs basically dual traps man. My two cents.

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Will be doing oil every run from now on and looking into a cleaning of the pump. Gonna try and pull her down again this morning and if all goes well do a small pass . The oil was changed yesterday after all the tinkering and testing and will do after today’s activities to see what the oil looks like .

So after testing the pump straight to the vacuum sensor I got it to 70 micron and was still super slowly going down 1 micron at a time . Hooked system up with t80 trap with nothing in it and got down to 2400 it stabilized and keeps pulling down but very slowly . I realize it takes time to evacuate the whole system but my gut says it should be at a much lower micron before stabilizing to a slower pull down? Am I wrong in thinking this ?

The pump itself pulls down into the 70 micron range and slowly 1 micron every 10 15 mins from that point .

Give this a try. You may have a chance to salvage her without having to take a loss.


Im guessing this is like a cleaning/flush for the pump? Someone was telling me about some type of flushing fluid and doing the same type of thing :thinking: will def give this a try .


Give it whirl. May may give her a nice new attitude.

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What you described is a blown seal on the second stage. Its allowing molecules to slip through it. Your pump even in mediocre condition should hit 1-5 micron locked off in three seconds. Or 5 microns hooked up to a spd in about 20 or so seconds max.

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Is all flushing fluid created equal? I may give the trivac a good flushing.…0…1…8…46i39i275j35i39j0i131j46i131.yWJJhxPy078

Little known secret. Flushing fluid is lower fractionated oil. You can use almost any i19 oil and both flush better and cleaner. I don’t like flushing fluids becuase they slightly leave thier composition behind. There’s a better way to clean a pulp. Open the oil drain and the inlet and dump oil down the throat for a second or two while it is running with the oil plug out and unit fully drained. This will nearly restore most pumps back to near New because it flushes contaminants from the vanes directly with force.


I kinda did that last time.

Run 30 mins to get warm
Drain 3/4
Plug drain
Start pump for 10 seconds
Drain rest
Refill with fresh
Run for 20 mins
Repeat above

I did not open the gas ballast.


I usually do this

Cap off inlet.
Run under vac 30+ min.
Open everything up and fully drain while pump is laying on its drain side entirely or tilted to the max.
Leave pump tilted. Put trash can up to drain plug hole. Slowly pour some oil in while someone turns pump on. Allow throat to rocket oil throughout casing and self clean vanes.
Then cap the drain plug up and fill pump up with fresh oil.
Run for 30+ min under vac with inlet capped off.
I’ll repeat the throat and vane cleaning procedure once more and then fill up pump and let run for a few hours to clean remainder water and contamination out via ejecting hot gases out exhaust. You can also displace volatiles while dispensing like 5sccm of nitrogen down the inlet. But that’s usually not needed.

This process takes less effort and doesn’t require flushing fluid and will clean the internals alot better than using a fluid. That’s becuase the fluid itself can’t rocket parts clean via centrifugal force. The oil and cleaner or whatever prevents it.


Ove heard people mention using kerosene to clean pumps. Do you guys recommend that?

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