Posted March 14, 201510 yr 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, 201510 yr by barbonenet
March 14, 201510 yr 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, 201510 yr by barbonenet
March 14, 201510 yr 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, 201510 yr by barbonenet
March 15, 201510 yr nice work!! i recomanded to change teflon with threadlocker LOCTITE 243( medium strenght)
March 15, 201510 yr 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!
March 15, 201510 yr 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;)
April 7, 201510 yr Its a shame that already the pictures are gone, somebody should put them to a more reliable server.
September 8, 20159 yr I still have some options in mind. I'll think more what I'm doing. All suggestions are welcome
September 8, 20159 yr 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.
September 8, 20159 yr 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!
September 13, 20159 yr 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
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