Horrible vac issue

am i reading this right? the only gauge I have is what came with one of the chinese rotovaps i use. are my conversions wrong/impossible because of the method? 0.09 MPa = 675000 micron? pump is a welch 1400 that was bought 3rd hand.

gauge reads accurate on my pilot 5000 (.077 MPa = 23 in Hg advertised max is 24 in Hg for that pump and it has a taped together inlet trap)

can you not simply do a straight conversion and be accurate or is this welch 1400 in serious need of rehab/paper weight status

yeah, one of the two is broken. Assuming gauge works, pump doesn’t.

0.01MPa is atmospheric as is 760000microns.

you’d be better off just moving to Denver :wink:

change the oil. or run kerosene through it. then change oil.

1 Like

this is after a whole tear down, acetone cleaned all the parts, reassemble, fresh oil. was getting .85 before…when i first got the pump the first thing i noticeds was how gross the oil was and how stinky it was when you ran the pump, which led me to educate myself how to take the thing apart and clean it.
during the breakdown i noticed a ‘chipped’ rotor? its not on the edges near the retainer ring or near the vanes but in the center of the rotor literally against the back end plate. almost looks like a contaminate or something got between the rotor and the wall (back end plate) and something rubbed away at it causing a tiny hole about the size of a needle head. and i can see light ware in the rotor itself from spinning around… but neither repair kit in the welch line come with new rotors? would that even be part of the problem? not sure if i should gamble on getting a repair kit, but its also very possible something else is worn (gaskets etc.
) that i couldn’t notice with a human eye.

1 Like

Is there a knot in that tube? Perhaps that your leak? That pump may need assessment with a more accurate sensor. That Guage I’m sure isn’t the most accurate.

the knot you see is closing the loop to get pressure out of the gauge. that is the same number i see when my glassware is setup or just plug the end of the line.

I guess your pump needs some more work. Try finding a manual for the pump with an exploded diagram. Find out the part name or better yet part number. Than call or email a place that services vaccum pumps, see if they have any of the parts you need.

…yes i used the items mentioned, and as of now i have decided to ask knowledgeable people who on this forum vs call someone and ask if they can sell me a part i dont know if will help me.

Take a pic of the part and post it.

unless you missed a part when you reassembled, it sounds like a fairly expensive rebuild. possibly more than you paid for the the pump if you got it used.

boat anchor? pull the motor and save it for something else first.

although to be honest, I’d probably try welding the pinhole (or getting someone better than me to try it) before tossing it if the rebuild was more than a replacement.

Not sure how an expanded diagram will help? I have one already when i learned to take the pump apart and also when looking at what parts are included in welch’s repair kits…
but i was thinking of cleaning the rotor with brake cleaner or something and using a dot of jb weld and seeing if it helps at all the next time I am able to tear the pump down again…but again the chip/hole is about the size of a needle head, because at the time i used the tip of a thumbtack to rid of any tiny tiny flakes and tried to make it even as possible, like a microscopic sinkhole in a solid piece of metal. im hoping someone will say that the seals/gaskets matter 100x more vs a microscopic hole in the rotor. i just dont want to waste a few hundred bucks on a repair kit to find out i was just putting lipstick on a pig.

1 Like

I like your style!

On the farm decades ago in the high desert and VERY remote the unsophisticated among us only realized the true utility of bailing wire and duct tape to keep the farm going. The experts among us knew the real secret… they had a tube of JB Weld too :shushing_face:.

I understand what you are trying to accomplish in the same manner that I understood why Micheal Jordan tried to make a comeback as a professional baseball player. If it had succeeded then an epic achievement sure but pigs just were not flying for him on that one, right? At some point you just gotta stop hoping that somebody is gonna show up to the outhouse with some toilet paper and get on with a new plan? :stuck_out_tongue_winking_eye: Release that pump from it’s curse so that it may journey to the halls of its fathers…


Try to braze, silversolder, or jb the hole up.
The exploded parts diagram will tell you what that part is called by part # . If you find said part number we could look it up and find it for you. We just don’t know what you need until you tell us. Let’s get this pump squared away and working!

I just scored a brand new welch 1400b for 550 shipped. Iirc, there are 2 more unavailable.

Just a heads up

2 more available or unavailable? where did you purchase? care to share?

1 Like

I found a person who sells directly from gardner. Of all places, on ebay. I did get my pump with the fn fluid leaked out and all over.

A little iso cleaning is all she needed. I haven’t been able to grab a bottle of oil and run it yet, but it’s a brand new unit.

His ebay sn is roll000
I just checked, I didn’t see any more pumps. You may be avle.to email him about it

@Beaker lol, dont forget Jordan came back and led the Bulls to three more championships! Also quite hillarious/scary you mention the high desert, because I am currently there (here). on a farm. in a VERY remote location. all off grid. I’m sure I dont need to explain the deserts version of Murphys law to you…

1 Like

@Demontrich I pretty much live on ebay… Never considered doing a search for a pump there… I was only considering buying a repair kit for my current pump…i will now be taking a brick to the back of my head now.

is there any main difference in the 1400 series model numbers? -b -z? im like 10 seconds away from buying a ‘new pump only’


That I’m not sure, difference from a 1400 and a 1400b. I certainly HOPE not! If so this pump is going back, as the seller listed as 1400, and NOT a 1400b like I recieved.

I’ve purchased 2 other welch 1400 pumps yes ago when I was going to dive into distillation. Ended up just flipping them both for a 400 profit on each.

My guess is the 1400b…1400z…3z… etc… either has to do with configuration of outlet, gas ballast valve, exhaust plug/filter because different ones look slightly different in the pictures or time/date of manufacture - Welch only describes the pump as the 1400 series on their website with no mention of any distinction of performance difference, so i imagine they are mostly cosmetic or when they switched styles of the options mentioned earlier.

1 Like

Welllp… I bought a new ‘pump only’ on ebay hooked it up and did a run today with the same results. the new pump shows the exact same vac level as the old pump…

so it made me think that the gauge i had was just trash itself, perhaps leaking itself, so on the 2nd pass I took off the gauge completely but with the same results.

is it possible for a motor to not spin the pump fast enough? motor seems fine to me, i tried playing with the belt tightness with no result. belt also appears to be in fine condition,

I see on the motor it says to change the wires to change polarity of the motor, it is currently cranking the pump clockwise.

with all the glassware setup or just the pump connected to the gauge. same result.