Sciencemadness Discussion Board

Replacing a broken bleeder valve on a vacuum pump

SuperOxide - 28-11-2021 at 11:25

Just a few months ago, I purchased a used but well working vacuum pump off of ebay for a decent price. I'm like 99% sure it's this one: KNF N811 KV.45P Filtration Pump, Gauge/Reg, PTFE/PPS/FKM; 0.45cfm/27"Hg-30psi/115V. The guy who owned it and sold it to me was away at college, and he had his sister package it and ship it to me. And needless to say, she did a pretty fricken terrible job at packing it up. The body was wrapped up decently well, but the vacuum gauge/port was sticking all the way out of the padding, and it was clearly dropped. The gauge was totally busted:

here is a video of the pump working with it hooked up to my hand operated vacuum pump that has a valve.
I didn't care too much about the gauge because the pump and bleeder valve worked, and those gauges are cheap, and I can easily replace it.... or so I thought.

The problem is, the dude must have used some super duper fricken adhesive when he last re-attached the gauge to the block thing with the bleeder valve. I tried using proper fitting wrenches, which I wasn't strong enough for. So I used a long pipe on the wrench to give myself some mechanical advantage, as well as heating it to loosen up any glue he may have used, and I managed to turn it around a bit, then chew up the bronze.


So, now not only does the gauge not work, but it just looks silly as hell, lol.

I know I can take off the entire block with the gauge and bleeder valve and replace it with just a port that I can attach a tube to, but I really like the bleeder valve. I need that to be able to pull a vacuum gradually without over-doing it. That's why I've just left it on there for now.

Questions:


  1. Does anyone know what would be a good replacement for the bleeder valve and what the block thing it's attached to with the gauge is? I emailed MasterFlex and asked them for details or asked if I could buy one of those, and after weeks of waiting, I got someone offering to sell me some overpriced kit with some extra accessories, which didn't even have the parts I was looking for. I know they sell a model that's basically the same pump, but doesn't have the gauge or bleeder valve, so I was hoping to just buy a kit that had it - no dice.
  2. What is the name for the part that the vacuum gauge, bleed valve and nipple are attached to? I mean the black square lookin thingy.
  3. I don't see many affordable bleed valves for vacuum pumps on Ebay and Amazon, but I see a lot for positive pressure pumps. Would a bleed valve for a positive pressure pump also work for this vacuum pump? I don't see why not, but I thought I should ask.

If anyone can recommend some parts from somewhere that I could use to add the port/valve/gauge, then I would greatly appreciate it. Im not much into plumbing or anything and I didn't see anything for it at Home Depot. I suppose I could try Ace Hardware, but that didn't occur to me til just now.

Any advice is appreciated. Thanks!

Edit: I think this has the type of stuff I'm looking for. However, whenever I see "Price on request", I usually interpret that as "Too damn expensive for you". So if anyone knows what parts I can get that would work sufficiently well for a hobbyists, please let me know :)

[Edited on 28-11-2021 by SuperOxide]

Organikum - 28-11-2021 at 15:52

Are you able to unscrew any of the parts so you can determine the threading used? Or do you know which threading is on the pump, is it in the manual?

As soon you know the threading you can find the block with the many ports on Aliexpress quite cheap I believe it is called a X-port terminal or such. The Gauge is not original KNF I think and on the picture at KNF you see the original has a much longer connector. You should do the same, it is done for a reason. More steady gauge readings and far less corrosion. Looking at this little disaster area I would recommend you get a thread cutter of the size so you can recut all those threads they are badly fucked for sure, corrosion and glue (looks more like epoxide actually).

Good luck
/ORG

SuperOxide - 28-11-2021 at 17:53

Quote: Originally posted by Organikum  
Are you able to unscrew any of the parts so you can determine the threading used? Or do you know which threading is on the pump, is it in the manual?
As soon you know the threading you can find the block with the many ports on Aliexpress quite cheap I believe it is called a X-port terminal or such.
I can unscrew the main block attached to the pump itself, and I will try to find out the threading. I don't have the threading sizes memorized, but I know it's the common size. I think it's like 1/2" or something.

Quote: Originally posted by Organikum  
The Gauge is not original KNF I think and on the picture at KNF you see the original has a much longer connector. You should do the same, it is done for a reason. More steady gauge readings and far less corrosion. Looking at this little disaster area I would recommend you get a thread cutter of the size so you can recut all those threads they are badly fucked for sure, corrosion and glue (looks more like epoxide actually).
Actually I'm like 99% sure it is the stock one. If you look at the product page for the vacuum pump, it looks identical:


The 2nd link I posted in my original post was to something that looked similar.

SuperOxide - 15-1-2022 at 10:06

Quote: Originally posted by Organikum  
Are you able to unscrew any of the parts so you can determine the threading used? Or do you know which threading is on the pump, is it in the manual?

As soon you know the threading you can find the block with the many ports on Aliexpress quite cheap I believe it is called a X-port terminal or such. The Gauge is not original KNF I think and on the picture at KNF you see the original has a much longer connector. You should do the same, it is done for a reason. More steady gauge readings and far less corrosion. Looking at this little disaster area I would recommend you get a thread cutter of the size so you can recut all those threads they are badly fucked for sure, corrosion and glue (looks more like epoxide actually).

Good luck
/ORG


I finally remembered to bring one of the nipple/ports with me to Home Depot to test the threads :-D

Apparently it's a M10x1.0 thread.

I hate to sound lazy - But do you think you could provide some links to the products you're talking about? Im likely to select the wrong stuff. I've sent messages to a few people on Ebay asking if their product would work for what I'm trying to do and the answer is "no", and im worried I'll keep purchasing the wrong products.
I wish there was a store I could go to that would have this bleeder/regulator/gauge/block, but I certainly wasn't able to find any.

monolithic - 15-1-2022 at 10:24

All you need is a vacuum gauge, a needle valve (look on Amazon or eBay), and a 3/4 way pipe fitting. I built one myself and it works really well.

[Edited on 1-15-2022 by monolithic]

SuperOxide - 15-1-2022 at 10:27

Quote: Originally posted by monolithic  
All you need is a vacuum gauge, a needle valve (look on Amazon or eBay), and a 3/4 way pipe fitting. I built one myself and it works really well.
A needle valve? I thought this was a "bleeder valve", or so the product description said (it came with it).

monolithic - 15-1-2022 at 10:37

Quote: Originally posted by SuperOxide  
Quote: Originally posted by monolithic  
All you need is a vacuum gauge, a needle valve (look on Amazon or eBay), and a 3/4 way pipe fitting. I built one myself and it works really well.
A needle valve? I thought this was a "bleeder valve", or so the product description said (it came with it).


This is what I bought. https://www.amazon.com/gp/product/B00FDWABLS/ref=ppx_yo_dt_b...

Any "needle valve" should work fine. You don't need one of those super fine bleeder valves. Picture is worth a thousand words, here's two: https://imgur.com/a/iyySbwW

SuperOxide - 15-1-2022 at 10:46

Quote: Originally posted by monolithic  
Quote: Originally posted by SuperOxide  
Quote: Originally posted by monolithic  
All you need is a vacuum gauge, a needle valve (look on Amazon or eBay), and a 3/4 way pipe fitting. I built one myself and it works really well.
A needle valve? I thought this was a "bleeder valve", or so the product description said (it came with it).


This is what I bought. https://www.amazon.com/gp/product/B00FDWABLS/ref=ppx_yo_dt_b...

Any "needle valve" should work fine. You don't need one of those super fine bleeder valves. Picture is worth a thousand words, here's two: https://imgur.com/a/iyySbwW



Hell yeah, thanks for the link!

I was wondering if a needle valve should work, and I actually messaged a couple sellers on Ebay asking if they would work (as mentioned earlier) who said no. So I figured they wouldn't. But if it works for you, im sure it'll be fine for me. Thanks!

monolithic - 15-1-2022 at 10:52

They might be thinking about high vacuum applications. You won't get 1 micron resolution or whatever out of a setup like this, you would need a $$$ purpose made bleeder valve. But for stuff like distillations with a diaphragm pump, a needle valve is great. Most of the adjustment (from atmosphere to full vacuum) is in the last turn of the valve but it's more than adequate for me. I use it to control my distillations whenever they go crazy with bumping or frothing.

SuperOxide - 15-1-2022 at 11:26

Quote: Originally posted by monolithic  
Most of the adjustment (from atmosphere to full vacuum) is in the last turn of the valve but it's more than adequate for me. I use it to control my distillations whenever they go crazy with bumping or frothing.
I've noticed that too. Pretty much 3/4 turn is basically on/off. But its enough to prevent me from pulling a vacuum down too quickly.

SuperOxide - 15-1-2022 at 11:35

oops.. duplicate post. Feel free to delete, admins.

[Edited on 15-1-2022 by SuperOxide]

SuperOxide - 16-1-2022 at 15:43

BEHOLD!.... A very ugly plumbing but perfectly well working vacuum pump, with a working gauge!



The needle valve has the crappy bar knob thingy on it, so I will order a new one with a real knob, but this is just stuff I got from Ace Hardware. It actually works better than the other setup did. Great!

Thanks monolithic!

P.S. The needle valves with the round knobs are all mostly 1/4", I can't find any 1/8" >_< Damnit. I don't want to add more plumping for an adapter. Oh well.

[Edited on 16-1-2022 by SuperOxide]

monolithic - 16-1-2022 at 20:42

Glad it works. :)

SuperOxide - 17-1-2022 at 11:06

Quote: Originally posted by monolithic  
Glad it works. :)

One last thing though - I thought that the part that had the gauge/valve/nipple branching off of it was a 4 port block, but now that I get a better look, I notice it actually has female threads on every one of the sides:


Any idea what this part is called? I looked on amazon for lots of things: 6 port manifold 1/8" npt, 6 side thread block 1/8" npt, 6 sided fitting 1/8" NTP, etc, and haven't been able to find much. Im sure if I knew the exact name for it I would be able to find it.
What I have now works, but it's a bit taller than I'd like (which makes it a pain to store where I usually keep it). If I can find that manifold thing, that would be excellent.

Thanks again!

[Edited on 17-1-2022 by SuperOxide]

monolithic - 17-1-2022 at 13:06

I'd call it a manifold, too. I can't really find anything like that. Probably be easier to befriend someone with a drill press and NPT tap set.

SuperOxide - 17-1-2022 at 13:07

Quote: Originally posted by monolithic  
I'd call it a manifold, too.
I thought so.
Quote: Originally posted by monolithic  
I can't really find anything like that. Probably be easier to befriend someone with a drill press and NPT tap set.
Right, that's what I was thinking. Oh well.

I suppose I could try to salvage the one that's got all this shit in it. Since I have a working alternative, it's not too big of a deal if I bust it (which is what I was scared of doing before). The old owner used so much locktite or superglue, and tightened everything so fucking tight that I couldn't get anything out of it. I can put it in a vice and blast it with a torch to see if that helps get the threads moving.


[Edited on 17-1-2022 by SuperOxide]