[How To] Renewal Dewar Vacum

[Guest barbonenet]

All this material need to apply Brass Acces Valve (1/4sae-1/4sae) or (1/4sae-7/16"-20) !!!!

If you didn't find this valve, Drill Bit & TAP size to use, change!!!!!!

 

What you Need

 

1x 2Stage Vacuum Pump (ebay)

 

1x TAP 7-16"-20 UNF (ebay)

 

2x O-Ring (better if you find O-Ring for Low Temp)

 

1x Loctite 243

 

1x Brass Acces Valve (1/4sae-1/4sae) or (1/4sae-7/16"-20) http://ph.parker.com/us/17054/en/refrigeration-access-valves/avu1f1-4

 

1x Drill Bit 9.5mm for Steel

 

All this material need to apply Brass Acces Valve (1/4sae-1/4sae) or (1/4sae-7/16"-20) !!!!

If you didn't find this valve, Drill Bit & TAP size to use, change!!!!!!

Edited April 9, 2015 by barbonenet

[Guest barbonenet]

First at all, search the correct Brass Access Valve....if you find Valve like post#1, you can go to next step!

 

DEWAR CAP MOD

 

-Remove cover cap of dewar. you can help with a screw

 

 

-Now make an hole of 9,5mm with Drill, and then make thread with 7/16"-20 TAP (Attenction: Stay perpendicular and use OIL)

 

this is a good job

 

Ok the main work is done!

 

-Now put on your valve Loctite 243 (here i use Teflon, but Loctite 243 it's better)

 

...screw up it (here i use Teflon, but Loctite 243 it's better)

 

-change O-Ring and mount this modded Cap on Dewar (use a littlebit of grease on O-ring)

 

put the second O-ring like me

 

push push

 

F I N I S H !!!!!!

Edited April 9, 2015 by barbonenet

[Guest barbonenet]

Renew Vacuum

 

Attach 2Stage Vacuum Pump to your Dewar, and start up vacuum!

 

Do vacuum for 30minutes.....

 

then turnoff pump, and check vacuum after 1-2hour.....

 

 

if dewar doesn't lost vacuum, turn on again Vacuum pump and remove quickly the tube from dewar!!!

Turn off pump and screw up the valve caps!!!!

 

Finish !!!!

 

Tips:

-For a better performance, warm up dewar before making vacuum!!!

-If dewar lost vacuum, try to put more teflon on valve......

-if you know a Mechanic, you can ask if he can do vacuum with his Vacuum Pump (with his recharger for air conditioning).

 

Ask here if you need help.

Edited April 9, 2015 by barbonenet

[Sergio73 10]

WOW!!!! Nice work !!!

[Guest barbonenet]

Thanks

Edited March 14, 2015 by barbonenet

[DrWeez 11]

Thanks, great info

[der8auer 147]

Amazing stuff. Great work!

[dinos22 20]

awesome stuff man

[nachtfalke 41]

nice work!! i recomanded to change teflon with threadlocker LOCTITE 243( medium strenght)

[ogblaz 10]

Hi, great guide my friend, I did this a week ago and my dewars now evap rate is much better than before, I lost 10L in three days now its less than a liter per day. Its bad, but I think this is normal for my type of dewar.

I took the plug out of the dewar, the vaccum was present but was bad, then i go and bought the 1\4 valve like you told me, took the plug and the valve to a guy with the mill and he made threads on the plug and the valve, i used locktite "rope", bought a new oring, and used silicone grease on the plug. In original is high vaccum grease, but its 30€ i dont think it makes much diference.

 

Thanks again for all your help!

[Guest barbonenet]

Nice suggestion locktite.....i didn't think to it i'll add it .

 

After you apply this valve.....you can search if there is a little hole in your dewar....instead make vacuum, put inside air to 1-1,5bar and search the hole with soap....

 

Sorry guys it's too tecnic for my poor english;)

[Vivi 20]

this is awesome

 

thanks for the tips!!

[ogblaz 10]

Its a shame that already the pictures are gone, somebody should put them to a more reliable server.

[Guest barbonenet]

I put on another server. .....dropbox is not the best for share images......

[Guest barbonenet]

all picture are on......i puted image on altervista space......

[subaruwrc 77]

I should try this with my old dewar ..

[Guest barbonenet]

I should try this with my old dewar ..

 

Let we know

[d0minat0r 82]

I need to do this on my dewar, lose 20l Ln2 for night

[Guest barbonenet]

After that, your dewar will be as new;)

[d0minat0r 82]

I need to make new round brass part.Can not pull out old part.

[d0minat0r 82]

I still have some options in mind. I'll think more what I'm doing. All suggestions are welcome

[ogblaz 10]

Just take to a shop so they drill thru the whole brass piece, make a thread and screw in the valve. Check the seals on the whole thing and you should be ready to vacuum the thing.

[Guest barbonenet]

Just take to a shop so they drill thru the whole brass piece, make a thread and screw in the valve. Check the seals on the whole thing and you should be ready to vacuum the thing.

yeah exactly. maybe the thread is perfect on the brass piece.....check if you can find a valve 1/4SAE for this thread.

 

So, if you find a right valve for that thread, you have only to make an hole on the other side!

[techjesse 43]

My Sponsored Taylor-Wharton 32L Liquid Nitrogen Dewar PGT Testing hold time in 90f temp to see if I need to use this excellent procedure. A special thanks to barbonenet

[Guest barbonenet]

you' re welcome